United States

Department of

Agriculture

Forest Service

Pacific Northwest

Research Station

General Technical

Report

PNW-GTR-692

February 2007

Riparian and Aquatic Habitats of the

Pacific Northwest and Southeast

Alaska: Ecology, Management

History, and Potential Management

Strategies

Fred H. Everest and Gordon H. Reeves
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Authors

Fred H. Everest is an associate professor of environmental technology (retired),

University of Alaska Southeast, Sitka Campus, 1332 Seward Avenue, Sitka, AK

99835; and Gordon H. Reeves is a research fishery biologist, U.S. Department of

Agriculture, Forest Service, Pacific Northwest Research Station, Forestry Sciences

Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331. Everest is currently

located at P.O. Box 1444, Sitka, AK 99835.
i

Abstract

Everest, Fred H.; Reeves, Gordon H. 2006. Riparian and aquatic habitats of the

Pacific Northwest and southeast Alaska: ecology, management history, and

potential management strategies. Gen. Tech. Rep. PNW-GTR-692. Portland,

OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 130 p.

Management of riparian habitats is controversial because land use policies have

historically emphasized economic values (e.g., timber production) at the expense

of ecological and social values. Attempting to manage these valuable resources to

attain the greatest combination of benefits has created a long-term controversy that

continues to the present. Our analysis indicates that at mid to large spatial scales,

healthy riparian ecosystems and land management activities are not mutually

exclusive, but the degree of compatibility is determined by policy decisions based

on competing demands and pressing timelines as well as available scientific knowledge. Current management schemes on federal lands in the Pacific Northwest and

Alaska are appropriately addressing large spatial scales and incorporating the

principles of disturbance ecology. We found no scientific evidence that either the

default prescriptions or the options for watershed analysis in the Northwest Forest

Plan and Tongass Land Management Plan provide more protection than necessary

to meet stated riparian management goals. We believe that additional alternative

riparian management strategies could be implemented and evaluated in concert to

shorten the time needed to realize effective strategies that fully meet riparian

management goals.

Keywords: Riparian ecosystems, management, dynamics, Northwest Forest

Plan, Tongass Land Management Plan.
ii

Preface

Management of riparian habitats, especially on forest lands west of the Cascade

crest in Oregon and Washington, and in southeast Alaska, has been a subject of

controversy for decades. Why the controversy? Riparian zones produce and maintain many resources of economic, ecological, and social value. Often the most

valuable timber in watersheds, e.g., Port Orford cedar in the Pacific Northwest

and Sitka spruce and red and yellow-cedar in southeast Alaska, grows in moist sites

provided by riparian zones.1 2 In addition, science has demonstrated that riparian

habitat in western Oregon and Washington, southeast Alaska, and other locations

supports higher densities and diversities of flora and fauna than other portions of

the landscape.3 4 5 The natural functions of riparian ecosystems are important contributors to the maintenance of watershed hydrology, streamflows, water quality,

stream nutrients, and habitat characteristics needed to maintain the viability of

native aquatic species, including many economically significant species.6

 Riparian

1 Franklin, J.F.; Dyrness, C.T. 1973. Natural vegetation of Oregon and Washington. Gen.

Tech. Rep. PNW-8. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific

Northwest Research Station. 417 p.

2 U.S. Department of Agriculture, Forest Service [USDA Forest Service]. 1997. Tongass

land management plan revision. Final environmental impact statement Part 1: summary,

chapters 1 and 2, and chapter 3 (physical and biological environment). R10-MB-338b.

Washington, DC. [Irregular pagination].

3 Crow, T.R.; Baker, M.E.; Barnes, B.V. 2000. Diversity in riparian landscapes. In: Verry,

E.S.; Hornbeck, J.W.; Dolloff, C.A., eds. Riparian management in forests of the

continental Eastern United States. New York: Lewis Publishers: 43-66.

4 Oakley, A.L.; Collins, J.A.; Everson, L.B. [et al.]. 1985. Riparian zones and freshwater

wetlands. In: Brown, E.R., ed. Management of wildlife and fish habitats in forests of

western Oregon and Washington. Part 1–Chapter narratives. Portland, OR: U.S.

Department of Agriculture, Forest Service, Pacific Northwest Region: 57-80.

5 Olson, D.H.; Chan, S.S.; Weaver, G. [et al.]. 2000. Characterizing stream, riparian, and

upslope habitats and species in Oregon managed headwater forests. In: Wiggington, J.;

Beschta, R., eds. Riparian ecology and management in multi-land use watersheds. AWRA

Publication TPS-00-2. International conference of the American Water Resources

Association. Middleburg, VA: American Water Resources Association: 83-88.

6 Naiman, R.J.; Beechie, T.J.; Benda, L.E. [et al.]. 1992. Fundamental elements of

ecologically healthy watersheds in the Pacific Northwest coastal region. In: Naiman, R.J.,

ed. Watershed management: balancing sustainability and environmental change. Seattle,

WA: University of Washington, Center for Streamside Studies: 127-188.
iii

zones are focal areas for recreation and have high aesthetic appeal for many outdoor activities.7 8

 Other social and economic benefits of riparian zones accrue to

fishers, hunters, farmers, loggers, resort owners, municipalities, miners, and

others.9 Unfortunately, not all benefits of riparian areas can be realized simultaneously at all times, because some are mutually exclusive at small spatial scales.

However, it is possible to manage riparian ecosystems to achieve a combination

of benefits at larger spatial scales, e.g., the large watershed scale. The uses of

riparian ecosystems, and the question of how to achieve a socially acceptable

balance among economic, ecological, and social uses, lies at the heart of the

riparian debate.

Alteration of riparian habitats has been implicated as a contributor in the

decline of freshwater habitat for anadromous salmonids in the Pacific Northwest.

Several stocks of anadromous salmonids in the region were listed as threatened or

endangered in the 1990s, and attempts to recover those populations currently

address concerns with freshwater habitat, fish harvest, hydropower development,

and fish hatcheries. Recovery efforts include development of new riparian management strategies that provide more protection for riparian and aquatic habitats on

forest lands than previous management schemes. The new strategies have intensified

the ongoing debate surrounding the appropriate goals and practices for management

and protection of riparian habitats.

The controversy surrounding management of riparian areas extends to all land

uses, including agriculture, urban landscapes, water development projects, forestry,

and others, and to all land ownerships. However, in the Pacific Northwest and

southeast Alaska, the controversy currently focuses largely on riparian management

in forested watersheds. Expansion of that focus to include whole river basins and

other land uses and ownerships, however, could provide a more holistic and perhaps

more viable approach to management of riparian ecosystems, land management

activities as a whole, and recovery of threatened and endangered species.

7 Schroeder, H.W. 1996. Voices from Michigan’s Black River: obtaining information on

“special places” for natural resource planning. Gen. Tech. Rep. NC-184. St. Paul, MN:

U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station.

26 p.

8 Stynes, D.J. 1997. Recreation activity and tourism spending in the Lake States. In:

Webster, H.H.; Vasievich, J.M., eds. Lake States regional forest resources assessment:

technical papers. Gen. Tech. Rep. NC-189. St. Paul, MN: U.S. Department of Agriculture,

Forest Service, North Central Forest Experiment Station: 139-164.

9 Dwyer, J.F.; Jakes, P.J.; Barro, S.C. 2000. The human dimensions of riparian areas:

implications for management and planning. In: Verry, E.S.; Hornbeck, J.W.; Dolloff, C.A.,

eds. Riparian management in forests of the continental Eastern United States. New York:

Lewis Publishers: 193-206.
iv

An examination of land ownership, land cover, and land uses in the Northwest

and southeast Alaska provides perspective on the comparative importance of riparian

lands managed by private and public landowners. Approximately 52 percent of the

land base in the Northwest is privately owned forest land, rangeland, cropland,

pasture, and urban and residential properties.10 Most of the privately owned landscape consists of lowlands and valleys in downstream areas of the region’s major

river basins, where riparian and aquatic ecosystems historically provided important

habitats for production of fish and other aquatic resources.11 12 13 14 Dams, reservoirs,

irrigation systems, cultivation, use of pesticides and fertilizers, urbanization, and

transportation systems have altered many riparian and aquatic habitats in these areas,

with perhaps the greatest effects associated with agriculture and hydropower production.15 16 17 Because of intensive land use on large expanses of private land, and

10 Pease, J. 1993. Land use and ownership. In: Jackson, P.; Kimerling, A., eds. Atlas of the

Pacific Northwest. 8th ed. Corvallis, OR: Oregon State University Press: 31-39.

11 Brown, T.G.; Hartman, G.F. 1988. Contribution of seasonally flooded lands and minor

tributaries to the production of coho salmon in Carnation Creek, British Columbia.

Transactions of the American Fisheries Society. 117: 546-551.

12 Li, H.; Schreck, C.B.; Bond, C.E.; Rexstad, E. 1987. Factors influencing changes in fish

assemblages in Pacific Northwest streams. In: Matthews, W.J.; Heins, D.C., eds.

Community and evolutionary ecology of North American stream fishes. Norman, OK:

University of Oklahoma Press: 193-202.

13 Peterson, N.P.; Reid, L.M. 1984. Wall based channels: their evolution, distribution, and

use by juvenile coho salmon in the Clearwater River, Washington. In: Walton, J.M.;

Houston, D.B., eds. Proceedings of the Olympic Wild Fish Conference. Port Angeles,

WA: Fisheries Technology Program, Peninsula College: 215-226.

14 Sedell, J.R.; Reeves, G.H.; Hauer, F.P. [et al.]. 1990. Role of refugia in recovery from

disturbance: modern fragmented and disconnected river systems. Environmental

Management. 14: 711-724.

15 Beechie, T.; Beamer, E.; Wasserman, L. 1994. Estimating coho salmon rearing habitat

and smolt production losses in a large river basin, and implications for restoration. North

American Journal of Fisheries Management. 14: 797-811.

16 Bradford, J.M.; Irvine, J.R. 2000. Land use, fishing, climate change, and the decline of

Thompson River, British Columbia, coho salmon. Canadian Journal of Fisheries and

Aquatic Sciences. 57: 13-16.

17 Everest, F.H.; Kakoyannis, C.; Houston, L. [et al.]. 2004. A synthesis of scientific

information on emerging issues related to use and management of water resources on

forested landscapes of the Pacific Northwest. Gen. Tech. Rep. PNW-GTR-595. Portland,

OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.

128 p.
v

dams whose effective lifespans may be measured in centuries, return to the historical character of riparian and aquatic habitats is unlikely on much of this landscape.18 Many of the changes in riparian and aquatic ecosystems resulting from

agriculture and hydropower development can probably be considered irreversible,

at least in the near term.

In contrast to the widespread and persistent alteration of riparian and aquatic

habitats on nonforest lands, management of public forest lands generally has made

fewer and less persistent changes in riparian and aquatic ecosystems. The most extensive habitat changes west of the Cascade crest in Oregon and Washington and

in southeast Alaska are associated with timber harvest, but those effects, with the

exception of roads, are potentially temporary and reversible.

The federal government manages nearly 48 percent of the land base in the

Pacific Northwest. National forests managed by the U.S. Forest Service and rangelands managed by the Bureau of Land Management, national parks, and national

wildlife refuges, account for a large percentage of Oregon (48.2 percent) and

Washington (29.8 percent) (table 1). Federal lands west of the Cascade crest in

Oregon and Washington total about 4.6 million ha, of which about 4.1 million ha is

forested. About 59 percent of the forested landscape has been managed for production of timber and other resources. The remainder is in wilderness, or areas administratively withdrawn from forest management. Federal holdings consist largely of

forests and rangelands that are generally in the higher elevation mountains of the

region. Many of these areas produce large amounts of water and contain some of the

best remaining habitats for native aquatic organisms (see footnote 17).19 These lands

contain numerous small streams and associated riparian ecosystems that, in combination, are largely responsible for the quantity and quality of water and aquatic

habitats within the forested landscape.

More than 62 percent of Alaska is owned and managed by the federal government (table 1), but to date, management activities have resulted in limited modification of riparian and aquatic habitats on these lands. In the sparsely populated

18 Gregory, S.V.; Bisson, P.A. 1997. Degradation and loss of anadromous salmonid

habitat in the Pacific Northwest. In: Stouder, D.J.; Bisson, P.A.; Naiman, R.J., eds. Pacific

salmon and their ecosystems. New York: Chapman and Hall: 277-314.

19 Sedell, J.; Sharpe, M.; Dravneiks, D. [et al.]. 2000. Water and the Forest Service. FS660. Washington, DC: U.S. Department of Agriculture, Forest Service. 26 p.
vi

temperate rain forests of southeast Alaska, the federal government owns about 95

percent of the landscape: about 80 percent of federal rain forest in Alaska is in the

Tongass National Forest and most of the remainder is in Glacier Bay National Park

(see footnote 2). About 2.2 million ha of productive old-growth forest exists in the

Tongass National Forest; about 1.7 million ha is designated wilderness or administratively withdrawn from forest management, and about 162 000 ha was harvested

during the last half of the 20th century. Most streams, riparian habitats, and watersheds in the region remain largely unaffected by human activities.20

The conclusion to be drawn from the overview of land ownership and land use,

especially in the Pacific Northwest, is that many low-elevation aquatic and riparian

habitats in major river basins, mostly on private lands, have been converted from

lowland and flood-plain forests to nonforested agricultural lands, reservoirs, and

urban lands (see footnote 14). Riparian and aquatic ecosystems on these lands

historically provided important habitats for many aquatic species. These habitats,

prior to alteration, may have been the most important rearing areas for specific

life-history stages of some anadromous salmonids at certain seasons of the year (see

20 Bryant, M.D.; Everest, F.H. 1997. Management and condition of watersheds in

southeast Alaska: the persistence of anadromous salmon. Northwest Science. 72(4):

249-267.

Table 1—Land ownership and land use in the Pacific Northwest and Alaska

Land use Ownership Oregon Washington Alaska

km2 % km2 % km2 %

Forests Federal 75,680 30 38,350 22 311,610 21

Forests Nonfederal 47,980 19 51,127 29 210,440 14

Rangeland Federal 53,160 21 6,750 4 29,310 2

Rangeland Nonfederal 37,040 15 22,560 13

Cropland Nonfederal 24,680 10 37,970 22 130 <1

Pasture Nonfederal 7,750 3 5,750 3 2,411 <1

Urban Nonfederal 3,810 2 6,333 4 380 <1

National parks Federal 680 <1 7,330 4 195,460 13

Other 0 0 728,355 49

Total federal 129,520 52 52,430 30 922,670 62

Total nonfederal 121,260 48 123,737 70 554,600 38

Total combined 250,780 100 176,167 100 1,477,270 100

Sources: Pacific Northwest, Pease 1993; Alaska, Alaska DNR 2000, US GSA 2000, NPS 2005, Public

Land Statistics 2000, USDA Forest Service 2000.
vii

footnotes 11, 12, and 13). Many of these habitats no longer support historical

indigenous aquatic communities.

Some riparian and aquatic habitats on forest lands under federal management

have also been altered, but to a lesser extent than on privately owned lands. These

habitats were also important historical producers of anadromous salmonids and

other aquatic species and still contain some of the best remaining aquatic habitats in

the region. Recovery of riparian and aquatic habitats on both forest lands and

nonforest lands in western Oregon and Washington is currently being addressed by

federal and state agencies and nongovernmental organizations.

Current and previous state and federal goals for riparian management are

similar in that they all aim to protect water quality as well as riparian and aquatic

habitats. However, policymakers have developed different strategies for achieving

the goals state to state and by land ownership, fueling the debate about how to

achieve management goals. Some questions in the riparian management debate are

decades old and still unanswered. For example:

• Are land management activities and healthy aquatic and riparian ecosystems

mutually exclusive?

• If not, how much and what type of land management can be conducted

without undesirable social, economic, or ecological effects on riparian

ecosystems?

Other questions are of more recent origin, for example:

• Are current riparian management schemes addressing the appropriate

spatial and temporal scales?

• Have the riparian management schemes recently applied on federal lands

gone too far in protecting ecological values at the expense of some social

and economic values?

• Are there new or emerging options for managing riparian ecosystems that

will improve multiple resource use at the watershed scale yet still maintain

desired characteristics of riparian and aquatic resources?

 We will explore these questions in this paper.
viii

Executive Summary

Riparian habitats on forest lands west of the Cascade crest in Oregon and Washington and in southeast Alaska produce a variety of ecological, economic, and social

values. Management of riparian habitats, however, is controversial because land use

policies have historically favored some of these values (e.g., timber production) at

the expense of others. The attempt to manage these valuable resources to attain the

greatest combination of benefits has created a long-term controversy that continues

to the present.

Some of the questions in the debate are decades old and still unanswered. For

example, are land management activities and healthy aquatic and riparian ecosystems mutually exclusive? If not, how much and what type of land management can

be conducted without undesirable social, economic, or ecologic effects on riparian

ecosystems? Other questions are of more recent origin; for example, are current

riparian management schemes addressing the appropriate spatial and temporal

scales? Have the riparian management schemes recently applied on federal lands

gone too far in protecting ecological values at the expense of some social and

economic values? Are there new or emerging options for managing riparian ecosystems that will improve multiple resource use at the watershed scale, yet still maintain desired characteristics of riparian and aquatic resources? We attempt to answer

these questions in this paper.

Our objectives focus on (1) how riparian areas can be defined and delineated;

(2) a brief examination of the structure, function, and benefits of riparian ecosystems; (3) a review of the role that natural and human disturbances play in the function of riparian and aquatic ecosystems in forests of the Pacific Northwest and

southeast Alaska; (4) a review of the development of forest practice rules in the

Pacific Northwest and southeast Alaska; and (5) an examination of potential riparian

management strategies that might increase compatibility among the different values

sought from forest lands.

Riparian zones can be defined by either their physical or functional attributes,

but recent definitions tend to emphasize function and, therefore, from a management perspective, increase the geographic extent of riparian ecosystems.

The structural features of riparian ecosystems are highly variable, but all

share common physical elements that are controlled by environmental phenomena.

Physical characteristics of riparian habitats are defined in time and space by climatic

conditions, vegetation types, stream order, and geomorphic features like channel
ix

gradient, elevation, slope, aspect, and perhaps other factors. When defined physically, riparian ecosystems generally have a linear structure that may be hundreds of

kilometers in length and highly variable in width. The flood plains of large rivers,

for example, may contain extensive riparian habitats with widths of a kilometer or

more. Conversely, riparian zones along small, incised headwater streams may be

only a few meters wide.

When viewed functionally, riparian ecosystems provide a variety of important

linkages and ecological functions for adjacent aquatic and upland ecosystems. Key

functions include the maintenance of water quality, control of sediment delivery

from uplands and sediment movement in streams, control of the movement of

nutrients and contaminants, control of streambed and bank stability, and the maintenance of fish and wildlife habitats in adjacent ecosystems.

Benefits provided by riparian zones are strongly related to their structure and

function. Although it is possible to think of the benefits in ecological, social, or

economic terms, in most cases, the benefits blend across the three categories. Some

of the benefits are strongly associated with unmanaged riparian habitats, whereas

others may be derived from active riparian management. Some major benefits that

accrue to society from riparian ecosystems include maintenance of water quality

in streams, lakes, shallow groundwater strata, and hyporheic zones; maintenance

of stream channel stability and hydrologic function in watersheds; contribution to

maintenance of biodiversity in watersheds and the maintenance of viable populations of riparian, aquatic, and terrestrial species; focal sites for outdoor recreation;

enhancement of the value of private residential and commercial properties; contribution to visual aesthetics in managed landscapes; maintenance of aesthetics in wild

and scenic river corridors; flood control; maintenance of streamflows for human

uses; high-quality potable water for domestic and industrial use; production of highvalue aquatic resources (e.g., anadromous salmonids); timber production; livestock

production from grazing on riparian forage; and mining for gold and other minerals. The variety of ecological, social, and economic benefits provided by riparian

zones contribute to the controversy surrounding their management in Western

watersheds.

Watersheds throughout the Pacific Northwest and southeast Alaska are subject

to disturbances from natural events such as fire, floods, and wind and human activities such as construction of dams and reservoirs, agriculture, and timber harvest.
x

The type and timing of disturbances largely determine their effects on ecosystem

resilience, ecological processes, and indigenous biota. Ecosystem disturbances can

be classified as either “pulse” or “press” disturbances based on their temporal and

spatial frequency. Pulse disturbances (e.g., wildfire) occur infrequently, and allow

sufficient time between disturbances to enable ecosystems to recover to predisturbance conditions. Pulse disturbances generally allow ecosystems to remain within

their normal historical range of states and conditions. Press disturbances (e.g., timber harvest), on the other hand, are characterized by frequent or continual events

interspersed with insufficient recovery time to allow ecosystems to return to

predisturbance conditions. Press disturbances generally reduce the resiliency of

ecosystems, and may ultimately impose new regimes of variability that are outside

of the natural historical range of a watershed or ecoregion. Natural and human

disturbance regimes can fall into either the pulse or press category, although natural

disturbances are most often associated with the former and human disturbances with

the latter.

States and federal agencies have developed rules and practices to protect riparian zones from forest management. Those practices evolved over a period of more

than 30 years to accommodate new scientific information and provide increased

riparian protection. The culmination of forest practice rules resulted in development of the Northwest Forest Plan (NWFP) and the Tongass Land Management

Plan (TLMP) for protection of riparian zones on federal lands and revised state

forest practices acts for protection on state and private lands in the region. Current

state-of-the-art forest practices provide extensive protection to riparian ecosystems,

but they have not been fully evaluated, so their efficacy remains unknown.

In regard to the original questions we posed, first our analysis indicates that at

mid to large spatial scales, healthy riparian ecosystems and land management activities are not mutually exclusive, but the degree of success in achieving compatibility

is determined by policy decisions based on competing demands and pressing timelines as well as available scientific knowledge. Second, we found that current management schemes are appropriately addressing large spatial scales and incorporating

the principles of disturbance ecology. Third, we found no scientific evidence that

either the default prescriptions or the options for watershed analysis in the NWFP

and TLMP provide more protection than necessary to meet stated riparian management goals. Finally, we found that additional alternative riparian management
xi

strategies could be implemented and evaluated in concert to shorten the time needed

to realize effective strategies that fully meet riparian management goals. Emerging

and future strategies for riparian management that are science-based, consider

natural processes, and address large temporal and spatial scales in an interagency

forum that includes all concerned stakeholders appear to hold promise for the

future. Precedent has been set, for example, in organizations like the Deschutes

River Basin Conservancy and the Coastal Landscape Analysis and Modeling Study

in Oregon. In reality, however, the direction of riparian management will be determined, not by science, but by the normative decisions of policymakers who attempt

to achieve a balance between ecosystem sustainability and the competing demands

of resource users.
xii

Contents

1 Introduction

3 Geographic Scope

4 Objectives

5 Definition of Riparian Ecosystems and Delineation of Riparian Zones

7 Structure, Function, and Benefits of Riparian Zones

8 Structure

9 Function

17 Benefits

19 Effects of Watershed Disturbances on Riparian Structure and Function

20 Natural Disturbances

31 Summary of Natural Disturbances

33 Human Disturbances

42 Summary of Human Disturbances

44 Evolution of Riparian Management in Oregon, Washington, and

Southeast Alaska

50 Establishment and Evolution of Forest Practice Rules

72 Commonalities in Development of Forest Practice Rules

75 Benefits and Costs of Forest Practice Rules Development

79 Potential Options for Riparian Management Strategies

80 Temporal and Spatial Considerations

81 Focus on Forested Lands

88 Considerations for Future Riparian Management on Forest Lands

89 Criteria for Next Steps

91 Examples of Potential Riparian Management Strategies

97 Conclusions

99 English Equivalents

99 Literature Cited
1

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Introduction

Riparian ecosystems are important components of watersheds worldwide, and much

of what is known about their structure and function has universal application. In the

humid mountain ecosystems of the Pacific Northwest United States (PNW), southeast Alaska, and elsewhere, riparian areas are used by a rich and diverse assemblage

of species (Odum 1979) and provide critical transition zones linking terrestrial

and aquatic ecosystems within watersheds (Naiman et al. 1992, 2002; Oliver and

Hinckley 1987). Riparian ecosystems, from a functional standpoint, also exert

important controls over the characteristics of rivers and streams. Healthy riparian

ecosystems contribute to natural temporal and spatial regimens of streamflow,

water quality (U.S. Army Corps of Engineers 1991), nutrient supply (Clinton et al.

2002, Nakano et al. 1999), and the physical structure of aquatic habitats (Reeves et

al. 1993). Also, transfer of nutrients from freshwater to terrestrial habitats provides

benefits to riparian ecosystems (Collier et al. 2002; Drake et al. 2002; Helfield and

Naiman 2001, 2002; Sanzone et al. 2003). Scientists and managers recognize that

from a large-scale holistic perspective, it is difficult to isolate riparian ecosystems

from the watershed- or river-basin-scale ecosystems in which they occur. Nevertheless, riparian ecosystems that are substantially altered by human activities can have

such large effects on adjacent and downstream aquatic and terrestrial habitats that

research investigations and management schemes and constraints often focus on

these ecosystems.

Forested watersheds of the United States are major sources of water and aquatic

biodiversity. Forests currently cover about one-third of the Nation, but receive

more than half of the total precipitation and yield more than three-fourths of the

total annual runoff (Norris et al. 1991). The 77.3-million-ha National Forest System is the Nation’s largest source of fresh water. In the Pacific Northwest, more

than 38 percent (about 80 billion m ) of the region’s annual runoff of about 170

billion m flows from the area’s national forests (Sedell et al. 2000). This generally

water-rich forested landscape contains thousands of kilometers of streams, lakes,

wetlands, and associated riparian zones that function in concert to maintain the

diverse aquatic ecosystems and fish communities of the region.

Aquatic species have adapted to the natural disturbance regimes and climate

cycles prevalent in forested watersheds (Reeves et al. 1995). Historically, episodic

events in upland and riparian forests, such as fires, floods, mass erosion, wind, and

insect outbreaks, shaped and maintained the productivity of aquatic and riparian

habitats (Benda et al. 1998). Despite the effects of episodic and chronic natural

Riparian ecosystems

exert important

controls over the

characteristics of

rivers and streams.
2

General Technical Report PNW-GTR-692

disturbances and climate cycles that caused historical aquatic productivity in

individual watersheds to vary with time, riparian ecosystems in forested landscapes

of the West provided habitat for an abundance of terrestrial species and contributed

to productive aquatic habitats that supported tens of millions of anadromous

salmonids and other aquatic species (Volkman 1997).

Settlement of the West in the 19th and 20th centuries superimposed a variety of

physical human disturbances atop existing climate cycles and natural disturbances.

In the Pacific Northwest, deforestation for agriculture and human developments,

drainage of wetlands for agriculture, activities associated with agricultural production, urbanization, and water impoundments to support agriculture, urbanization,

and hydropower production are the primary human disturbances affecting riparian

and aquatic habitats in lowland areas of river basins. Timber harvest and roads,

however, are the dominant physical human disturbances in the forested uplands.

In southeast Alaska, timber harvest and, to a lesser extent, mining are the major

human disturbances affecting the landscape. In either location, human disturbances

generally occur more frequently in time and space and leave different legacies than

natural disturbances, and their effects are additive to natural disturbance regimes.

In addition to physical changes to riparian and freshwater habitats, ecological disturbances such as fish harvest and fish hatchery production have added additional

stresses to aquatic ecosystems.

Human disturbance regimes have directly and indirectly changed the characteristics of aquatic and riparian habitats in the past 150 years. The changes have contributed to the decline of many aquatic species in the PNW (Gregory and Bisson

1997), including numerous stocks of anadromous salmonids (Nehlson et al. 1991).

Although other factors (e.g., climate cycles, fishing, hunting) may also have contributed to species declines, habitat loss is considered to be the primary factor

(Gregory and Bisson 1997).

The recognition that human disturbances have changed the natural spatial and

temporal distribution of aquatic and riparian habitats and the species that depend

on them eventually led to development and evolution of special guidelines and

practices for management of riparian zones, water resources, and watersheds. The

guidelines may differ by type of management activity (e.g., agriculture, urbanization, hydropower, forestry), but the common goal is to protect streamflows, water

quality, or habitats of a variety of riparian and aquatic organisms, or a combination

of the three, while allowing management and use of other resources. Management

Human disturbance regimes

have directly and

indirectly changed

the characteristics

of aquatic and riparian habitats in the

past 150 years.
3

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

strategies that apply to forested watersheds differ by federal, state, and private

ownership patterns, but all attempt to maintain ecological functions as well as

social and economic use of resources.

