U.S. ENVIRONMENTAL PROTECTION AGENCY 

REGION9 

REDWOOD CREEK 

SEDIMENT 

TOTAL MAXIMUM DAILY LOAD 

APPROVED BY: 

Alexis Strauss 

Acting Director 

Water Division 

EPA Region IX 

December 1998 

.,iy~Jl8 

Date 
TABLE OF CONTENTS 

Section 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Section 2. TMDL Summary ................................................. 3 

Section 3. Supporting Documentation ......................................... 9 

Section 3.1. Problem Statement ......................................... 10 

Section 3.2. 

Section 3.3. 

Section 3.4. 

Section 3.5. 

Section 3.6. 

Section 3.7. 

Section 3.8. 

Numeric Targets ........................................... 20 

Source Analysis ........................................... 39 

Loading Capacity Linkage Analysis .......................... 49 

Total Maximum Daily Loads, and Allocations .................. 52 

Margin of Safety ........................................... 56 

Seasonal Variations ........................................ 59 

Critical Conditions .............. : .......................... 59 

Section 4. Public Participation .............................................. 60 

Section 5. Implementation and Monitoring Recommendations ................... 60 

Section 6. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 

Section 7. References ...................................................... 68 

Sediment lMDL for Redwood Creek, CA 
Section 1. Introduction 

What Is A TMDL? 

Section 303(d)(1)(A) ofthe Clean Water Act (CWA) requires that "Each State shall identify 

those waters within its boundaries for which the effluent limitations ... are not stringent enough to 

implement any water quality standard applicable to such waters." The CWA also requires states to 

establish a priority ranking for waters on the 303(d) list of impaired waters and establish Total 

Maximum Daily Loads (TMDLs) for such waters. As part of California's 1996 and 1998 303(d) list 

submittals, the North Coast Regional Water Quality Control Board (RWQCB) identified Redwood 

Creek as water quality limited due to clean sediment loading and designated the watershed as a high 

priority for TMDL development. The RWQCB began work on the sediment TMDL in 1997, and 

EPA and tl;le RWQCB worked together to complete the sediment TMDL in 1998. 

The elements of a TMDL are described in 40 CFR 130.2 and 130.7 and Section 303( d) of the 

CWA, aS well as in EPA guidance documents (e.g., EPA, 1991 ). A TMDL is defined as "the sum of 

the individual waste load allocations for point sources and load allocations for nonpoint sources and 

natural background" (40 CFR 130.2) such that the capacity of the waterbody to assimilate pollutant 

loadings (the Loading Capacity) is not exceeded. A TMDL is also required to be developed with 

seasonal variations and include a margin of safety to address uncertainty in the analysis. In addition, 

pursuant to the regulations at 40 CFR 130.6, states must develop water quality management plans 

which incorporate approved TMDLs and implementation measures necessary to implement the 

TMDLs. 

Upon establishment ofTMDLs by EPA or the State, the State is required to incorporate the 

TMDLs along with appropriate implementation measures into the State Water Quality Management 

Plan (40 CFR 130.6(c)(1), 130.7). The Regional Board Basin Plan, and applicable state-wide plans, 

serve as the State Water Quality Management Plan governing the Redwood Creek watershed. If the 

State subsequently adopts and submits for EPA approval TMDLs which are different from the 

TMDLs established by EPA, EPA will review the State-submitted TMDLs to determine if they meet 

all TMDL requirements. If EPA approves the State TMDLs, EPA expects the State-established 

TMDLs would be applicable for the Redwood Creek watershed. 

Why Is EPA Establishing These IMDLs? 

The Environmental Protection Agency (EPA) has oversight authority for the 303( d) program 

and is required to review and either approve or disapprove the TMDLs submitted by states. If the 

EPA disapproves a TMDL submitted by a state, the EPA is required to establish a TMDL for that 

waterbody. 

On October 31, 1997, EPA entered into a consent decree (decree), Pacific Coast Federation 

of Fishermen's Association. et. aL v. Marcus, (N.D. CaL No. 95-4474 MHP), which established a 

timetable for development of TMDLs for several watersheds in northwest California, including 

Redwood Creek. The decree required development oftwo TMDLs by December 31, 1998. Pursuant 

to the decree, EPA developed a Supplemental TMDL Establishment Schedule which set December 

31, 1998 as the deadline for the establishment of a sediment TMDL for Redwood Creek. 

Sediment TMDL for Redwood Creek, CA 1 
The R WQCB has drafted a TMDL for clean sediment for Redwood Creek, but has not taken 

final action to adopt it. Before the TMDL can be submitted to EPA for approval, the RWQCB and 

State Water Resources Control Board must adopt the TMDL, and the State Office of Administrative 

Law must concur on the TMDL. Because the State has not completed and submitted the Redwood 

Creek TMDL, EPA is now establishing the Redwood Creek TMDL for sediment, along with a 

sediment TMDL for South Fork Trinity River, in order to meet the requirements of the decree. 

TMDL Organization and Comparison With State TMDLs 

This TMDL report is organized in the following sections which provide the analytical basis 

for the TMDLs: 

- Problem Statement 

-Numeric Targets 

- Source Analysis 

- Loading Capacity Linkage Analysis 

- TMDLs and Allocations 

- Margin of Safety 

- Seasonal Variations 

- Critical Conditions 

- Public Participation 

In addition, the report discusses TMDL implementation and follow-up monitoring needs. 

The TMDL proposed in this document very similar to the TMDL public noticed by the 

RWQCB on November 10, 1998. The organization of the EPA report follows the format used in 

EPA Region 9-established TMDLs. The RWQCB's draft TMDL format is designed to meet the 

needs of the Basin Planning administrative procedures and to focus more on specific implementation 

provisions. Therefore the formats of the State and EPA TMDL documents are somewhat different. 

This final TMDL is based on a draft TMDL proposed by EPA on October 19, 1998. Changes 

were made in the final TMDL to address comments received from the public through written 

comments and oral testimony at a public hearing held November 19, 1998. The final TMDL 

incorporates changes in the following areas: 

- clarification of instream numeric targets 

- addition of hillslope numeric targets 

-minor clarifications of the source analysis, linkage analysis, TMDL, and allocations 

- restructuring of the margin of safety discussion, and 

- additional detail in the implementation and monitoring recommendations. 

2 
Section 2. TMDL Summary 

The Redwood Creek TMDL is being established at levels sufficient to result in attainment of 

applicable water quality standards for clean sediment, including designated beneficial uses and 

narrative water quality objectives. The TMDL is virtually identical to the draft sediment TMDL 

developed by the RWQCB in July, 1998 and is very similar to the. TMDL public noticed by the 

RWQCB in November, 1998. 

Redwood Creek watershed is a forested watershed located north of Eureka in northwestern 

California. The purpose of the Redwood Creek TMDL is to identify total allowable loads and 

loading allocations that, when implemented, are expected to result in attainment of applicable water 

quality standards for sediment. 

Redwood Creek watershed was listed on California's Clean Water Act (CWA) Section 

303(d) list beginning in 1992 as water quality limited due to sedimentation. The level of 

sedimentation in Redwood Creek watershed was judged to exceed the existing narrative water 

quality objectives (WQO) ne~essary to protect beneficial uses of the basin, particularly the cold 

water fishery. Accelerated erosion from land use practices and other causes is impacting the 

migration, spawning, reproduction, and early development of cold water anadromous fish such as 

coho salmon, chinook salmon, and steelhead trout. 

The TMDL includes a problem assessment, which includes an assessment of existing 

instream and hillslope conditions; instream numeric targets, which interpret and are consistent with 

the narrative water quality standards and also represent the instream conditions for cold water fish 

where sediment is not a limiting factor, an assessment of significant sediment sources that have in 

the past or are presently impacting the stream system; an estimate of the loading capacity of the 

system for sediment discharges (and associated reductions) necessary to attain the numeric targets; 

allocations of loads among different sediment source categories; and several other sections designed 

to address considerations set forth in Section 303(d) of the Clean Water Act and U.S. EPA's 

guidance and implementing regulations at 40 CFR 130.7. 

The TMDL is based on existing, readily available information concerning Redwood Creek 

watershed conditions and land management plans and other watersheds in the Pacific Northwest, 

along with TMDLs previously developed by the State and U.S. EPA. Detailed explanations of the 

basis for the calculations are provided in the report, and further background information can be 

found in the Redwood Creek Watershed Analysis (Redwood National and State Parks, hereinafter 

referred to as RNP, 1997). 

Problem Statement 

Anadromous fish populations in Redwood Creek have diminished substantially over the past 

40 years (RNP, 1997). Reliable data about historical fish populations in Redwood Creek are lacking. 

In 1965, the California Department ofFish and Game roughly estimated spawning escapement of 

5000 chinook, 2000 coho, and 10,000 winter steelhead. Although channel deepening and pool 

development may have begun to increase in all but the lower few miles of Redwood Creek, the 

mainstem generally lacks an adequate pool-riffle structure and cover. Coarse sediment deposited in 

3 
the mainstem allows a large proportion of summer base flows to infiltrate and flow subsurface, 

thereby limiting the surface water available to fish and increasing surface water temperatures. Large 

deltas in some tributaries block tributary mouths and prevent migration of fish. A lack of suitable 

rearing habitat in the mainstem and tributaries has forced juvenile fish to the estuary, where they are 

subject to the impacts of sudden, extreme changes in salinity resulting from breaching of the sand 

bar by ocean waves and currents. Spawning habitat is improving slowly as gravels are cleaned of 

fine sediment. Key changes in the mainstem of Redwood Creek include (1) increases in the volume 

of stored sediment, (2) decreases in pool numbers and depth, (3) increases in stream width and 

decreases in stream depth, (4) reduced recruitment of large woody debris, (5) deposition of high 

levels of fine sediments on the stream bottom, and (6) reduced volumes of large woody debris. 

Redwood Creek is particularly prone to storm-induced erosional events, and would probably 

experience extensive erosion under natural conditions. However, land management activities have 

accelerated this natural process, overwhelming the stream channel's ability to efficiently move the 

delivered sediment. Land management patterns and practices have contributed to increased erosion 

beyond natural rates through mass wasting (landsliding) and fluvial erosion (gullying and stream 

bank erosion). The resultant erosion caused sediment to enter the stream, filling deep pools and 

depositing silt in spawning gravels. Past studies indicate that streamside landsliding and fluvial 

hillslope erosion may be the most important processes delivering sediment to Redwood Creek. A 

large proportion of observed erosion is associated with an extensive road network (7.3 milmF) on 

private lands, improperly designed and maintained roads and skid trails, and timber harvesting. 

Numeric Targets 

Numeric targets were derived from the literature, available monitoring data for the watershed, 

recommendations of agencies commenting on the TMDL, and best professional judgment. The 

numeric targets are intended to be consistent with the narrative water quality standards in the Basin 

Plan and focus on the elimination of sediment as a limiting factor for salmonids. As such, they are 

an expression of desired future conditions. The TMDL contains numeric targets for instream 

channel indicators and for hillslope indicators which are associated with stable watersheds capable of 

supporting healthy salmonid habitat. The numeric targets are included in Table 1 a and 1 b, pp. 5-6. 

Source Analysis 

Ten categories of sediment delivery were identified for the Redwood Creek watershed (Table 

2), eight of which are to some extent controllable: 1) erosion associated with roads, skid trails and 

landings; 2) gully erosion; 3) bare ground erosion associated with human activities; 4) stream bank 

erosion associated with human activities; 5) tributary landslides (road related); 6) tributary landslides 

(harvest related); 7) mainstem landslides (while many are natural, the delivery of sediment may be 

controllable to varying degrees); and 8) debris torrents. Controllable discharges or depositions are 

those discharges or depositions resulting from human activities that can influence water quality that 

can be reasonably controlled. The rates of delivery were estimated for those sources as well as 

sources deemed non-controllable using sediment source information from Redwood National Park. 

It was estimated that on average, about 4 750 tons per square mile per year are produced from the 

Redwood Creek watershed, about 60% of which is controllable (see Table 2, p. 7). 

4 
Table la. Instream Numeric Targets for the Redwood Creek Watershed. 

Parameter Numeric Targets (Desired Conditions) 

Percent fines <0.85 mm in riffle crests of <14% 

fish-bearing streams2 

Percent fines <6.5 mm in riffle crests of fish- <30% 

bearing streams 

Percent of Stream Length in Riffles3 < 25-30% of stream reaches in riffles (reach 

gradient < 2%) 

Pool depth in mainstem Redwood Creek the mean depth of pools at low flow exceeds 

reaches with pool-riffle morphology 2m 

Depths of pools in 3rd and 4th order the mean depth of pools at low flow exceeds 

tributaries with pool-riffle morphology4 1-1.5 m 

Median particle size diameter ( d50) from riffle 2: 37 mm (minimum for a reach ) 

crest surfaces 2:69 mm (mean for a reach) 

Percent fines < 2 mm at riffle crest surfaces <10-20% 

in fish-bearing streams 

Large Woody Debris in any watercourse Improving trend towards increased large 

capable of transporting sediment to a higher woody debris 

order watercourse 

1 Targets should be evaluated as ten year rolling annual averages to avoid premature assessment of trends 

based on inadequate information. This approach addresses the variations in sediment loading and instream 

indicators which are characteristic of Redwood Creek and which may not indicate management related 

effects. · 2 Fish-Bearing Streams: Fish present seasonally or year-round, or having fish habitat capable of supporting 

fish. Fish habitat is the aquatic environment and the immediately surrounding terrestrial environment that, 

combined, afford the necessary biological and physical support systems required by fish species during 

various life history stages. Generally, these streams have gradients less than 3%. 

3 Riffle- low gradient: shallow stream channel areas with swiftly flowing turbulent water with some partially 

exposed substrate. Gradient< 4 %, substrate is usually cobble dominated. The gradient is the general 

slope, or rate of change in vertical elevation per unit of horizontal distance, of the water surface of a 

flowing stream; or the rate of change of any characteristic per unit of length. 

4 Stream order is the designation of the relative position of stream segments in the drainage basin network. 

For example, a first order stream is the smallest, unbranched, tributary which terminates at the upper point. 

A second order stream is formed when two first order streams join. 

5 
Table lb· . Hillslope Numeric Targets for the Redwood Creek Watershed . 

Parameter Numeric Targets (Desired Conditions) 

Road stream crossings with No crossings have diversion potential (i.e., all crossings are 

diversion potential reconfigured permanently to assure that no diversion will occur). 

Road culvert/crossing sizing All culverts and crossings are sized to pass the 50 year flood and 

associated sediment and debris. In addition, crossings and culverts 

in the snow zone (generally, upstream of Highway 299, are sized 

large enough to accommodate flows and associated sediment and 

debris caused by precipitation and snow melt runoff. 

Landing and road fill stability All landings and road fills (e.g., sidecasts) on slopes >50% and which 

could potentially deliver sediment to a water course are pulled back 

and stabilized. 

Road surfacing and drainage All roads have surfacing and drainage facilities or structures which are 

appropriate to their patterns and intensity of use. 

Road inspection, maintenance, All roads are inspected and maintained annually or decommissioned. 

and decommissioning Decommissioned roads (roads which are closed, abandoned, or 

obliterated) are hydrologically maintenance free. 1 

Road location in inner gorge or Roads are not located in steep inner gorge or unstable headwall areas 

unstable headwall areas except where alternative road locations are unavailable.2 

Use of clearcut and/or tractor Clearcut and/or tractor yarding harvest methods are not used in steep 

yarding timber harvest inner gorge, unstable, or streamside areas unless a detailed 

methods geological assessment is performed which shows there is no 

potential for increased sediment delivery to water courses as a result 

of using these methods. 3 

1 Hydrologically mamtenance free means that: 

- drainage in the road area mimics natural hydrology, 

- all drainage is dispersed to the slope through use, as appropriate, of outs loping or cross-road drains, 

- all culverts and associated fill material is removed from crossing areas, 

-all potentially unstable road fill and landing sidecasts are pulled back, and 

- excavated spoils are placed in locations where they will not enter a water course. 

2 This target is intended to address roads located adjacent to water courses with inner gorge topography or 

which cross steep, unstable headwall areas, and is not intended to apply to road crossings of inner gorge 

areas. Steep inner gorge areas generally exceed 65% in slope and are located adjacent to class 1 and 2 

water courses.· Characteristics of steep unstable headwall areas generally include the following: 

- slopes greater than 50%, 

- erosive or incompetent soil types or underlying geology, 

- concave slope shape, 

- convergent groundwater present, and/or 

- evidence of past movement is present. 

3 Characteristics of steep inner gorge, unstable, or streamside areas generally include the following: 

- slopes greater than 50%, 

-located within 300 feet of a Class 1, 2, or 3 watercpurse, 

- erosive or incompetent soil types or underlying geology, 

- concave slope shape, 

- convergent groundwater present, and/or 

- evidence of past movement is present. 

6 
Table 2. Summary of Source Loading Estimates, Loading Capacity, and TMDL Allocations 

for the Redwood Creek watershed. 

Historic Percent Controllable Remaining 

Source Mechanism Sediment Controllable2 Load3 Load 

Load1 ( t/sq.mi./yr) (Allocation)4 

( t/sq.mi./yr) (t/sq.mi./yr) 

Roads, Landings and 690 85% 586 104 

Skid Trails erosion 

Gully Erosion 1020 85% 870 150 

( -90% road related) 

Bare GroUJ.id Erosion 400 85% 340 60 

Stream Bank Erosion 590 35% 210 380 

Tributary Landslides: 210 0% 0 210 

Naturally Occurring 

Tributary Landslides: 360 80% 290 70 

Road Related 

Tributary Landslides: 390 50% 190 200 

Harvest Related 

Mainstem Landslides 810 40% 320 490 

(Human Induced and 

Naturally Occurring) 5 

Debris Torrents 100 50% 50 50 

Other Mass 180 0% 0 180 

Movements (Naturally 

Occurring): 

- earthflows 

- block slides 

Totals 4750 60%6 2850 1900 

1 The estimated historic sediment load for each source. 

2 The percent of that historic load that is estimated as controllable. Controllable discharges are those 

discharges resulting from human activities that can influence the quality of the waters of the State and that 

can be reasonably controlled. 

3 The load that is estimated as controllable (the percent controllable multiplied by the historic load). 4 The difference between the historic load estimate and the controllable load estimate. This is the estimated 

load at which salmonids in the Redwood Creek watershed would no longer be limited by sediment. 

5 Study of 5 86 mainstem landslides revealed that approximately 50 % of the slides had one or more 

associated roads (Kelsey, et. aL, 1981) The volume of each slide may be variable but may represent an 

average 50 percent ofthe total load. ofmainstem landslides. 

6 Calculated Controllable Load (2850tlsq.mi./yr.) is 60% of Estimated Historic load (4750tlsq.mi./yr.). 

Reducing 4750tlsq.mi./yr. by sixty percent leaves a remainder of 1900tlsq.mi./yr. 

7 
Loading Capacity, Total Maximum Daily Loads. and Load Allocations 

After considering the quantitative comparison of estimated loading rates and controllable 

portions of various types of loading, and the qualitative comparison of instream indicators with 

existing conditions, EPA estimates that a 60% reduction in total sediment loading from historical 

loading rates is needed in the Redwood Creek watershed as a whole to meet the instream targets. 

The estimated total allowable sediment load (the TMDL) is estimated to be approximately 1900 

tons per square mile per year. This number was derived from estimated average annual sediment 

loads for the period 1954 -1997 for three reference watersheds within the Redwood Creek basin. 

There are no point sources of discharge to Redwood Creek; therefore, there are no 

wasteload allocations established through this TMDL. The Redwood Creek load allocations: 1) 

were developed for erosion processes; 2) are associated with land use activities where feasible; and 

3) are based on: the source analysis of the various erosional processes. The load allocations were 

developed as long term annual average loads per square mile at the watershed scale and appear in 

Table 2, p. 7. 

Margin of Safety. Seasonal Variations. and Critical Conditions 

In every one of the components used to develop the TMDL, assumptions were made where 

sufficient data were lacking. Conservative assumptions were made in each case as a way of 

addressing uncertainty associated with the data; this constitutes an implicit margin of safety. 

In Redwood Creek, there is inherent annual and seasonal variation in the delivery of 

sediment to stream systems and in the impacts sediment has on aquatic species during different life 

stages. However, sediment impacts often occur for periods long after the sediment loading to the 

stream, and in locations far removed from the loading site. For this TMDL, it was technically 

infeasible to vary the TMDL to account for temporal and spatial variations in sediment loadings 

and impacts. Instead, the TMDL is designed to account for long term erosion patterns and 

instream impacts associated with sediment in Redwood Creek by using longer time frames for 

implementation and evaluation. Furthermore, allocations are designed to apply to the sources of 

sediment, themselves, not the movement of sediment across the landscape or delivery of sediment 

directly to the stream channel. The TMDL and associated allocations are set at levels which 

reduce sediment loading to the point that creek habitat structure is able to recover and support the 

beneficial uses of concern. 

Implementation and Monitoring Recommendations 

Although they are not required components of federally-established TMDLs, this TMDL 

document includes implementation and monitoring recommendations to assist the State and 

watershed stakeholders in implementing the TMDL and conducting followup monitoring and 

review in the future. EPA strongly supports the RWQCB's draft TMDL implementation plan 

contained in the November 10, 1998 draft Water Quality Attainment Strategy for Redwood Creek. 

EPA also supports the State's commitment to work with landowners, agencies, and other 

stakeholders to develop a specific monitoring plan. In this document, EPA is recommending 

several specific provisions which would strengthen the implementation and monitoring provisions 

proposed by the State. 

8 
Section 3. Supporting Documentation 

A Note On Methods Used To Establish the TMDL 

Redwood Creekhas been extensively studied by many researchers for over 30 years. As a 

result, substantial information and data concerning erosion causes, trends, and impacts has been 

developed for the basin, particularly by scientists associated with Redwood National and State 

Parks (RNP). The Redwood Creek TMDL is based on this existing body of analysis, as 

supplemented by the expert judgment offered by several researchers at RNP and by additional 

analysis conducted by EPA. 

EPA recognizes that erosion processes which are responsible for sediment inputs to the 

system are highly dynamic and variable from year to year and in different locations in the basin. 

The main driving factor influencing variation in erosion and sediment inputs from year to year is 

variability in precipitation and, particularly, periodic high magnitude storms. Ideally, the TMDL 

and associated allocations could be expressed in dynamic terms as a function of the driving forces 

which determine the extent of erosion events (e.g., runoff intensity, topography, geology) and their 

impacts on receiving waters (e.g., proximity to water courses, stream morphology, and habitat 

distribution). However, it was infeasible to develop a dynamic predictive model of future erosion 

amounts, timing, and locations and the impacts of sediment delivery on the waterbody reaches 

most important for aquatic habitat based on existing information and scientific knowledge. 