The type and extent of protective measures applied to forested landscapes

have been driven by these same concerns. Since the late 1960s, forest management

practices have moved steadily in the direction of reducing or mitigating human

disturbances to upland, riparian, and aquatic ecosystems while still allowing economic harvest of timber and providing for other resource uses (e.g., recreation)

from forested watersheds. Social pressure to protect environmental assets, including

riparian habitats and integrity of aquatic ecosystems, has contributed to the evolution of forest practices (Whitelaw 1992).

Changes in rules and policies for riparian management on private, state, and

public forest lands have, along with many other factors, reduced timber harvests

from historical levels. For example, the boundary of riparian ecosystems on federal

land was greatly expanded by the Northwest Forest Plan (NWFP) (USDA and

USDI 1994b). Prior to the NWFP, riparian areas were generally defined as 30 m

on either side of fish-bearing streams. The boundary was extended to about 90 m

on fish-bearing streams by the NWFP. Additionally, and perhaps most significantly,

the riparian zone was delineated as up to 45 m on each side of non-fish-bearing

streams. A similar strategy, described in the 1997 Tongass Land Management Plan

(TLMP), is used on the Tongass National Forest in southeast Alaska (USDA Forest

Service 1997). Recent changes in forest practices acts and rules for riparian and

aquatic habitat protection in Oregon (Oregon Revised Statutes 1999), Washington

(Washington State Legislature 2005), and Alaska (Alaska Division of Forestry

2001) have generally reduced the amount of extractive activity allowed in riparian

zones, or required greater retention of riparian timber. These strategies have, along

with other changes in management (e.g., protection of wildlife habitats and more

green-tree retention in harvest areas), reduced timber harvests in both regions, but

because their effectiveness has not yet been fully assessed, their implementation has

heightened the debate about how to best accomplish multiple resource management

and sustainable forestry on national forests.

Geographic Scope

Although riparian ecosystems universally link upland, riparian, and aquatic habitats, we will focus primarily on the relationship between riparian areas, aquatic

habitats, and aquatic species as affected by management of riparian ecosystems on
4

General Technical Report PNW-GTR-692

forested landscapes of western Oregon and Washington and southeast Alaska. In the

former case, we address primarily the area encompassed by the NWFP, and in the

latter, the Tongass National Forest. This focus is not meant to minimize the importance of riparian habitats on nonforested lands or other geographic regions of the

Pacific Northwest or Alaska, and we will address those areas as necessary to

provide context for our primary focus.

Objectives

This paper will not provide another exhaustive review of literature on the structure, function, and importance of riparian ecosystems, although we will briefly

touch on those areas. Several detailed reviews of those subjects have been completed in recent years (Correll 2003, Desbonnet et al. 1994, U.S. Army Corps of

Engineers 1991, Van Deventer 1992, Verry et al. 2000, Wenger 1999). Instead, we

will focus on:

• How riparian areas can be defined and delineated.

• A brief review of the structure, function, and benefits of riparian

ecosystems.

• The role of natural and human disturbances in the function of riparian and

aquatic ecosystems in forests of the Pacific Northwest and southeast Alaska.

• The development of forest practice rules in the Pacific Northwest and

southeast Alaska.

• Potential riparian management strategies that might increase compatibility

among the different values sought from forest lands.

Although we have chosen not to review the ecological effects of grazing on

riparian habitats in rangelands of western Oregon and Washington, some literature

exists on the subject (e.g., Bolton and Monohan 2001, Chapman and Knudsen

1980).

We recognize the importance of scientific knowledge in resolving problems

related to management of natural resources (Everest et al. 1997, Swanston et al.

1996), including management of aquatic and riparian habitats, but we also recognize that science is not the only factor used to arrive at decisions. Policymakers and

managers use a normative process that draws upon scientific information, social and

economic considerations, politics, and other factors to make such decisions (Mills

et al. 1998), including those addressing management of riparian resources. We do,

however, advocate that policymakers and managers use the best available science
5

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

when formulating decisions relevant to management of riparian and aquatic habitats

and check their final decisions for consistency with relevant scientific information

(Everest et al. 1997).

Definition of Riparian Ecosystems and Delineation

of Riparian Zones

Riparian ecosystems are defined by either their physical or functional attributes

(Brosofske 1996, Ilhardt et al. 2000, Palone and Todd 1997). Most current

physical definitions include a perennial or ephemeral water body, an adjacent

zone dominated by hydric vegetation, and a terrestrial area where vegetation and

microclimate are influenced by perennial or intermittent water tables (Obedzinski

et al. 2001) (fig. 1). Physical definitions generally have a site-specific focus.

Riparian zones defined and delineated by physical definitions can be highly variable

in width, ranging from a few meters on small steeply incised streams to a kilometer

or more on the flood plains of large rivers (fig. 2).

Functional definitions of riparian zones include the functional interactions

among streams, hyporheic zones, riparian vegetation, and terrestrial vegetation at

small to large watershed scales. These attributes of forested ecosystems influence

water quality, temporal and spatial distribution of streamflow, and the structural

characteristics of stream networks in watersheds. Riparian zones defined by functional criteria tend to be wider than those defined by physical attributes; for example, they may include source areas for recruitment of large woody debris in

steep terrestrial land some distance from potential receiving streams.

A recent review of riparian definitions by Ilhardt et al. (2000) concluded that

the way riparian ecosystems have been defined has evolved over time. Early

definitions tended to focus on physical attributes, or describe the static state or

physical condition of riparian areas at the site scale, whereas more recent definitions tend to be functional and define riparian ecosystems by their flows of energy

and materials at larger spatial scales.

Ilhardt et al. (2000) offered the following example of a functional definition

that recognizes the ecological functions of riparian areas that occur at various

scales:

Riparian areas are three-dimensional ecotones of interaction that

include terrestrial and aquatic ecosystems, that extend down into

More recent definitions tend to be

functional and define riparian ecosystems by their flows

of energy and materials at larger spatial

scales.
6

General Technical Report PNW-GTR-692

Figure 1—Riparian zones separate aquatic and terrestrial ecosystems (from Oakley et al. 1985).

Widths may vary at a given site depending on whether physical (narrower) or functional (wider)

definitions are used to delineate the zone.

Figure 2—The effects of topography on the characteristics of riparian areas (from Oakley

et al. 1985).
7

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

the groundwater, up above the canopy, outward across the flood

plain, up the near slopes that drain to the water, laterally into the

terrestrial ecosystem, and along the water course at a variable

width.

It is important to recognize that the way riparian ecosystems are defined affects

their delineation on the ground. It is relatively easy to define the boundaries of

riparian zones in forested watersheds when using only the physical characteristics

of soils, water, and vegetation. Based on these ecosystem attributes, trained technicians can delineate riparian zones at the site scale in the field. It is more difficult to

delineate riparian zones when using functional definitions that include near-stream

terrestrial areas beyond the boundaries of water influence. In the latter case, highresolution mapping at the watershed scale, followed by ground verification, may be

necessary.

Riparian ecosystems tend to be complex and dynamic and exhibit variability

within and across ecoregions (Lins 1997). For example, the vegetative characteristics of riparian habitats in water-rich areas can differ substantially from those in

arid and semiarid areas, but both contribute to the health of aquatic ecosystems in

the regions where they occur. Much of the variability in riparian habitats within

ecoregions can be attributed to landscape disturbance regimes and topographic

setting (Montgomery 1999). Topographic settings influence the type of vegetation

as well as the frequency with which it is subjected to disturbance. Disturbances

from natural and human sources can affect seral stages of vegetation in riparian

zones and create variable mosaics of riparian habitats that wax and wane with the

spatial and temporal features of disturbance.

Structure, Function, and Benefits of Riparian Zones

The structure and function of riparian ecosystems have been exhaustively studied in

the United States and abroad. Literature summaries and bibliographies of thousands

of individual riparian and riparian-related studies have been published in the past

three to four decades (e.g., Bolton and Monohan 2001 [2,090 citations], Correll

2003 [annotated bibliography with 522 citations], University of Washington 2004

[interagency bibliography with over 8,000 riparian and riparian-related citations],

U.S. Army Corps of Engineers 1991 [review and synthesis with 196 citations], Van

Deventer 1992 [bibliography with 3,252 citations], Verry et al. 2000 [review and

synthesis with 931 citations], Wenger 1999 [review and synthesis with 161 citations], Wenger and Fowler 2000 [review and synthesis with 72 citations]. Many of
8

General Technical Report PNW-GTR-692

these studies have focused on an individual function of riparian zones, e.g., recruitment of large woody debris to stream channels in forested watersheds, in an

attempt to determine the minimum width of riparian buffer needed to maintain a

specific ecological function. Using the extensive literature base, we will briefly

describe the structural features of riparian ecosystems and their primary ecological

functions within the broader fabric of regional ecosystems, and direct readers to

existing syntheses for more detailed treatment of the subject.

Structure

The features of riparian ecosystems are highly variable (Thomas et al. 1979), but

all share common physical elements that are controlled by environmental phenomena. Physical characteristics of riparian habitats are defined in time and space by

climatic conditions, vegetation types, stream order, and geomorphic features like

channel gradient, elevation, slope, aspect, and perhaps other factors (see Oakley

et al. 1985, Thomas et al. 1979). These factors, acting in concert with terrestrial

ecosystems, contribute to the amount, intensity, timing, and frequency of high-flow

events that shape both stream channel structure and riparian vegetation in flood

plains.

When defined physically, riparian ecosystems generally have a linear structure

that may be hundreds of kilometers in length and highly variable in width. The

flood plains of large rivers may contain extensive riparian habitats with widths

of a kilometer or more. Conversely, riparian zones along small, incised headwater

streams may be only a few meters wide. The width of riparian habitat for a given

stream size varies by climatic zone in the Northwest, with the greatest widths in

the humid regions west of the Cascade Mountains and at higher elevations across

the region, and progressively narrower widths in drier areas. Riparian zones in the

temperate rain forests of southeast Alaska, because of high annual precipitation that

creates expansive upslope fens, bogs, and forested wetlands, may extend considerable distances upslope from streams.

The elongated shape and vegetative structure of riparian zones maximizes edges

internally and along adjacent aquatic and terrestrial ecosystems. Depending on

structure of the vegetative community, three to five distinct edges between water,

grasses, forbs, deciduous, and coniferous vegetation may occur within a single

riparian zone. The high density of edges contributes to habitat and species diversity,

and the productivity, of riparian ecosystems.

Riparian ecosystems

generally have a

linear structure that

may be hundreds of

kilometers in length

and highly variable

in width.
9

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Topographic features of the landscape strongly affect the characteristics of

riparian ecosystems (fig. 2). Streams in areas with gentle topography (<30 percent

slope) may have wide flood plains subject to frequent sediment deposition, deep

soils, low gradients, and little channel entrenchment. Riparian zones along such

streams may be wide, vegetatively diverse, exposed to sunlight at all seasons, and

subject to natural disturbances primarily from wind and floods. Streams of equivalent size in areas with steep topography (>60 percent slope) may have narrow flood

plains subject to active erosional processes, shallow soils, steep gradients, and

deeply incised channels. Riparian zones along these streams are usually narrow,

have limited vegetative structure, may be topographically shaded during summer or

winter, and are subject to natural disturbances primarily from fire, floods, and mass

erosion events.

The combination of natural disturbances affecting riparian zones varies at the

regional scale across the Northwest and southeast Alaska, but the frequency and

magnitude of local disturbances shapes and maintains the temporal and spatial

characteristics of riparian habitats at the watershed scale. Riparian zones, in general, occur in geologically unstable areas subject to erosion, deposition, and a

variety of other natural disturbances (Leopold et al. 1964). These disturbances may

also contribute to diversity of riparian vegetation and associated habitats used by a

suite of aquatic and terrestrial organisms.

Function

Riparian ecosystems provide a variety of important linkages and ecological

functions for adjacent aquatic and upland ecosystems. Key functions include the

maintenance of surface and ground water quality in aquatic ecosystems; (especially

hyporheic zones: the area of penetration of surface water into flood-plain gravels)

maintenance of streambank and streambed stability; maintenance and protection of

habitat structure for fish, wildlife, and vegetation; and maintenance of favorable

microclimates for riparian-dependent species. All of these functions operate in

concert in the near-stream environment. It is possible to review the individual

functions of riparian ecosystems in isolation based on the results of individual

studies, as we do in the following pages. However, management strategies developed from studies of individual functional aspects of riparian zones (e.g., contribution of large wood to stream channels) have often failed to meet riparian

management goals (IMST 1999, Murphy 1995, USDA Forest Service 1995).

Management strategies that consider ecosystem-level scientific information of

Riparian ecosystems

provide a variety of

important linkages

and ecological

functions for adjacent aquatic and

upland ecosystems.
10

General Technical Report PNW-GTR-692

riparian functions in concert are more likely to achieve stated riparian management

goals (IMST 1999, Murphy 1995).

Functions related to water quality—

Riparian zones exert controls over the temperature of adjacent surface waters, the

movement of suspended sediment, dissolved and particulate organic matter, nutrients, pesticides, and heavy metals from upslope areas to downslope water bodies,

and streambed and bank stability. Healthy riparian ecosystems help to maintain

high-quality water and structural habitat elements for aquatic biota in adjacent

aquatic ecosystems.

Water temperature—

Riparian vegetation is one of the most important factors controlling water temperature in streams (U.S. Army Corps of Engineers 1991), especially during summer

when solar radiation peaks and sun angle is at its seasonal zenith. In small streams,

aspect and degree of incision may provide some topographic shading, although

vegetation usually remains the primary source of shade. Water temperature greatly

influences metabolism, development, and activity of fish and other stream organisms (Naiman et al. 1992), as well as recreational use and the value for domestic

water supplies (Hornbeck and Kochenderfer 2000). Streamside vegetation controls

the amount of solar radiation striking the water surface in summer, thus reducing

potential heating of surface waters. In winter, riparian vegetation tends to maintain

warmer water temperatures, especially in high-latitude and high-elevation streams

where vegetation both insulates and blocks radiative cooling (Beschta et al. 1987).

Warmer winter water temperatures reduce the potential for formation of shelf,

frazil, and anchor ice.

The effect of riparian vegetation on stream temperature varies by stream size

and season of the year. Riparian vegetation exerts the greatest temperature control

on small streams (U.S. Army Corp of Engineers 1991). Small, forested streams

that are heavily shaded by riparian vegetation typically receive only about 1 to 3

percent of total available solar radiation (Naiman 1983, Naiman and Sedell

1980). Consequently, their daily water temperatures are relatively cool and stable

(Naiman et al. 1992), and their fauna are adapted to low light and cool temperatures (Naiman and Sedell 1980). Loss of riparian vegetation along small streams

can cause large increases in water temperature (>10 °C) and changes in energy

flux, resulting in the disruption of indigenous aquatic communities.
11

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Riparian vegetation also influences the water temperature of mid-size streams

and rivers but to a lesser degree than in small streams. Gaps in the riparian canopy

along mid-size streams allow 10 to 25 percent of total available solar radiation to

reach the stream surface, allowing wide variations in diel and seasonal temperatures

(Naiman et al. 1992). Manipulation or loss of riparian vegetation along mid-size

streams, however, can still cause increases in summer water temperatures of several

degrees and affect energy flow and the health of aquatic communities.

The water temperature of large rivers is less affected by riparian vegetation.

Most available solar radiation reaches the surface of large streams, but diel temperature variations are minimized by stream depth and volume of flow. Changes in

the density of riparian vegetation along large rivers have less effect on aquatic biota

than along small or mid-size streams. Most benefits of shading by streamside vegetation are derived within about 30 m of streams (fig. 3) (Brazier and Brown 1973,

FEMAT 1993, Steinblums et al. 1984) although distance varies by stream size and

topographic features.

In addition to direct shading, the microclimate surrounding streams and riparian zones also may affect stream temperatures and the suitability of riparian habitats for vertebrates. Specific features of microclimate (e.g., soil moisture, solar

radiation, soil temperature, air temperature, windspeed, and relative humidity)

are influenced by near-stream vegetation (Chen 1991, Chen et al. 1995) and may

Figure 3—Generalized curves indicating percentage of riparian ecological

functions and processes occurring within varying distances from the edge of

a forest stand (from FEMAT 1993).
12

General Technical Report PNW-GTR-692

indirectly affect water temperature. Chen (1991) estimated the widths of riparian

vegetation needed to maintain 100 percent of microclimate effects near streams

(fig. 4). Maintenance of air temperature and windspeed, factors that can influence

stream temperatures, may require a vegetated corridor up to 125 m wide.

Sediment—

Sediment is the Nation’s most common contaminant of surface waters by weight

and volume and has been identified by the U.S. Environmental Protection Agency

as the number one problem threatening America’s waterways (Koltun et al. 1997).

Suspended and bedload sediments are natural components of flowing waters. Watersheds that are unmanaged have a natural range of sediment production and delivery

to stream channels, and streams have a natural capacity to process and transport

sediment downstream. Surface and mass erosion in unmanaged watersheds vary

widely in time and space owing to large infrequent natural events.

Many human activities in watersheds, including timber harvest and roadbuilding and use, accelerate soil erosion and sedimentation in receiving waters by

exposing mineral soil to erosive forces. If sediment delivery from human actions

significantly exceeds natural levels, alterations in natural system functions occur

(Platts and Megahan 1975), resulting in sediment deposition, channel instability,

Figure 4—Generalized curves indicating percentage of microclimate

attributes occurring within varying distances of the edge of a riparian forest

stand (Chen 1991) (from FEMAT 1993).

If sediment delivery

from human actions

significantly exceeds natural levels, alterations in

natural system

functions occur.
13

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

and high levels of turbidity (Everest et al. 1987, Nehlson et al. 1991). Elevated

concentrations of inorganic sediments in streams may impair many biological

functions. For example, elevated levels of sediments can reduce the family richness

and abundance of invertebrate drift and reduce growth of trout in affected streams

(Shaw and Richardson 2001).

Riparian vegetation can reduce sedimentation and its effects on stream and lake

habitats in the following ways (see U.S. Army Corps of Engineers 1991, Wenger

1999):

• Vegetative cover reduces erosion in riparian zones (U.S. Army Corps of

Engineers 1991).

• Vegetation and organic litter in riparian zones filter and trap sediment

moving downslope in surface waters (Karr and Schlosser 1977).

• Roots of riparian vegetation reduce erosion of streambanks (Beeson and

Doyle 1995).

• Large woody debris originating from riparian zones traps and retains

sediment moving in stream channels (Bisson et al. 1987) and keeps it from

accumulating downstream.

• Large riparian areas in flood plains reduce erosion by moderating

streamflow and scour during flood events (Gregory et al. 1991, Naiman et

al. 1988).

All of these riparian functions effectively reduce sedimentation in streams and

lakes, although their effectiveness may change seasonally. Riparian vegetation may

be less effective in controlling sedimentation in winter than in summer when vegetative growth is at its maximum (Schwer and Clausen 1989). Widths of riparian

vegetation needed to filter and retain sediment in transport from source areas to

streams are generally reported to be <50 m (e.g., U.S. Army Corps of Engineers

1991).

Nutrients and contaminants—

Pathways of nutrient flow between riparian and aquatic ecosystems have received

considerable study, especially in recent years. Energy flow is complex, moving both

downslope from riparian ecosystems to streams and upslope from streams to riparian ecosystems. Allochthonous contributions of small and large organic debris from

riparian vegetation provide an important energy source to hyporheic (Clinton et al.

2002) and stream waters (Vannote et al. 1980, Verry et al. 2000), and terrestrial

invertebrates contribute to the food web of aquatic systems (Nakano et al. 1999).
14

General Technical Report PNW-GTR-692

Nutrient energy also flows from aquatic to riparian systems. In the Pacific Northwest and Alaska, anadromous salmonids bring large quantities of nutrients from

the sea to freshwater streams where decomposing carcasses provide fertilizer to

riparian vegetation (Drake et al. 2002; Helfield and Naiman 2001, 2002; Naiman et

al. 2002). The net result can be positive feedback to salmonid spawning and rearing

habitats (Helfield and Naiman 2001) through enhanced growth of riparian vegetation that affects shade, sediment and nutrient filtration, and quantities of invertebrates and large woody debris in stream channels. Aquatic arthropods also transfer

energy from aquatic systems to terrestrial predators (Collier et al. 2002, Sanzone et

al. 2003).

Riparian vegetation and subsurface processes in riparian zones have the capability of trapping, binding, storing, and detoxifying many types of pesticides, heavy

metals, and other contaminants (see Desbonnet et al. 1994, U.S. Army Corps of

Engineers 1991, Wenger 1999). In the PNW, many of these functions are more

important in agricultural and urban areas that are more subject to the polluting

effects of human activities than are forested watersheds (e.g., Rienhold and Witt

1992, Rinella and Janet 1998). Essentially no agricultural pesticides or fertilizers

are used in southeast Alaska.

Current application of chemical pesticides, herbicides, and fertilizers is minimal on private and federal forest lands of the Pacific Northwest. Only about

1 percent of the commercial forest land in the region and 0.2 percent of the federal land1

 receives some form of forest chemical treatment each year. Nitrogenand phosphorus-based fertilizers are used occasionally in forestry to enhance

tree growth on private forest lands in the Pacific Northwest. Use of fertilizer is rare

on federal forest lands in the Pacific Northwest, and is usually limited to nurseries

and seed orchards. Use on private forest lands is more common but still limited in

extent. Water quality sampling programs in the Willamette River basin indicate that

nitrogen and phosphorus concentrations in waters flowing from forested watersheds

are similar to those at national benchmark sites on streams minimally disturbed by

human activities (Wentz et al. 1998).

Healthy riparian zones can strongly affect the movement of pesticides and

nutrients from terrestrial to aquatic ecosystems in forested, agricultural, and urban

landscapes (see U.S. Army Corps of Engineers 1991, Wenger 1999). Some of the

most important riparian functions include:

1 Smith, G. 2000. Personal communication. Silviculturist, U.S. Department of Agriculture,

Forest Service, Pacific Northwest Region, Portland, OR 97208.
15

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

• Trapping of a high percentage of phosphorus bound to sediments (the most

common phosphorus transport mechanism [Karr and Schlosser 1977]).

• Uptake by vegetation and denitrification of a high percentage of nitrate

nitrogen moving through the root zone and anaerobic zones of riparian

areas (e.g., Fennessy and Cronk 1997, Gilliam 1994).

• Trapping and detoxification of pesticides bound to sediments (e.g., Frick

et al. 1998).

• Intercepting aerosol drift of aerially applied pesticides (e.g, Wenger 1999).

All of these functions are generally provided by riparian corridors >50 m wide

(e.g., Desbonnet et al. 1994, U.S. Army Corps of Engineers 1991, Wenger 1999),

although riparian vegetation is more effective at retaining sediment-bound nutrients

than soluble nutrients. Aerosol sprays may require riparian buffer strips up to 100

m wide to prevent stream contamination (Nriagu and Lakshminarayana 1989).

Streambank and streambed stability—

Riparian vegetation functions as a stabilizer of streambanks and streambeds, and

thus helps to maintain water quality and the natural structural elements of stream

channels. Streams can be classified by channel type (e.g., Paustian 1992) based on

channel entrenchment, width-to-depth ratio, and sinuosity. Human or natural

disturbances can cause a stream to shift from one type to another, with a corresponding change in channel geometry. Such shifts may result in a long period of

channel instability, as the channel tends to re-establish its original type or reach

stability in a new type.

Riparian vegetation is one of several important factors that influence the

stability of streambeds and banks. Between disturbance events, riparian vegetation contributes to the maintenance or re-establishment of channel stability in the

following ways:

• Reduces streambank erosion.

• Helps maintain established stream channel geometry within historical

norms.

• Slows flood flows and dissipates stream energy.

• Reduces streambed erosion.

Riparian corridors >15 m wide have been shown to control streambank erosion

in small Eastern U.S. streams (Wipple et al. 1981), and 30-m corridors maintained

streambank stability in low-order streams in northern California (Erman et al.

1977).
16

General Technical Report PNW-GTR-692

Functions related to wildlife habitat—

At the landscape scale in the Pacific Northwest, riparian vegetation plays an important role in maintenance of regional biodiversity (Naiman et al. 1993) and provides

disproportionately important habitat for many wildlife species (Gregory and

Ashkenas 1990, Kelsey and West 1998). Of the 414 wildlife species in western

Oregon and Washington, 359 use riparian zones or wetland habitats during some

seasons of the year, or some parts of their life cycle (Oakley et al. 1985). Wildlife

benefit from several key functions of riparian ecosystems that provide:

• Reliable sources or water, food, and cover in areas where water is scarce

(Thomas et al. 1979).

• Maximum habitat diversity and edges for wildlife species because of the

elongated shape of riparian zones (Patton 1975).

• Specific microclimates (Brosofske et al. 1997) that are desired by some

species of wildlife, or required at some seasons.

• Preferred foraging, breeding, rearing, hiding, and resting habitats, and

thermal cover for particular species at certain times of the year (Oakley

et al. 1985).

• Travel corridors and migration routes between habitat types or summer and

winter ranges (Noss 1983).

Overall, the temporal and spatial needs of riparian and terrestrial vertebrates

for specific seral stages and stand conditions in riparian habitats are poorly known,

and more research is needed. Small generalists may need only a few meters of a

variety of vegetated riparian conditions to meet their needs (e.g., Raphael et al.

2002), whereas large mammals may need >150 m of late-successional riparian

habitats to meet specific needs (Buskirk et al. 1989, Raphael and Jones 1997,

USDA Forest Service 1997). After reviewing the relationship between riparian

areas and the habitat needs of wildlife, Wenger (1999) concluded that narrow

buffers provide habitat benefits for many species, but protecting diverse riparian

wildlife communities requires some buffers at least 100 m wide.

Functions related to habitat for fish and other aquatic life—

The condition of aquatic ecosystems at the watershed scale is strongly tied to the

condition of riparian vegetation within a watershed (Welsch 1991). The structure

and productivity of habitats for fish and other aquatic organisms are controlled to

a large extent by adjacent and upstream riparian vegetation. Some of the functional interactions between riparian and aquatic ecosystems, such as control of water

Riparian vegetation

plays an important

role in maintenance

of regional

biodiversity.
17

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

quality issues like temperature, sediment, nutrients, and contaminants and streambed

and bank stability, have already been discussed. Additional critical functions of

riparian vegetation for development and maintenance of habitat for fish and other

aquatic species include:

• Contribution of large woody debris that provides habitat structure for

salmonids and a variety of other aquatic organisms (Bisson et al. 1987,

Sullivan et al. 1987).

• Contribution of leaves and particulate organic matter, the primary energy

source for aquatic food webs in most small and mid-size streams (Minshall

et al. 1985, Wipfli and Gregovich 2002).

Widths of riparian corridors needed to maintain these functions generally are

<70 m (fig. 3) (FEMAT 1993).

Conclusions on riparian functions from the scientific literature—

Most studies on the functions of riparian ecosystems have addressed single functions at site scales with the intent of determining the width of riparian zone needed

to maintain the individual function under study. Much valuable information has

resulted from such studies, but caution is needed in their interpretation, and especially in their application to riparian management plans. Focusing on single functions (e.g., large woody debris or water temperature) simplifies delineation of

riparian zones but fails to account for the three-dimensional (width, length, depth

at the watershed scale) complexity and multiple functions inherent in riparian ecosystems. The key point is that complex riparian ecosystems and their functions can

only be understood at large temporal and spatial scales. The multiple functions of

riparian ecosystems operate in concert, with differing widths of unmanaged nearstream vegetation needed to maintain different functions (table 2). Attempts to protect or maintain a single function, based even on well-designed scientific studies,

may result in damage or loss of other functions. If managers choose to protect the

most vulnerable functions of riparian ecosystems, i.e., the ones requiring the widest

strips of unmanaged vegetation in the near-stream environment, then all riparian

functions are likely to be retained.

Benefits

Ecosystems at the watershed scale provide many ecological, social, and economic

benefits to society. Although the potential to realize all of the benefits at some

level is present in major watersheds (about 7th order and larger), despite decades

If managers choose

to protect the most

vulnerable functions

of riparian ecosystems, ...then all

riparian functions

are likely to be

retained.
18

General Technical Report PNW-GTR-692

of research and study, it remains unclear as to whether all of the benefits can be

derived simultaneously at desired levels as defined by society, especially at small

scales. The principal benefits derived from riparian areas in ephemeral headwater

catchments may differ from those associated with mid-sized perennial streams,

which in turn may differ from benefits of riparian zones along major rivers. However, at all scales, questions remain about interactions between potential benefits,

and whether some are mutually exclusive of others.

Benefits provided by riparian zones are strongly related to their structure and

function. Although it is possible to think of the benefits in ecological, social, or

economic terms, in most cases the benefits blend across the three categories. Some

of the benefits are strongly associated with unmanaged riparian habitats, whereas

others may be derived from active riparian management. Some major benefits that

accrue to society include:

• Maintenance of water quality in streams, lakes, shallow ground-water

strata, and hyporheic zones.

• Maintenance of stream channel stability and hydrologic function in watersheds.

• Contribution to maintenance of biodiversity in watersheds and the maintenance of viable populations of riparian, aquatic, and terrestrial species.

Table 2—Estimated widths of unmanaged near-stream vegetation in forested watersheds needed

to maintain various functions of riparian ecosystems

Width unmanaged

Riparian function vegetation required References

Maintain water temperature ~50 m Brazier and Brown 1973, FEMAT

1993, Steinblums et al. 1984

Maintain microclimate ~125 m* Chen 1991, FEMAT 1993

Control sediment ~50 m For example, U.S. Army Corps of

Engineers 1991

Control nutrients/contaminants ~100 m±* Desbonnet et al. 1994, Nriagu

and Lakshminarayana 1989,

Wenger 1999

Maintain streambed/banks ~30 m* Erman et al. 1977

Maintain wildlife habitats ~150 m±* Schoen 1977, USDA Forest

Service 1997

Maintain fish habitats >70 m* Bisson et al. 1987, FEMAT 1993

Note: Widths were derived from site-scale studies but correctly apply to riparian networks at watershed scales.

* = Requires late-successional or old-growth forest vegetation.

Some benefits are

strongly associated

with unmanaged

riparian habitats,

whereas others may

be derived from

active riparian

management.
19

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

• Focal sites for outdoor recreation.

• Contribution to the value of private residential and commercial properties.

• Contribution to visual aesthetics in managed landscapes.

• Maintenance of aesthetics in wild and scenic river corridors.

• Flood control.

• Maintenance of streamflows for human uses.

• High-quality potable water for domestic and industrial use.

• Production of high-value aquatic resources, for example, anadromous

salmonids.

• Timber production.

• Livestock production from riparian forage.

• Mining for gold and other minerals.

The variety of ecological, social, and economic benefits provided by riparian

zones contributes to the controversy surrounding their management in Western

watersheds.

Effects of Watershed Disturbances on Riparian

Structure and Function

Watersheds throughout the Northwest and southeast Alaska are subject to disturbances from natural events and human activities. The type and timing of disturbances largely determines their effects on ecosystem resilience, ecological

processes, and indigenous biota. Ecosystem disturbances can be classified as either

“pulse” or “press” disturbances based on their temporal and spatial frequency.

Yount and Niemi (1990) referred to disturbance regimes that maintain the resiliency of ecosystems as pulse disturbances. Pulse disturbances occur infrequently,

and there is sufficient time between disturbances to enable ecosystems to recover to

predisturbance conditions. Pulse disturbances generally allow ecosystems to remain

within their normal historical range of states and conditions.

Press disturbances, on the other hand, are characterized by frequent events

interspersed with insufficient recovery time to allow ecosystems to return to predisturbance conditions. Press disturbances generally reduce the resiliency of ecosystems and may ultimately impose new regimes of variability that are outside of the

natural historical range of a watershed or ecoregion. Natural and human disturbance regimes can fall into either the pulse or press category, although natural

disturbances are most often associated with the former and human disturbances

with the latter.

Watersheds

throughout the

Northwest and

southeast Alaska

are subject to disturbances from

natural events and

human activities.
20

General Technical Report PNW-GTR-692

Natural Disturbances

Natural disturbances in Northwest watersheds are generally classified as pulse

disturbances because they are cyclic or episodic in nature, usually widely scattered

in time and space, and stem from a variety of physical and biological sources. The

effects of natural disturbances are often asynchronous, so adjacent watersheds have

decoupled disturbance patterns resulting in different levels of disturbance at any

given time (Naiman et al. 1992). The result is an incremental, regional-scale

process of ecosystem change and renewal that is an essential part of maintaining

ecosystem productivity in the long term. Changes associated with natural disturbances are generally gradual enough for indigenous biota to cope with and adapt to

at regional or province scales. Effects of natural habitat disturbances (e.g., standreplacement fires) may cause temporary extirpation of species at small spatial

scales, but adjacent populations in favorable habitats are likely to rapidly recolonize

recovering habitats.

Natural disturbances provide a baseline from which to interpret the effects of

human disturbances, or the significance of cumulative effects from natural and

human impacts (Benda et al. 1998). Natural physical disturbances include climate

cycles and their associated effects on terrestrial, riparian, freshwater, and marine

ecosystems, and natural events (often climate induced) such as drought, fire, floods,

mass erosion, wind, and ice storms, whereas biological disturbances are often

related to insect and disease outbreaks (Harris and Farr 1974, Rogers 1996). The

frequency of climate cycles may range from a few years to millennia, and the scale

of effects is generally regional. Other natural events may occur on timeframes

ranging from decades to centuries and on spatial scales ranging from a few square

meters to thousands of square kilometers.

The dominant natural disturbance processes that affect riparian ecosystems in

forested watersheds of Oregon, Washington, and southeast Alaska vary geographically. Although all of the disturbance agents mentioned above can potentially affect

any watershed, fire was the dominant agent across the Pacific Northwest (Agee

1993, Wright and Bailey 1982). Also, synergy between fire and subsequent intense

rainstorms and flooding may be the sequence of disturbances with the greatest

effect on riparian ecosystems in that geographic area (Benda et al. 1998). Conversely, wind may be the primary natural disturbance in forested watersheds and

riparian systems in the rain-forest ecosystems of the western Olympic Peninsula,

and wind has been documented as the primary agent in coastal British Columbia,

and southeast Alaska (Harris 1989, Nowacki and Kramer 1998).

Natural disturbances

provide a baseline

from which to interpret the effects of

human disturbances, or the

significance of

cumulative effects

from natural and

human impacts.
21

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

The cumulative effects of natural disturbances shape and maintain regionalscale terrestrial, riparian, and aquatic ecosystems of the Northwest and southeast

Alaska. The flora and fauna of these regions have evolved with, and adapted to, the

temporal and spatial landscape mosaic of natural disturbances (e.g., Reeves et al.

1995). As long as natural disturbance processes operate within historical levels of

variability at the regional scale, it is likely that productive habitats for the region’s

flora and fauna will exist in the long term. However, substantive changes in the

spatial and temporal distribution of disturbance regimes increase the risk of permanent habitat changes, challenge species adaptability, and could lead to extirpations

and extinctions.

Climate cycles—

The climate of the Pacific Northwest is naturally variable and cyclic. Maritime,

continental, and arctic influences, each modified by the orographic effects of major

mountain ranges, contribute to high geographic variability in precipitation, runoff

(Everest et al. 2004), and the characteristics of riparian ecosystems across the region

(Oakley et al. 1985, Thomas et al. 1979). The natural spatial variability of riparian

and aquatic habitats is further complicated by temporal climatic cycles of variable

duration and predictability. The most obvious temporal cycle is the annual cycle

of seasons that drives three types of hydrographs dominated by rain in the coastal

zone and valleys west of the Cascade Mountains, rain-on-snow in the transition

snow zone of the Coast Range and Cascade Mountains, and snow in the highelevation mountains of the region. But, other longer term climatic events strongly

contribute to the natural range of variability in the riparian and aquatic ecosystems

of the region.

El Niño Southern Oscillation (ENSO) affects precipitation and runoff in the

Northwest and contributes to short-term and long-term variability of riparian and

aquatic habitats. El Niño is a recurrent interannual climatic event characterized by

unusually warm ocean temperatures in the equatorial Pacific Ocean. Such ENSO

events typically occur every 2 to 7 years and generally last 12 to 18 months (Hare

et al. 1999). Receding El Niños are often followed by the opposite extreme, La

Niña, which is characterized by unusually cold ocean temperatures in the equatorial

Pacific. The two events have opposite, but significant effects on global weather

patterns. El Niños cause winters warmer and drier than average in the Pacific

Northwest whereas La Niñas produce winter conditions that tend to be cooler and

wetter than normal, although the effects of individual events can be highly variable.
22

General Technical Report PNW-GTR-692

La Niñas that occurred between 1895 and 1989 generally produced cooler temperatures in coastal climate zones of the Pacific Northwest and in some areas of the

western Cascades of Oregon, while much of the region experienced higher than

normal precipitation and favorable conditions for riparian and aquatic habitats.

Drought conditions caused by El Niños can stress riparian ecosystems, cause

below-normal summer streamflows, and reduce production of aquatic biota.

The Pacific Decadal Oscillation (PDO) also affects riparian and aquatic habitats

in the Pacific Northwest and southeast Alaska but in a less predictable way than

ENSO. The PDO is an interdecadal Pacific climate pattern with profound effects

on the North Pacific Ocean and terrestrial environments of the Pacific Northwest

(Mantua et al. 1997). Two main characteristics distinguish the PDO from ENSO.

First, PDO events in the 20th century have persisted for two to three decades, and

second, the effects are most visible in the North Pacific Ocean and the North

American continent (Hare 1998). The PDO also has warm and cool regimes that

affect temperature, precipitation, runoff patterns, and riparian and aquatic ecosystems in western North America and affect the productivity of anadromous salmonid

rearing areas in the North Pacific Ocean. For example, during the cool PDO regimes of 1925-1946 and 1977 to at least 1995, salmonid production was favored

in the northern areas and was at low ebb in the PNW and California. Production

of anadromous salmonids was highest in the PNW and California during the

1890-1924 and 1947-1976 periods when Alaska’s production was low. During

cool phases of the PDO, storm activity and precipitation increase in the Alaska

region, and weather is calmer, warmer, and drier in the Pacific Northwest. The

reverse is true during warm PDO phases. The major effect of the PDO is on water

temperature and streamflow, but persistent drought during warm phases can affect

the health of riparian vegetation in the PNW.

Global climate change is a third factor that may complicate management of

riparian ecosystems in the Pacific Northwest and Alaska. However, the exact nature

of the impact of global warming in these regions and world has not been determined. Some predict (e.g., Aber et al. 2001, Climate Impacts Group 2004) that

warmer and drier summers will yield less water for the maintenance of summer

instream flows, riparian habitats, and fish populations in the PNW. Also, predicted

wetter winters will likely enhance growth of vegetation, and predicted warmer,

drier summers will likely increase the potential for wildfires (McKenzie et al.

2004). Because predictions differ considerably from model to model, the net result

for riparian health is unclear.
23

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Predicted results of global warming in Alaska (e.g., US EPA 1998, Rupp et al.

2000) include increased precipitation, runoff, and streambank erosion; advance of

the northern extent of forested areas including riparian vegetation; increased

wildfire with consequent transition to younger forest stands in the interior; and

increased susceptibility to insect pests in certain forest biomes. The net effect of

these predictions on riparian health is also uncertain.

The science community is currently investigating key aspects of global warming, including the potential severity and likely climatic and environmental consequences. The scientific evidence indicates that the Earth is in a gradual warming

phase, and climate change models predict temperature increases in the Pacific

Northwest of about 1.3 °C by 2020 and about 1.9 °C by 2040 (Climate Impacts

Group 2004). Temperatures in Alaska could increase by 2.4 °C in spring, summer,

and fall, and 4.8 °C in winter by 2100 (US EPA 1998).

The natural climate cycles of the Northwest have created variable and complex

intrawatershed precipitation and runoff patterns that produce natural landscape

events such as floods, droughts, fire, and landslides, and influence the distribution

of flora and fauna at the watershed scale. Human use of land and water in the

region has often failed to adequately consider these events in resource plans, or

the way in which human activities can alter the frequency and magnitude of these

events.

Fire—

Fire is a dominant natural disturbance process in the Pacific Northwest and strongly

influences the age distribution of riparian (Bendix 1994) and upland forests (Agee

1993). Variation in climate, topography, fuels, lightning strikes, and the actions of

aboriginal and modern humans control the frequency, intensity, and size of fires in

the region (Schoonmaker et al. 1997).

Wildfire can affect riparian and aquatic ecosystems in at least the following

ways:

• Increased sediment delivery to channels

• Increased woody debris delivery to channels

• Loss of riparian vegetation and streamside cover

• Decreased litterfall

• Increased streamflow

• Increased nutrient levels in streams

The effects of fire, which generally operate in concert, can temporarily destroy the structure and function of riparian ecosystems in burned areas and cause a
24

General Technical Report PNW-GTR-692

short-term reduction in the productivity of aquatic systems (Bisson et al. 2003;

Minshall et al. 1997, 2001; Rinne 1996). Fire frequency (rotation) can affect

wood recruitment and wood volume in streams (Benda and Sias 2002), with

shorter rotations having a higher probability of causing low instream volume of

large woody debris. After an initial decline following fire, riparian and aquatic

species may experience renewed vigor as aquatic ecosystems process sediments and

large woody debris added to channels via subsequent storm runoff, and watersheds

and riparian habitats revegetate (Minshall et al. 2001, Reeves et al. 1995).

The frequency of fire in the period predating European settlement ranged

from about 21 years in the temperate rain forests of the Olympic Mountains of

Washington (Wetzel and Fonda 2000) to about 16 years in the eastern Siskiyou

Mountains of Oregon (Agee 1991). In all cases, fire-return intervals were scale

related, and many of the fires at the frequencies noted above were small, lowintensity blazes that more strongly affected understory than overstory vegetation.

Low-intensity fires probably had local and minimal impacts on riparian vegetation

adjacent to streams in cool, damp valley bottoms (Agee 1993).

Stand-replacing fires (Agee 1993) of high intensity occurred at lower frequency across the region. As summarized by Benda et al. (1998), the average standreplacing fire interval in the Pacific ecoregion is about 400 years on the Olympic

Peninsula (Agee 1993), about 200 to 300 years in the central Oregon Coast Range

(Long 1995, Teensma et al. 1991), about 150 to 200 years in the western Cascade

Mountains of Oregon and Washington (Morrison and Swanson 1990, Teensma

1987), and about 80 to 100 years in southwestern Oregon (Gara et al. 1985). Highintensity fires were capable of resetting succession in riparian zones at intervals of

from less than one to several centuries.

Stand-replacing fires interacted synergistically with other natural disturbances,

especially floods and mass erosion, to cause additional long-term effects in riparian

and aquatic habitats. Severe rainstorms following large stand-resetting fires can

trigger mass erosion events, extreme surface erosion from burned areas (Klock and

Helvey 1976), accelerated runoff, and increased flooding. The combined short-term

effects can bury stream channels with sediment, delay re-establishment of riparian

vegetation in disturbed areas, and reset the age of riparian vegetation in downstream areas (Benda et al. 1998). The long-term effects can be positive as more

complex and productive riparian and aquatic habitats emerge in the decades and

centuries following stand-resetting fires.

The effects of fire on riparian and aquatic systems, and recovery rates following fire, are related to previous management history in watersheds. For example,

The effects of fire

on riparian and

aquatic systems,

and recovery rates

following fire, are

related to previous

management history

in watersheds.
25

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Minshall (2003) indicated that fire in watersheds already affected by extensive

human disturbances such as logging and road construction can be expected to

produce more severe effects than fire in largely intact watersheds. Also, observations by Minshall (2003) indicated that stream ecosystem recovery following wildfire is more dependent on riparian vegetation and flood-plain conditions than on the

condition of upland portions of watersheds. Therefore, added human disturbances

such as salvage logging and road construction in riparian areas following fire can

greatly extend the time required for ecosystem recovery.

Floods—

Floods are common natural events in western Oregon and Washington and southeast

Alaska. The most common effects of floods on riparian and aquatic systems include:

• Bank erosion and undercutting of riparian trees.

• Sediment inundation of riparian vegetation.

• Increased movement of sediment and transport of woody debris in

channels.

• Redistribution and clumping of woody debris in channels.

• Channel scour that widens channels and redistributes coarse sediments.

• Flushing and deposition of fine sediments in channels.

Floods caused by rapid spring snowmelt and regional floods caused by intense precipitation from large Pacific storms affect riparian habitats in western

Oregon and Washington. Both types of events can cause overbank flows that alter

riparian ecosystems and stream channels. Effects of floods as listed above usually

occur in concert, but the severity may vary by stream size, gradient, and valley

configuration.

The magnitude and frequency of floods is highly variable. Floods caused by

rapid snowmelt are the least common events in the region. The only major flood

in western Oregon and Washington attributed to this source occurred in 1948

(NOAA 2001). The event, which lasted 45 days, caused widespread flooding along

hundreds of kilometers of the Columbia River, scoured stream channels and riparian zones, and caused extensive damage to cities along the lower Columbia River.

Large regional floods have more extensive effects on riparian habitats and

stream channels than other types of events. Numerous regional-scale floods have

occurred in Oregon and Washington in the last century (table 3). In addition to

causing extensive property damage and significant loss of human life, the events

altered riparian vegetation and stream channels over thousands of kilometers of
26

General Technical Report PNW-GTR-692

streams in the area. Recurrence intervals for major floods in individual river basins

may range from years to decades and may vary regionally with the greatest frequency in coastal zones. Major floods are habitat resetting events for riparian and

aquatic systems, often removing large tracts of riparian vegetation and changing

the locations of stream channels. Flooding is a long-term natural process that

regulates productivity and facilitates renewal of riparian and aquatic ecosystems.

Floods in sparsely settled southeast Alaska are less documented than those in

the Pacific Northwest. The Alexander Archipelago of southeast Alaska is composed of more than 2,000 islands and a narrow strip of mainland. Hundreds of

short streams and rivers in the area are characterized by steep gradients in the

headwaters, and low-gradient mainstems in glacial valleys. Much of the area

receives more than 250 cm of rainfall per year, but the terrain is covered primarily

with old-growth spruce-hemlock rain forests that provide controlled runoff. Few

rivers in southeast Alaska are gauged, so records of unusually high streamflow and

river stage are rare.

The effects of floods can be accentuated by fire, volcanism, and mass erosion.

High-intensity precipitation and floods following wildfire can magnify the effects

of flooding on stream channels and riparian vegetation in downstream areas. Lahars

associated with volcanic eruptions, e.g., Mount St. Helens in 1980, are a unique

type of flood event that can bury stream channels with mud and destroy riparian

vegetation in affected areas. Mass erosion events that occur simultaneously with

flooding can also compound the effects of floods on riparian and aquatic habitats.

Table 3—Frequency and location of major floods in Oregon and

Washington, 1860-2000

Date Oregon Washington

1861 Coastal, Willamette River

1890 Coastal, Willamette River

1923 Coastal, Willamette River

1943 Coastal, Willamette River

1948 Columbia River Eastern, Columbia River

1964 Statewide Southern

1990 Statewide

1995 North central

1996 Statewide Western, southeast

Source: NOAA 2001, National Weather Service 1999a.
27

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Mass erosion—

Mass erosion events such as slumps, earthflows, debris avalanches, and debris torrents are common in the steep and unstable terrain of the Pacific Northwest and

southeast Alaska (Swanston 1969, 1971). The characteristics of these events and

the mechanics of slope failure in forested terrain are well documented in the literature (Swanson et al. 1987, Swanston 1974, Swanston and Swanson 1976). Mass

erosion is episodic in time and space in unmanaged forests, but the effects can

change stream channels and riparian habitats in affected stream reaches. The common effects are:

• Bank erosion and undercutting of riparian vegetation.

• Channel scour and destruction of vegetation in riparian zones.

• Inundation of riparian zones with sediment.

• Increased woody debris and redistribution of woody debris in channels.

• Damming and obstruction of channels.

• Sedimentation and shifts in channel configuration.

The frequency of occurrence of mass erosion varies by the type of event.

Earthflows in deep soils in steep terrain, although relatively rare, may be active

annually during the wet season for decades. Debris avalanches and debris torrents

are more common, and at the landscape scale are initiated by intense storms with

return intervals of about 7 years in the Northwest (Swanston and Swanson 1976)

and 5 years in southeast Alaska (Swanston 1969). The recurrence interval for a

given site, however, is usually more than a millennium (Benda 1988).

Wind—

Windstorms are common natural disturbances in the Pacific Northwest (Benda et al.

1998, Sinton et al. 2000) and southeast Alaska (Deal et al. 1991, Lawford et al.

1996). Ecological effects of wind are scale-related (Nowacki and Kramer 1998,

Ulanova 2000), ranging from small-scale canopy disturbances (gap dynamics

associated with blowdown of a single tree or small group of trees) to large-scale

stand-resetting events in which most trees on hundreds or thousands of hectares of

land are blown down by a single storm.

Windthrow can fell individual trees or whole stands in riparian areas and affect

adjacent and downstream aquatic habitats in several ways. Extensive windthrow of

riparian vegetation can cause:

• Increased sediment delivery to channels.

• Decreased litterfall.
28

General Technical Report PNW-GTR-692

• Increased large woody debris in channels.

• Loss of shade (elevated stream temperatures).

• Shift from allochthonous (offstream) to autochthonous (instream) energy

sources in small streams.

• Maintenance of soil productivity in riparian zones through mixing.

Although windstorms are among the most frequent natural disturbances occurring in the Pacific Northwest and southeast Alaska, forested areas of the landscape

are affected differentially based primarily on aspect, topography (Harris 1989,

Kramer 1997), climate, stand age, tree height and diameter, and tree species present

(Canham et al. 2001, Larson and Waldron 2000, Lohmander and Helles 1987, Ruel

2000). At the regional scale, recurrence intervals of events that cause substantive

blowdown of timber occur on a decadal basis or even more frequently (table 4), but

smaller individual units of the landscape may be unaffected for centuries. Wind

often interacts synergistically with human disturbances (e.g., clearcut logging) to

increase timber blowdown, especially along the edges of clearcuts (Sinton et al.

2000), power lines (Ruel and Pin 1993), and riparian buffer strips (Hairston-Strang

and Adams 1998, Ruel et al. 2001).

Small-scale wind disturbances create gaps in forest canopies through stem snap

and uprooting of individual trees. Ott (1997) found that 76 percent of gaps created

by wind in southeast Alaska forests were the result of stem snap, usually involving

one to three trees. Gaps created had a median size of 35 to 55 m2

. Heart rot contributed to stem snap by weakening or killing trees in old-growth forests (Hennon

1995). Although little research has been done on gap dynamics in riparian buffer

strips, it seems reasonable to assume that both stem snap of weakened trees and

uprooting of healthy trees from saturated soils are normal disturbance processes in

riparian ecosystems. Gaps created by wind in riparian zones contribute large woody

debris to aquatic habitats, but probably have minimal effects on summer and winter

water temperatures, energy inputs, or nutrient cycling.

Catastrophic blowdown events that affect large areas of the landscape occur

infrequently in the Pacific Northwest and southeast Alaska, but they can have major

ecological effects. In a review of historical windstorms in Oregon, the National

Weather Service (2000), listed 13 major events between 1880 and 1995 (table 4),

an average of more than one per decade. A retrospective analysis of windthrow on

northeast Chichagof Island in southeast Alaska indicated that between 1710 and

1996, significant windthrow events occurred in 16 of the 30 decades covered by the

study (Nowacki and Kramer 1998). The frequency of major windstorms prevented
29

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

the establishment of old-growth timber stands on mountainous terrain exposed to

prevailing southeast storms. In this geographic area, valley bottoms and riparian

areas were the least frequently disturbed locations.

Stand resetting events of this type can improve timber site productivity through

tree uprooting that churns soils, increasing permeability and nutrient cycling

(Bormann et al. 1995), but the effects on riparian and aquatic habitats are mixed.

Long reaches of riparian timber in undisturbed stands and in buffer strips adjacent

to clearcuts can be blown into streams, increasing woody structure for aquatic

organisms (Bisson et al. 1987, Swanson and Lienkaemper 1978). But the resulting

loss of streamside canopy can change water temperature (Beschta et al. 1987),

energy inputs (Hicks et al. 1991, Murphy and Hall 1981), and nutrient cycling in

affected riparian areas for at least several years (Bormann et al. 1995).

Certain areas of the landscape are more vulnerable to windthrow than others.

Harris (1989) and Kramer (1997) found blowdown in southeast Alaska concentrated on hilltops and ridge noses on south-facing slopes directly exposed to

prevailing southeast storms, and on east- and west-facing slopes where winds

accelerate as they bend around mountain flanks. Sinton et al. (2000) found that

windthrow in the Bull Run watershed of Oregon, prior to timber harvest in the

watershed, was confined primarily to topographic features exposed to prevailing

Table 4—Historical windstorms in Oregon that caused major windthrow of timber

resources

Date Location Prevailing wind Maximum speed

Kilometers per hour

01/09/1880 Western South 130

01/20/1921 Western Southwest 210

04/21-22/1931 Northern Northeast 125

11/10-11/1951 Statewide Southwest 130

12/04/1951 Western Southwest 160

12/21-23/1955 Statewide Southwest 145

11/03/1958 Western Southwest 120

10/12/1962 Statewide Southwest 220

03/27/1963 Western Southwest 160

10/02/1967 West, northeast Southwest 185

03/25-26/1971 Statewide Southwest 135

11/13-14/1981 Statewide South 160

12/12/1995 Western Southwest 190
30

General Technical Report PNW-GTR-692

east and northeast gales from the Columbia Gorge. Timber in wide valleys with

gentle side slopes is also vulnerable to windthrow (Nowacki and Kramer 1998,

Ruel et al. 2001), especially when prevailing winds flow parallel to the long axis

of valleys (National Weather Service 2000). In the latter case, riparian timber in

open valleys running parallel to prevailing storm tracks may be vulnerable to

periodic windthrow.

Ice and snowstorms—

Ice, snowstorms, and ice formation and transport in streams of southeast Alaska, as

well as at high elevation across the Pacific Northwest, are normal annual events.

However, ice formation in streams during unusually cold weather, and abnormally

severe ice and snowstorms, can have infrequent but significant effects on riparian

and aquatic habitats. The most common effects of ice and snowstorms, or ice flows

in streams are:

• Ice gouging of streambed, banks, and destruction of near-stream riparian

vegetation.

• Stream damming, flooding, and scour of riparian vegetation.

• Transport of sediment attached to anchor ice.

• Limbing, stem snap, and felling of riparian trees because of weight of ice

formation from freezing rain.

• Increased woody debris in streams and redistribution of woody debris.

Severe ice and snow damage to riparian vegetation usually occurs at the local

or subregional scale and at infrequent intervals.

At least two notable events occurred in the Pacific Northwest in the 20th century

(National Weather Service 1999a, 1999b). Western Washington received the maximum snowfalls on record in January and February of 1916. Areas around Puget

Sound received up to 1.2 m of snow, and winds created snowdrifts in excess of 1.5

m. Trees across the area, even at sea level, were felled and damaged by accumulations of heavy wet snow. Another record snowstorm occurred in 1950, affecting

western Oregon, the Columbia Gorge, and southwestern Washington. Heavy snow,

followed by sleet and freezing rain severely damaged riparian and upland vegetation across the area. Events of this type occur a few times per century at the scale

of the Pacific Northwest, but recurrence at a given location may take centuries to

millennia.
31

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Insects and disease—

Forests of the Pacific Northwest and southeast Alaska are subject to chronic and

episodic mortality from insects and disease. Damage from boring and defoliating

insects is usually episodic and can weaken or kill trees across tens of thousands of

hectares in a single outbreak. Forests under stress from drought or other climatic

factors are most vulnerable to attack. Disease kills fewer trees (USDA Forest Service 1977) than do insects, but root rots and heart rots occur frequently enough in

old forests to contribute to mortality and increase the vulnerability of individual

trees to windthrow.

Insect and disease outbreaks may affect riparian and aquatic habitats in the

following ways:

• Decreased litterfall

• Increased large woody debris in channels

• Loss of shade (elevated stream temperatures)

• Shift from allochthonous (instream) to autochthonous (offstream) energy

sources in small streams

The effects, even of episodic outbreaks, are usually of short duration and

widely scattered in time and space. Several outbreaks of spruce budworm and

Douglas-fir tussock moth occurred in the Northwest in the 20th century (Mason et

al. 1998, Stipe 1987, Stoszek and Mica 1978). The effects on riparian zones are

poorly documented, and were probably minimal at all scales.