This TMDL analysis was based primarily on historical data concerning sediment loading, 

stream flows, and stream responses to erosional impacts, along with information on instream and 

hillslope conditions which in other locations were associated with well-functioning watersheds and 

aquatic ecosystems. It is difficult to predict future erosion and associated impacts based on past 

erosion patterns and on aquatic habitat conditions studied elsewhere. However, this TMDL does 

account for the important issues of temporal and spatial variability in erosion and stream responses 

in several ways: 

Temporal Considerations 

Indicators were selected for use in instream numeric target development and follow-up 

monitoring which are believed to integrate cumulative effects over annual timeframes (e.g. annual 

low flow measurements of stream bottom composition) instead of indicators which measure 

instantaneous conditions (e.g. turbidity). 

Numeric targets (goals for instream indicators), the total allowable load, and specific load 

allocations are expressed in terms of 10 year rolling averages in recognition that trends are not 

discernible within shorter time frames and to allow for natural variation due to seasonal and annual 

differences. 

The source analysis is based on sediment loading estimates developed for a time period of 

more than 40 years which encompasses a wide range of climatic and land use conditions. This 

period included several major storms which caused catastrophic sediment inputs as well as 

significant periods of drought during which precipitation, runoff, and associated sedimentation 

9 
were far below normal. This timeframe also includes periods of widespread, intensive timber 

harvesting prior to the implementation of modem logging practices along with periods in which 

logging stopped in the lower basin (after the National Park was created) and intensive logging 

continued in the middle and upper basin using modem logging practices required by State timber 

harvest rules. Future erosion patterns may be different from historic patterns largely due to the 

removal of one third of the basin from timber harvest management and the institution of more 

protective forest practice rules. However, available information indicates that future erosion 

potential in the basin, chiefly associated with roads built before the advent of modem forest 

practice rules, remains very high (RNP, 1997). The degree to which modem timber harvest 

practices will protect Redwood Creek from excessive sedimentation has not been established or 

adequately tested. Therefore, it is reasonable to set a TMDL and associated allocations which will 

·guide future land management decisions based on the extensive historical loading analysis. 

Spatial Considerations 

The TMDL was derived based primarily on analysis of conditions in different tributaries to 

Redwood Creek which are representative of different geologies and associated vulnerabilities to 

erosion. An effort was made to account for the differences in erosion potential associated with 

different geological conditions present in the watershed because geology was believed to be a key 

driving force influencing variability in erosion potential throughout the basin. 

For some indicators, separate numeric targets are identified for different parts of the basin 

·to account for differences in geomorphic conditions and habitat issues in different parts of the 

watershed. That is, separate numeric targets for fish rearing habitat were developed for tributaries 

versus the mainstem of Redwood Creek. In addition, hillslope targets are provided which 

recognize and address the higher erosion potential associated with roads and timber harvesting in 

steep, unstable terrain near water courses. 

Section 3.1. Problem Statement 

This section is based primarily on information contained in the draft Redwood Creek 

Watershed Analysis (RNP, 1997) and other publications by RNP researchers. 

Watershed Overview 

Redwood Creek watershed is a 285 square mile forested watershed in Humboldt County, 

California .. Redwood Creek flows into the Pacific Ocean near Orick. The drainage area upstream 

of the U.S. Geological Survey stream gauging station at Orick is 278 square miles (Figure 1). The 

Redwood Creek watershed consists mostly of mountainous, forested terrain from sea level to about 

5,300 feet elevation. Primary land uses are tourism and fishing on park lands and timber and 

livestock production on lands upstream of Redwood National Park. The watershed is narrow and 

elongated, about 65 miles in length, from 4 to 7 miles wide. The lower basin includes the Park 

area and the middle and upper basin are located upstream from the Park. 

The cold water fishery is identified by the Regional Water Board as a beneficial use of the 

Redwood Creek watershed. The creek historically supported large numbers of coho salmon, 

10 
chinook salmon, steelhead trout, and other fish species. Reliable data about historical fish 

populations in Redwood Creek are lacking. In 1965, the California Department ofFish and Game 

roughly estimated spawning escapement of 5000 chinook, 2000 coho, and 1 0,000 winter steelhead. 

Coho salmon, a species native to the Redwood Creek, is listed by the National Maririe Fisheries 

Service as a threatened species. In addition, steelhead and chinook salmon populations have 

declined significantly in the watershed. By 1994, five fish species found in Redwood Creek were 

classified as a species of concern, threatened or endangered by U.S. Fish and Wildlife Service 

and/or the California Department ofFish and Game: tidewater goby, coast cutthroat trout, coho 

salmon, spring run chinook salmon, and summer steelhead trout (RNP, 1997). Sedimentation due 

to natural geologic instability, past and present land use practices, and other factors has contributed 

to the reduction and loss of habitat necessary to support cold water fish including salmonids. 

Climate and Hydrology 

The climate of the Redwood Creek watershed is Mediterranean, with mild, wet winters 

(November to March), and warm, dry summers. Mean annual precipitation is roughly 80 inches, 

mostly rain, with snow frequently at altitudes above 1 ,600 feet. The snow zone of Redwood Creek 

watershed is roughly located upstream of Highway 299, which crosses the watershed 

approximately at the boundary between the middle and upper basin. Snow melt can increase 

streamflow peaks during rain~on·snow events, as occurred in 1964. 

Streamflow in Redwood Creek is highly variable from year to year as a result of annual 

rainfall variations. Streamflow also varies seasonally, owing to the highly seasonal distribution of 

rainfall. Winter flood flows can be as much as four orders of magnitude higher than summer low 

flows. 

Floods are critical events for the resources of Redwood Creek because they erode 

hillslopes, reshape channels, and transport large proportions of fluvial sediment loads. Recent 

large floods occurred in 1953, 1955, 1964, 1972 (two floods), and 1975. The 1964 storm was a 

regionally significant event that caused major damage to towns, highways, and other structures, as 

well as significant hillslope erosion and channel changes. 

No large floods occurred after 1975, until the recent 1l·year return period flood in January 

of 1997. During January 1997, the relatively small 11-year return period flood initiated debris 

torrents of mud, boulders, and whole trees directly into Redwood Creek adjacent to Tall Trees 

Grove; the effects of a major storm would probably be much more severe. Within the time period 

from 1975 to 2015, there is an 80% chance of a 25-year flood. It has been 23 years since the last 

25-year flood in Redwood Creek, in 1975. It has been 34 years since the last 50-year flood, and 

erosion potential in this basin from such a storm is estimated at more than 5 million cubic yards. 

Of this, 90% is from the private roads upstream from the park. Within the time period from 1964 to 

2014, there is a 64% chance of a 50-year flood. 

Geology 

Geologic Structure in the Redwood Creek watershed is governed by several parallel northnorthwest trending faults. For much of its length, the channel of Redwood Creek closely follows 

the Grogan Fault. 

11 
Redwood Creek Watershed 

Panther Creek 

s 

RF 1:400,000 

Mapscale in 1\llles 

Redwood National 

and State Parks 

(tint) 

Estuary 

little lost 

Man Creek 

2 0 2 4 fi 8 

Streams 

00216. 2.13.97 

Private lands 

(white) 

12 

Roads 
Redwood Creek watershed is characterized by relative steep, unstable hillslopes, very steep 

inner gorge slopes along much of the mainstem and some tributaries, and narrow valley bottoms. 

Most of the Redwood Creek watershed has experienced uplift over the past several hundred 

thousand years. The basin is underlain by the Franciscan complex of unmetamorphosed 

sandstones, mudstones, schists, and scattered blocks of other rock types. In general, slopes west of 

the Creek (which generally follows the Grogan fault) are underlain by schist, and slopes east of the 

Creek are underlain by sandstones and mudstones. 

A very high percentage of the land area of Redwood Creek basin is underlain by rock types 

which are relatively weak and susceptible to erosion and mass soil movements (e.g., schists and 

mudstones). Remaining areas of the watershed which are underlain by more competent rock types 

(e.g. interbedded sandstone/mudstones) are somewhat more resistant to erosion, but form steep 

slopes which are susceptible to rapid, shallow landsliding processes. 

Plants and Animals 

The natural vegetation of the Redwood Creek watershed consists mostly of coniferous 

forest, but also includes areas of oak woodland and grassland prairie. The distribution of plant 

communities depends primarily on water availability and fire regime. 

Old-growth forest currently covers 24,315 acres in the watershed, equivalent to 14% of its 

total area. Near the coast, the most common forest tree is the Sitka spruce. Most of the lowerbasin forest, however, is dominated by coast redwoods. Farther inland, where summer· 

temperatures are higher and fog is less frequent, Douglas fir is more common than redwood. 

Several hardwood species grow in association with both redwood and Douglas fir, including bigleaf maple, red alder, tanbark oak, madrone, and bay. Prairies and oak woodlands occur on southand west-facing ridgetops and hillslopes on the east side of Redwood Creek. 

Approximately 250 species of wildlife (amphibians, reptiles, mammals, and birds) are 

known to occupy habitats found in the Redwood Creek watershed. Thirty three species of wildlife 

are identified as species of special concern (threatened, endangered or sensitive to human 

activities, see RNP, 1997 for details). 

The Redwood Creek watershed provides aquatic habitat for a variety of fish species. 

Anadromous and resident salmonids identified in Redwood Creek include steelhead and rainbow 

trout, coastal cutthroat trout, coho salmon, and chinook salmon. Other fish identified or reported 

include the tidewater goby, Humboldt sucker, threespine stickleback, coast range sculpin, Pacific 

lamprey, and eulachon. Five species of fish have been listed as species of special concern, 

endangered species, or sensitive species by federal and state agencies. 

Land Use and Sedimentation Issues 

Relations between floods, sediment, and land use have been central to the debate over 

resource protection in the Redwood Creek watershed. Damage to forest resources, fish, and other 

resources coincided with both intensive land use and a series of large storms that were 

accompanied by widespread flooding and erosion. Erosion rates in northwestern California are 

13 
naturally high, and land use has significantly increased erosion above natural levels associated with 

storms. The question has obvious practical importance because erosion related to land use 

potentially can be prevented. In the Redwood Creek Watershed, the large number of improperly 

designed and maintained roads, landings and skid trails causes: 1) increased surface erosion and 

fine sediment production and delivery and 2) an increased potential for stream diversions (stream 

channel capture), rill and gully erosion, and road related landslides with corresponding increases in 

sediment production and delivery (See roads map, figure 3). Timber harvest operations on unstable 

slopes and removal of riparian vegetation have also contributed to increased erosion and sediment 

production. 

Water Quality Objectives 

Water quality objectives (the term used by the State of California to refer to water quality 

standards) adopted for the Redwood Creek basin are contained in the RWQCB Basin Plan. The 

beneficial uses of water for Redwood Creek are described in the Basin Plan as either existing or 

potential. The water quality objectives are designed to protect the most senSitive beneficial uses. 

The beneficial uses addressed in the Redwood Creek TMDL include: cold freshwater 

habitat (COLD); migration of aquatic organisms (MIGR); estuarine habitat (EST); uses of water 

for community, military, or individual systems including, but not limited to drinking water supply 

(MUN); uses of water that support habitats necessary, at least in part, for the survival and 

successful maintenance of plant or animal species established under state or federal law as rare, 

threatened or endangered (RARE); and spawning, reproduction, and/or early development 

(SPAWN). The water quality objectives addressed include settleable material ("Water shall not 

contain substances that result in deposition of material that causes nuisance or adversely affect 

beneficial uses") and sediment ("The suspended sediment load and suspended sediment discharge 

rate of surface water shall not be altered in such a manner as to cause nuisance or adversely affect 

beneficial uses."). Discharges of sediment are also addressed by a discharge prohibition. 