Summary of Natural Disturbances

We have discussed natural disturbances and their effects on riparian and aquatic

habitats as individual phenomena, but at the regional scale, these events operate

simultaneously. In any given year, a combination of fire, floods, wind, unusual

storms, mass erosion, ice, insects, and disease are likely to affect portions of some

watersheds in the Pacific Northwest and southeast Alaska. At the landscape scale,

however, there is likely to be a natural spatial and temporal heterogeneity of

disturbances among watersheds.

Some events can occur sequentially and operate synergistically. For example,

some of the greatest changes in riparian and aquatic systems in mountainous areas

of the Northwest occur when wildfire is followed by intense winter storms that

trigger floods, surface erosion, slope failures, and widespread mass erosion events

(Benda et al. 1998). The synergistic combination of tree diseases, saturated soils
32

General Technical Report PNW-GTR-692

from intense precipitation, and windstorms can also magnify the effects of natural

disturbances on riparian and aquatic habitats in southeast Alaska (Nowacki and

Kramer 1998).

Considered together at the regional scale, natural disturbances historically affected relatively small areas of the landscape at any given time (e.g., subwatershed

scale), although their cumulative effects can be important processes in ecosystem

change and renewal. These events may remove riparian stands at the site to subwatershed scales, replenish large woody debris and sediments in stream channels,

and cause riparian and aquatic species to wax and wane in response (Reeves et al.

1995). The recurrence intervals of disturbances at a given location, however, are

often measured in centuries or millennia.

Cumulative effects of natural disturbances can control the vegetative structure

of the landscape. For example, a study modeling the fire history in western Oregon

(Wimberly et al. 2000) indicated that over the past 3,000 years, a shifting mosaic

of late-successional forests in the Coast Range historically occupied between about

49 and 91 percent of the landscape at the province scale. One can assume that

riparian zones in the region had at least a similar proportion of late-successional

forest, and probably more because trees in normally damp riparian habitats were

less subject to fire mortality than timber on dry upper slopes (Agee 1993). Based

on this study, a shifting pattern of 49 to 91 percent late-successional forest could

be considered the normal range to which riparian, terrestrial, and aquatic species

in the Coast Range have adapted in at least the past three millennia. Regional shifts

in abundance of late-successional forest habitats outside this range could increase

the risk of extinction of some species, or cause changes in the community structure

of indigenous biota.

Moderate site-specific disturbances can lead to temporary shifts in community

structure during the process of habitat renewal. Severe environmental changes at

a site scale can lead to extirpation of species, but since natural disturbances are

usually limited in time and space, populations in adjacent undisturbed habitats are

able to quickly recolonize affected areas as habitats return to predisturbance conditions (Reeves et al. 1995).

In summary, we emphasize again that the effects of natural disturbances (preEuropean settlement) are not only scale-related, but represent the baseline against

which human disturbances (by European settlers), and the cumulative effects of

natural and human disturbances, are measured and evaluated. Although the pulse

of natural disturbances can cause severe changes in riparian and aquatic ecosystems

at site scales, the effects are less severe at regional scales. At the scale of the

Natural disturbances

historically affected

relatively small

areas of the landscape at any given

time (e.g., subwatershed scale),

although their cumulative effects can

be important processes in ecosystem

change and renewal.
33

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Northwest, the mosaic of natural events is integrated into the structure and function

of regional ecosystems and represents the disturbance regime to which indigenous

species historically adapted.

Human Disturbances

Human disturbances in watersheds of the Pacific Northwest and southeast Alaska

are often profoundly different in temporal and spatial distribution than natural

disturbances. Disturbances from a complex array of human actions generally tend

to fit the press disturbance category, because they occur more frequently in time

and space, affect larger areas of the landscape, and leave different legacies, and

many are more permanent than natural disturbances (Ebersole et al. 1997, Reeves

et al. 1995). Most human disturbances that affect riparian ecosystems are related

primarily to land use activities such as agriculture, forestry, urbanization, and dams

and reservoirs that store and use water resources for a variety of purposes. These

activities, which can have universal effects on riparian vegetation in watersheds, are

exacerbated by increasing human populations in the Northwest and, to a lesser

degree, in southeast Alaska.

Human populations are increasing rapidly in Oregon, Washington, and Idaho.

Oregon and Washington were the 10th and 7th fastest growing states, respectively,

in the Nation in the 1990s, and census projections indicate that the populations of

all three states will grow between 31 and 43 percent in the next quarter century

(U.S. Bureau of the Census 1997). The projected increase in population, from

both internal growth and immigration, will place additional demands on the

region’s natural resources in the near future. Although human populations are

increasing more slowly in southeast Alaska, growing populations of the Nation

and world also will place additional demands on Alaska resources. Without some

moderation of population growth, human disturbances on the landscape are likely

to accelerate and further alter riparian and aquatic habitats of the regions.

Dams and reservoirs—

Dams and reservoirs located on rivers and streams in the Pacific Northwest have

caused persistent alterations of thousands of kilometers of riparian habitats. About

2,050 dams at least 3 m in height and storing at least 12 300 m of water were

built in Oregon and Washington by the end of the 20th century (ASDSO 2006,

Washington State Department of Ecology 2003). Most of the dams and the preponderance of storage capacity were developed after 1940 (fig. 5). Low-cost hydropower has facilitated many aspects of regional development, but the generating

Human disturbances in watersheds of the Pacific

Northwest and

southeast Alaska

are often profoundly

different in temporal

and spatial distribution than natural

disturbances.
34

General Technical Report PNW-GTR-692

facilities have substantially changed the natural physical and ecological characteristics, including the riparian ecosystems, of the rivers on which they occur.

Reservoirs impounded by the dams inundate and destroy riparian habitats that

formerly bordered streams within reservoir boundaries. New riparian systems,

often with different characteristics, may develop along reservoir shorelines, but

fluctuating reservoir levels may prevent re-establishment of riparian ecosystems.

Reservoirs also tend to delay the downstream movement of storm flows and thus

reduce both the height and duration of peak flow for a given storm (Ziemer and

Lisle 1998). Riparian communities bordering downstream waters may respond by

changing community structure, density, and proximity to stream channels. Many

major river systems in western Oregon and Washington are notably affected by

reservoir storage (e.g., the Rogue, Willamette, Santiam, Lewis, and Skagit Rivers).

Figure 5—Cumulative number of federal and nonfederal dams (a), and

cumulative volume of storage (b), in the Pacific Northwest (Idaho,

Oregon, Washington, and northern California) from 1860 to 1990 (from

Lee et al. 1997). Cumulative volume (million acre-feet)
35

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

A unique class of dams called “splash dams” facilitated log drives on Pacific

Northwest streams in the 1870 to 1920 period (Sedell et al. 1991). Use of splash

dams for log transportation was extensive in western Washington and Oregon at the

turn of the 20th century. Over 150 such dams existed in coastal Washington rivers,

and over 160 splash dams were used on coastal streams and Columbia River tributaries in Oregon (Sedell et al. 1991). Boulders and woody debris were removed

from channels of these streams for decades to facilitate downstream movement

of logs. The frequent, near-instantaneous release of water (man-made flash floods)

to transport logs resulted in scour and removal of near-stream riparian vegetation

and persistent simplification of channel structure along thousands of kilometers

of streams in the Northwest. Man-made “flash floods” of this type and frequency

have no natural analogs. The greatest effects occurred in small and mid-sized

basins. Splash dams altered riparian ecosystems and stream and river channels to

the extent that they have not yet returned to predisturbance conditions in many

systems (Sedell et al. 1991). But, unlike storage reservoirs and run-of-the-river

hydropower generating facilities, the effects of splash dams are less persistent,

although long recovery times from splash dam disturbances may be required.

Agriculture—

Agriculture has also made major persistent changes in riparian and aquatic habitats

in the Pacific Northwest (see bibliography, Bolton and Monohan 2001, that contains more than 2,000 literature citations). Agricultural activity in western valleys

and on historical flood plains has modified native vegetation and the physical

drainage features of the landscape on many major rivers. Agriculture has caused loss

of native vegetation and large woody debris, streambank instability, and loss of

flood-plain function (Spence et al. 1996); altered flow regimes; increased sedimentation; increased water temperature; changed nutrient supply (Rinella and Janet

1998, Wentz et al. 1998); increased chemical pollution (Rienhold and Witt 1992,

Wentz et al. 1998); modified and consolidated stream channels (Sedell and Froggatt

1984); and simplified aquatic and riparian habitats (Spence et al. 1996).

Urbanization—

Urban areas, although affecting only about 2 percent of the Northwest landscape

(Pease 1993), are usually located along major waterways, at the confluence of

rivers, or on estuaries (Gregory and Bisson 1997). Riparian and aquatic habitats

are more highly altered in urban landscapes than in any other land use types in

the Pacific Northwest, and streams within urban areas are more degraded than in

Splash dams altered

riparian ecosystems

and stream and river

channels to the extent that they have

not yet returned to

predisturbance conditions in many

systems.

Riparian and aquatic

habitats are more

highly altered in

urban landscapes

than in any other

land use types in

the Pacific Northwest.
36

General Technical Report PNW-GTR-692

agricultural, range, or forest lands (Booth 1991). Stream channels and riparian

habitats within urban areas are often altered to facilitate flood control and rapid

routing of water away from developed areas. Small streams are often consolidated

and piped through cities, and larger streams are realigned and confined to concretelined channels.

Urban areas have expanded in the late 20th century into lowland forests and

agricultural lands to accommodate the growing population of the Northwest.

Consequently, some privately owned forest lands, and their associated streams

and riparian habitats, have been converted to urban lands (Kline and Alig 2001).

Nationwide, urban and developed areas expanded by more than 285 percent between 1945 and 1992 (USDA Economic Research Service 1995). Forests, the

largest source of land for development in the Northwest, can be converted to urban

areas or fragmented by land developments (Alig et al. 2000). The human population of the Pacific Northwest is projected to increase by approximately 4 million

people by 2050, resulting in further reductions in private forest areas and more

than a 20-percent increase in urban areas (Kline and Alig 2001), with commensurate changes in riparian, aquatic, and terrestrial habitats.

Timber harvest and roads—

Timber harvest and roads have made extensive changes in watershed hydrology and

riparian vegetation (Jones et al. 2000) and aquatic communities (Trombulak and

Frissell 2000) in the Pacific Northwest and, to a lesser degree, in southeast Alaska.

In the past four decades, commercial timber has been removed from thousands of

kilometers of riparian zones by clearcutting and selective harvesting, resulting in

long-term changes in the structure and function of riparian ecosystems. The National Forest System alone contains about 200 000 km of roads in upland and

riparian ecosystems in Oregon and Washington and about 8000 km in Alaska

(Coghlan and Sowa 1998). Roads were built in and along flood plains and through

riparian zones of many fish-bearing streams to provide access for timber harvest

operations and other purposes (Oakley et al. 1985). Construction and maintenance

of roads altered riparian function over much of the area with long-lasting effects on

riparian zones (Thomas et al. 1979).

Timber harvest has changed riparian vegetation in at least two ways. First,

harvest of commercial timber on private, state, and federal lands was conducted

near streams until the enactment of forest practices acts in the 1970s. Although

vegetated buffer strips of variable configurations have been left along most perennial fish-bearing streams since that time, riparian timber beyond designated buffer
37

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

strips was often clearcut along with upslope stands and the logging slash burned

before reforestation of the area. Second, even within buffer strips that were left

along perennial streams, some or most commercial timber was regularly removed

by selective harvest techniques. The result was widespread thinning in near-stream

forest canopies, loss of large standing timber near streams, and disturbance of litter,

soil, and hydrologic function in riparian habitats. Changes in riparian zones from

these sources rapidly translated to changes in aquatic ecosystems. Major changes to

aquatic systems resulting from alteration of riparian habitats include:

• Increased stream temperatures in summer and increased or reduced stream

temperatures in winter depending on geographic location.

• Changes in stream energy sources: reduced particulate organic inputs and

increased solar radiation in streams.

• Increased sedimentation.

• Reduced streambank and stream channel stability.

• Long-term reduction in large woody debris.

Many of these changes degraded habitats for aquatic and riparian-dependent

species and contributed to Endangered Species Act (ESA) listings of salmonid

populations and other organisms.

Water temperature—

Loss of riparian vegetation through a variety of land management activities (principally timber harvest and roads in western Oregon and Washington) allows more

solar radiation to reach stream surfaces in summer, increasing water temperature

and light available for photosynthesis (Brown and Krygier 1971). Loss of forest

canopy can also increase winter temperatures in low-elevation coastal drainages

(Beschta et al. 1987), but in northern latitudes and at higher elevations, a reduction

in winter temperatures may occur owing to loss of vegetative insulation and an

increase in radiative cooling of stream waters (Hicks et al. 1991).

Significant biological consequences may result from moderate alteration of

water temperature that results from disturbance of riparian areas. Changes in

water temperature can alter the structure and composition of fish communities by

changing the outcome of interaction among potential competitors (Baltz et al.

1987, Dambacher 1991, Hillman 1991, Reeves et al. 1987). Changes in the temperature of surface waters can also affect the temperature and biota of hyporheic

zones (NRC 1999). Hyporheic zones and their biota, because of their subsurface

location, are naturally resistant to environmental change and are therefore rather

Significant biological

consequences may

result from moderate alteration of

water temperature

that results from

disturbance of

riparian areas.
38

General Technical Report PNW-GTR-692

nonresilient when changes do occur. Disturbances that cause changes in water

quality within hyporheic zones may affect bioproduction and threaten endemic

groundwater biota within the channels of gravel-bed streams (Notenboom et al.

1994) and alter the distribution and abundance of riparian vegetation throughout

river corridors (Stanford and Ward 1993). Elevated temperatures can also affect

migration timing and patterns of fish and exacerbate outbreaks of disease (Spence

et al. 1996).

Elevated water temperatures first caused concerns about timber harvesting near

forest streams in the 1960s and 1970s, and passage of the federal Clean Water Act

in 1977 resulted in revised forest practice rules designed to maintain or restore

stream temperatures to prelogging levels. Current forest practice rules throughout

the Northwest contain regulations for maintenance of water quality, including

water temperature. Nevertheless, elevated water temperatures resulting from logging remain in some watersheds. For example, elevated water temperature is listed

as the primary source of impairment in national forest lands listed in Oregon’s

303(d) impaired water bodies under the Clean Water Act. (Lee et al. 1997).

Stream energy sources—

Timber harvest and other alterations in riparian vegetation can alter the energy

dynamics of small streams. Removing the vegetative canopy over streams can shift

heterotrophic systems driven by inputs of organic litter to autotrophic systems

whose primary energy source is sunlight (Allan 1995). Such changes can also shift

the peak time of energy input from fall for heterotrophic systems to summer for

autotrophic systems (Schlosser and Karr 1981). Changes in riparian vegetation not

only reduce the source of organic litter that can provide 75 percent or more of the

organic food base in small streams, but also reduce the capacity of riparian zones

to retain nutrients for slow release to streams (Welsch 1991). Changes in energy

dynamics can affect salmonid food supplies by reducing input of terrestrial insects

from forest canopies and altering the structure of aquatic insect communities within

channels (Wipfli and Gregovich 2002).

Small non-fish-bearing streams can also be important sources of energy for

fish. Recent work by Wipfli and Gregovich (2002) estimated that a small, headwater stream in southeast Alaska exported enough macroinvertebrates and detritus to

support 100 to 2,000 young-of-the-year salmonids per kilometer in fish-bearing

streams. Modification of vegetation along these small streams by timber harvest can

alter this pathway. Altering riparian forest canopy will reduce input of detritus and

organisms from outside the channel and likely increase primary production (Wipfli

Small non-fishbearing streams

can also be important sources of

energy for fish.
39

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

and Gregovich 2002). The extent of change depends, in part, on the degree to

which the vegetation is altered. Complete removal could decrease productivity by

shifting to predominately primary production. Intermediate levels of vegetation

removal may elevate headwater productivity and downstream transport of materials

because of increased amounts of solar radiation reaching the streams while there

continues to be the input of materials from remaining trees and understory vegetation (Wipfli and Gregovich 2002). The latter result is dependent on the extent to

which physical conditions remain intact.

Sediment inputs from roads—

Interactions between roads, riparian health, and sedimentation are strongly linked

throughout the Pacific Northwest and southeast Alaska. Road densities in managed

forests average about 1.15 km/km2

 and 0.12 km/km2, in the Northwest and southeast

Alaska, respectively. Forest roads affect the health of riparian ecosystems in two

primary ways. First, roads frequently represent the primary source of accelerated

sediment production from human activities in steep forested watersheds (Haupt

1959, Reid and Dunne 1984, Swanston and Swanson 1976). Roads are responsible

for large increases in both surface erosion and mass erosion (Furniss et al. 1991)

that both affect, and are affected by, riparian vegetation. In western Oregon, roads

in mid- to upper-slope areas of watersheds were found to accelerate debris torrents

by factors of 30 to 300 times that observed in undisturbed forest (Morrison 1975,

Sidle et al. 1985, Swanston and Swanson 1976).

Large volumes of sediment also are delivered to streams from surface erosion.

Surface erosion originates from unpaved road surfaces, drainage ditches, and cut

and fill surfaces, regardless of their locations in watersheds (Brown and Krygier

1971, Burns 1972, Larse 1971, Weaver et al. 1987). Sediments from surface

erosion traverse riparian zones enroute to receiving channels. Intact riparian

vegetation may capture and store large portions of the sediment, but riparian vegetation disturbed by roads, logging, or other activities may allow most of the sediment to pass through to stream channels where it affects the health of stream biota

and compromises the quality of salmonid spawning habitats (Everest et al. 1987).

Second, roads parallel streams in many forested river valleys on public and

private land (Oakley et al. 1985), encroaching on stream channels (Everest et al.

1985) and occupying portions of the former sites of riparian gallery forests

(Furniss et al. 1991). Encroachment and loss of riparian vegetation in areas occupied by roads causes persistent changes in the character and function of riparian

areas and corresponding changes in the productivity of associated aquatic habitats.
40

General Technical Report PNW-GTR-692

Roads in riparian areas become sediment sources in areas that were sediment sinks

in their undisturbed states. Road encroachment on riparian zones and stream channels is so common and so persistent in the United States that some forest practice

guidelines increase the prescribed width of riparian buffers by the width of riparian

habitats occupied by roads (U.S. Army Corps of Engineers 1991).

The sediment entering stream channels from mass erosion (slumps and earthflows, debris avalanches, debris flows, and debris torrents) affects riparian vegetation in several ways. Earthflows and landslides may remove all riparian vegetation

at their points of entry into stream channels. Debris flows and torrents may also

scour all riparian vegetation from the banks of small delivery streams and also for

some distance downstream in the larger receiving channels (Swanston 1991). The

pulse of sediment entering streams can cause channel scour, long-term instability,

and loss of riparian vegetation through scour and sediment deposition (Sullivan

et al. 1987).

Riparian vegetation can mitigate the effects of mass erosion if the events are

not overwhelmingly large. Sediment from small mass erosion events may be

trapped and stored in riparian zones (Welsch 1991), and large woody debris transported by mass erosion and deposited in channels may help protect streambanks and

channel and habitat complexity and accelerate sediment processing from affected

areas (Bisson et al 1987).

Woody debris—

Historical timber harvest, salvage of windthrown timber from stream channels, road

construction, and water transportation of logs in forested watersheds has decreased

standing timber in riparian zones and large woody debris in stream channels

throughout the Northwest and in parts of southeast Alaska. Windthrow and subsequent salvage of riparian timber is one area where synergism occurs between natural

wind disturbance and logging. Logging of timber stands, especially clearcutting,

creates openings in large contiguous blocks of timber and enhances the potential for

windthrow along exposed edges. In an analysis of windthrow in the Bull Run watershed in Oregon, Sinton et al. (2000) reported that 10 percent of the basin had been

affected by windthrow since 1890, but only 2 percent was affected prior to forest

harvest in 1958. A strong windstorm in 1983 caused extensive blowdown in the

basin, and 80 percent of windthrown trees came from recently exposed clearcut

edges. Ruel et al. (2001) also noted that high levels of windthrow were associated

with riparian buffers in wide valleys where winds blew perpendicular to the long

axis of the valley. Wherever narrow buffer strips of riparian timber are left to

Historical timber

harvest, salvage of

windthrown timber

from stream channels, road construction, and water

transportation of

logs in forested

watersheds has

decreased standing

timber in riparian

zones and large

woody debris in

stream channels

throughout the

Northwest and in

parts of southeast

Alaska.
41

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

protect aquatic habitats, the exposed edges of the buffers are vulnerable to accelerated windthrow. Windthrow adds woody debris to stream channels, but historical

salvage operations quickly removed most of the large material. Today, windthrown

timber is often left in stream channels for fish habitat, although simplified stream

channels resulting from the historical salvage of riparian windthrow remain widely

distributed across the landscape of the Pacific Northwest.

Current amounts of large woody debris in coastal streams of Oregon and

Washington are a fraction of historical levels (Bilby and Ward 1991, Bisson et al.

1987, NRC 1992). Much of the loss is the result of timber harvest that predates

the establishment of forest practices acts and federal regulations regarding timber

harvest. Additional losses resulted from stream cleaning policies of the 1970s and

1980s when large woody debris was intentionally removed from channels to protect capital investments (e.g., bridges) and improve fish habitat. Stream surveys by

private timber companies and federal land management agencies in the Northwest

reveal an overall loss of stream habitat quality (FEMAT 1993, Kaczynski and

Palmisano 1993, Wissmar et al. 1994) that is strongly related to changes in riparian

vegetation, especially harvest of merchantable riparian timber. For example, the

Bureau of Land Management (BLM) estimated that 65 percent of riparian areas on

their lands in Oregon and Washington did not meet management objectives in the

late 1980s (USDI Bureau of Land Management 1991).

Reductions in large standing timber in riparian zones and large woody debris in

streams have:

• Changed channel hydraulics and morphology by reducing roughness

elements in streams (Bisson and Sedell 1984, Martin et al. 1998), consolidating channels (Sedell and Froggatt 1984), increasing stream gradients

(Bilby 1979), decreasing channel stability (Bilby 1984), and generally

accelerating streamflows.

• Simplified aquatic habitats by reducing pools, side channels, and resting

and hiding cover for aquatic species (Cherry and Beschta 1989, Reeves et

al. 1993).

• Reduced the retention time of organic matter and inorganic sediments in

stream channels (Sedell et al. 1988).

Most of these changes have reduced the quality and productivity of rearing and

spawning habitats for salmonids and other aquatic species. The changes are likely

to persist for a century or more until riparian conifers grow to sufficient size to

again provide large woody debris recruitment to streams.
42

General Technical Report PNW-GTR-692

Summary of Human Disturbances

Human disturbances in river basins of the Pacific Northwest and southeast Alaska

occur more frequently in time and space and often are more persistent than natural

disturbances. Dams, reservoirs, agriculture, and urban areas have caused extensive

long-term changes in the structure and function of riparian systems and the species

that depend upon them (Everest et al. 2004). Thousands of kilometers of riparian

and aquatic habitats on major rivers have been converted to slack-water reservoirs,

meandering and braided streams in river valleys have been consolidated into single,

realigned channels with loss of riparian and side channel aquatic habitats (NRC

1996), and riparian forests in many valleys have been cleared to provide arable land

for agriculture (Miller et al. 1999).

Timber harvest and associated roads, typically press disturbances as applied

in the Northwest, have reduced late-successional forests in the Oregon Coast

Range province by more than 80 percent from the historical preharvesting average

(Wimberly et al. 2000). Smaller changes have occurred in southeast Alaska where

about 2.5 percent of late-successional forest has been harvested in the last century

(Everest et al. 1997). Timber on some portions of the Northwest landscape, especially on private lands on the Olympic Peninsula and in the Puget Sound area, has

been harvested two or three times in the past 150 years. Timber rotation age commonly ranges from 40 to 60 years over most of the private forest lands in the

region, and between 100 and 200 years on the federal landscape. Although only

about 20 percent of federal forest lands within the area of the NWFP in Oregon

and Washington are currently dedicated to timber production, the overall rate of

harvest for the region still assures that forest succession over more than half of the

forested landscape will be reinitiated at least once a century. Such frequent cutting

over large areas can prevent development of ecologically important seral stages,

such as late-successional and old-growth timber stands (Hall et al. 1985).

As previously noted, Wimberly et al. (2000) reported that late-successional

forests (ages 80 to 200 years) in the Oregon Coast Range historically occupied

between about 49 and 91 percent of the landscape at the provincial scale (fig. 6).

Following decades of intensive timber harvest in the Coast Range, the remaining

late-successional forest currently totals about 11 percent—well outside the historical range. One would also expect that 11 percent or less of riparian habitats in the

region retain late-successional characteristics, because for decades large timber was

removed from most riparian areas when upslope harvest units were cut. The change

Human disturbances

in river basins of the

Pacific Northwest

and southeast

Alaska occur more

frequently in time

and space and often

are more persistent

than natural disturbances.
43

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

in the distribution and abundance of late-successional forest may reduce the potential for upland and riparian-dependent biota to recover unless riparian restoration is

rapidly accomplished.

The effects of forestry are potentially less persistent than dams, agriculture,

and urbanization. Ecological effects of forestry can be changed through laws,

regulations, and silvicultural practices, and reversed through watershed restoration

(Williams et al. 1997) and rehabilitation of altered habitats (Reeves et al. 1991)

perhaps more easily than many other human disturbances. For example, urbanization and agriculture often cause major modifications of the extent and composition

of riparian vegetation, and extensive alterations of stream channels. The altered

riparian ecosystems bear little resemblance in either composition or behavior to

the natural ecosystems they replaced. Because of concerns about economics and

safety, there is little room to allow the altered ecosystems to revert to their unaltered state. Timber harvest, on the other hand, is a periodic disturbance and therefore has greater flexibility to allow riparian systems to be dynamic and to recover

predisturbance conditions.

The spatial and temporal distribution of human disturbances in the landscapes

of the Northwest and southeast Alaska, coupled with existing natural disturbance

regimes, have significantly altered the structure and function of riparian and freshwater ecosystems in the two regions. Industrial forestry is only one contributor to

human disturbance regimes, and one that is being addressed by forest practices acts

and other laws and regulations. Other human disturbances are also being addressed

Figure 6—Simulated historical abundance of late-successional forest habitat in the Oregon Coast

Range over the past 3,000 years. Heavy line represents the mean, and thinner lines are 95-percent

confidence intervals. The current level is about 11 percent—well outside the historical range (from

Wimberly et al. 2000). Effects of forestry

are potentially less

persistent than

dams, agriculture,

and urbanization.
44

General Technical Report PNW-GTR-692

at various intensities. The frequency and persistence of human disturbances in the

Northwest have contributed to the extinction of more than 100 stocks of anadromous salmonids in the past century (Nehlson et al. 1991) and the listing of at least

47 other aquatic species (US FWS 2000) (table 5). Many species that were able to

adapt to natural disturbances have been unable to cope with the combined disturbance regimes of human actions and natural events. These consequences of landscape disturbances are likely to be exacerbated in the future by increasing human

populations in the Northwest, and to a lesser degree, in southeast Alaska.

Forest practice rules and regulations attempt to mitigate the consequences of

disturbances caused by the effects of timber harvest, grazing, and roads, and maintain natural ecosystem functions within a fundamentally changed landscape. Practices related to timber harvest have evolved from simple site-specific rules in the

1970s to complex actions that currently address disturbance at more ecosystemlevel and landscape-scale perspectives than ever before (see below). The goal

of the revised forest practices is to restore and maintain riparian and aquatic

communities and still allow timber harvest and active management to achieve

other goals and other uses (e.g., second-growth thinning to reduce fire risk, improve wildlife habitat, and accelerate old-growth development, and improve

recreation opportunities).