Beneficial Use Issues 

Salmonids are born in fresh water streams where they spend one to several years of their 

lives feeding, growing, and hiding from predators. Once they are large enough, fresh water 

salmonids undergo a physiological change which allows them to swim out to the ocean where they 

then spend the next one to several years. Salmonids return to the streams in which they were born 

to lay eggs and begin the life cycle again. They require gravels free from excessive fine sediment 

to lay their eggs and for the eggs to develop into free-swimming fish. They also require deep pools 

for the young fish to feed and grow while protected from predators. 

Redwood Creek is largely free of the effects of non-native aquatic species or hatchery 

stocks which might impact the native fishery. Although numbers of native salmonid species 

present in Redwood Creek have declined substantially (by perhaps 90% by the mid-1970s), 

remnant populations of coho, fall and summer chinook, winter and summer steelhead, and 

cutthroat trout are still present. Coho salmon were listed under the federal Endangered Species Act 

as a threatened species on May 6, 1997 by the National Marine Fisheries Service. Redwood Creek 

is located within the Evolutionarily Significant Unit (ESU) known as the Southern 

Oregon/Northern California Coast where coho salmon were listed. 

14 
Redwood Creek's ability to support fish populations is determined by habitat availability 

and quality. Habitat availability is limited by streamflow, stream gradients,. and physical barriers 

such as boulders and log jams. Habitat quality is limited by channel bottom composition, pool 

structure, water temperature, dissolved oxygen, food supply, and predation (RNP, 1997). 

However, the TMDL only addresses habitat quality impacts associated with excessive sediment 

discharges. The key habitat problems in Redwood Creek associated with sedimentation appear to 

be pool quality, gravel quality (for spawning and food production), and changes in channel 

structure which contribute to temperature elevation. 

Residents in the upper Redwood Creek basin commonly have instream domestic water 

intakes. These water supplies can be adversely impacted by high sediment loads, but that 

beneficial use is not currently impaired. Excessive sediment may result in turbidity, adverse tastes, 

and nuisance condition due to clogging of filters. It is anticipated that implementation of the 

TMDL will also help protect drinking water. 

Summary of Existing Conditions 

The Draft Redwood Creek Watershed Analysis (RNP, 1997) provides a summary analysis 

of existing stream conditions. In general, stream channels in the Redwood Creek basin are wider, 

shallower, and more homogeneous than is desirable or were historically present. 

1. Stream Channel Conditions and Fish Habitat Impacts 

Stream channel structure along the mainstem of Redwood Creek and its tributary 

watersheds has changed substantially over the last 40 years. Key changes in the mainstem of 

Redwood Creek include (1) increases in the volume of stored sediment, (2) decreases in pool 

numbers and depth, (3) increases in stream width and decreases in stream depth, (4) reduced 

recruitment oflarge woody debris, (5) deposition of high levels of fine sediments on the stream 

bottom, and (6) reduced volumes oflarge woody debris. 

Stored Sediment 

More sediment has been supplied to the low gradient reaches of the mainstem than it can 

effectively transport. Low gradient reaches of the mainstem Redwood Creek have acted as long 

term repositories of eroded sediment which originated in upstream areas. Although the creek is 

apparently beginning to downcut through aggraded sediments in its lower basin reaches, this stored 

sediment has the potential to affect channel structure and habitat values for centuries. In contrast, 

the higher gradient mainstem reaches in the upper watershed have removed about half the sediment 

deposited by the 1964 flood within 20 years (RNP, 1997). 

Pool Distribution and Depth 

Most mainstem pools were filled by sediments born primarily by the 1964 flood, and to a 

lesser extent by other high magnitude events between 1954 and 1975. Pool frequency and mean 

depth appeared to increase since 1975 as the creek began to move out previously deposited 

sediment loads, and pool recovery is more apparent in the upper basin. However, many pools were 

again filled by sediments following the moderate 1997 storm season. Reduced pool frequency and 

depth impairs rearing habitat by reducing availability of cool water refuges and increasing 

predation. 

15 
Channel Width and Depth 

Many reaches of Redwood Creek became substantially wider and shallower in response to 

excessive sediment inputs and destructive flood flow~ which occurred between the mid 1950s and 

mid 1970s. Stream width increased and depth decreased in response to streambank erosion and 

channel aggradation. Although many reaches of Redwood Creek have begun to downcut through 

aggraded sediments (especially in the middle and upper basins), stream widths have not decreased 

substantially. Fish habitat impacts associated with increased width and decreased depth include 

increases in water temperature, decreased cover to hide from prey, and increased difficulty in 

moving up and down the stream in search of food and cool water refugia. In addition, aggraded 

sediment deposits have formed "deltas" at the mouths of many tributaries which impede fish 

passage upstream into tributaries. Finally, as the creek has widened and riparian timber has been 

harvested, canopy coverage of the stream has been reduced substantially, contributing to water 

temperature increases. 

Fine Sediments 

Although limited data are available concerning stream substrate composition in Redwood 

Creek, it appears that there is a slight trend toward coarsening of bed material since the 1970s. 

However, levels of fine sediment (which can be harmful to fish spawning success) appear to be 

higher than desirable for successful fish spawning in many reaches of Redwood Creek, principally 

in the lower basin. 

Large Woody Debris 

Large woody debris (L WD} in North Coast streams provides multiple functions which are 

key to the maintenance of healthy stream habitat and the moderation of sedimentation impacts on 

those streams. Presence of adequate L WD is a key factor in pool formation, sediment storage, and 

nutrient loading in many streams. Due to extensive harvesting of riparian forests along Redwood 

Creek and its tributaries along with extensive streambank erosion, recruitment of L WD is well 

below historic levels needed to support healthy fish habitat and to moderate sediment transport. 

To summarize, fish populations in Redwood Creek are much reduced in comparison to 

historic accounts. Habitat conditions are probably still quite degraded relative to pristine 

conditions, but are showing signs of improvement. Although channel deepening and pool 

development have been observed in all but the lower few miles of the Creek, the mainstem 

generally lacks an adequate pool-riffle structure and cover. Coarse sediment deposited in the 

mainstem allows a large proportion of summer base flows to infiltrate and flow subsurface, thereby 

limiting the surface water available to fish and increasing surface water temperatures. Large deltas 

in some tributaries block some tributary mouths and prevent migration of fish. The lack of suitable 

rearing habitat in the mainstem and tributaries has forced juvenile fish to the estuary, where they 

are subject to the impacts of uncontrolled breaching of the sand bar. Spawning habitat is 

improving slowly as gravels are cleaned of fine sediment. Canopy closure along the upper reaches 

of Redwood Creek is increasing, but is still far less than it was early this century. Tributary water 

temperatures are generally suitable for salmonids, but are suboptimal for fish along much of the 

mainstem. Recruitment of large woody debris and nutrients are probably well below historic 

levels. This condition is likely to persist into the future as deciduous willows and alders take the 

place of evergreen conifers along much of the mainstem and tributaries, and as large conifers along 

watercourses in the upper basin are harvested (NPS, 1997). Willows and alders generally yield 

less durable L WD than conifers. 

16 
2. Hillslope Conditions 

Timber harvesting is the most widespread land use in Redwood Creek basin. Over 85% of 

the basin upstream of the park has been logged, including about 30% which was logged between 

1978-1992. About three-quarters of this recently logged area was logged using intensive 

silvicultural methods which remove all or almost all trees from the harvest area. Substantial areas 

of the park were intensively logged prior to their inclusion in the park. Harvested areas remain at 

greater risk of increased erosion (principally through landsliding) for at least a year or two 

following harvest, and possibly for longer periods oftime. It is expected that timber harvesting of 

second growth timber in the upper basin will continue in the future, so erosion potential associated 

with these harvests will need to be addressed through the TMDL. 

Most of the likely future erosion potential in the basin caused by human activity is 

associated with logging roads and skid trails, although roads constructed for other purposes also 

pose significant erosion potential. Roughly 1400 miles of forest roads and over 5000 miles of skid 

trails have been build within the basin, of which about 445 miles of roads and 3000 miles of skid 

trails were included within the national park boundaries. About half tlie roads and a very high 

percentage of skid trails upstream of the park are not properly maintained or have been abandoned. 

The Redwood Creek Watershed Analysis contains a detailed analysis of the status and condition of 

existing roads, and concludes that remaining erosion potential associated with poorly designed and 

maintained roads remains the largest future erosion source in the basin which can be controlled. 

Although there has been some recovery in the Redwood Creek and tributary channels, it is 

expected that a very high percentage of improperly constructed or maintained roads will fail during 

the next high magnitude storm. Unless corrected through road upgrading, maintenance, and/or 

decommissioning, such road failures are expected to cause substantial direct erosion (through 

crossing failures, stream diversions, etc.) and indirect erosion events (e.g. gully formation and 

mass wasting events). 

Other continuing land uses in the basin pose less substantial erosion potential although 

potential impacts could be significant in local settings. Intensive timber harvesting, particularly 

using clearcutting and tractor logging in sensitive streamside areas may pose significant erosion 

potential in the future. State and county roads pose significant erosion potential in some locations. 

Ranching operations and residential property management may also have the potential to cause 

significant erosion, particularly in locations where livestock access contributes to bank erosion. 

General Problem Statement 

The Redwood Creek watershed has experienced a reduction in the quality and quantity of 

instream habitat which is capable of supporting the cold water fishery, particularly that of coho 

salmon, chinook salmon, and steelhead. Controllable factors contributing to this habitat loss 

include the acceleration of sediment production and delivery due to land management activities, 

including existing roads, and the loss of instream channel structure necessary to maintain the 

system's capacity to efficiently store, sort, and transport delivered sediment. 

Three factors are important in describing the issue of sedimentation: sediment production, 

delivery, and transport. Water quality concerns arise when sediment is delivered to the stream in 

amounts or to locations that overwhelm the stream's capacity to transport it. Such is the case in the 

17 
Redwood Creek watershed. Habitat niches are filled by sediment and the stream channel is 

aggraded, in some places. It is important to note, though, that the aggradation of the upper 

mainstem and most tributaries appears to be reversing-- an indication that the process of recovery 

has begun. Adequate pool riffle structure and stream cover are still absent in the lower mainstem. 

Excessive sedimentation has also contributed to habitat degradation in the estuary. 

For gravel-bed streams, such as the Redwood Creek, the presence of channel structure 

plays a crucial role in the efficient storage, sorting, and transport of sediment through the river 

system. Channel structure takes the form of large woody debris, boulders, armoured stream banks, 

and other structural elements. For streams in the Pacific Northwest, including northern California, 

large woody debris has been identified as a particularly important structural element. Thus, 

sediment delivery and instream channel structure, particularly large woody debris, are integral 

companions in the problems (and solutions) related to sedimentation and the reduction in the 

quality and quantity of instream habitat. 

Instream Problem Statements 

1. Fine Sediment in Spawning Gravels 

Spawning gravels of the Redwood Creek watershed are impacted and likely to suffer 

additional impacts by the delivery of fine sediment to the stream which fills the interstices of the 

framework particles: 1) cementing them in place and reducing their viability as spawning substrate, 

2) reducing the oxygen available to fish embryos, 3) reducing intragravel water velocities and the 

delivery of nutrients to and waste material from the interior of the redd (salmon nest), 4) and 

impairing the ability of young salmon to emerge as free-swimming fish. This statement relates to 

the SPAWN beneficial use and the potential for settleable material to affect spawning redds. 

2. Channel Aggradation 

Spawning gravels of the Redwood Creek watershed are impacted by the delivery of fine 

and coarse sediment to the stream which causes aggradation, the burial of large woody debris and 

other structural elements, a loss of the stream's ability to effectively sort gravel, and a potential 

reduction in the dominant particle sizes. This statement relates to the SPAWN and COLD 

beneficial uses and the potential for sediment and settleable material to adversely affect spawning 

substrate. 

3. Lack of suitable pools for Rearing Habitat 

Pools of the Redwood Creek watershed potentially suitable as rearing habitat are impacted 

by the delivery of fine and coarse sediment to the stream which: 1) reduces the volume of available 

rearing habitat by filling in pools and burying pool-forming structural elements such as large 

woody debris, 2) reduces pool depth and therefore the cool water refuge associated with 

temperature stratification, 3) reduces the availability of fish cover as a result of decreased depths 

and the burial of large woody debris and other structural elements, and 4) causes loss of surface 

flow as pools are filled in resulting in less available habitat and protection from predators. This 

statement relates to the SPAWN and COLD beneficial uses and the potential for sediment and 

settleable material to impact rearing habitat. 

18 
4. Stream Channel Instability 

Increased sediment delivery to the Redwood Creek watershed impacts stream channel 

stability by causing: 1) aggradation, stream channel widening, greater flood potential, and greater 

stream bank erosion, and 2) the burial of channel structural elements such as large woody debris 

with a reduction in sediment transport efficiency. This statement relates to the COLD and EST 

beneficial uses and the potential for sediment to impact stream channel stability and habitat niches. 

5. Physical Barriers to Migration 

The migration of anadromous fish in the Redwood Creek watershed from the ocean, within 

the basin, and back to the ocean is impacted by the presence of migration barriers including 

shallow or dewatered stream segments due to aggradation (rising stream bed elevation). This 

statement relates to the MIGR beneficial use and the potential for sediment in the form of 

aggradation or road fill to prevent the migration of salmonids. (Natural barriers, such as bedrock 

falls, are not addressed here since they are not pollutants for which TMDLs are needed. In 

addition, the TMDL does not address anthropogenic barriers associated with culverts because EPA 

does not consider culverts a pollutant for which TMDL preparation is needed (EPA, 1997a)). 

Hillslope Problem Statements 

1. Improperly Designed or Maintained Roads 

The large number of improperly designed and maintained roads, landings and skid trails in 

the Redwood Creek watershed causes: 1) increased surface erosion and fine sediment production 

and delivery and 2) an increased potential for stream diversions (stream channel capture), rill and 

gully erosion, and road related landslides with corresponding increases in sediment production and 

delivery. This statement relates to the COLD beneficial use and the potential for sediment and 

settleable matter to impact stream channel stability and habitat niches. 

2. Sediment from Unstable Areas 

Timber harvest operations on unstable slopes (e.g., inner gorges, headwall swales, active or 

potentially active landslides, or steep slopes) in the Redwood Creek watershed cause increased 

landsliding and the production and delivery of fine and coarse sediment. In addition, agricultural 

operations in streamside areas increase streambank erosion in localized settings. This statement 

relates to the COLD beneficial use and the potential for sediment and settleable matter to impact 

stream channel stability and habitat niches. 

3. Removal of Riparian Trees and Loss of Large Woody Debris 

The removal of vegetation (particularly large conifers) from the riparian zone of the 

Redwood Creek watershed causes: 1) a loss of stream bank stability and increased stream bank 

erosion, 2) a loss of sediment filtering capacity and increases in sediment delivery, and 3) a 

reduction in the potential for large woody debris recruitment to the stream and in the stream's 

sediment transport efficiency. This statement relates to the COLD beneficial use and the potential 

for sediment and settleable matter to impact stream channel stability and habitat niches. 

19 
Section 3.2. Numeric Targets 

Section 303(d)(l)(C) of the Clean Water Act states that TMDLs "shall be established at a 

level necessary to implement the applicable water quality standards .... " The numeric targets 

developed for the Redwood Creek TMDL are intended to interpret the narrative water quality 

standards adopted in the Basin Plan (1994). EPA notes that the Regional Board has indicated that 

it does not intend to bring enforcement action based on instream numeric target exceedences. 

Instream numeric targets, as included in the TMDL, represent adequate stream habitat 

conditions for salmonid reproductive success. Instream targets provide a vital set of measures of 

whether, in the long run, beneficial uses impacted by sedimentation are recovering. 

Hillslope numeric targets represent desired conditions for land management which are 

associated with properly functioning erosional processes and erosion rates which are not 

excessively accelerated by human influences. If these hillslope target conditions are attained, 

erosion rates and sediment delivery to streams should decline to levels which allow Redwood 

Creek stream habitat to recover from the effects of excessive sedimentation which occured in the 

past. EPA expects that recovery from these effects may take many years. Hillslope targets 

provide an immediately useful set of measures of whether land uses known to contribute much of 

the human-caused share of sediment loading to Redwood Creek are being modified in ways which 

will minimize future erosion potential and sediment delivery. 

The numeric targets are based on scientific literature, available monitoring data for the 

basin and best professional judgment. When implemented, the TMDL should fully meet these 

targets and, as a result, the WQS. Table 3 depicts the instream numeric targets, and table 4 depicts 

the hillslope numeric targets .. 

Numeric targets interpret existing narrative water quality objectives in order to: 

• describe physical conditions of Redwood Creek and the hillslopes around the Creek which are 

associated with attainment of the narrative objectives and beneficial uses, 

• assist in estimating Redwood Creek's capacity to receive future sediment inputs and still support 

beneficial uses, 

• compare existing and target conditions for sediment related indicators, 

• provide an evaluation framework for analysing monitoring data collected in the future and 

making changes in the TMDL and/or Implementation Plan in response, and 

• assist in evaluating whether land management and restoration actions are effective in adequately 

reducing erosion and subsequent sediment loading to the Creek. 

Instream Numeric Targets 

The indicators for which EPA is establishing instream numeric targets include percent fmes 

<0.85 mm, percent fmes <6.5 mm, median surface particle size ( d50), percent of surface fines <2 mm, 

percentage of mainstem creek length in riffles, residual large woody debris, and mean residual pool 

depth. Fine sediment targets are intended to apply in fish bearing reaches of generally low gradient 

(<3% slope). Separate pool depth targets are established for the mainstem and for tributaries to 

20 
Redwood Creek to reflect the differences in stream sizes and related differences in desirable pool 

characteristics. In addition, the stream riffle target is being set only for the lower gradient part of 

Redwood Creek to reflect the fact that pool riffle structure may be substantially different in higher 

gradient streams. Scientific literature suggests that these indicators are the most easily linked to fish 

habitat conditions which support salmonids and can assist in evaluating long term impacts of 

hillslope erosion and erosion reduction efforts (Knopp, 1993, Chapman, 198 8, Peterson, et.al. 1992, 

NMFS, 1997). The targets are monitoring and evaluation goals intended to represent the desired 

condition where sediment is not a limiting factor for salmonid production. 

Table3. Instream Numeric Targets for the Redwood Creek Watershed. 

Parameter Numeric Targets (Desired Conditions) 

Percent fines <0. 85 mm in riffle crests of fish- <14% 

bearing streams2 

Percent fmes <6.5 mm in riffle crests of fish- <30% 

bearing streams 

Percent of Stream Length in Riffles3 < 25-30% of stream reaches in riffles (reach 

gradient < 2%) 

Pool depth in mainstem Redwood Creek the mean depth of pools at low flow exceeds 

reaches with pool-riffle morphology 2m 

Depths of pools in 3rd and 4th order the mean depth of pools at low flow exceeds 

tributaries with pool-riffle morphology4 1-1.5 m 

Median particle size diameter ( d50) from riffle 2:. 37 mm (minimum for a reach) 

crest surfaces 2::,69 mm (mean for a reach) 

Percent fmes < 2 mm at riffle crest surfaces in <10-20% 

fish-bearing streams 

Large Woody Debris in any watercourse Improving trend towards increased large 

capable of transporting sediment to a higher woody debris 

order watercourse 

1 Targets should be evaluated as ten year rolling annual averages to avoid premature assessment of trends 

based on inadequate information. This approach addresses the variations in sediment loading and instream 

indicators which are characteristic of Redwood Creek and which may not indicate management related 

effects. 

2 Fish-Bearing Streams: Fish present seasonally or year-round, or having fish habitat capable of supporting 

fish. Fish habitat is the aquatic environment and the immediately surrounding terrestrial environment that, 

combined, afford the necessary biological and physical support systems required by fish species during 

various life history stages. 3 Riffle- low gradient: shallow stream channel areas with swiftly flowing turbulent water with some partially 

exposed substrate. Gradient< 4 %, substrate is usually cobble dominated. The gradient is the general 

slope, or rate of change in vertical elevation per unit of horizontal distance, of the water surface of a 

flowing stream; or the rate of change of any characteristic per unit of length. 4 Stream order is the designation of the relative position of stream segments in the drainage basin network. 

For example, a first order stream is the smallest, unbranched, tributary which terminates at the upper point. 

A second order stream is formed when two first order streams join. 

21 
Some of the selected indicators and target values are sensitive to variations in conditions in 

different areas of the watershed which are influenced by differences in geology and stream 

morphology. However, the indicators and associated numeric targets are relatively insensitive to 

probable annual variations in future sediment loading and impacts over time. It would be desirable 

to use more dynamic indicators which set erosion reduction and habitat improvement goals as· a 

function of the factors which determine year-to-year variations in sediment loading and stream 

responses. Ideally, the tMDL would include indicators which directly account for variations in 

precipitation and resultant runoff and flows. Use of this type of indicator would enable analysts to 

distinguish changes in erosion and instream effects associated with land management actions from 

changes attributable to differences in runoff intensity. This approach could make it easier to 

evaluate the effectiveness of the TMDL based on limited data. Because such indicators could not 

be identified for this TMDL, most of the numeric targets are expressed as ten year rolling averages. 

This approach helps ensure that conclusions concerning watershed responses to erosion control 

actions are not drawn prematurely. The drawback of this approach is that we must wait several 

years before we will be able to complete this critical evaluation ofTMDL effectiveness. 

1. Percent Fines <0.85 mm 

Once the eggs are laid and fertilized, the spawners cover the redds with material from upstream, 

including clean gravels and cobbles. The interstitial spaces between the particles allow for water to 

flow into the interior cavity where dissolved oxygen, needed by the growing embryos, is 

replenished. Similarly, the interstitial spaces allow water to flow out of the interior cavity carrying 

away metabolic wastes. However, fine particles either delivered to the stream or mobilized by 

storm flow can intrude into those interstitial spaces, blocking the flow of oxygen into the redd and 

the metabolic wastes out of it. The reduced permeability into and out of the redd results in a 

reduction in the rate of embryo survival. 

a. Numeric Target 

The numeric target for fines <.85mm for Redwood Creek is less than or equal to 14%. The target 

should be monitored at stream riffles in reaches around existing monumented cross sections to be 

selected during the design of the monitoring plan. EPA intends that this target indicator should be 

measured through the use of bulk sampling of the surface and subsurface substrate layers 

(preferrably measuring dry weights). The target is selected as the midpoint between the 

percentages of fines reported in unmanaged streams in the Peterson (1992) and Burns (1970) 

studies. The target takes into account that the 11% fines <0.85 mm which was observed in 

unmanaged streams in the Pacific Northwest (Peterson et al., 1992) is probably lower than would 

be expected in California. On the other hand, the 17% fines <0.85 mm which was seen in 

unmanaged California streams beginning in 1967 (Burns, 1970) is probably too high given the 

huge sediment loads which were discharged to streams as a result of the 1964 storms. In addition, 

Tappel and Bjorn (1983) predicted that 14% fines <0.85 mm in combination with about 30% fines 

<9.5mm would provide an average of 50% survival to emergence for steelhead and an average of 

70% survival to emergence for chinook salmon. These appear to be acceptable rates of survival to 

emergence. The literature sources reviewed in setting the target generally support the 14% target 

level as reasonably protective. EPA recognizes that there will be spatial and temporal variability 

around the target level for instream indicators. 