Evolution of Riparian Management in Oregon,

Washington, and Southeast Alaska

As timber harvest in the federal, state, and private forest lands of the West accelerated after World War II, the primary focus of forest managers was on harvesting

high-volume stands of old-growth timber in the most economical ways. Environmental concerns associated with timber extraction, the value of forested landscapes

for recreation activities, and even reforestation of cutover lands, were often not

recognized. Sedimentation, increased stream temperatures, loss of riparian vegetation, and degradation of aquatic habitat quality were widely documented across

forested landscapes of the Pacific Northwest (e.g., Gibbons and Salo 1973, Gregory

and Bisson 1997, Hartman and Scrivener 1990, Iwamoto et al. 1978, Karr and

Schlosser 1977, Krygier and Hall 1971, Meehan 1991, Naiman 1992, Peterson et

al. 1992, Raedeke 1988, Salo and Cundy 1987). Loss of habitat quality on forest

lands coupled with land use changes on nonforested lands and other factors such as

commercial fishing, contributed to the eventual ESA listing of many economically

The goal of the revised forest practices is to restore

and maintain riparian

and aquatic communities and still allow

timber harvest and

active management

to achieve other

goals and other

uses.

Loss of habitat

quality on forest

lands coupled with

land use changes

on nonforested

lands and other

factors such as

commercial fishing,

contributed to the

eventual ESA listing

of many economically important

stocks of fish and

other aquatic species.
45

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Table 5—Threatened (T) and endangered (E) aquatic animals in the Pacific Northwest

Status Common name Scientific name

Idaho:

E Banbury Springs limpet Lanx sp.

E Bliss Rapids snail Taylorconcha serpenticola

E Bruneau Hot Springs springsnail Pyrgulopsis bruneauensis

T Bull trout (U.S. conterminous 48 states) Salvelinus confluentus

T Chinook salmon (fall Snake R.) Oncorhynchus tshawytscha

T Chinook salmon (spring/summer Snake R.) Oncorhynchus tshawytscha

E Idaho springsnail Fontelicella idahoensis

T Snake River Basin steelhead Oncorhynchus mykiss

E Snake River snail (physa) Physa natricina

T Sockeye salmon (Snake R.) Oncorhynchus nerka

E Utah snail (valvata) Valvata utahensis

E White sturgeon Acipenser transmontanus

Oregon:

E Borax Lake chub Gila boraxobius

T Bull trout (U.S. conterminous 48 states) Salvelinus confluentus

T Chinook salmon (fall Snake R.) Oncorhynchus tshawytscha

T Chinook salmon (lower Columbia R.) Oncorhynchus tshawytscha

T Chinook salmon (spring/summer Snake R.) Oncorhynchus tshawytscha

T Chinook salmon (upper Willamette R.) Oncorhynchus tshawytscha

T Chum salmon (Columbia R.) Oncorhynchus keta

T Coho salmon (OR, CA pop.) Oncorhynchus kisutch

T Foskett speckled dace (Foskett) Rhinichthys osculus ssp.

T Hutton tui chub (Hutton) Gila bicolor ssp.

T Lahontan cutthroat trout Oncorhynchus clarki henshawi

E Lost River sucker Deltistes luxatus

E Oregon chub Oregonichthys crameri

E Shortnose sucker Chasmistes brevirostris

E Sockeye salmon (Snake R.) Oncorhynchus nerka

T Steelhead (lower Columbia R.) Oncorhynchus mykiss

T Steelhead (middle Columbia R.) Oncorhynchus mykiss

T Steelhead (Snake R. basin) Oncorhynchus mykiss

T Steelhead (upper Willamette R.) Oncorhynchus mykiss

T Vernal pool fairy shrimp Branchinecta lynchi

E Warner sucker Catostomus warnerensis
46

General Technical Report PNW-GTR-692

important stocks of fish and other aquatic species. States, land management agencies, and regulatory agencies responded to changes in aquatic habitats on forested

landscapes by initiating or improving regulations governing timber harvest and

management on private and public forest lands.

The driving forces that shaped forest management and forest practice rules on

private and public land consisted of at least the following six elements:

• Stated goals for management of timber and other resources

• Market value of timber and other resources

• Nonmarket value of resources

• Social values regarding resource use and preservation

• Scientific information

• State and federal laws

These elements, when considered in concert, created considerable complexity

for decision- and policymakers who developed forest practice rules through normative decisionmaking processes. To add to the complexity, many of the elements

(e.g., laws, scientific information, and especially social values) changed with time

(Bliss 2000, Shindler and Cramer 1999).

Table 5—Threatened (T) and endangered (E) aquatic animals in the Pacific Northwest

(continued)

Status Common name Scientific name

Washington:

T Bull trout (U.S. conterminous 48 states) Salvelinus confluentus

T Chinook salmon (fall Snake R.) Oncorhynchus tshawytscha

T Chinook salmon (lower Columbia R.) Oncorhynchus tshawytscha

T Chinook salmon (Puget Sound) Oncorhynchus tshawytscha

T Chinook salmon (spring/summer Snake R.) Oncorhynchus tshawytscha

T Chinook salmon (spring upper Columbia R.) Oncorhynchus tshawytscha

T Chum salmon (Columbia R.) Oncorhynchus keta

T Chum salmon (summer run Hood Canal) Oncorhynchus keta

T Sockeye salmon (Ozette Lake and tribs.) Oncorhynchus nerka

E Sockeye salmon (Snake R.) Oncorhynchus nerka

T Steelhead (lower Columbia R.) Oncorhynchus mykiss

T Steelhead (Snake R. basin) Oncorhynchus mykiss

E Steelhead (upper Columbia R.) Oncorhynchus mykiss

T Steelhead (upper Willamette R.) Oncorhynchus mykiss

Source: US FWS 2000.
47

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Beginning in the 1970s, state legislators and forest managers in Oregon,

Washington, Alaska, and other Western States formulated their initial forest practices acts. The acts were developed in response to mounting research evidence

(studies conducted from 1956 to 1970) that logging increased water temperature

and sedimentation in fish habitats in forested watersheds (table 6) and to public

concerns that logging was damaging fish habitat (e.g., Moore 1971). Each act

established goals for management of forest lands and developed a suite of general

practices and guidelines for forest management operations, including timber harvest, road construction and maintenance, reforestation, and protection of riparian,

aquatic, and terrestrial ecosystems. At about the same time, federal land management agencies also developed strategies and rules for harvesting timber and managing other forest resources. The initial state and federal rules were aimed primarily

at maintaining stream temperatures and preventing accelerated sedimentation.

Forest management goals and the practices used to accomplish the goals differed by ownership. Management of private forest lands emphasized sustained

economical timber production, whereas public land managers were charged with

multiple use of forest resources. Although timber management goals differed by

management entity, the goals for management of other forest resources, including

riparian and aquatic ecosystems, were similar for all ownerships. In general terms,

all of the management entities emphasized sound management of soil, air, water,

fish, wildlife, recreation, and scenic resources consistent with their timber harvest

programs.

Forest practices acts for Oregon, Washington, and Alaska were passed in 1971,

1974, and 1978, respectively. Forest practice rules in the initial acts (generally

called “best management practices” or BMPs) often depended on voluntary compliance to meet stated goals for riparian and aquatic ecosystems. Nearly three

decades later, after many major revisions of the rules to achieve the original

riparian management goals, the rule sets are still referred to as BMPs.

Forest management goals and practices for protection of riparian and aquatic

habitats on Forest Service and BLM lands were also initiated in the 1970s. Specific

goals for management of riparian and aquatic habitats emphasized maintenance

and improvement of water quality and aquatic habitat characteristics. Federal forest practice rules progressed through three decades of evolutionary change during

which management practices provided incrementally more protection of riparian

and aquatic habitats to achieve stated management goals. The NWFP and the

TLMP are the current strategies employed for protection of riparian and aquatic

habitats on national forests and forested BLM lands west of the Cascade crest in

Forest management goals and

the practices used

to accomplish the

goals differed by

ownership.
48

General Technical Report PNW-GTR-692

the Pacific Northwest and the Tongass National Forest in southeast Alaska, respectively. Subsequently, the federal government developed a unified federal policy for

management of watersheds on federal lands (Federal Register 2000). The goal of

the unified federal policy is to standardize watershed protection and management

nationwide by eight federal agencies that administer large federal land holdings.

Initially, when each state formulated forest management goals and adopted

management practices to achieve the goals, little recognition was given to the

potential cumulative effects of practices or the geomorphic or physiographic

variability within forested watersheds of the state. Since the 1970s, forest practices

have evolved in response to new information on environmental effects of timber

harvest, recognition that the original management goals for riparian and aquatic

habitats were not being met, and changing laws and social values (NWIFC 2001,

Table 6—Selected studies (1970 and earlier) that contributed to formulation of state forest practices

acts and federal regulations for protection of riparian and aquatic habitats in managed forests of

Oregon, Washington, and Alaska

Study date Authors Effects of forest management Area

1956 Cordone, A.J. Increased sediment CA, OR, WA, AK

1957 Packer, P.E. Increased sediment/roads AK

1962 Chapman, D.W. On fish resources CA, OR, WA

1963 Calhoun, A.; Seeley, C. Increased ”logging damage”

to streams CA

1964 Bishop, D.M.; Stevens, M.E. More landslides AK

1964 Packer, P.E.; Christensen, G.F. Increased sediment/roads OR, WA, AK

1965 Dyrness, T.C. Increased sediment OR

1967 Dyrness, T.C. Increased mass erosion OR

1967 Levno, A.; Rothacher, J. Increased stream temperature OR

1968 Meehan, W.R. Increased stream temperature AK

1968 DeWitt, J.W. Less riparian vegetation CA, OR, WA, AK

1968 Sheridan, W.L.; McNeil, W.J. On salmon streams AK

1969 Meehan, W.R. et al. On salmon habitat AK

1969 Hall, J.D; Lantz, R.L. On coho, cutthroat OR

1970 Anderson, H.W. Increased sediment CA, OR, WA, ID

1970a Brown, G.W.; Krygier, J.T. Increased sediment OR

1970b Brown, G.W.; Krygier, J.T. Increased stream temperature OR

1970 Fredriksen, R.L. Increased sediment OR

1970 Ringler, N. On spawning habitat OR

1970 Sadler, R.R. Less riparian vegetation OR
49

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

ODF 2002, Oregon State Archives 2002). Management strategies and their associated forest practice rules for state and private lands generally contain the following

common themes, although priorities differ by ownership:

• Emphasis on timber production from forest lands.

• Protection of water quality, riparian and aquatic habitats, and other forest

resources consistent with the goal of timber production.

• A set of forest practice rules (that differ by state) to achieve stated goals

through application of standard-width buffer strips along perennial streams

and control of disturbances from felling, yarding, and roads to maintain

water quality.

Strategies for forest management on federal forest lands of the Pacific Northwest and southeast Alaska changed substantially in the 1990s. Current management

strategies and their associated forest practice rules contain the following common

themes:

• Emphasis on multiple resource use.

• Strategies that emphasize watershed reserves, watershed restoration, and

use of default buffers or watershed analysis to meet management goals.

• Maintenance of water quality, riparian and aquatic habitats, and species

viability consistent with some timber production.

• Strategies that address watershed, provincial, and regional scales.

• Harvest at extended timber rotation ages (long temporal scale for

disturbance).

• Human disturbance regimes that remain within the natural historical range

of disturbance for specific provinces.

The current federal rules, like those of Washington state, contain provisions for

watershed analysis that allow managers flexibility to develop and apply strategies

tailored to the particular vegetative, geomorphic, and climatic characteristics of

watersheds where human disturbances are proposed. Watershed analysis includes

the following components for future planning efforts:

• Watershed-scale planning.

• Planning at long temporal scales.

• Adapting plans to the unique biogeophysical features of watersheds.

• Planning in harmony with natural disturbance regimes.

Forest practices

have evolved in

response to new

information on

environmental

effects of timber

harvest, recognition that the original

management goals

for riparian and

aquatic habitats

were not being met,

and changing laws

and social values.
50

General Technical Report PNW-GTR-692

• Planning to protect source areas and processes that form and maintain

riparian and aquatic habitats.

• Considering the effects of management of nonforested lands in the watershed.

These criteria provide managers with a more holistic view of the watersheds

they manage and provide the necessary flexibility to achieve management goals.

Establishment and Evolution of Forest Practice Rules

Oregon—

The Oregon state legislature authored and approved the Nation’s first comprehensive

state Forest Practices Act in 1971 (ODF 1995). The goal of the policy is to

encourage economically efficient forest practices that ensure the

continuous growing and harvesting of forest tree species and the

maintenance of forestland for such purposes as the leading use on

privately owned land, consistent with sound management of soil,

air, water, fish and wildlife resources and scenic resources within

visually sensitive corridors as provided in ORS 527.755 and to

ensure the continuous benefits of those resources for future

generations of Oregonians.

The law became effective on July 1, 1972, and implementation began immediately

following adoption of the first set of forest practice rules, referred to collectively

as “best management practices.” The initial rules made modest changes in the way

timber harvest and regeneration was accomplished on state and private forest lands

in response to increasing concerns by resource managers and the public that timber

harvest was degrading aquatic ecosystems and fish and wildlife habitats. The first

rule set was largely site specific and focused on standards for reforestation, road

construction and maintenance, and streamside buffer strips. Although many of

the initial rules were advisory in nature, some were quantitative enough to be

enforceable.

The 1972 forest practice rules divided streams into two classes, fish-bearing

streams (class I) and non-fish-bearing streams (class II). Treatment of riparian

vegetation along class I and II streams was aimed at maintaining state water quality

standards in fish-bearing waters. The original rules called for maintenance of 75

percent of the original shade cover on streams, which could be accomplished by

leaving nonmerchantable tree species, or in cases where nonmerchantable vegetation was insufficient, leaving a fringe of merchantable trees. It was possible to
51

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

waive the latter requirement, however, if other means of maintaining stream

temperatures were available. Management of vegetation along class II streams

required retention or re-establishment of undergrowth sufficient to maintain water

quality in class I waters downstream. No specific width of buffer strip was mandated for either class of stream. The original rules, which incorporated some of the

available scientific knowledge of the day, addressed neither the effects of forest

management at a watershed scale, nor the structural aspects of fish habitat and

stream channel morphology.

The original set of forest practice rules evolved significantly over the approximately 30-year history of the act. Many of the major revisions incrementally increased protection for riparian areas, water quality, and other fish and wildlife

habitat requirements. In 1974 and 1975, new rules were adopted for tractor skidding and mechanical clearing, and water quality protection from surface mining

activities. In 1978, in response to Section 208 of the federal Clean Water Act, rules

regarding water quality were clarified and “prior approvals” by the Department of

Forestry were required for several practices that could directly affect water quality.

In the same year, new rules were added to address “filling and removal” of material

from stream channels, other stream channel alterations, and the use of herbicides

(ODF 1995).

Major changes also occurred in the 1980s. Following severe storms and mass

erosion in western Oregon in 1981 and 1982, new rules requiring written plans for

operations in areas with high risk of mass erosion were adopted. A major amendment to the act in 1987 required site-specific protection for state and federally

listed threatened and endangered species, and in 1988, written plans for forestry

operations within about 30 m of class I streams and within about 90 m of sites of

threatened or endangered species, wetlands, and several other sensitive sites were

required (ODF 1995).

Additional significant changes occurred in the 1990s. In 1991, Senate bill 1125

instructed the Board of Forestry to revise stream protection rules to provide equal

protection for fish present in all Oregon waters (ODF 1999). Subsequently, in

1992, new interim stream protection rules were adopted. In 1993, rules were

adopted for listing biological sites that are scientifically and ecologically significant, and in 1994, new final rules were adopted for classification and protection

of waters of the state with the objective of reaching a desired future condition of

mature streamside timber stands. These rules acknowledged the need to maintain

stream structure through perennial addition of large woody debris. The rule set

The original set of

forest practice rules

evolved significantly

over the approximately 30-year history of the act.
52

General Technical Report PNW-GTR-692

provided protection for streams based on their size and beneficial uses, as well as

protective measures for lakes, wetlands, and other water bodies. The rules also

provided incentives for stream enhancement and conversion of hardwood riparian

areas to conifers as needed (ODF 1995).

Despite the advances made in 1995, the new rule set was still criticized for

not providing adequate riparian and aquatic habitat protection. In a report for the

Oregon Department of Forestry, Botkin et al. (1995) reviewed the forest practice

rules and concluded that they would effectively maintain integrity of intact and

pristine riparian ecosystems (relatively rare in the 21st century), but that they were

unlikely to restore degraded riparian zones on state and private lands in Oregon.

Oregon’s current forest practice rules, adopted in 1999 (Oregon Revised

Statutes 1999), bear little resemblance to the initial set developed in 1972. The

current rules provide more comprehensive protection for aquatic and riparian

habitats than any previous set, but several years of monitoring and evaluation will

be needed to fully test their effectiveness. The Governor of Oregon commissioned

an Independent Multidisciplinary Science Team (IMST 1999) to assess the effectiveness of the current forest practice rules for protecting salmonid habitats. Based

on the professional judgment of the scientists on the IMST, the 1999 rules for

riparian protection, large wood management, and sedimentation control are unlikely to contribute to the recovery of habitat of depressed populations of anadromous salmonids.

The overall goal of current water protection rules is “to provide resource

protection during operations adjacent to and within streams, lakes, wetlands, and

riparian management areas so that, while continuing to grow and harvest trees, the

protection goals for fish, wildlife, and water quality are met.” The protection goal

for water quality is “to ensure through the described forest practices that, to the

maximum extent practicable, non-point discharges of pollutants resulting from

forest operations do not impair the achievement and maintenance of water quality

standards.” The protection goal for fish habitat is “to establish and retain vegetation

consistent with the vegetation retention objectives for streams and lakes that will

maintain water quality and provide aquatic habitat components and functions such

as shade, large woody debris, and nutrients.”

To achieve the current goals for aquatic and riparian ecosystems, streams are

classified into three categories: type F, fish bearing, or fish bearing and source of

domestic water; type D, source of domestic water but without fish use; and, type

N, other streams. Streams are further classified into three categories by volume of

flow. Small streams have average annual flows of <0.03 m /s, medium streams have

Despite the advances made in

1995, the new rule

set was still criticized for not providing adequate

riparian and aquatic

habitat protection.
53

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

average annual flows of ≥0.03 and <0.28 m /s, and large streams have average

annual flows of ≥0.28 m /s. Forest operations within about 30 m of type F and D

streams, within about 90 m of significant wetlands, and within about 30 m of large

lakes require a written plan by the operator and written approval by the state

forester.

Widths of riparian management areas (defined as slope distance from the

streambank) are specified for each category of stream (table 7). Operators may

vary the width of riparian management areas depending on topography, operational

requirements, vegetation, fish and wildlife resources, and water quality protection

as long as vegetation retention requirements are met. However, the average width

of a riparian management area within an operation must equal or exceed the required width. Additional provisions protect side channels, wetlands, and unstable

stream-adjacent slopes that extend beyond the widths of designated riparian management areas.

Additional protection for aquatic and riparian systems is provided by rules

governing timber felling and yarding. The rules focus on minimizing ground disturbance on steep slopes, control of sediment entering streams, and minimizing

disturbance to riparian vegetation and stream channels during yarding operations.

Felling operations are required, wherever possible, to keep trees out of streams and

avoid damage to retained riparian vegetation, and promptly remove any logging

slash that enters stream channels.

Rules related to road construction and maintenance are designed to maintain

forest productivity, water quality, and fish and wildlife habitat. Specific rules

govern road location, design, crossing structures, and fish passage. Crossing structures must be designed to pass peak streamflows with a recurrence interval of 50

Table 7—Riparian management area widths (slope distance) for

streams of various sizes and beneficial uses as required by Oregon

Department of Forestry administrative rules

Stream size Type F Type D Type N

Feet

Large 100 70 70

Medium 70 50 50

Small 50 20 Apply specific water

protection measures

Note: Type F = fish bearing, or fish bearing and source of domestic water; type

D = source of domestic water but without fish use; type N = other streams.

Source: Oregon Revised Statutes 1999.
54

General Technical Report PNW-GTR-692

years and to allow passage of adult and juvenile fish upstream and downstream

during periods when migration normally occurs.

Overall, Oregon forest practice rules have evolved over the past 30 years from

a simple initial rule set to current rules that address most of the ecological issues

related to protection of the state’s aquatic and riparian habitats. Despite all of the

advances for protection of riparian and aquatic ecosystems, the current rules still

emphasize uniform buffer strip widths according to the size and human uses of

streams, and site-specific, small-scale application of rules. The true effectiveness

of the current set of rules, however, remains unknown because insufficient time has

elapsed to implement, monitor, and evaluate their effects.

Washington—

The current Washington Forest Practices Act was enacted in 1974 (Holter 2001)

and has been amended numerous times in its nearly 28-year history. The initial set

of forest practice rules, adopted in 1976, focused on road construction and maintenance, timber harvesting, reforestation, and use of forest chemicals. In 1979, a

special committee identified 14 issues related to forest practice impacts on the

environment, including a number of riparian-related issues such as unstable soils,

watersheds, fish habitat, slide areas, and forest chemicals. Study groups were

established to analyze the issues and determine which ones were likely to result

in significant future adverse impacts. Based on the studies, new rule changes on

threatened and endangered species, chemical applications, forest roads, timber

harvest, slash and debris disposal, and other issues were adopted in 1982. Additional

studies on cumulative effects and riparian habitat were commissioned in 1984, and

in the same year, the State Environmental Policy Act (SEPA) required state agencies to adopt SEPA rules.

Additional major amendments to the rules related to riparian issues were

adopted in 1987, 1988, 1992, and 2001. In 1986, a group of stakeholders (Timber, Fish, Wildlife Group [TFW]) that included state agencies, industrial and small

forest landowners, tribes, counties, and environmental groups developed a consensus process for rule proposals that could be recommended to the Forest Practices

Board. A new and robust TFW rules package that included specific rules for

riparian management zones (RMZs), adaptive management, and other issues was

adopted in November 1987.

Another major set of rule changes for management of wetlands, cumulative

effects, stream temperatures, clearcut sizes and timing, and several other issues
55

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

including watershed analysis for harvest operations, was adopted in 1992. The ESA

listing of a number of salmonids in 1997, 1998, and 1999 resulted in adoption in

2000 of an emergency set of rules for water typing, RMZs, unstable slopes, roads,

and wetlands and SEPA guidance for watershed analysis. A revised permanent rule

set for these issues was adopted in 2001.

The current rules are complex, designed to fit different stream sizes, timber site

characteristics, and physiographic regions of the state; to use watershed analysis as

needed or desired; and to provide for present and future riparian and aquatic habitat

needs. The two goals of riparian management are to (1) protect aquatic and related

habitats to achieve restoration of riparian function and (2) maintain these resources

once they are restored. The rules are comprehensive and only key excerpts are mentioned here. For complete reference to the current rules, refer to Washington Administrative Code (WAC) 222 (Washington State Legislature 2005). The current

rules use a four-level water typing system with specified management practices for

each type of water. Type S waters include all inventoried “shorelines of the state”

(streams with mean annual flow ≥0.57 m /s and lakes ≥8 ha with associated wetlands and shore lands). Type F waters are segments of natural streams (other than

type S); lakes >0.2 ha that contain fish habitat or are used for domestic water, fish

hatcheries, or campgrounds; and off-channel habitats used by fish at some time

of the year. Type Np waters are segments of natural waters with perennial flow

but not used by fish. Type Ns waters are seasonal, non-fish-bearing streams in

which surface flow is not present during at least some portion of the year.

The rules for RMZs associated with the water types are designed to protect

aquatic resources and related habitat to achieve restoration of riparian function, and

the maintenance of these resources once they are restored. Separate rule sets apply

to RMZs in western and eastern Washington, but both sets divide RMZs into three

components for type S and type F streams: a core zone,2

 an inner zone,3 and an

outer zone.4

 The combined RMZ in western Washington is managed for a desired

future stand condition with basal areas that differ by site class (a measure of the

productivity of forest sites for growing timber—fastest potential growth on site I

and slowest on site IV lands). When the stand is 140 years old, the basal area requirements range from 55.4 m2

/ha for site I to 51.4 m2/ha for site IV (table 8).

2 Designated zone immediately adjacent to a stream.

3 Designated area adjacent to, but upslope from, the core zone.

4 Designated area adjacent to, but upslope from, the inner zone.

The current rules

are complex, designed to fit different stream sizes,

timber site characteristics, and physiographic regions of

the state; to use

watershed analysis

as needed or desired; and to provide for present and

future riparian and

aquatic habitat

needs.
56

General Technical Report PNW-GTR-692

When existing riparian stands along type S and F waters in the combined core

and inner zones do not meet stand requirements, no harvest is permitted in the

inner zone. When no harvest is permitted in the inner zone or the landowner

chooses not to enter the inner zone, the width of core, inner, and outer zones

are defined according to site class and stream size (table 9). Harvest may still occur

in the outer zone, but 49 riparian leave trees/ha, either clumped or dispersed, must

remain after harvest (table 10). A third strategy allows landowners to place large

woody debris in streams in lieu of leaving riparian leave trees in the outer zone.

Trees can be harvested and removed from the inner zone when surplus basal

area, consistent with stand requirements, is present. When this situation occurs,

there are two strategies for harvest and removal. The first is a thinning option in

which the smallest diameter trees are removed first, the proportion of conifers in

the stand is not decreased, and at least 141 conifers/ha are left. A different set of

RMZ widths applies to this strategy (table 11). The second is a complex strategy

for leaving trees in the RMZ closest to the water in a way that speeds trajectory

toward the desired future condition of basal area. Another set of RMZ widths

applies to this strategy (table 12).

Perennial non-fish-bearing waters (Np) also receive no-harvest buffer strips of

15-m width and variable length depending on the length of Np water extending

above the confluence of type S or F waters downstream. The length of buffer is

determined by table 13 when the length of Np water is 305 m or less. If an operating area is located more than 152 m upstream from the confluence of a type S or F

Table 8—Basal area targets for western Washington

riparian management zones for type S and F waters

Site class Desired future condition target basal area

(at 140 years)

Square meters per hectare

I 55.4

II 53.4

III 50.1

IV 51.4

Note: Type S = all inventoried “shorelines of the state”; type

F = segments of natural streams (other than type S); lakes >0.2

ha that contain fish habitat or are used for domestic water, fish

hatcheries, or campgrounds; and off-channel habitats used by

fish at some time of the year.
57

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Table 9—Riparian management zone (RMZ) widths for type S and F waters in western Washington when no

harvest is allowed in the inner zone

Inner zone width Outer zone width

(Measured from outer (Measured from outer

edge of core zone) edge of inner zone)

Core zone width

(Measured from outer edge of Stream Stream Stream Stream

bankfull width or outer edge of width ≤10 ft width >10 ft width ≤10 ft width >10 ft

Site class RMZ width channel migration zone of water) (3.1 meters) (3.1 meters) (3.1 meters) (3.1 meters)

Meters

I 61.0 15.2 25.3 30.4 20.4 15.5

II 51.8 15.2 19.2 23.8 17.4 12.8

III 42.7 15.2 13.1 16.8 14.3 10.7

IV 33.5 15.2 7.0 10.1 11.3 8.2

V 27.4 15.2 3.1 5.5 9.3 6.7

Note: Type S = all inventoried “shorelines of the state.” Type F = segments of natural streams (other than type S); lakes >0.2 ha that

contain fish habitat or are used for domestic water, fish hatcheries, or campgrounds; and off-channel habitats used by fish at some time

of the year.

Table 10—Riparian management zone outer zone leave tree requirements for type S and F

waters in western Washington

Application Leave-tree spacing Tree species Minimum d.b.h. required

Centimeters

Outer zone Dispersed Conifer 30.5

Outer zone Clumped Conifer 30.5

Protection of Clumped Trees representative of the 20.3

sensitive features overstory including both

hardwood and conifer

Note: d.b.h. = diameter at breast height. Type S = all inventoried “shorelines of the state.” Type F = segments of

natural streams (other than type S); lakes >0.2 ha that contain fish habitat or are used for domestic water, fish

hatcheries, or campgrounds; and off-channel habitats used by fish at some time of the year.
58

General Technical Report PNW-GTR-692

Table 11—Riparian management zone (RMZ) widths for type S and F waters in western Washington when using

the thinning strategy to reduce time needed to meet large wood, fish habitat, and water quality needs

Inner zone width Outer zone width

(Measured from outer (Measured from outer

edge of core zone) edge of inner zone)

Core zone width

(Measured from outer edge of Stream Stream Stream Stream

bankfull width or outer edge of width ≤10 ft width >10 ft width ≤10 ft width >10 ft

Site class RMZ width channel migration zone of water) (3.1 meters) (3.1 meters) (3.1 meters) (3.1 meters)

Meters

I 61.0 15.2 25.3 30.4 20.4 15.5

II 51.8 15.2 19.2 23.8 17.4 12.8

III 42.7 15.2 13.1 16.8 14.3 10.7

IV 33.5 15.2 7.0 10.1 11.3 8.2

V 27.4 15.2 3.1 5.5 9.3 6.7

Note: Type S = all inventoried “shorelines of the state.” Type F = segments of natural streams (other than type S); lakes >0.2 ha that

contain fish habitat or are used for domestic water, fish hatcheries, or campgrounds; and off-channel habitats used by fish at some time

of the year.