22 
b. Existing Conditions 

Fine sediment size fractions are difficult to measure accurately. The percentage of fine sediment in 

the channel bottom is often measured through various bulk sampling methods which gather both 

surface and subsurface sediments from the stream bottom. No bulk sampling data has been 

published for Redwood Creek; however, the fraction of fme sediments <2 mm commonly exceeds 

20% (personal communication with Mary Ann Madej, USGS~ June 1998). Levels of very fine 

sediments are believed to be relatively higher in lower Redwood Creek than in the middle and 

upper basin (personal communication with Mary Ann Madej, USGS, June 1998). This is a 

reasonable expectation because (1) particles tend to break down as they move downstream, 

increasing the percentage of fines present, (2) lower Redwood Creek has a low gradient which 

would be more suited for deposition of fine sediments, and (3) lower Redwood Creek is still 

experiencing sediment aggradation associated with catastrophic historic floods and sediment loads. 

c. Comparison ofNumeric Target and Existing Conditions 

A comparison of the numeric target and existing information helps provide information on the 

extent of the problem as well as the sediment reduction needed to meet water quality standards. 

However, it was infeasible to conduct a quantitative comparison of the numeric target and existing 

conditions because inadequate reliable data were available. If the rough assessment that levels of 

fines often exceeds 20% is true, portions of Redwood Creek probably exceed the numeric target. 

2. Percent fines <6.5 mm 

After 4 to 6 weeks or life, the embryos are ready to emerge from the gravel as fry (young 

swimming fish.) The presence of fme sediment in the gravel interstices can impede fry emergence. 

However, the size of fine particles likely to fill the interstices of redds sufficient to block passage 

of fry are larger than those likely to suffocate embryos. That is, particles ranging from 0.85 mm to 

9.5 mm are capable of blocking fry emergence, depending on the sizes and angularity of the 

framework particles, while still allowing sufficient water flow through the gravels to support 

embryo development. Besides a correlation between percent fines and the rate of survival to 

emergence, there is also a correlation between percent fines and the length of incubation; i.e., the 

amount of time it takes for the fry to emerge from the egg. Percent fines is also inversely related to 

the size of emerging fry (Chapman, 1988). Each of these factors impact the ultimate survivability 

of the embryos and fry. 

a. Numeric Target · 

The numeric target for fmes <6.5 mm is less than or equal to 30% for Redwood Creek. The lower 

basin target should be monitored at stream riffles in reaches around existing monumented cross 

sections to be identified during the design of the monitoring program. EPA intends that this target 

indicator.should be measured through the use of bulk sampling of the surface and subsurface 

substrate layers (preferrably measuring dry weights). The numeric target was selected based on a 

review of literature which evaluated the relationship between fines <6.5mm and survival to 

emergence rates for salmonids. Research results concerning the relationship between salmonid 

survival to emergence and levels of fines <6.5mm are relatively consistent. Tappel and Bjorn 

(1983) predicted that 30% fines <9.5mm in combination with 14% fines< 0.85mm would provide 

23 
an average of 50% survival to emergence for steelhead. The same study predicted that 32% fines 

<9.5mm in combination with 14% fines< 0.85mm would provide an average of70% survival to 

emergence for chinook salmon. Both steelhead and chinook are expected to have greater 

emergence success than coho salmon when redds are sedimented. Kondolf (unpublished data), 

evaluating data from other studies, concluded that if one chooses a 50% survival to emergence rate, 

the data indicate that fines defined either as <3.35 or <6.5 mm should not comprise more than 30% 

of substrate composition. Finally, Chapman (1988) reported data from several other studies 

concerning fine sediment levels in unlogged Oregon watersheds which varied from 27-55%. The 

30% target rate appears consistent with the research fmdings concerning acceptable survival to 

emergence rates and the levels of fines found in unlogged watersheds. EPA recognizes that there 

will be spatial and temporal variability around the target level for instream indicators. 

b. Comparison of Numeric Target and Existing Conditions 

Although no specific bulk sampling data have been published for Redwood Creek, the fraction of 

fine sediments <8 mm commonly exceeds 50% (personal communication with Mary Ann Madej, 

USGS, June, 1998). 

Because data are so limited for fine sediment levels in Redwood Creek, it was not feasible to make 

quantitative comparisons between existing and target conditions. If the rough assessment of the 

amount of sediments < 8mm mentioned above is correct, levels of fine sediment in some reaches of 

Redwood Creek probably exceed the numeric target. 

3. Pool-Riffle Structure. and Percent Riffles 

Juvenile coho require pools for both summer and overwintering rearing. In the summer, pools 

provide cool, quiet habitat where coho feed and hide from predators. During the winter, offchannel pools provide habitat in which coho and steelhead both can get out of flood flows to avoid 

being swept downriver and out to sea. Steelhead prefer riffles for rearing during their first 

summer, but make more regular summer uses of pool habitat as they grow in size. Pool volumes 

are reduced either when a stream's hydrologic power is reduced (e.g., by increased sediment 

loading) or by the reduction of pool-forming elements. The number of pool-forming elements can 

be reduced by modification of the channel morphology (e.g., burial), physical removal (e.g., logjam removal), reduction in supply (e.g., logging of near stream trees), or a combination of all three 

causes. 

Various pool measures have been used (e.g., pool, frequency, spacing, or area) but are of limited 

value since the definition of the beginning and end of a pool is quite subjective. It is generally 

easier to identify riffle locations. Although some riffles are vital to north coast streams, excessive 

riffle habitat indicates that deep water habitat is deficient. Therefore, because riffles are easier to 

measure and provide an indirect indicator of pool abundance, this TMDL includes a target for the 

percentage of creek length in riffles (personal communication.with Mary Ann Madej, June, 1998). 

a. Numeric Target 

The target for percent riffles is no more than 25-30% riffles for creek reaches less than 2% in 

gradient. This target is based on judgment of a Redwood Park researcher who is very familiar with 

24 
the pool/riffle structure of Redwood Creek and ofnorth coast rivers with different habitat qualities 

(personal communication with Mary Ann Madej, June, 1998). The 25-30% level is believed to be 

consistent with the riffle patterns found in well-functioning north coast streams. This target only 

applies in the lower gradient sections of the creek because percent riffles may exceed the target 

level in steeper streams which support excellent habitat. In the long run, it may prove more 

effective to measure pool quality and distribution based on statistical analysis of longitudinal 

profile data collected at monumented reaches of Redwood Creek. This monitoring method has 

promise in providing a more discriminating indicator of channel roughness and variability, which 

can be adjusted (normalized) to account for and allow comparisons between streams of different 

sizes. 

b. Existing Conditions and Comparison With Numeric Targets 

In the 1970s and early 1980s, riffles comprised from 50 to 70% of observed reaches in study areas 

(personal communication with Mary Ann Madej, June, 1998). By the mid 1990s, riffles comprised 

20 to 40% of observed reaches in study areas. Some reaches of Redwood Creek are still 

characterized by excessive riffle and insufficient pool structure. 

4. Pool Depth 

Salmonids rely on deep, cool pools during the rearing stage for protection from predators and as 

refuges from high temperature water. Pool depth is partly a function of stream disturbance (and 

associated channel changes) and partly a function of stream size. Pools in larger streams tend to be 

deeper, on average, than pools in smaller streams (assuming other factors are equal). Flosi and 

Reynolds (1994) concluded from the Department ofFish and Game's habitat typing data that better 

California coastal coho streams (stream order 3 or 4) have pools with depths of at least 3 feet. 

a. Numeric Target 

The numeric target for low flow pool depth is >2 meters on average for the mainstem of Redwood 

Creek. and 1-1.5 meter' for third and fourth order tributaries to Redwood Creek. This target is 

based principally on the results reported by Flosi and Reynolds (1994) and applies only in reaches 

which have pool-riffle morphology. The targets for the mainstem of Redwood Creek are higher 

than the results reported by Flosi and Reynolds because Redwood Creek is a larger, higher order 

stream than the stream type referred to in this study. Several commenters have reported the 

existence of many pools greater than 10 feet deep prior to the onset of excessive sediment loading 

to the stream more than 30 years ago. In addition, there is some evidence that chinook salmon 

prefer deeper pools than coho. The targets are also consistent with the "species habitat needs 

matrix" developed by an interagency group in connection with resource management discussions 

with Pacific Lumber Company (NMFS, 1997). 

b. Existing Conditions and Comparison with Numeric Target 

Limited information is available concerning pool depths in Redwood Creek. The Redwood Creek 

Watershed Analysis (RNP,.1997) indicated that mean pool depths at three locations in Redwood 

Creek mainstem in 1986 were about 1.4-1.8 meters. Following the 1997 storm (11-year recurrence 

interval), pool recovery trends observed in previous monitoring were reversed (written comments 

25 
of Redwood National Park, November 18, 1998) These results are too limited to draw a 

meaningful comparison with the numeric target levels for the mainstem and for tributaries. 

5. Median Surface Particle Size Diameter (d5o). 

The d50 is the median value of the size distribution in a sample of surface pebble counts. It is a 

measure of the central tendency of the whole sample, and thus is one of several indicators of how 

"fine" or "coarse" the sample is overall. As discussed in the discussion for the percent fines targets, 

both amount and size of fine and coarse sediments can impact salmonid lifestages. Various 

measures of central tendency have been used by researchers (Young, et al. (1991) lists several). 

The d50 indicator is selected for Redwood Creek because it is easy to calculate based on results 

from pebble counts. In a study that evaluated the relationship between hillslope disturbance and 

various instream indicators, Knopp (1993) found that clear trend of decreasing particle sizes in the 

riffles was evident with increasing hillslope disturbance. Moreover, Knopp found that a 

statistically significant difference in average and minimum d50 values when comparing reaches in 

undisturbed and less disturbed watersheds with reaches in moderately and highly disturbed 

watersheds. Therefore, the d50 levels identified in undisturbed and less disturbed locations are 

good candidates for numeric targets for Redwood Creek. Knopp also found that the moderately 

disturbed reaches were not statistically different from the highly disturbed reaches. This indicates 

that d50 results may take upwards of 40 years before mitigation of current disturbance is positively 

reflected. 

a. Numeric Targets 

The targets for d50 are means greater than or equal to 69 mm and a minimum of greater than or 

equal to 3 7 mm. The d50 indicator has two targets associated with it. The higher number >69 mm 

represents the optimum target, while the lower number ?..37 mm represents the minimum number 

that should be found. By setting two numbers, EPA recognizes that there may be annual 

variability in this target. These values are based on Knopp's findings (1993) concerning d50 levels 

in north coast watersheds which were relatively undisturbed. Because Knopp found the d50 to be a 

discriminating indicator (that is, an indicator capable of distinguishing between watersheds which 

were more or less disturbed as a result of prior management), the indicator and associated target 

levels identified in Knopp's study are appropriate. 

b. Existing Conditions 

Table 4 is a summary of surface d50 data collected by USGS and Redwood National Park in 1979 

and again in 1994 at 8 monitoring sites along the mainstem of Redwood Creek. It should be noted 

that these data were collected using a surface pebble count method. This method may not produce 

reliable results regarding percentages of very fine sediments due to operator variability. In 

addition, monitoring was conducted at a relatively small number of sites on only 2 occasions. For 

these reasons, firm conclusions concerning actual past or present conditions for fine sediment in 

Redwood Creek should not be drawn based on this limited data set. However, the limited data are 

reported to provide some basis for comparing historical and target co.nditions. 

26 
Table 4: Summary of Existing Data for Median Particle Size (d50 ) 

Cross Section d50 (1979) d50 (1994) 

2 16 16 

5 8 12 

16 15 27 

17 9 12 

20 11 16 

32 19 41 

34 12 27 

40 41 not available 

MEAN 16 22 

Source: Unpublished USGS and NPS data reported in RNP, 1995. 

c. Comparison of Numeric Targets and Existing Conditions 

Quantitative comparisons of historical and target conditions are infeasible due to the limitations in 

the available data. While definitive comparisons cannot be drawn, it appears that d50 levels in the 

watershed may not meet the numeric target, and that mean particle sizes are higher in the 

middle/upper watershed than in the lower watershed. The numeric target for the mean particle size 

diameter is set for the watershed as awhole. However, particles tend to become finer as they are 

transported downstream due to streatn power and friction. The targets set for the mean particle 

size diameter for the lower portion of the watershed may be higher than needed for recovery of 

spawning habitat. As more information becomes available during instream monitoring, the 

numeric targets for the lower part of the watershed may be adjusted during subsequent TMDL 

revisions. 

6. Percent Surface Fines < 2 mm 

As discussed above, salmonid egg growth and emergence of young fry are adversely affected when 

excessive levels of fine sediments are present on the stream bottom. In addition to the two 

measures of fine sediment used above, which are based on data for both surface and subsurface 

particle sizes collected through bulk sampling methods, a numeric target is included based on fine 

sediment on the surface of stream riffies which can be measured through the same pebble count 

method used to calculate the d50 particle size target established above. The target is being 

established for fines at the 2 mm size because this is approximately the smallest size particle which 

can be reliably identified through pebble count analysis. This indicator is being used because most 

past and expected future monitoring of substrate composition in Redwood Creek basin relies upon 

the pebble count method. In addition to providing a measure of fine sediment levels which may be 

associated with impacts to salmonid egg growth and emergence of fry, the level of fines on the 

stream surface is also a useful measure of the degree to which the stream is experiencing sediment 

loading in excess of sediment transport capacity. 

27 
a. Numeric Target 

The numeric target for surface fines <2mm for Redwood Creek is less than or equal to 10-20%. 

The target should be monitored through pebble counts in riffle crests located at monumented cross 

sections in fish bearing streams, to be selected.during the design of the monitoring plan. The target 

is selected based on a review of several literature sources, including Chapman and McLeod (1987) 

and Young, et.al. (1991). The target is set as a range to reflect (1) the relatively sparse research 

results regarding the levels of surface fines associated with good and poor quality salmonid 

habitats and (2) to reflect the significant variability which would be expected from year to year and 

in different locations within the watershed. ··EPA expects the target range to be exceeded in some 

years and is setting the target as a 10 year rolling average to account for expected interannual 

variability. 

b. Existing Conditions 

Fine sediment size fractions are difficult to measure accurately. The percentage of fine sediment in 

the channel bottom is often measured through various bulk sampling methods which gather both 

surface and subsurface sediments from the stream bottom. No bulk sampling data has been 

published for Redwood Creek; however, the fraction of fine sediments <2 mm commonly exceeds 

20% (personal communication with Mary Ann Madej, NPS, June 1998). Surface particle size 

distributions can also be measured through the pebble count method. Table 5 is a summary of 

unpublished fine sediment monitoring data collected by USGS and Redwood National Park in 

1979 and again in 1994 at 8 monitoring sites along the mainstem of lower and middle Redwood 

Creek. Table 5 on the following page reports data for the <2 mm size. It should be noted that the 

results are not reliable estimates for the stream as a whole or for the recent past. In addition, 

monitoring was conducted at a relatively small number of sites on only 2 occasions. For these 

reasons, firm conclusions concerning actual past or present conditions for fine sediment in 

Redwood Creek should not be drawn based on this limited data set. These data are presented here 

to provide a general sense of substrate surface particle sizes observed in 1979 and 1994. Because 

fines are often winnowed from the surface by stream flow, the fraction of fine sediment is expected 

to be higher when subsurface fines are also measured, as is done through bulk sampling methods 

(Lisle and Madej, 1992). 

c. Comparison of Numeric Target and Existing Conditions 

A comparison of the numeric target and existing information helps provide information on the 

extent of the problem as well as the sediment reduction needed to meet water quality standards. 

However, it was infeasible to conduct a quantitative comparison of the numeric target and existing 

conditions because inadequate reliable data were available. 

28 
Table 5: Summary of Existing Data for Fine Sediment Sizes on the Channel Bottom Surface 

Cross %fines<2mm %fines<2mm 

Section (1979) (1994) 

2. 20 15 

5 14 12 

16 3 6 

17 9 22 

20 4 28 

32 3 13 

34 14 19 

40 9 not available 

MEAN 10 16 

Source: RNP and USGS data reported in RNP (1995). 

7. Lar~e Woody Debris 

The removal of vegetation (particularly large conifers) from the riparian zone of the Redwood 

Creek watershed causes: 1) a loss of stream bank stability and increased stream bank erosion, 

2) adverse effects on stream channel morphology, including pool formation, and channel geometry, 

3) a loss of sediment filtering capacity and increases in sediment delivery, and 4) a reduction in the 

potential for large woody debris recruitment to the stream and in the stream's sediment transport 

efficiency. This statement relates to the COLD beneficial use and the potential for sediment and 

settleable matter to impact stream channel stability and habitat niches. 

a. Numeric Target 

The numeric tar~et for lar~e woody debris is increasin~ trends in lar~e woody debris. Insufficient 

data and information were available to support the delineation of a specific numeric target. To 

assist in reviewing whether large woody debris conditions are approaching satisfactory levels, table 

5 lists suggested large woody debris frequency and size for streams of different widths based on 

research conducted by Bilby and Ward (1989) concerning woody debris levels in forested 

watersheds dominated by old growth douglas fir. The suggested woody debris levels are most 

appropriately used for comparative purposes in parts of Redwood Creek basin in which douglas fir 

is the predominant conifer type (generally, in the areas of the watershed upstream of the National 

Park). These suggested values are not being established as numeric targets for the TMDL because 

their applicability to Redwood Creek is not well understQod at this time. 

29 
Table 5: Relationship between channel width and mean for debris diameter, length and 

volume and the number of pieces of debris in old-growth Douglas-fir streams. 

Channel Width Debris/100 ft Geometric mean Geometric mean Mean debris 

(ft) debris diameter debris length piece volume 

(inches) (ft) (cubic feet) 

15 16 14 18 13 

20 12 16 20 26 

25 9 17 22 38 

30 7 18 25 51 

40 5 21 29 75 

50 4 23 33 100 

55 4 25 35 113 

60 3 26 37 125 

65 3 27 40 137 

Source: Adapted from Btlby and Ward (1989). 

b. Existing Conditions and Comparison with Numeric Target 

Limited information is available concerning large woody debris within the riparian management 

zone in Redwood Creek. In a study by Pitlick (1982), 16 tributaries in Redwood Creek Basin were 

evaluated for percentage of sediment stored by large woody debris. Values ranged from a low of 

13 percent to a high of 94 percent. On average, greater than 40 percent of the sediment volume 

was stored by large woody debris. 

Hillslope Numeric Targets 

As described above, numeric targets are designed to interpret narrative State water quality 

standards in effect for Redwood Creek and identify the desired condition for the watershed with 

respect to sedimentation. The suite of instream numeric targets included in the TMDL are 

intended to identify key characteristics of the instream environment which, if attained, are expected 

to be adequate to ensure recovery of aquatic habitat health. To account for temporal variability in 

conditions, the instream targets are expressed as ten year rolling averages (i.e., they are not 

expected to yield reliable diagnostic results in periods ofless than ten years). The drawback of this 

approach is that it does not provide indicators which are capable of guiding shorter term evaluation 

of whether the watershed is moving toward recovery of conditions which will support all beneficial 

uses of concern which were affected by excessive sediment delivery. 

Hillslope numeric targets are included in the TMDL to describe desired conditions with 

respect to several land management uses which are ongoing in the watershed and which are 

expected to continue to pose significant erosion potential in the future. Hillslope targets are being 

established to identify appropriate road design, location, inspection, and maintenance patterns 

30 
along with appropriate silvicultural practices in sensitive areas. If attained, these hillslope targets 

are expected to result in the reduction of erosion potential and future sediment delivery to streams 

to levels which will allow recovery of instream habitat from sediment impacts over the coming 

decades. Therefore, hillslope targets supplement instream targets by providing measureable goals 

which are not subject to the variability associated with water year type. They have the advantatge 

to the individual landowner that they can be converted directly into implementation plans and 

management practices which can be evaluated more frequently than the 10 year rolling average. 

While inadequate information was available for this TMDL to support development of 

hillslope targets to address all potentially significant sediment sources (e.g. livestock impacts on 

streambanks), EPA believes the hillslope targets collectively describe the attributes of a wellfunctioning watershed which supports both healthy aquatic habitat and ongoing road use and 

logging. EPA also believes these hillslope targets are consistent with the proposed implementation 

provisions in the State's TMDL and implementation plan draft dated November 10, 1998. As 

additional information is collected in the future regarding the effectiveness of erosion prevention 

and control methods and associated stream habitat recovery trends, it may be appropriate to review 

and revise these hillslope targets accordingly. 

Table 6 on the following page summarizes the hillslope targets, which are discussed in detail below. 

8. Road stream crossings with diversion potential 

A key source of continuing erosion potential in Redwood Creek watershed is the existence of many 

road crossings with diversion potential (i.e., the tendency to divert stream flow out of the channel 

and along and across the road surface) (RNP, 1997, Hagans and Weaver, 1987). Diversion of flow 

is associated with major road surface erosion and creation of debris flows and other mass wasting 

events. The potential for diversion is eliminated in well-designed crossings through the use of 

rolling dips or other measures which ensure that if the crossing fails, the flow remains in the 

channel. 

a. Numeric Target 

The numeric target is that no crossings have diversion potential (i.e .. all crossings are reconfigured 

permanently to assure that no diversion will occur). This target is selected based on 

recommendations from Redwood National Park and USGS scientists (see comments from RNP 

and M. Madej, USGS) and EPA's review of literature sources concerning the potential for 

eliminating road-related erosion potential (Weaver and Hagans, 1994 and 1996; Spence et.al. 

1996). 

b. Existing Conditions and Comparison with Numeric Target 

Although specific data concerning diversion potential of roads in Redwood Creek were not 

available to EPA for this TMDL, Redwood National Park researchers have estimated that about 

55% ofthe approximately 1400 miles of roads in the basin are not maintained and are therefore 

more likely to fail during a storm than maintained roads. There are several thousand crossings 

associated with these roads. Therefore, it is likely that hundreds if not thousands of crossings 

continue to have diversion potential. 

31 
Table 6· . Hillslope Numeric Targets for the Redwood Creek Watershed . 

Parameter Numeric Targets (Desired Conditions) 

Road stream crossings with No crossings have diversion potential (i.e., all crossings are 

diversion potential reconfigured permanently to assure that no diversion will occur). 

Road culvert/crossing sizing All culverts and crossings are sized to pass the 50 year flood and 

associated sediment and debris. In addition, crossings and culverts 

in the snow zone (generally, upstream of Highway 299, are sized 

large enough to accommodate flows and associated sediment and 

debris caused by precipitation and snow melt runoff. 

Landing and road fill stability All landings and road fills (e.g., sidecasts) on slopes >50% and which 

could potentially deliver sediment to a water course are pulled back 

and stabilized. 

Road surfacing and drainage All roads have surfacing and drainage facilities or structures which are 

appropriate to their patterns and intensity of use. 