Table 12—Riparian management zone (RMZ) widths for type S and F waters in western Washington when using

the management strategy for leaving reserve trees closest to the water to reduce time needed to meet large wood,

fish habitat, and water quality needs

Inner zone width Outer zone width

(Measured from outer

Stream width ≤3.1 meters Stream width >3.1 meters edge of inner zone)

Minimum Minimum

floor floor

Core zone width distance distance

(Measured from outer (Measured (Measured (Measured (Measured Stream Stream

edge of bankfull width from outer from outer from outer from outer width width

Site RMZ or outer edge of channel edge of edge of edge of edge of ≤10 ft >10 ft

class width migration zone of water) core zone) core zone) core zone) core zone) (3.1 meters) (3.1 meters)

Meters

I 61.0 15.2 25.6 9.1 25.6 15.2 20.1 20.1

II 51.8 15.2 19.5 9.1 21.3 15.2 17.1 15.2

III 42.7 15.2 13.4 9.1 ** ** 14.0 **

Note: Type S = all inventoried “shorelines of the state.” Type F = segments of natural streams (other than type S); lakes >0.2 ha that

contain fish habitat or are used for domestic water, fish hatcheries, or campgrounds; and off-channel habitats used by fish at some time

of the year.
59

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

water and the type Np water is more than 305 m in length, then a buffer of 15.2 m

on each side of the stream is determined by using table 14. In addition, a 9-m-wide

equipment limitation zone is enforced along all type Np and Ns streams and sensitive sites such as seeps. Alluvial fans also receive 15.2-m buffers.

The current forest practice rules also provide detailed guidance for road construction and maintenance, timber felling and bucking, cable and ground yarding

operations, slash disposal, and use of forest chemicals in riparian zones and wetlands (see WAC 222 for details). Rules associated with these activities are aimed at

maintaining and restoring desired riparian functions and conditions.

The current Washington forest practice rules use a variety of practices and

strategies to protect aquatic and riparian ecosystems in both the east and west

physiographic regions of the state. The 10-year direction for Washington forest

practices calls for:

• Transition from an individual forest practice-based program to one that is

landscape based (provides for watershed analysis, or varies prescriptions by

stream size and timber site class) and that recognizes cumulative effects on

public resources.

• Refocuses forest practice rules on outcomes rather than process or action.

• Continuation of an active role in the Timber/Fish/Wildlife process and

coordination with all stakeholders.

Because the current set of rules was adopted in 2001, implementation and

monitoring of their effects has just begun. Consequently, it remains unknown

Table 13—Required no-harvest, 15.2-meter (50-foot) buffers on type Np waters

in western Washington

Length of 15.2-meter buffer

required on type Np water (starting

Length of type Np water from the at the confluence of the type Np and

confluence of type S or F water connecting water)

Greater than 305 meters 152.4 meters

Greater than 91.4 meters but less than Distance of the greater of 91.4 meters

305 meters or 50 percent of the entire length

of the type Np water

Less than or equal to 91.4 meters The entire length of type Np water

Note: Type Np = segments of natural waters with perennial flow but not used by fish. Type

S = all inventoried “shorelines of the state.” Type F = segments of natural streams (other than

type S); lakes >0.2 ha that contain fish habitat or are used for domestic water, fish hatcheries,

or campgrounds; and off-channel habitats used by fish at some time of the year.
60

General Technical Report PNW-GTR-692

whether the current rules will restore and maintain aquatic and riparian ecosystems

at historical norms and sustainable levels.

Alaska—

The Alaska Forest Resources and Practices Act was enacted in 1978 (Alaska Division of Forestry 2001). The original act was designed to protect fish habitat and

water quality and to ensure prompt reforestation of forest lands. The act divides the

state into three forest practices regions, coastal spruce-hemlock (Region I), interior

spruce-hardwood south of the Alaska Range (Region II), and interior spruce hardwood north of the Alaska Range (Region III). Standards for riparian management

and reforestation differ by region and land ownership. The original act did not

provide comprehensive rules coverage for all land ownerships. Major revisions were

adopted in Region I in 1990 in response to the Tongass Timber Reform Act (TTRA)

to address riparian management on private, state, and federal lands, improve notification procedures for timber operations, and establish enforcement procedures.

Additional changes to the stream classification system and riparian management

standards for coastal forests (Region I) were adopted in 1999.

Table 14—Minimum percentage of length of type Np waters to be buffered when more than

500 (152.4 meters) feet upstream from the confluence of a type S or F water

Percentage of length of type Np water that

must be protected with a 50-foot (15.2 meter)

no-harvest buffer more than 500 feet (152.4

Total length of a type Np water upstream meters) upstream from the confluence of a

type S or F water type S or F water

Meters Percent

305.0 or less Refer to table in subsection i of Oregon

forest practice rules

305.1 to 396.0 19

396.1 to 490.0 27

490.1 to 610.0 33

610.1 to 762.0 38

762.1 to 1067.0 42

1067.1 to 1524.0 44

Greater than 1524.0 45

Note: Type Np = segments of natural waters with perennial flow but not used by fish. Type S = all inventoried

“shorelines of the state.” Type F = segments of natural streams (other than type S); lakes

>0.2 ha that contain fish habitat or are used for domestic water, fish hatcheries, or campgrounds; and

off-channel habitats used by fish at some time of the year.

Standards for riparian management and

reforestation differ

by region and land

ownership.
61

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

The Alaska forest practice rules divide water bodies into four classes. Type A

water bodies must meet one of the following criteria: (1) have anadromous fish and

streams with gradients of <8 percent and with particulate substrates, (2) have wetlands and lakes including their outlets, and (3) have estuarine areas delimited by

salt-tolerant vegetation. Type B water bodies are used by anadromous fish, but

otherwise fail to meet the criteria for type A water bodies. Type C waters are not

used by anadromous fish, are tributary to type A and B waters, and have gradients

of <12 percent. Type D waters have the same criteria as type C waters, except that

gradients are >12 percent.

Forest practice regions, land ownerships, and water types are used to stratify

forest practice rules for riparian management in Alaska (table 15). On state and

other public lands, in the coastal spruce-hemlock region, no-harvest buffer strips

of 30 m along the water body and partial harvest between 30 m and 91 m from the

water body consistent with maintenance of fish and wildlife habitat are required

along anadromous fish streams and high-value resident fish streams. Slope stability

standards also apply within the buffer strips (table 15).

Forest practice rules for private lands in the spruce-hemlock region also require

20-m-wide buffer strips on type A waters, either 20-m buffers or a buffer to the

slope break, whichever is smaller, on type B waters, and 8-m buffers with specific

criteria for type C and D waters. Slope stability standards also apply on private

lands.

Forest practice rules for the interior spruce-hardwood region south of the

Alaska Range are similar to those of the coastal region, except that no designated

buffer strip widths apply to private lands. Timber harvest on private land within

30 m of anadromous and high-value resident fish waters must be designed to protect fish habitat and water quality (table 15).

Forest practice rules for riparian management in the interior spruce-hardwood

region north of the Alaska Range require smaller buffer strips on public lands as

compared to the other forest practice regions in Alaska. Slope stability standards

also apply to public lands. No buffer strips are required on private lands, but management conducted within 30 m of any waters containing anadromous fish must be

consistent with the goal of maintaining adequate fish habitat protection.

Forest practice rules for Alaska have evolved to address many critical ecological issues related to protection of aquatic and riparian habitats and have been

tailored to meet the needs of different physiographic regions of the state. As in the
62

General Technical Report PNW-GTR-692

Table 15—Current Alaska Forest Resources and Practices Act riparian management standards by region, land

ownerships, and water types

Landowner

Region and authority Standard

I: Coastal spruce- State Harvest of timber may not be undertaken within 30.5 meters immediately

hemlock AS 41.17.118(a)(2) adjacent to an anadromous or high-value resident fish water body.

Between 30.5 and 91.5 meters from the water body, timber harvest may occur but must

be consistent with the maintenance of important fish and wildlife habitat.

Slope stability standards apply within 30.5 meters from the water body on anadromous

and high-value resident fish waters and tributaries to these waters with <12 percent

gradient, and within 15.2 meters of other tributaries to anadromous and high-value

resident fish waters.

Other public Harvest of timber may not occur within 30.5 meters from the shore or bank on

AS 41.17.119(1) anadromous or high-value resident fish waters located south of the Alaska Range.

Slope stability standards apply within 30.5 meters from the water body on anadromous

and high-value resident fish waters and tributaries to these waters with <12 percent

gradient, and within 15.2 meters of other tributaries to anadromous and high-value

resident fish waters.

Private Along a type A water body, harvest of timber may not be undertaken within 20.1 meters

AS 41.17.116(a) of the water body.

Along a type B water body, harvest of timber may not be undertaken within 20.1 meters

of the water body or to the break of the slope, whichever area is smaller.

Along a type C water body, the operator shall, where prudent, retain low-value timber

within 7.6 meters of the stream or to the limit of the riparian area, whichever is greater

(slope break or 30.5 meters) where the width of the water body is >4.0 meters at the

ordinary high-water mark (OHWM) or >2.4 meters at OHWM if the channel is incised.

Along a type D water body, the operator shall, where prudent, retain low-value timber

within 7.6 meters of the stream or to the limit of the riparian area, whichever is greater

(slope break or 50 feet) where the width of the water body is >4.0 meters at

OHWM or >2.4 meters at OHWM if the channel is incised.

Slope stability standards apply to 30.5 meters from the water body on types A, B, and C

water bodies, and within 15.2 meters on type D water bodies.

II: Interior spruce- State Harvest of timber may not be undertaken within 30.5 meters immediately adjacent to an

hardwood south of AS 41.17.118(a)(2) anadromous or high-value resident fish water body.

the Alaska Range

Between 30.5 and 91.5 meters from the water body, timber harvest may occur but must

be consistent with the maintenance of important fish and wildlife habitat.

Slope stability standards apply within 30.5 meters from the water body on anadromous

waters, and within 15.2 meters of tributaries to anadromous waters.

Other public Harvest of timber may not occur within 30.5 meters from the shore or bank of an

AS 41.17.119(1) anadromous or high-value resident fish water body that is located south of the

Alaska Range.

Slope stability standards apply within 30.5 meters from the water body on anadromous

waters, and within 15.2 meters of tributaries to anadromous waters.

Private A timber harvest operation within 30.5 meters from the shore or bank of an anadromous

11 AAC 95.260 or high-value resident fish water body must be located and designed primarily to protect

fish habitat and surface water quality from significant adverse effects.
63

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

states in the Pacific Northwest, Alaska’s forest practice rules are largely sitespecific and applied at small scales. Little attempt has been made to address cumulative effects of forest management at the watershed scale. An attempt has been

made to monitor and assess the effectiveness of forest practice rules for protecting

riparian and aquatic habitats on private lands (e.g., Martin 2001, Martin et al.

1998). However, spatial and temporal expansion of the current monitoring efforts

is needed to provide definitive answers on the effectiveness of the current rules.

USDA Forest Service—

The importance of riparian areas on national forest lands was recognized in the

National Forest Management Act of 1976 (NFMA) 36 CFR 219.27, which states:

Riparian areas. Special attention shall be given to land and

vegetation for ~30 m from the edges of all perennial streams,

lakes, and other bodies of water [note the physical rather than

functional definition]. This area shall correspond to at least the

recognizable area dominated by riparian vegetation. No management practices causing detrimental changes in water temperature or

chemical composition, blockages of water courses, or deposits of

sediment shall be permitted within these areas which seriously and

adversely affect water conditions or fish habitat...

Prior to passage of the act, Forest Service regulations recognizing the importance of riparian habitats were inconsistent, as was management of riparian habitats

Table 15—Current Alaska Forest Resources and Practices Act riparian management standards by region, land

ownerships, and water types (continued)

Landowner

Region and authority Standard

III: Interior spruce- State Harvest of timber may not be undertaken within 30.5 meters immediately adjacent to an

hardwood north of AS 41.17.118(a)(1) anadromous or high-value resident fish water body unless the division determines that

the Alaska Range adequate protection remains for the fish habitat.

Slope stability standards apply within 30.5 meters from the water body on anadromous

waters, and within 15.2 meters feet of tributaries to anadromous waters.

Other public Harvest of timber may not occur within 30.5 meters immediately adjacent to an

AS 41.17.119(2) anadromous or high-value resident fish water body north of the Alaska Range unless

the commissioner determines that adequate protection remains for the fish habitat.

Slope stability standards apply within 30.5 meters from the water body on anadromous

waters, and within 15.2 meters of tributaries to anadromous waters.

Private A timber harvest operation within 30.5 meters from the shore or bank of an anadromous

11 AAC 95.260 or high-value resident fish water body must be located and designed primarily to protect

fish habitat and surface water quality from significant adverse effects.

Alaska’s forest

practice rules are

largely site-specific

and applied at small

scales. Little attempt

has been made to

address cumulative

effects of forest

management at the

watershed scale.
64

General Technical Report PNW-GTR-692

across the National Forest System. Forest planning efforts postdating the act were

required to address riparian ecosystems, but subsequent management guidelines and

practices remained inconsistent and changed with ensuing iterations of forest

planning.

 The chronological changes in riparian management in the USDA Forest

Service in the past three decades are difficult to track because of the decentralized

decisionmaking structure of the agency. The Forest Service Manual (FSM) provides overall direction for riparian and aquatic ecosystem management on national

forest lands, but each region and national forest can supplement the FSM to provide progressively more local direction for resource management. Frequently,

when sections of the manual are revised, previous sections are removed, discarded,

and replaced with the new material. The result is a progressive loss of corporate

memory at the local level of how management direction changed over time. The

following information was gleaned from U.S. Forest Service administrative offices

and archives and probably does not represent a complete history of the changes in

riparian and aquatic habitat in management in the Pacific Northwest and Alaska,

although some highlights of change are noted.

Pacific Northwest Region (national forests in Oregon and Washington)—

Recognition of the importance of anadromous salmonids on Forest Service lands

was noted in 1959 in the Pacific Northwest Region’s Wildlife Management Handbook. Section 2633.3–Engineering states, “The protection of anadromous fish in

streams requires special precautions in the design of roads and in the installation of

stream crossing facilities.” The two primary considerations were:

• Providing unrestricted passage of sea-run fish to and from spawning beds,

including spawning migrations from lakes and reservoirs.

• Preventing siltation, disturbance, or destruction of spawning beds during

the spawning and incubation periods.

The Forest Service Manual for the Pacific Northwest Region in 1967 also

addressed the issue of woody debris removal from streams. Section 2522.11 of

the Watershed Management Manual provides considerations for debris cleaning

from stream channels. The section mentions that preventing debris from entering

streams is a high priority. Suggestions for achieving prevention include, “Felling

and yarding timber away from streams, leaving streamside ‘filter’ strips, special

Chronological

changes in riparian

management in the

USDA Forest Service

in the past three

decades are difficult

to track because of

the decentralized

decisionmaking

structure of the

agency.
65

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

timber sale layout design, road construction and logging slash treatment on floodplains and immediate channel side slopes are examples.” The focus of the section,

however, is on potential damage from debris concentrations and considerations and

priorities for debris removal. Primary considerations for removal were:

• Water quality. “Debris concentrations adversely affect the quality of water

for domestic, industrial, agricultural, and fishery use.”

• Physical damage. “There is much to justify the removal of concentrations

of debris which can interfere with the ability of a stream channel to carry

peak discharges.”

• Fish migration. “In addition to the effect of water quality on fishery

resources, debris jams can limit fish movement and prevent or retard fish

from reaching more suitable spawning areas.”

The first regional-level streamside management guidelines for the national forests of Oregon and Washington appeared in section 2526 of the Watershed Management Manual in 1974, following passage of the Federal Water Pollution Control

Act of 1972 (P.L. 92-500). The goal of the guidelines was to prevent non-pointsource pollution and protect anadromous and resident fish habitats on the region’s

national forests. The first streamside management guidelines classified streams into

four categories based on their importance to fish production and water quality, and

certain practices were “suggested” for protecting each class of stream. Many of the

suggested guidelines, however, were qualitative and difficult to measure.

Streams were defined in the following manner:

• Class I: Perennial or intermittent streams or segments thereof,

used for domestic water, used by large numbers of fish for

spawning, rearing, or migration, or having a major effect on the

quality of downstream waters

• Class II: Perennial or intermittent streams or segments thereof,

used by moderate though significant numbers of fish for

spawning, rearing, or migration, or having a moderate effect on

water quality in Class I streams, or a major effect on water

quality of Class II streams

• Class III: All other perennial streams or segments thereof not

meeting higher-class criteria

• Class IV: All other intermittent streams or segments thereof not

meeting higher-class criteria

The broad goal of the guidelines was “to apply best management practices”

consistent with achieving specific water quality goals and to protect the stream and
66

General Technical Report PNW-GTR-692

adjacent area so as to maintain the aquatic resources at high natural levels. To

accomplish the goals for class I and II streams, the guidelines “suggest” that timber not be felled into streams, logs not be skidded across streams, equipment and

logging debris be kept out of streams, vegetation on streambanks be left undisturbed, and sufficient shade be left to meet water quality standards. Guidelines for

road construction and maintenance suggested keeping sediment and debris out of

streams, minimizing disturbance to stream channels, using bridges and open-bottom

culverts as crossing structures when possible, and limiting construction activities to

seasons of the year that would minimize damage.

Management practices for class III streams were concerned primarily with

preventing mass soil movement, maintaining satisfactory downstream water temperatures, and preventing debris from moving downstream into higher class waters.

Specific guidelines suggest felling timber away from streams, retaining streambank

vegetation for bank stability and shade, keeping equipment and logging debris out

of streams, and protecting stream channels during road construction and maintenance.

Management practices for class IV streams were concerned primarily with preventing mass soil movement and preventing debris from moving downstream into

higher class waters. Specific guidelines suggest felling timber away from streams,

keeping equipment and logging debris out of streams, and protecting stream

channels during road construction and maintenance.

The original set of regional forest practice guidelines for the national forests

of Oregon and Washington provided regional guidance for forest management

activities around water and remained in force for about a decade. In the 1970s and

into the 1980s, the regional guidelines addressed sedimentation, loss of streamside

shade, and improved fish passage on the region’s national forests. Each of the 19

national forests in the region, however, working within the framework of regional

manual direction, developed its own variation of streamside management guidelines

for inclusion in forest plans. Consequently, application of the guidelines at the

forest level was highly variable.

The variation in management of riparian and aquatic habitats in the region

continued into the early 1990s. A Regional Fisheries Task Force, commissioned

by the regional forester in 1991, reviewed the forest plans of seven national forests

in Oregon and Washington. The task force examined sections of forest plans that

addressed descriptions of existing fish habitat conditions, effects assessments, management direction, monitoring, and measurability of management criteria. The

Each of the 19 national forests in the

region, developed

its own variation of

streamside management guidelines for

inclusion in forest

plans.
67

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

findings indicated that coverage of fish and riparian issues in forest plans ranged

from good to poor, with an overall rating of fair (Heller et al. 1991). Weaknesses

in the plans included the use of general, non-watershed-specific and nonquantitative

descriptions of existing fish habitat conditions, particularly for riparian areas,

vague, nonspecific discussions of effects, and standards and guidelines that were

qualitative and unmeasurable (Heller et al. 1991). The task force concluded that

specific habitat requirements of indigenous stocks of fish might not be met through

the implementation of BMPs.

The aquatic conservation strategy of the NWFP was the next iteration of

riparian and aquatic management in the region. The strategy, for the first time,

assumed an ecosystem approach to management of riparian and aquatic habitats by

identifying watershed reserves (at the provincial scale), interim default riparian

reserves (with greater width and upstream extension than previous strategies),

watershed analysis (watershed scale) to tailor management plans to the unique and

variable features of watersheds, and watershed restoration (watershed scale) to deal

with the legacy of past management effects.

The results from a set of scientific studies were used to develop and justify the

interim riparian boundaries identified for the NWFP by the Forest Ecosystem Management Assessment Team (FEMAT) (FEMAT 1993). These studies involved the

range of ecological functions and processes that occur within certain portions of

riparian zones along fish-bearing as well as non-fish-bearing streams. The latter

had been given little or no consideration previously. A thorough and comprehensive

review and synthesis of the scientific literature was used to develop the relations

between a given ecological process and the interim size of the riparian zone (figs.

3, 4). Considerations of the needs of wildlife were also incorporated into the

delineation process. Fourteen scientists from a range of physical and biological

disciplines integrated the findings into the delineation of the interim riparian zone

boundaries.

The NWFP interim riparian reserves, the heart of the strategy, exclude most

management activities within two site-potential tree heights (about 90 to 120 m)

along each side of perennial streams, and one site-potential tree height (about 45

to 60 m) along intermittent streams. Depending on the degree of dissection of the

forested landscape, riparian reserves along both perennial and intermittent streams

may occupy between 40 and 90 percent of the landscape (Hohler et al. 2001).

Interim riparian reserves of this magnitude, coupled with key watershed reserves,

have provided a connected watershed-level reserve system for terrestrial, riparian,

The aquatic conservation strategy, for

the first time, assumed an ecosystem approach to

management of

riparian and aquatic

habitats.
68

General Technical Report PNW-GTR-692

and aquatic ecosystems. The amount of forested landscape protected by these

strategies has fueled the controversy regarding riparian protection and resulted in

both new research to evaluate prescribed buffer widths, and a re-examination of

existing scientific literature on the subject.

Alaska Region (Tongass National Forest)—

Industrial forestry began on the Tongass National Forest in southeast Alaska in the

1950s, but specific goals and guidelines for protecting riparian and aquatic habitats

were not instituted until the late 1970s. The TLMP, completed in 1979, was the

first national forest plan approved following passage of NFMA. The original plan

stressed full protection of the biological potential of streams and rivers, with the

stated goal to “preserve the biological productivity of every fish stream on the

Tongass” (USDA Forest Service 1997). The plan, however, offered few guidelines

or practices to achieve that goal. For example, there were no requirements to leave

standing timber in buffer zones along fish-bearing streams. The plan was amended

in 1986, and forestwide standards and guidelines for riparian management, based

on the forest’s Aquatic Habitat Management Handbook (USDA Forest Service

1986) and BMPs for soil and water conservation, were established. Stream channels

were classified by topographic and geomorphic characteristics (Paustian 1992). All

stream reaches were relegated to three classes based on the presence of anadromous

fish (class I), resident fish (class II), and their effects on the quality of downstream

waters (class III). Management practices were tiered to the stream and channel

classifications. Commercial timber harvest, however, was still allowed in riparian

buffers because the forest’s highest value spruce, hemlock, and cedar occurred there

(USDA Forest Service 1989).

Despite improving riparian management practices during the 1970s and 1980s,

the productivity of freshwater habitats on the forest showed declines between

1950 and 1986 (Tongass National Forest Interdisciplinary Team 1990). Losses

of productivity were significant within disturbed watersheds where large areas had

been clearcut, but were minimal at the forest scale. Heightened concerns for the

area’s world-class anadromous fisheries stimulated additional changes in riparian

management.

The Tongass Timber Reform Act (TTRA) was passed by Congress in 1990 with

additional direction for management of riparian and aquatic habitats on the forest.

The act required 30-m no-cut buffers along all class I streams (anadromous fish

streams) and on class II streams (resident fish streams) flowing directly into class I

streams. The TTRA again increased protection of riparian and aquatic habitats, but
69

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

problems with consistent application were noted. A riparian activity review conducted on the forest in 1991 to assess application of the requirement of TTRA

(USDA Forest Service 1991) found that TTRA was inconsistently interpreted and

applied on the forest.

The next attempt to increase protection for riparian and aquatic habitats on the

Tongass was associated with a federal management program in the Pacific Northwest called, “Interim Strategies for Managing Anadromous Fish-Producing Watersheds in Eastern Oregon and Washington, Idaho, and Portions of California,” also

known as PACFISH (USDA and USDI 1994a) in 1994. The PACFISH strategy was

developed in response to compelling evidence that salmonid habitats on Forest

Service and BLM lands in the Northwest had been severely degraded and that the

trend was likely to continue under current USFS and BLM land and resource

management plans (USDA and USDI 1994a). The PACFISH strategy was intended

to guide management of riparian and aquatic habitats until a new round of forest

planning was completed. The strategy included the same four components included

in the NWFP, i.e., key watershed reserves, riparian habitat conservation areas,

watershed analysis, and watershed restoration.

When the Forest Service and BLM developed the PACFISH strategy, the

intention was to apply it to all national forest lands used by Pacific anadromous

salmonids, including the Tongass and Chugach National Forests in Alaska. The

strategy provided conservative default protection for riparian zones, until watershed

analysis was conducted to adapt plans to the local conditions of specific watersheds.

A directive from Congress in the Conference Committee Report to the Fiscal Year

1994 Appropriation Act for the Interior and Related Agencies forbade application

of PACFISH to Alaska forests. In the directive, the Alaska Region was instructed

to: “proceed with stream analyses and studies and review procedures related to the

PACFISH strategy in 1994 in order to study the effectiveness of current procedures

[for protecting the habitat of anadromous salmonids], and determine if any additional protection [for anadromous fish habitat] is needed.”

In response to the directive, an assessment (Anadromous Fish Habitat Assessment) of current forest management practices and the condition of fish habitats was

made on the forest (USDA Forest Service 1995). The core of the review consisted

of three components. First, a comprehensive literature review was conducted of

Pacific salmon and steelhead habitat characteristics, processes, uses, and management interactions in Alaska. More than 1,500 relevant publications were located

and reviewed. Second, a team of scientists from Alaska and the Pacific Northwest

conducted a field review of current management practices for protecting riparian
70

General Technical Report PNW-GTR-692

and aquatic habitats on the Tongass National Forest. Finally, watershed analyses

were conducted on three Tongass watersheds to compare past management activities with postwatershed analysis management plans. Findings from these activities

(USDA Forest Service 1995) indicated that fish habitats on the forest were declining and that current practices for managing riparian and fish habitats were inadequate to protect habitat quality and the freshwater portion of the anadromous fish

life cycle.

Numerous recommendations were made for improving management and

essentially all were incorporated into the 1997 TLMP revision (USDA Forest Service 1997). The final strategy for protection of riparian and aquatic habitats in the

1997 TLMP revision is remarkably similar to the PACFISH strategy in that it contains watershed reserves, default prescriptions for riparian habitat conservation

areas on four stream classes and all stream channel types on the Tongass, the option

to use watershed analysis to change default prescriptions, and watershed restoration

to repair degraded habitats.

Bureau of Land Management—

Initial riparian management guidelines for forested BLM lands in the Pacific

Northwest were linked with the Oregon Forest Practices Act (see page 47). In 1972

agency direction mandated that forestry activities either meet or exceed the BMPs

required for timber harvest and road construction in the state Forest Practices Act.

Later, in 1975, when BLM resource management plans were developed for districts

in the region, standard buffers of about 23 m applied to anadromous fish habitats

west of the Cascades, and buffers of 15-m width applied to fish-bearing streams east

of the mountains.

Despite use of these guidelines and BMPs, widespread degradation of anadromous fish habitats on BLM lands was mentioned as part of the need to apply the

PACFISH strategy to BLM lands in the Pacific Northwest (USDA and USDI

1994a). Subsequently, riparian and aquatic habitat management on BLM lands in

the Northwest was included under the PACFISH umbrella in 1994. The result was

application of a consistent management strategy for riparian habitats across the

region by the major federal land management agencies.

The unified federal policy—

Despite the unprecedented move in 1994 to develop a consistent umbrella strategy

for management of riparian and aquatic habitats on Forest Service and BLM lands

in the Northwest, past inconsistencies within and among watershed management
71

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

strategies of federal agencies in the United States prompted Congressional development of a unified federal policy in 2000. The policy was developed to ensure a

consistent nationwide watershed management approach to federal land and resource

management (Federal Register 2000). The U.S. Departments of Agriculture,

Interior, Commerce, Defense, and Energy, and the Environmental Protection

Agency, the U.S. Army Corps of Engineers, and the Tennessee Valley Authority are

participating in implementation of the policy on >320 million ha of federal land.

The policy, which is part of the Clean Water Action Plan for restoring and protecting America’s waters, has two goals: (1) use a watershed approach to prevent and

reduce pollution of surface and ground waters resulting from federal land and

resource management activities and (2) accomplish this in a unified and costeffective manner.

The following guiding principles were used to develop the policy:

• Use a consistent and scientific approach to manage federal lands and

resources and to assess, protect, and restore watersheds.

• Identify specific watersheds in which to focus funding and personnel and

accelerate improvements in water quality, aquatic habitat, and watershed

conditions.

• Use the results of watershed assessments to guide planning and management activities in accordance with applicable authorities and procedures.

• Work closely with states, tribes, local governments, private landowners,

and stakeholders to implement the policy.

• Meet the requirements of the Clean Water Act to comply with applicable

federal, state, tribal, interstate, and local water quality requirements to the

same extent as nongovernmental entities.

• Take steps to help ensure that federal land and resource management

actions are consistent with applicable federal, state, tribal, and local government water quality management programs.

Although implementation is underway, it is expected to take some time to

achieve consistent goals and strategies in watershed management among the departments and agencies involved in the policy. Implementation of the policy might

encourage agencies to pool funds and staff effort to focus on priority management

needs.

It is expected to

take some time to

achieve consistent

goals and strategies

in watershed management among the

departments and

agencies involved

in the policy.
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General Technical Report PNW-GTR-692

Commonalities in Development of Forest Practice Rules

The goals for management and protection of riparian and aquatic habitats are

similar for state and federal forested lands in the Pacific Northwest and Alaska.

That is, all offer a significant level of protection for riparian and aquatic habitats

based on a consistent body of scientific information applicable to the region. The

rules and practices for accomplishing riparian protection goals, however, are variable and are based on the normative decisions of policymakers within each management jurisdiction. In some cases, different practices apply to contiguous riparian

and aquatic habitats on opposing sides of state lines, even though the goals for

resource protection are similar. These variations appear not to be based on a need

for flexibility in management to accommodate different physiographic or geomorphic situations but rather a difference of opinion among policymakers about how

much protection of riparian ecosystems is needed to achieve stated goals.

Despite variations among state and federal forest practice rules, all share commonalities in development. For example:

• All were initiated in the 1970s.

• All shared the goals of protecting riparian and aquatic habitats.

• All employed some type of vegetative buffer strips to protect riparian

vegetation and streambanks.

• All sought to find the minimum width of vegetated buffer strips that would

protect riparian and aquatic values.

• All addressed timber felling and yarding practices near streams.

• All developed special rules for road construction and maintenance to

minimize sedimentation and stream channel disturbance.

• All, in time, recognized that initial forest practice rules did not meet stated

goals for riparian protection, and through a sequential process of evaluation

and amendment provided progressively more protection for riparian and

aquatic habitats over a period of two to three decades.

• Many of the strategies still focus on small-scale, relatively short-term

criteria.

The progression in development of state and federal riparian and aquatic

management strategies has moved from the initial 1970s focus on single functions

at site scales, to the 1980s focus on multiple functions at site scales, to the 1990s

focus on multiple functions at watershed scales (fig. 7). Rule development was

Rules and practices

for accomplishing

riparian protection

goals, are variable

and are based on

the normative decisions of policymakers within each

management jurisdiction.
73

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Figure 7—Temporal progression in the way state and federal riparian management

strategies addressed riparian functions at various scales.

driven in part by new science and emerging legal issues (table 16). Future progression in this sequence may lead to landscape-scale classifications that aid managers

in identifying and grouping similar watersheds so that watershed analyses become

more efficient and perhaps apply to areas larger than individual watersheds (Benda

et al. 1998, Montgomery 1999).

During each phase of development, implementation of forest practices received

some degree of monitoring and evaluation (e.g., Adams and Stack 1989, Caldwell

et al. 1991, Dent and Walsh 1997, Feller 1981, Moring 1975, Morman 1993,

Rashin and Graber 1992, Robison et al. 1999, Runyon and Andrus 1994, USDA

Forest Service 1995). Although the monitoring was generally incomplete, and

often designed at inappropriate temporal and spatial scales, it did frequently provide managers with evidence that practices were not meeting riparian and aquatic

protection goals for water temperature, coarse woody debris, and fish habitat

structure—hence, the progressive increases in protection over time.

Current rules, with all of their commonalities and differences, protect more

of the ecological processes that form and maintain riparian and aquatic ecosystems

than any of their predecessors. However, monitoring and evaluation at the appropriate temporal and spatial scales are needed to evaluate the effectiveness of current
74

General Technical Report PNW-GTR-692 Table 16—Summary of regulations for management of riparian zones on state and federal lands in the Pacific Northwest and southeast Alaska; ecological and legal concerns and key scientific papers that influenced development of the regulations over time; and potential directions State lands Federal lands Non-fish- Non-fish- Fish-bearing bearing Fish-bearing bearing Legal Key science streams streams streams streams Ecological purpose(s) concerns/issues papers Pre- 1970s None None None None 1970s Best manage- None BMPs— Limited for Water temperature Clean Water Act, Alsea Watershed Study ment practices minimal temperature and sediment control Sec. 208 (Hall and Lantz 1969, (BMPs) buffers that were and erosion Moring and Lantz 1975), predominately control Gibbons and Salo 1973

nonconifers

1980s BMPs with None 100 feet Limited for Large wood Clean Water Act Salo and Cundy 1987

special rules temperature recruitmentfor operating and erosion Sedimentation

near streams control

1990s To 30.4 meters— Limited Defaults to 91.2 Defaults to Variety of ecological Tongass Timber Murphy and

no harvest near protection in meters (2 heights 45.6 meters processes at water- Reform Act Koski 1989,

stream and varing perennial non- of site-potential (1 height of site- shed scale McDade et al.amounts in remain- fish-bearing tree) until water- potential tree) Clean Water Act 1990, Robinsoning area streams in WA shed analysis until water- and Beschta 1990,

shed analysis Endangered FEMAT 1993

Species Act—fish and wildlife

2000 Same Possibly along Same Same Variety of ecological Clean Water Act Reeves et al. 1995,

selected processes at Benda et al. 1998,channels Consideration of Consideration of watershed/landscape Endangered Cissel et al. 1999

landscape context landscape context scale Species Act—

fish and wildlife

Maintain dynamic

nature and processesof aquatic ecosystems
75

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

strategies. Therefore, each of the current rule sets only represents another step in

the evolutionary process of forest practices development, and all could be changed

again in the future to more, or perhaps less, restrictive rules depending on results

of evaluations and changing legal, social, and science issues. Even after more than

two decades of development, Murphy (1995) reported that all state forest practice

rules in the Northwest and Alaska were judged to be ineffective in meeting goals

for riparian management. Also, the Independent Multidisciplinary Science Team

(IMST 1999) concluded that the most current Oregon forest practice rules would

not recover habitat of listed stocks of salmonids. The nature and timing of future

changes in forest practice rules is of vital interest to all parties concerned with

management of forest resources in the West.

The forest practices associated with the NWFP and TLMP riparian and aquatic

management strategies that apply to federally managed forests in western Oregon

and Washington, and southeast Alaska, respectively, potentially address ecosystem

management at the watershed scale (FEMAT 1993, USDA Forest Service 1997).

These strategies addressed large temporal and spatial scales, used the best available

science to protect features and processes that maintain riparian and aquatic ecosystems, allowed managers to use watershed analysis to design strategies that address

the physical and biological features of individual watersheds, and took into account

both natural and human disturbances when designing management strategies. The

way in which managers actually used the strategies, however, ranged from sitespecific applications to full-scale watershed analyses. Because implementation of

these strategies has been underway for less than 5 years, full evaluation of their

effects has not been made.

Benefits and Costs of Forest Practice Rules Development

The decades-long evolution in forest practices resulted in substantial ecological

cost to riparian and aquatic ecosystems in the Pacific Northwest, Alaska, and in

the United States in general. The loss of large trees in riparian areas in the Pacific

Northwest is difficult to quantify, but Malanson (1993) estimated that about 70 percent of natural riparian communities have been lost as a result of human activities.

In western Oregon and Washington, most riparian areas are in an early succession

condition (<60 years old) (Carlson 1991). In southeast Alaska, commercial timber

was harvested from about 13 percent of the riparian zones in old-growth forests on

the Tongass National Forest between 1954 and 1995 (USDA Forest Service 1997).

The decades-long

evolution in forest

practices resulted in

substantial ecological cost to riparian

and aquatic ecosystems in the Pacific

Northwest, Alaska,

and in the United

States in general.
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General Technical Report PNW-GTR-692

There were several reasons for the delay in implementing forest practices for

protection and maintenance of riparian and aquatic ecosystems. The first was

“burden of proof” in establishing that forest practices damaged aquatic habitats

and fish production. Without scientific proof, the timber industry and timber managers were reluctant to respond to concerns that timber harvest was damaging fish

habitat in the Northwest. Second, little research had been completed on the effects

of forest practices on aquatic ecosystems when industrial forestry accelerated

following World War II. Because ecological research requires long timeframes

for scientifically sound results, credible evidence that timber harvest near streams

caused damage to aquatic habitats was not available until the early 1970s. The

Alsea Watershed Study in western Oregon (Moring and Lantz 1975) was one of

the first comprehensive studies of the effects of forest harvest on streams and fish

habitats, and the results of that work contributed to enactment of the Oregon Forest

Practices Act in 1972. In that act, and in subsequent acts in other states, an attempt

was made to develop a set of BMPs that did not interfere with timber production,

yet provided adequate protection for streams and fish habitats. Although that was a

worthy goal, 30 years later managers are still seeking strategies that will meet their

stated management goals and achieve the desired balance between timber harvest

and riparian and aquatic habitat protection.

A third reason was that evaluation of the effectiveness of forest practice rules

for aquatic ecosystem protection requires long-term monitoring. At least several

years, and realistically perhaps several decades, of implementation and monitoring

are needed to fully assess the effects that forest practice rules, or amendments to

the rules, have on the environment. Given the issues of burden of proof, the time

required for credible scientific research results, and the time required for monitoring and evaluating the effects of forest practices, it is little wonder that development of forest practice rules that could meet the goals of states and federal agencies

required decades.

The phases in development of forest practice rules followed a consistent pattern

across the Pacific Northwest and Alaska. Initial rule sets called “best management

practices” were negotiated between state agencies, tribes, the timber industry, and

other parties. When the rules were established or amended, the goal was to find the

minimum level of protection needed to maintain the productivity of riparian and

aquatic habitats. The resulting BMPs were the normative decisions of managers

who had examined the available biological, social, economic, and political information and attempted to balance the needs of all parties. After a few years of

implementation and feedback from anecdotal evidence, new research studies, and
77

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

ongoing monitoring and evaluation, the BMPs were deemed insufficient to meet the

management goals for riparian and aquatic habitat characteristics such as water

quality, streambank stability, and aquatic habitat structure, and with much debate

and contention, they were revised through another normative decisionmaking

process. The revised set of BMPs generally reduced timber harvest and provided

more protection for the ecological processes that form and maintain riparian and

aquatic habitats. After another period of implementation and evaluation, forest

managers and regulatory agencies concluded that the practices still did not meet

stated riparian management goals, and the process was repeated until the current

sets of rules evolved.

In retrospect, the term “best management practices” was a misnomer in terms

of providing protection sufficient to maintain the structure and functions of riparian

ecosystems, or meet the stated riparian management goals of the agencies that

formulated them. The BMPs were developed through the normative process that

weighed, evaluated, and incorporated many types of information. However, in

arriving at decisions, compromises were often made in social, political, economic,

and ecological goals for riparian management. The best available scientific information for protection of riparian and aquatic habitats was not always incorporated into forest practice rules. Consequently, between 1970 and 1990 while BMPs

were in effect, the quality of riparian and aquatic habitats on forested lands of the

Northwest declined (USDA and USDI 1995) (fig. 8). Results from studies in the

peer-reviewed literature suggest that past timber harvest practices negatively

affected fish (e.g., Hartman and Scrivener 1990, Reeves et al. 1993, Scrivener and

Brownlee 1989) and fish habitat (e.g., Hicks et al. 1991, McHenry et al. 1998,

Reeves et al. 1993, Spence et al. 1996) in the Pacific Northwest and southeast

Alaska. Studies found that salmonid species may respond positively to environmental changes at one life-history stage, but any gains can be lost or not realized

because of negative responses at a later time or subsequent life-history stage (e.g.,

Holtby 1988, Murphy et al. 1986). We are not aware of any examples in the peerreviewed literature where salmonid population or salmonid habitat responses to

intensive timber harvest activities were positive. Acknowledging the impacts of

forest management on riparian and aquatic habitats and understanding the reasons

for them provides the basis for identifying and developing new management

options.

Declining aquatic habitats on forested lands could be considered a cost of the

lengthy incremental development of forest practices, but the process also yielded

economic benefits. During this period (1970 to about 2000) more than 235 million

The term “best

management practices” was a misnomer in terms of

providing protection

sufficient to maintain the structure

and functions of

riparian ecosystems,

or meet the stated

riparian management goals of the

agencies that formulated them.
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General Technical Report PNW-GTR-692

m of timber was harvested from the national forests of the Pacific Northwest, and

the total harvest from both public and private lands in the region exceeded 590

million m . Much of the commercial timber in riparian zones within timber sales

was harvested during this period. The exact amount is unknown because tallies of

timber removed from riparian habitats were included with general harvest statistics.

The NWFP, PACFISH, and TLMP made the first substantive departures in the

way forest practice rules were formulated (fig. 8). These plans were unlike previous site-specific schemes for management of riparian and aquatic resources in two

ways. First, they addressed riparian management at the watershed scale with specific emphasis on maintaining ecosystem functions over the long term. Second,

they rejected both the previous philosophy of trying to define and achieve the

absolute minimum set of practices that would meet stated riparian management

goals and the concept that goals could be met by implementing yet another set of

BMPs. The new management philosophy under the NWFP represented a paradigm

shift in how managers view resource coordination. In previous riparian rule sets,

riparian and aquatic technical specialists shouldered the burden of proof for demonstrating resource damage from forestry activities and the need for more comprehensive forest practice rules to meet riparian management goals. Under the umbrella

of the NWFP, the burden of proof shifted. Forest managers who wanted to alter the

Figure 8—Theoretical chronological relationship between forest practice rules (BMPs) and riparian and

fish habitat quality in forested watersheds of the Pacific Northwest and Alaska. BMP = best management

practices, NWFP = Northwest Forest Plan, TLMP = Tongass Land Management Plan, PACFISH =

Interim strategies for managing anadromous fish-producing watersheds in eastern Oregon and Washington, Idaho, and portions of California.
79

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

comprehensive default prescriptions for riparian management under the NWFP

in order to pursue other management goals were required to demonstrate, through

watershed analysis, that the changes would not compromise established riparian

management goals. Additional concerns about rare and little-known organisms

also made managers reluctant to alter default prescriptions. These factors have contributed to the controversy surrounding concurrent management of timber, riparian,

and aquatic resources on federal lands in the Pacific Northwest.

With the comprehensive forest practices in the NWFP and TLMP and the provision within each strategy to use watershed analysis to tailor management plans to

the characteristics of individual watersheds, there is a reasonable probability that

ecosystem functions at large spatial scales will be maintained on Forest Service and

BLM lands over the long term. The legacy of past management activities, however,

will in some cases remain on the landscape for at least a century. One reason for

such a lag is that renewed recruitment of large woody debris in stream channels can

require a century or more following harvest of mature trees from riparian habitats

(FEMAT 1993).

Without full implementation and evaluation of the aquatic habitat conservation strategies in the NWFP and TLMP, and considering that the legacy of past land

management in the Pacific Northwest and southeast Alaska may persist for decades

or longer, is it possible to look ahead at future scenarios for riparian and aquatic

management, or is it too early to explore future options? Because the state of

scientific knowledge continues to advance, we believe it is now possible to explore

some additional science-based options for managers to consider.

Potential Options for Riparian Management

Strategies

Thirty years of development have produced the current strategies for forest management on private and public lands of the Northwest and southeast Alaska. From

the 1970s to the end of the 20th century, these strategies were shaped by policymakers who variously considered economics, social values, scientific knowledge,

and state and federal laws in their decision process. During the 1990s, new scientific findings, changing social values regarding forest management, and new and

existing state and federal laws, figured prominently in development of the NWFP

and TLMP, and in modification of state forest practice rules and management

strategies. These features will likely continue to dominate any future changes in

forest management on public forest lands of the Pacific Northwest and southeast

Alaska and on private and public forest lands within this area.

The legacy of past

management activities will in some

cases remain on

the landscape for

at least a century.
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General Technical Report PNW-GTR-692

The science underlying 1990s forest management strategies, like the NWFP

and TLMP, emphasized:

• The importance of considering landscapes at large temporal and spatial

scales, for example, watershed scales (Bolton and Monohan 2001, Hohler

et al. 2001).

• Understanding the natural variability and natural disturbance regimes that

shape and maintain the characteristics of particular landscapes (Cissel et al.

1998, 1999; Reeves et al. 1995).

• Understanding the interactions among upland, riparian, and aquatic ecosystems in forest lands (Benda et al. 1998, Reeves et al. 1995).

These scientific findings, largely from the 1990s, have provided a technical

base for development of new forest management strategies.

Changing social values in the 1990s were perhaps even more important in

shaping management strategies than new scientific information (Shindler and

Cramer 1999). Increasing populations in the Pacific Northwest have led to increased public desire for recreation from forest land and the maintenance of visual

aesthetics (Bliss 2000). These features, coupled with public desire to maintain the

viability of prominent terrestrial and aquatic species on public and private forest

lands (e.g., spotted owls and anadromous salmonids) (Lee et al. 1997, Thomas et

al. 1993, USDA and USDI 1994b), also strongly influenced development of forest

management strategies in the 1990s.

Finally, state and federal laws such as Oregon SB 1125 (revised stream protection rules), the Washington Salmon Recovery Act ESHB 22091, amendments to the

federal Clean Water Act, the Safe Drinking Water Act, the Coastal Zone Management Act, and the ESA, also helped shape private and public forest management

strategies in the 1990s. All of these features, science, social values, and law, will

continue to shape future forest management strategies. We will examine some of

these in more depth below, especially as they apply to public forest lands.

Temporal and Spatial Considerations

Before exploring alternatives to current schemes for management of riparian

habitats in the Pacific Northwest and southeast Alaska, it is critical to review some

spatial and temporal considerations for development of new management strategies.

First, the current focus on federally owned forested landscape by land management

agencies and regulatory agencies, although important and appropriate, is too

narrow because it only addresses forested portions of river basins. Most major river
81

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

basins in the Pacific Northwest are only partially forested and are subject to many

land uses besides industrial forestry. Many of the riparian and aquatic habitats in

flood plains of large low-gradient valleys, those that were formerly the most

productive portions of major watersheds for salmonids and other aquatic species,

have been highly altered by agriculture, urbanization, and hydropower installations.

Currently, aquatic habitats least affected by altered flows and disturbed riparian

zones are located in forest lands managed by the federal government. These habitats have also been altered and simplified by forest management, but continue to

produce salmonids at reduced levels. Although greater salmonid production, particularly coho and Chinook salmon, historically occurred in larger low-gradient

downstream waters (Burnett et al. 2003) that are now poor salmonid producers

because of dams, reservoirs, and agricultural activities (Clark et al. 1998), streams

on forested lands currently provide refuge habitats for remnant populations of

anadromous salmonids.

Management plans designed to maintain the integrity and functional characteristics of riparian and aquatic ecosystems and recover listed populations of salmonids, must consider all types of land uses at river basin scales, rather than depend

solely on current strategies that focus recovery efforts primarily on forested watersheds, especially those in public ownership. Burnett et al. (2003) developed a

process to identify portions of watersheds that have the highest potential to provide habitat for various species of anadromous salmonids. Their methods estimate

gradient, valley width, and mean annual flow for reaches of the stream networks

from digital elevation models (DEM) and provide species-specific formulas to

assess the suitability of the measured features.

Restoration of riparian and aquatic habitats on forested landscapes can contribute to stock recovery, but if done in isolation, it will not assure broad-scale recovery of listed salmonids. Recovery programs are at high risk of failure unless the

spatial scales of the efforts are expanded to include all ownerships and land uses in

river basins, and also address other factors that have affected listed fish (e.g., fish

passage and commercial and sport fish harvest).

Focus on Forested Lands

Assuming that, in the future, state and federal regulatory agencies responsible for

environmental quality and recovery of listed species equally address all land uses,

ownerships, fish harvest, and other factors affecting fish populations, how can forest landowners participate in a coordinated effort to reduce the risks their operations pose to riparian and aquatic ecosystems and still meet their stated management

Management plans

designed to maintain the integrity and

functional characteristics of riparian and

aquatic ecosystems

and recover listed

populations of

salmonids, must

consider all types

of land uses at river

basin scales, rather

than depend solely

on current strategies that focus

recovery efforts

primarily on forested

watersheds.
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General Technical Report PNW-GTR-692

goals? Management strategies based on ecological principles could help managers

achieve goals for timber production and riparian and aquatic resource protection.

The state of scientific knowledge has recently advanced with regard to the effects

of natural and human disturbances on forested landscapes at various scales, and

how to apply that knowledge to resource management strategies. In recognition of

this new information, it could be beneficial for management entities to re-examine

their (1) riparian management goals and practices, (2) scales at which the strategies

apply, (3) overall strategies, and (4) monitoring and evaluation plans to see if

efficiencies in forest resource use and protection can be achieved.

First, the goals for management of riparian and aquatic ecosystems on federal,

state, and private lands are generally similar, but the practices and guidelines for

achieving those goals have historically differed by management entity. The variability in practices and guidelines, which still exists among state and federal rules

for riparian management, can be related more to different management emphases

as defined by policymakers, than to different biological and physical landscape

features. Variable practices and guidelines, however, failed to meet the management

goals of states and federal agencies as evidenced by their frequent revision over the

past three decades.

State forest practices acts and rules for forestry operations on federal lands

often require application of site-specific inflexible rules and practices within and

among states and land ownerships. Even where flexibility is allowed through watershed analysis, managers often resort to uniform default prescriptions for a variety

of reasons. Use of ecological principles in developing forest practice rules, and

flexibility in their application, could enhance the probability of meeting riparian

and aquatic habitat management goals while still producing timber, recreation

opportunities, and other benefits from forests. For example, Berg (1995) demonstrated through modeling how active management of riparian zones could be

economically as well as ecologically beneficial. Watershed analysis under the

umbrella of the NWFP and TLMP has also shown that multiple benefits can be

achieved through management of riparian zones. Adherence to inflexible default

prescriptions, on the other hand, might preclude management options that would be

available based on watershed analysis.

The management of riparian zones along small streams, which are generally

defined as non-fish-bearing perennial and intermittent streams, is an emerging issue

for policy- and decisionmakers. These streams may compose up to 90 percent of

the stream network’s length (Everest and Harr 1982, Everest et al. 1985). New

It could be beneficial for management entities to

re-examine their

(1) riparian management goals and

practices, (2) scales

at which the strategies apply, (3) overall strategies, and

(4) monitoring and

evaluation plans to

see if efficiencies in

forest resource use

and protection can

be achieved.
83

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

aspects of their ecological role have recently been identified. For example, these

channels can be important sources of food and energy for juvenile fish (Wipfli and

Gregovich 2002). Small streams are also important sources of sediment and wood

that create and maintain habitat in fish-bearing streams. Almost half of the volume

of wood found in fish-bearing streams in a pristine coastal Oregon watershed

originated from small, steep tributary streams (Reeves et al. 2003). Sediment is

also stored in small streams, often as a result of wood accumulations. Stored

sediment is metered out to the fish-bearing streams over time (May 2001, May and

Gresswell 2003). The absence of wood results in these channels having bedrock

exposed for extended periods because sediments move rapidly down the channel

rather than being stored. The result is alteration of the sediment delivery regime

and a reduction in the complexity of habitat in fish-bearing streams. Small streams

are also the sites of habitat for several species of native amphibians (Bisson et al.

2002, Olson et al. 2000).

Consideration given to management of small streams varies widely by ownership and state. Riparian zones along small streams on federal lands receive more

extensive protection than those on state and private lands. Murphy (1995) reviewed

forest practice requirements for riparian zones in Pacific Northwest states and

Alaska. He concluded that buffers on small non-fish-bearing streams were often

inadequate for protection of water quality and that reliance on BMPs alone may

be inadequate to protect headwater areas.

The variation in the degree of connection between small streams and fishbearing streams provides options for managing riparian zones. In mountainous

stream systems, debris torrents deliver substantial amounts of wood and sediment

to fish-bearing streams from upslope areas (Reeves et al. 2003). However, the

potential for debris torrents that originate in small streams to reach fish-bearing

streams is highly variable. The primary features determining the degree of connection are the slope of the delivery stream and the angle at which it enters downstream waters (Benda and Cundy 1990). For example, see figure 9 for the location

of small tributary streams in the Knowles Creek watershed with the highest potential to deliver sediment and wood to fish-bearing streams. A digital elevation model

is available that can readily identify small streams that are potential contributors of

large wood. All such streams have been identified in the Oregon Coast Range as

part of the Coastal Landscape Analysis and Modeling Study. Specific riparian management goals for these streams could provide recruitment of large wood to downstream fish habitats. Commodity production could be emphasized in other parts of

The variation in the

degree of connection between small

streams and fishbearing streams

provides options for

managing riparian

zones.
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General Technical Report PNW-GTR-692

the network to the extent that the needs of wildlife, recreation, and other resources

are met by protecting the streams with the highest potential to deliver large wood to

fish-bearing streams.

The scale within which forest management practices are developed and implemented is the second critical issue that forest managers and regulators could

address to improve the prospects of attaining riparian and aquatic habitat management goals. Most early forest practice rules sought to define the minimum width

of buffer strips needed for aquatic habitat protection by examining the effects

of individual riparian functions on aquatic habitats at the site scale. Attempting to

quantify minimum buffer widths needed to maintain individual functions, however,

overlooked other important functions and left no margin for error resulting from

incomplete science or the unknown complexities of multiple functions operating in

concert. For example, some site-scale studies have indicated that (also see table 2):

• Most large woody debris recruited to stream channels enters from riparian

stands within 20 m of the channel (Martin et al. 1998, McDade et al. 1990,

Murphy and Koski 1989).

• Tree canopies within 30 m of small streams provide the preponderance of

shade to the water surface (Brazier and Brown 1973).

Figure 9—Location of small tributary streams in Knowles Creek watershed that are likely to deliver large

wood to streams via debris torrents.
85

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

• Most sediment traveling from hillslopes to streams is effectively retained

by buffers about 50 m wide (Ketcheson and Megahan 1996, Megahan and

Ketcheson 1996, U.S. Army Corps of Engineers 1991), although steep

hillslopes require greater widths for effective filtration (Lee et al. 1997).

• Brown bear feeding, loafing, and daybed areas in late-successional forests

extend up to 150 m from salmon streams (USDA Forest Service 1997).

The degree to which studies of this type apply off site, or can be extrapolated

to larger scales is sometimes unclear, but problems with such extrapolations have

been documented. For example, McDade et al. (1990) found that about 90 percent

of large woody debris came from within 20 m of the study stream. Their results,

however, were based only on pieces for which they could document the source,

thus excluding pieces transported into their study areas by high water or debris

flows, and are therefore incomplete. Other more recent and comprehensive studies

have shown very different results. For example, May and Gresswell (2003) have

shown that 63 percent of debris flows originating in headwater basins of the

Oregon Coast Range deliver wood directly to mainstem rivers. And, in a comprehensive study of wood recruitment in an Oregon coastal stream, Reeves et al.

(2003) found that about 65 percent of the pieces of wood in the channel were

delivered from upslope by landslides and debris flows and only 35 percent originated from streamside sources. Managers and policymakers need to carefully

consider the validity of the available science when developing landscape management plans and policies.

Data from site-scale studies, however, have often been used to define buffer

widths for private, state, or federal forest practices with uniform prescriptions for

fish-bearing streams and streams with important effects on downstream water

quality. Studies of this type, however, ignore watershed-scale ecological processes

and fail to consider:

• Cumulative effects of forest practices at watershed scales.

• The extensive legacy of past forest practices on riparian and aquatic

habitats.

• Holistic ecosystem-level functions of riparian areas that affect adjacent and

remote terrestrial and aquatic ecosystems and vary by watershed or

ecoregion.

In contrast, strategies currently in use on federal lands in the Northwest and

southeast Alaska and on state and private lands in Washington have the option to

use watershed- and provincial-scale scientific information in watershed analyses
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to pursue goals for riparian and aquatic habitat management. This leap in scale has

challenged managers and policymakers in other jurisdictions to consider riparian

and aquatic ecosystems at larger spatial scales, as opposed to the past focus on site,

and in some cases watershed scales. Addressing larger spatial scales is often viewed

simply as aggregating information from small scales for consideration at larger

scales. However, O’Neill et al. (1986) pointed out that aggregation results in false

and unattainable expectations for aquatic and riparian ecosystems, which in turn

contributes to the contention surrounding riparian issues.

Hierarchy theory provides an appropriate framework for considering ecosystem

issues at and between different spatial scales (Overton 1977). Each level within the

hierarchies of ecosystems has unique properties and behaviors that are expressed

over time. The properties of lower levels of organization are “averaged, filtered,

and smoothed” as they are aggregated at higher levels of organization (O’Neill et

al. 1986). Consequently, the range and variability in the properties and conditions

of systems are relatively wide at lower levels of organization as compared to higher

levels (Wimberly et al. 2000). For riparian ecosystems, the range of conditions seen

at the site scale might range from a recently disturbed site, where there are no or

only a few large trees, to a fully stocked site. The range at the watershed scale is

likely to be smaller, i.e., the likelihood that all riparian zones would have no or few

trees, or that all would be fully stocked with large trees, is small. The range of

variation in the condition of riparian zones over time at the landscape scale is even

smaller, implying that not all riparian zones within the landscape are likely to be in

“good” condition at any point in time nor are they likely to be “poor.”

Understanding the relation between different spatial scales is imperative to

developing successful future management policies and activities for riparian zones.

The initial focus on riparian zones was to manage for a desired set of conditions at

a specific site. The conditions were rather generic and applied to all riparian systems. Similar rules and regulations were adapted as the focus moved to the watershed. The failure to articulate or to recognize the consequences of doing so has

contributed to the often intense and divisive debate about riparian management

policies and practices. Shifting the focus to landscape levels will require recognition of the principles about hierarchy theory and the relation among levels of

organization if future riparian policies are to be successful.

One of the major tasks in focusing riparian policies and management at landscape scales will be to understand how the condition of riparian zones varies

through time at all spatial scales and the ecological, social, and economic implications of this variation. Currently, conditions of riparian ecosystems are expressed as

One of the major

tasks in focusing

riparian policies

and management

at landscape scales

will be to understand how the condition of riparian

zones varies

through time at all

spatial scales and

the ecological,

social, and economic implications

of this variation.
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Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

a single condition (either density of certain size trees or basal area). This condition

is expected (unrealistically) to be relatively constant through time and to be present

on all riparian zones at the same time. Assuming that this expectation can simply

be applied to higher spatial levels is at least partially responsible for the current

disenchantment with riparian management. Focus at the landscape scale, however,

will require an understanding of the dynamics of riparian systems over time at each

spatial scale. It will also require that appropriate goals and objectives be established

for the landscape. In the case of riparian zones, this will require identifying what is

the appropriate fraction of the riparian zones that should be in “good” condition at

any point in time. Also, it requires the articulation of policies that both recognize

the dynamic nature of riparian zones and describe practices that allow the systems

to express a range of desired conditions over time.

Third, there is emerging recognition that a comprehensive ecosystem approach

to forest management could help managers achieve riparian management goals.

As previously noted, we believe that forest practice rules applied from the 1970s

to the early 1990s failed to achieve their goals for riparian management because

they focused largely on defining minimum buffer widths for riparian protection

at site scales. The strategies recently applied to national forest and BLM lands

in western Oregon, Washington, and northwest California (NWFP), and to the

Tongass National Forest in southeast Alaska (TLMP), can use watershed analysis

to address ecosystem-level and watershed-scale processes that form and maintain

riparian and aquatic habitats. This approach is likely to enhance protection of

riparian ecosystems.

The basis for delineation of interim riparian zones in the NWFP, a less flexible

and potentially less preferred strategy, was derived from two sets of curves showing the relation between various ecological functions provided by riparian zones

and distance from the channel (figs. 3, 4). These curves were developed from the

scientific literature that was available at the time and on professional judgment

where sources of information were incomplete. The curves of ecological functions

also provide a margin for error allowing for incomplete science, unknown cumulative effects, or strategic uncertainty in defining interim riparian zones prior to

watershed analysis. We are unaware at this time of any evidence in the scientific

literature that supports modifying or retracting the original curves. The science

produced since then (i.e., 1993) has supported the original assumptions and judgments used in developing the FEMAT curves (e.g., Brosofske et al. 1997, Gomi et

al. 2002, Reeves et al. 2003).
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General Technical Report PNW-GTR-692

If provincial and watershed scales were universally employed in development

of riparian management strategies on and off forested landscapes, a rational unified

approach to management of riparian and aquatic ecosystems at the river basin scale

could be achieved.

A fourth issue that could help managers attain riparian and aquatic habitat

management goals is monitoring and evaluation of current forest practice rules.

As previously noted, forest practice rules currently in force in the Northwest and

Alaska have not as yet been fully evaluated. Although state and federal practices

for riparian management are variable, all share commonalities aimed at protection,

maintenance, and restoration of riparian and aquatic ecosystems. The effectiveness

of current strategies and practices in achieving their stated goals while allowing

utilization of timber or other resources, however, remains unknown. Large-scale,

long-term, coordinated interagency monitoring efforts could help to resolve this

issue. However, monitoring efforts of this scale are costly, have rarely been attempted, and even more rarely successfully completed. Some long-term monitoring

is in progress in southeast Alaska (Martin et al. 1998), Oregon (State of Oregon

1997), and in the Northwest (Reeves et al. 2004), but results are as yet incomplete.

Considerations for Future Riparian Management on Forest Lands

Is it prudent to suggest alternative strategies for riparian management at this time

given that current forest practice rules have not been fully evaluated? We believe

the answer is yes and that moving forward now could:

• Result in new strategies that better address multiple resource management

objectives at large spatial scales and timeframes.

• Facilitate concurrent monitoring and evaluation of several new and existing

riparian management strategies.

• Develop new long-term management scenarios based on natural disturbance

regimes that maintain the structure and function of riparian ecosystems

within historical norms at the large watershed scale.

• Result in silvicultural advances for rapid restoration of riparian vegetation

in the Pacific Northwest and parts of southeast Alaska that were historically

damaged or destroyed by human activities.

The next steps in management of riparian and aquatic habitats in forested

watersheds will build on recent advances in riparian management policies and

require an extension of current thinking. Many current forest management strategies rely on inflexible site-specific management prescriptions because of their

Forest practice

rules currently in

force in the Northwest and Alaska

have not as yet

been fully evaluated.
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Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

simplicity and ease of application at the field level. Most of these strategies allow

some harvest of standing timber in riparian zones within a tree-length of streams,

contributing to future loss of woody debris and channel structure. Even the NWFP

and TLMP have inflexible default interim prescriptions that managers often apply

in lieu of flexible custom watershed-scale designs that could be used.

Criteria for Next Steps

Short-term strategies could be developed within the context of watershed analysis

as described in the Washington forest practice rules, NWFP, and TLMP. However,

meeting riparian management goals at the large watershed scale is unlikely to

succeed unless:

• Management plans account for and address all land uses including agriculture, urbanization, and dams.

• All involved stakeholders are included in policy decisionmaking.

• The effects are intensively monitored at large temporal and spatial scales.

• Plans address the sites in specific watersheds where key ecological processes contribute to maintenance of the quality of riparian and aquatic

habitats.

• Plans account for the natural variations in watershed productivity at

regional scales.

Strategies that account for the dynamic nature of natural watershed processes,

the natural spatial and temporal fluctuations in the quality of riparian and aquatic

habitats within watersheds, and natural variations in the structure and function of

riparian ecosystems by ecoregion and geomorphic province could maintain and

restore the structure and function of riparian ecosystems. One element of these

strategies could emphasize silvicultural options for reducing the time required for

riparian coniferous regeneration to achieve sizes that contribute large woody debris

to stream channels. Focusing on these issues would strengthen future management

strategies.

The probability of forest managers meeting riparian management goals,

especially on state and private lands, could be enhanced by strategies that concurrently address two landscape conditions:

• Areas highly disturbed by human activities

• Areas largely undisturbed by human activities

Strategies that

account for the

dynamic nature of

natural watershed

processes, the

natural spatial and

temporal fluctuations in the quality

of riparian and

aquatic habitats

within watersheds,

and natural variations in the structure and function of

riparian ecosystems

by ecoregion and

geomorphic province could maintain

and restore the

structure and function of riparian

ecosystems.
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General Technical Report PNW-GTR-692

Two timeframes:

• Current timeframe (short term)

• A timeframe some decades in the future (long term)

And, two spatial scales:

• The watershed scale

• A regional scale

These features, if considered in concert, could help managers attain their goals

of sustained economical timber production from federal, state, and private forest

lands consistent with sound management of soil, air, water, fish, wildlife, recreation, and scenic resources. Application of these features could maintain and restore

the natural historical range of variability in riparian ecosystems but might result in

timber production reduced from current levels. Human disturbances and their

legacy are highly variable in watersheds across forested landscapes of the Pacific

Northwest and southeast Alaska. Some watersheds are highly disturbed by human

actions whereas others are not. Heavily disturbed watersheds may require different

strategies than watersheds whose riparian and aquatic ecosystems are undisturbed

or lightly disturbed by human activities and are well within historical norms of

structure and function. Attempting to apply rigid management prescriptions at the

watershed scale to these variable situations may not achieve desired riparian management goals.

Management strategies that consider both short and long timeframes enhance

the probability of achieving riparian management goals. In the Pacific Northwest

where the legacy of natural and human disturbances has altered habitats for numerous stocks of anadromous salmonids and other aquatic species listed as threatened

or endangered under ESA, options for riparian management need to be broadened

if recovery of stocks is to be achieved. In the near term (i.e., the next few decades),

we believe the management strategies used in the NWFP, PACFISH, and TLMP

that establish a landscape-scale network of habitat reserves, require watershed

restoration, and either prescribe an extensive array of riparian buffers or require

watershed analysis, could contribute to recovery of riparian and aquatic ecosystems.

Full recovery of riparian structure and function from these actions, however, may

require a century or more while riparian vegetation recovers sufficiently to again

contribute large woody structure and bank stability to aquatic systems. While longterm recovery is taking place, ESA listings of more salmonid stocks and other

aquatic species may occur, and additional extinctions are possible.
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Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Management of riparian and aquatic ecosystems could also be addressed in a

longer timeframe at the regional scale. The strategies used in the NWFP, PACFISH,

and TLMP aim to restore all riparian and aquatic habitats to a high level of productivity and maintain them at that level in perpetuity. The strategies, however, fail to

recognize the natural long-term dynamic processes of disturbance and renewal in

riparian and aquatic systems and to recognize that, historically at the regional scale,

productivity differed greatly among watersheds at any given point in time.

Management strategies recognizing the natural processes that degrade and

renew riparian and aquatic ecosystems could help managers maintain long-term

ecosystem productivity at the regional scale. Scientists are currently studying

and modeling the long-term history of landscape succession in the Northwest

(e.g., Benda et al. 1998, Boughton and Malvadkar 2002, Wimberly et al. 2000),

and managers are beginning to incorporate this knowledge into management

plans (Cissel et al. 1998). For example, as noted earlier, studies by Wimberly

et al. (2000), indicate that during the past 3,000 years, at the province scale, the

landscape of the Oregon Coast Range contained between 49 and 91 percent latesuccessional forest, and that the temporal and spatial distribution of late-successional forest stands varied with time across the region. Late-successional forests

in the Coast Range now total about 11 percent of the landscape, well outside the

historical range (fig. 6). One can assume that the productivity of riparian and

aquatic ecosystems varied accordingly, and that the most productive watersheds

for fishes also varied in time and space. To date, few management strategies

have attempted to emulate natural landscape conditions where the productivity of

watersheds and their riparian and aquatic habitats waxed and waned at large temporal and spatial scales. Long-term strategies that address riparian management at the

large watershed or regional scale, that recognize natural variations in watershed

productivity, and that plan to recover and maintain natural variability to assure

long-term productivity at the regional scale are the next challenging step for forest

managers.

Examples of Potential Riparian Management Strategies

Some good examples of ecologically based management strategies are emerging

within single land ownerships at small watershed scales in the geographic area

covered by the NWFP. Two examples from the Central Cascades Adaptive Management Area are worthy of note. Adaptive management areas were established for

Management strategies recognizing the

natural processes

that degrade and

renew riparian and

aquatic ecosystems

could help managers maintain longterm ecosystem

productivity at the

regional scale.
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General Technical Report PNW-GTR-692

testing assumptions and practices in the NWFP and for developing and evaluating

new management approaches. The two watersheds, Augusta Creek (7600 ha) and

Blue River (23 900 ha), are subwatersheds of the McKenzie River watershed,

tributary to the Willamette River in western Oregon. The plans for management

of riparian and aquatic ecosystems in the Augusta Creek and Blue River watersheds

(Cissel et al. 1998, 1999) are a significant departure from the inflexible default

strategies in the NWFP and represent an ecologically-based, post-watershedanalysis implementation of the NWFP. Both plans are based on landscape strategies

to sustain ecosystems with the goals of maintaining:

• Viable populations of native terrestrial and aquatic species.

• Ecosystem processes and structures.

• Long-term ecosystem productivity, including sustainable levels of timber

harvest.

Both plans were based on historical fire regimes, the primary natural disturbance in the watersheds, rather than on the default interim strategy of the NWFP.

Aquatic ecosystems and hillslope-to-stream disturbances were analyzed during the

first phase in development of the plans. Particular attention was given to the history

and potential of landslides and debris torrents and the susceptibility of certain areas

of the watersheds to peak flows resulting from rain-on-snow events. Subsequently,

reserves already designated under the Willamette National Forest Plan and the

NWFP were delineated. Then the planning areas were subdivided into zones with

similar ecological conditions and fire disturbance regimes, and management prescriptions were developed for each area. A network of aquatic reserves was then

established in harmony with upslope management plans and natural disturbance

processes. Aquatic reserves included riparian corridors along both sides of most

major streams to meet riparian goals and provide linkage to other small watershed

reserves located throughout the basins. In some cases, especially on small streams,

no riparian reserves were designated. In those areas, extended timber rotations of

200+ years were prescribed. This, in essence, provided functional riparian reserves

for about 140 years of each 200-year timber cycle for all small streams in those

designated areas.

When the land allocations and management prescriptions were completed, the

effects of the landscape plans were projected 200 years into the future with geographic information system models. After 100 years, the future landscape appeared

significantly different from the existing landscape, and additional gradual changes
93

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

continued until year 200. The landscape plans, in contrast to the pre-watershedanalysis default plan, resulted in:

• A less intense timber management regime with longer timber rotation age.

• Seventeen percent lower timber harvest but higher quality wood products,

and more economically feasible harvest.

• A small-watershed reserve system designed to meet multiple resource

objectives including maintenance of watershed processes and provision for

late-successional forest habitats.

• A less extensive riparian reserve network (buffers eliminated on many

streams in favor of long timber rotation ages) that allows for timber harvest

more in accord with the historical spatial and temporal fire regime, yet

meets aquatic and riparian objectives.

• Source management for large woody debris, sediment, and water quality to

assure continued delivery of those features to aquatic ecosystems.

• A landscape that more closely approximates, yet does not exactly mimic,

watersheds subjected only to natural disturbances.

The latter point is important. Management strategies cannot fully mimic natural

disturbance regimes at small watershed scales because the resulting human disturbances are superimposed on existing natural disturbance regimes. The combination

of natural and human disturbances may impose changes that push both structure

and function of riparian ecosystems beyond historical norms, or possibly change

structure but maintain function within historical norms. Long-term monitoring

will be needed to assess the outcome. Nevertheless, the landscape strategies for

Augusta Creek and Blue River watersheds come closer to emulating the natural

processes that form and maintain riparian and aquatic ecosystems than any of their

predecessors.

These two landscape plans were relatively easy to develop because they apply

to small single-owner forested subwatersheds on an experimental forest where

scientific energy has been focused for decades, and a large body of scientific

information was readily available. Also, the NWFP provided an approved mechanism, watershed analysis, for developing landscape management strategies to meet

NWFP goals. Broad application of landscape plans of this type, however, will be

difficult because most subwatersheds lack the scientific information needed for

their development. Although these plans are appropriate for their subwatersheds,

their scale is too small to address riparian issues at the river basin or regional scale.

The combination of

natural and human

disturbances may

impose changes that

push both structure

and function of

riparian ecosystems

beyond historical

norms, or possibly

change structure

but maintain function within historical

norms.
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General Technical Report PNW-GTR-692

Options for other disturbance-based strategies for riparian management have

been developed. Reeves et al. (1995) addressing the need for recovery of humandisturbed riparian and aquatic habitats in the Northwest, suggested that the shortterm and long-term ecological processes that create and maintain freshwater

habitats must be restored and protected. They assert that aquatic ecosystems

throughout the regions are dynamic in time and space, and lack of consideration

for their dynamic aspects has limited the effectiveness of habitat restoration programs. A new human-influenced disturbance regime that is analogous to historical

natural disturbance regimes could facilitate recovery and persistence of aquatic and

riparian habitats.

Reeves et al. (1995), using the Oregon Coast Range as an example, described

several features of the proposed disturbance regime. First, they indicated that

protecting riparian timber in source areas subject to mass erosion can accelerate

recruitment of large woody debris to channels and help maintain aquatic habitat

complexity in the long term. Second, they indicated that decreasing the frequency

of disturbance from timber harvest by extending timber rotation age to 150 to 200

years is more in tune with the time required for favorable habitats to form following infusions of sediment and woody debris from wildfires and storms. Finally,

they indicated that concentrating rather than dispersing management activities in

large watersheds would more closely resemble the pattern generated by natural

disturbances (fig. 10). Concentrating harvest activities in a single small subwatershed may create less disturbance and fragmentation of habitats than dispersing

the same amount of activity across the entire watershed. They also suggested that

concentrating activities could be linked to planning for future reserves as compensation for existing reserves that will ultimately cycle through nonproductive phases.

Contrary to the concept that concentrating rather than dispersing activities is

ecologically more similar to natural disturbances, most forest management activities in Northwest watersheds have been intentionally dispersed for decades. Dispersal was based on prior interpretations of scientific information that suggested

ecological systems could accommodate and rapidly recover from human disturbances that were widely dispersed in time and space. Consequently, few opportunities currently exist in the Pacific Northwest to test the effects of concentrated versus

dispersed human watershed disturbances. Testing this concept is technically feasible

in southeast Alaska where some watersheds remain largely untouched by human

activities. However, changes in forest practice rules might have to be made to allow

concentration of forest harvest in individual subwatersheds before this theory could

be evaluated.

Contrary to the

concept that concentrating rather

than dispersing

activities is ecologically more similar

to natural disturbances, most forest

management activities in Northwest

watersheds have

been intentionally

dispersed for

decades.
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Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

Development of landscape strategies at larger scales addressing multiple land

ownerships and a variety of land uses, especially where participants might not share

common goals, and where necessary scientific information may be lacking, can

greatly complicate the process. At larger scales, conflicts between user groups over

management of aquatic resources occur in nearly every river basin in the Pacific

Northwest. State and federal agencies have often been ineffective in solving the

broad array of riparian, aquatic, and water-related resource problems at this scale.

In some cases, however, coalitions of user groups have demonstrated their willingness and ability to work together to solve problems related to land management and

aquatic resources.

The Deschutes River Conservancy (DRC) provides a successful example of

a coalition that has effectively addressed difficult issues related to resource management at the river-basin scale in Oregon. The DRC, a 14-member coalition

representing all economic sectors in the basin, was formed in 1992 to address

water-related conflicts, including riparian and aquatic habitat management. The

conflicts revolve around rapidly increasing population; social values that no longer

fully support current uses of terrestrial and aquatic resources and impacts from

agriculture, ranching, and forest management; emerging interest in the region’s

recreation, tourism, residential, and industrial sectors; declining salmon runs;

Figure 10—Examples of patterns resulting from (A) dispersing and (B) concentrating management

activities in a watershed over time (from Reeves et al. 1995).
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General Technical Report PNW-GTR-692

mixed federal, state, tribal, and private land ownership; and the perception that

environmental quality in the basin is deteriorating (Big River News 1997).

The DRC developed an assessment of basin resources, incentive-based approaches to addressing resource problems, and pilot projects to improve efficiency

of agricultural water use in particular. Half of the water saved was dedicated to

maintenance of instream flows for recreation and recovery of endangered salmonid

species, and the remainder went to farming operations (Western Water Policy Review Advisory Commission 1998). The group also leased water to meet instream

flow needs. The DRC is now a formally chartered, private corporation with a board

composed of the basin’s cattle, agricultural, environmental, recreational, tribal,

hydropower, and land development interests and representatives from federal and

state agencies. Congress has recognized the value of DRC and appropriated $1

million per year of federal matching funds for DRC projects.

Basin advisory groups provide a forum and a context for addressing riparian

and aquatic habitat management at meaningful scales where advances in riparian

management on the forested landscape can be coordinated with similar efforts on

other land ownerships subjected to other land uses in river basins. Consequently,

basin advisory groups can be an important vehicle for restoration of riparian and

aquatic habitats and recovery of listed aquatic species in basins with mixed land

ownerships and land uses. Land use planning at even larger scales, however, may

be more effective than basin plans.

A province-scale research and planning effort, CLAMS, is under way in the

coastal zone of Oregon. The CLAMS effort includes research to provide an integrated view of current conditions in the province, and potential landscape trajectories and consequences from pursuing various land management strategies. The

project is precedent setting in several ways. First, it integrates ecological and

socioeconomic interests across a variety of land ownerships and land uses, and

addresses a key goal of recovering ESA-listed anadromous salmonid stocks through

protection and restoration of riparian and aquatic habitats (Perez 2001). The program uses techniques and tools including satellite imagery of vegetation, roads, fire

history, riparian forest condition, climate, geology, land ownership, and resource

allocation patterns to accomplish province-scale planning (Perez 2001). The extensive, multilayered database is being used to develop landscape models that

address cumulative effects of all land uses in long timeframes. A major strength

of the project is the use of integrated ecosystem-level research to help policymakers formulate management direction. Although the CLAMS project has not yet
97

Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

reached maturity, it has already demonstrated the usefulness of long-term integrated

province-scale planning. Such efforts may be considered the harbinger of future

ecosystem-level multiownership land use planning efforts.

We believe that continued movement toward science-based large-scale ecosystem-level management policies in which all concerned stakeholders are included in

policy formulation is a promising direction for riparian management. The current

state of scientific information on riparian ecosystems and disturbance ecology

indicates that such large-scale efforts have a better chance of achieving riparian

management goals than any previous management schemes. In reality, however, the

future direction of riparian management will be determined, not by science, but by

the normative decisions of policymakers who attempt to achieve a balance between

ecosystem sustainability and the competing demands of resource users.

Conclusions

• The natural functions of riparian ecosystems are critically important to the

maintenance of watershed hydrology, streamflows, water quality, stream

nutrients, and habitat characteristics needed to maintain the viability of

native aquatic species.

• An unusually rich assemblage of species uses riparian zones as compared to

other ecosystems.

• Current natural disturbance regimes may be different than those of preEuropean settlement (e.g., reduced frequency of stand-replacement fires).

• Human activities, including agriculture, urbanization, water developments,

and forestry, have altered the structure and function of riparian ecosystems

and their associated aquatic habitats over most of the landscape of the

Pacific Northwest and a small portion of southeast Alaska.

• The structural characteristics of some riparian habitats in the Pacific

Northwest are currently outside their natural historical range.

• Altered riparian ecosystems have contributed to changes in aquatic habitats,

populations of aquatic species, and the listing of many aquatic species and

fish stocks in the Pacific Northwest as threatened or endangered.

• Available evidence indicates that healthy riparian ecosystems and land

management for resource production are not mutually exclusive; however,

normative policy decisions can favor one outcome over the other.

• Improved riparian protection and restoration on forested lands is occurring,

but recovery of altered habitats and listed species can only be accomplished

by addressing all land uses at the river-basin scale.

Continued movement toward

science-based

large-scale

ecosystem-level

management policies in which all

concerned stakeholders are included

in policy formulation

is a promising direction for riparian

management.
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General Technical Report PNW-GTR-692

• Current forest management strategies may not fully recognize or take

advantage of known spatial and temporal variations in ecosystems.

• Despite more than half a century of timber harvest that has simplified

riparian and aquatic habitats on forested landscapes in the Northwest, the

highest water quality and best remaining fish habitats in the region are

located on federal forest lands.

• Forest practice rules of the 1970s, 1980s, and early 1990s, collectively

known as “best management practices” provided progressively more

protection for riparian and aquatic habitats during the period, but nevertheless allowed harvest of more than 590 million m of timber with practices

that we now see did not meet the stated goals of state and federal agencies.

• Current riparian management strategies in the NWFP and TLMP in southeast Alaska provide opportunities to achieve riparian ecosystem management at the watershed scale on federal forested lands.

• There is no scientific evidence that either the default prescriptions or the

options for watershed analysis in the NWFP and TLMP provide more

protection than necessary to meet stated riparian management goals.

• The current strategies for riparian management on private, state, and

federal lands have not been fully evaluated for effectiveness.

• Additional alternative riparian management strategies could be implemented and evaluated in concert to shorten the time needed to realize

effective strategies that fully meet riparian mangement goals.

• Emerging and future strategies for riparian management that are sciencebased, consider natural processes, and address large temporal and spatial

scales in an interagency forum that includes all involved stakeholders

appear to hold promise for the future.
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Riparian and Aquatic Habitats of the Pacific Northwest and Southeast Alaska

English Equivalents

When you know: Multiply by: To find:

Hectares (ha) 2.47 Acres

Cubic meters (m3

) 35.3 Cubic feet

Meters (m) 3.28 Feet

Kilometers (km) .6214 Miles

Square meters (m2) 10.76 Square feet

Square kilometers (km2) .386 Square miles

Centimeters (cm) .394 Inches

Cubic meters per second (m3/s) 35.3 Cubic feet per second

Square meters per hectare (m2/ha) 4.37 Square feet per acre

Kilometers per square kilometer (km/km2) 1.61 Miles per square mile

Literature Cited

Aber, J.; Neilson, R.; McNulty, S. [et al.]. 2001. Forest processes and global

environmental change: predicting the effects of individual and multiple

stressors. BioScience. 51(9): 735-751.

Adams, P.W.; Stack, W.R. 1989. Streamwater quality after logging in southwest

Oregon. Corvallis, OR: Oregon State University. 19 p. Project completion

report (PNW 87-400) to USDA Forest Service, Pacific Northwest Research

Station, Portland, Oregon.

Agee, J.K. 1991. Fire history along an elevational gradient in the Siskiyou

Mountains, Oregon. Northwest Science. 65(4): 188-190.

Agee, J.K. 1993. Fire ecology of Pacific Northwest forests. Washington DC: Island

Press. 493 p.

Alaska Department of Natural Resources [Alaska DNR]. 2000. Fact sheet: land

ownership in Alaska. Anchorage, AK: Division of Mining, Land, and Water.

http://www.dnr.state.ak.us/mlw/factsht/land_own.pdf. (12 May 2005).

Alaska Division of Forestry. 2001. Forest practices. http://www.dnr.state.ak.us/

forestry/forestpractices.htm. (4 April 2005).

Alig, R.; Butler, B.J.; Swenson, J. 2000. Fragmentation and national trends in

private forest lands: preliminary findings from the 2000 Renewable Resource

Planning Act assessment. In: DeCoster, Lester A.; Sampson, N., eds. Proceedings, fragmentation 2000—a conference on sustaining private forests

in the 21st century. Alexandria, VA: Sampson Group, Inc.: [Pages unknown].
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