Road inspection, maintenance, All roads are inspected and maintained annually or decommissioned. 

and decommissioning Decommissioned roads (roads which are closed, abandoned, or 

obliterated) are hydrologically maintenance free. 1 

Road location in inner gorge or Roads are not located in steep inner gorge or unstable headwall areas 

unstable headwall areas except where alternative road locations are unavailable? 

Use of clearcut and/or tractor Clearcut and/or tractor yarding harvest methods are not used in steep 

yarding timber harvest inner gorge, unstable, or streamside areas unless a detailed 

methods geological assessment is performed which shows there is no 

potential for increased sediment delivery to water courses as a result 

of using these methods.3 

1 Hydrologically mamtenance free means that: 

-drainage in the road area mimics natural hydrology, 

- all drainage is dispersed to the slope through use, as appropriate, of outsloping or cross-road drains, 

- all culverts and associated fill material is removed from crossing areas, 

- all potentially unstable road fill and landing sidecasts are pulled back, and 

- excavated spoils are placed in locations where they will not enter a water course. 

2 This target is intended to address roads located adjacent to water courses with inner gorge topography or 

which cross steep, unstable headwall areas, and is not intended to apply to road crossings of inner gorge 

areas. Steep inner gorge areas generally exceed 65% in slope and are located adjacent to class 1 and 2 

water courses. Characteristics of steep unstable headwall areas generally include the following: 

- slopes greater than 50%, 

- erosive or incompetent soil types or underlying geology, 

- concave slope shape, 

- convergent groundwater present, and/or 

- evidence of past movement is present 

3 Characteristics of steep inner gorge, unstable, or streamside areas generally include a the following: 

- slopes greater than 50%, 

-located within 300 feet of a Class 1, 2, or 3 watercourse, 

- erosive or incompetent soil types or underlying geology, 

- concave slope shape, 

- convergent groundwater present, and/or 

- evidence of past movement is present 

32 

i 
9. Road culvert/crossing sizing 

A second important source of continuing erosion potential in Redwood Creek watershed is the 

existence of many road crossings with inadequately sized culverts or drainage structures. When 

culverts or crossings are blocked with debris during runoff events, the crossing may be fail, 

triggering debris flows which can scour downstream channels and deliver massive amounts of fill 

and scoured material to stream channels (RNP, 1997, RNP, 1998c, Hagans and Weaver, 1987). 

The potential for crossing failure is minimized when culverts or drainage structures are sized to 

handle the flow and associated debris and sediment load associated with infrequent but potentially 

destructive storms. 

a. Numeric Target 

The numeric target is that all culverts and crossings are sized to pass the 50 year flood and 

associated sediment and debris. In addition. crossings and culverts in the snow zone (generally; 

upstream of Highway 299. are sized large enough to accommodate flows and associated sediment 

and debris caused by precipitation and snow melt runoff.. This target is selected based on 

recommendations from Redwood National Park and USGS scientists (see comments from RNP 

and M. Madej, USGS) and EPA's review ofliterature sources concerning the potential for 

eliminating road-related erosion potential (Weaver and Hagans, 1994 and 1996; Spence et.al. 

1996). 

b. Existing Conditions and Comparison with Numeric Target 

It has been estimated that on the basis of road maintenance status, hillslope gradient, geology, and 

soil types, stream crossing failures are likely to occur on about one third of the 1110 road miles 

upstream of the park during a large storm (RNP, 1998c). About 55% of the approximately 1400 

miles of roads in the basin are not maintained and are therefore more likely to fail during a storm 

than maintained roads. 

10. Landing and road fill stability 

A third source of continuing erosion potential in Redwood Creek watershed is the existence of 

landings and roads which contain perched, unstable fill on steep slopes. Unstable fill is vulnerable 

to failure in response to major storm runoff and stream diversions from channels, which may cause 

large-scale debris torrents and sediment delivery to streams. (RNP, 1997, RNP, 1998c ). The 

potential for failure of landing and road fills crossing failure is minimized when landings and road 

fills are properly located (e.g., not on excessively steep, unstable slopes) when in use and properly 

pulled back (i.e., excavated) following use. 

a. Numeric Target 

The numeric target is that all landings and road fills (e.g .. sidecasts) on slopes >50% which could 

potentially deliver sediment to a water course are pulled back and stabilized. This target is selected 

based on recommendations from Redwood National Park and USGS scientists (see comments from 

RNP and M. Madej, USGS) and EPA's review ofliterature sources concerning the potential for 

eliminating road-related erosion potential (Weaver and Hagans, 1994, 1996; Spence et.al. 1996). 

33 
b. Existing Conditions and Comparison with Numeric Target 

Specific estimates of the number of unstable landings and fills are unavailable. As described 

above, about 55% of the approximately 1400 miles of roads in the basin are not maintained and are 

therefore more likely to fail during a storm than maintained roads. About 80% of the roads in the 

basin were constructed before 1978, when lower road construction standards were generally in 

effect (RNP, 1998c ). This suggests that several hundred to several thousand unstable landings and 

fills may exist in the basin. The percentage of these unstable fills and landings with potential to 

contribute sediment to watercourses is unknown, but is expected to be significant. Of the 50 miles 

of roads constructed on steep inner gorge slopes in the middle and upper basin upstream from the 

park, over 43 miles had been effectively abandoned by 1992 (RNP,1998c). 

11. Road surfacing and drainage 

A very high percentage of roads in Redwood Creek are dirt surfaced roads with minimal or 

inadequate road surface drainage structures. Large quantities of sediments erode from road 

surfaces in response to storms, which can contribute to fluvial erosion and mass wasting on sites 

below roads (RNP, 1997, RNP, 1998c). The potential for excessive road surface erosion is 

minimized when roads are properly surfaced and have appropriate drainage structures. For 

example, roads which are used during wet weather periods should be rocked or paved, depending 

upon intensity of use. All roads should have appropriate drainage structures which disperse 

drainage across slopes and do not contribute to hillslope fluvial erosion or mass wasting. 

a. Numeric Target 

The numeric target is that all roads have surfacing and drainage facilities or structures which are 

appropriate to their patterns and intensity of use. This target is selected based on recommendations 

from Redwood National Park and USGS scientists (see comments from RNP and M. Madej, 

USGS) and EPA's review ofliterature sources concerning the potential for eliminating road-related 

erosion potential (Weaver and Hagans, 1994 and 1996; Spence et.al. 1996). 

b. Existing Conditions and Comparison with Numeric Target 

About 80% of the roads in the basin were constructed before 1978, when lower road construction 

standards were generally in effect (RNP, 1998c). These roads are less likely than recently 

constructed roads to have appropriate surfacing and drainage facilities. It is likely that road 

surfacing and drainage facilities have been upgraded on some roads at the time recent timber 

harvesting activities required the use of older roads in some parts of the basin. However, Redwood 

National Park researchers estimate that about 55% of the roads in the basin are not maintained 

(RNP, 1998c ). These roads are therefore more likely to have degraded road surfaces or failing 

drainage structures. This suggests that several hundred miles of roads in the basin may have 

inadequate road surfacing and drainage facilities. 

12. Road inspection. maintenance. and decommissioning 

A very high percentage of roads in Redwood Creek are dirt surfaced roads with minimal or 

inadequate road surface drainage structures. Large quantities of sediments erode from road 

34 
surfaces in response to storms, which can contribute to fluvial erosion and mass wasting on sites 

below roads (RNP, 1997, RNP, 1998c ). The potential for excessive road surface erosion is 

minimized when roads are properly surfaced and have appropriate drainage structures. For 

example, roads which are used during wet weather periods should be rocked or paved, depending 

upon intensity of use. All roads should have appropriate drainage structures which disperse 

drainage across slopes and do not contribute to hillslope fluvial erosion or mass wasting. 

a. Numeric Target 

Ihe numeric target is that all roads are inspected and maintained annually or decommissioned. 

Decommissioned roads (roads which are closed. abandoned. or obliterated) are hydrologically 

maintenance free. This target is selected based on recommendations from Redwood National Park 

and USGS scientists (see comments from RNP and M. Madej, USGS) and EPA's review of 

literature sources concerning the potential for eliminating road-related erosion potential (Weaver 

and Hagans, 1994 and 1996). EPA intends that annual road inspections need not involve intensive 

analysis of road conditions, and that this target would be attained if all roads are driven annually 

and inspected visually. The visual inspection may identify road-related problems which cause an 

increase in erosion potential, including, but not limited to culvert plugging, cracking or gullying of 

road fills and landings, and failures of drainage structures. These problems should be promptly 

corrected before the potential erosion and sediment delivery can occur. This road inspection and 

maintenance target would complement the initial, more intensive road inventory proposed in the 

State's draft TMDL implementation plan dated November 10, 1998. 

Roads which cannot be inspected and maintained annually should be decommissioned in a 

manner which assures that erosion potential is prevented and the roads are hydrologically 

maintenance free. Hydrologically maintenance free means that: 

- drainage in the road area mimics natural hydrology, 

- all drainage is dispersed to the slope through use, as appropriate, of outsloping or crossroad drains, 

-all culverts and associated fill material are removed from crossing areas, 

- all potentially unstable road fill and landing sidecasts are pulled back, and 

- excavated spoils are placed in locations where they will not enter a water course. 

b. Existing Conditions and Comparison with Numeric Target 

No information about road inspection activity in Redwood Creek was available for this TMDL; 

however, Redwood National Park researchers estimate that about 55% of the roads in the basin are 

not maintained on a regular basis (RNP, 1998c). Redwood National Park has decommissioned 

many roads since the park was established, and several private landowners have decommissioned 

roads which are no longer used. Under the park's proposed future management alternative, 155 

miles of roads within the park would be decommissioned and over 900 miles of roads upstream 

from the park on private land would be decommissioned or upgraded (RNP, 1998a). Attainment of 

this target is likely to require increases in annual road inspection and maintenance activity on 

private lands, while decommissioning activity may be consistent with the park management plan 

preferred alternative. 

35 
13. Road location in inner gorfie or unstable headwall areas 

Roads in inner gorge areas are particularly prone to failures· which can introduce substantial 

quantities of sediment into water courses. Roads in unstable headwall areas are also prone to 

failure, which may cause debris torrents which can transport large volumes of sediments to some 

watercourses (RNP, 1997, RNP, 1998c). It is difficult to engineer roads in these areas in a manner 

which assures that erosion potential is minimal; therefore, it is most appropriate that roads be 

eliminated in these areas. However, EPA recognizes that in some areas of the basin, there may be 

no alternative means of access if such roads are eliminated. In these situations, it may be 

appropriate for the roads to remain in place if a geological and engineering review is conducted 

which ensures that no erosion potential exists associated with the roads. In general, new roads 

should not be built in steep inner gorge or unstable headwall areas. 

a. Numeric Target 

The numeric target is that roads are not located in steep inner gorfje or unstable headwall areas 

except where alternative road locations are unavailable. This target is intended to address roads 

located adjacent to water courses with steep inner gorge topography or which cross steep, unstable 

headwall areas, and is not intended to apply to road crossings of inner gorge areas. Steep inner 

gorge areas generally exceed 65% in slope and are located adjacent to class 1 and 2 water courses. 

Characteristics of steep unstable headwall areas generally include a combination of the following: 

- slopes greater than 50%, 

-erosive or incompetent soil types or underlying geology, 

- concave slope shape, 

-convergent groundwater present, and/or 

- evidence of past movement is present. 

This target is selected based on recommendations from Redwood National Park and USGS 

scientists (see comments from RNP and M. Madej, USGS) and EPA's review of literature sources 

concerning the potential for eliminating road-related erosion potential (Weaver and Hagans, 1994 

and 1996). 

b. Existing Conditions and Comparison with Numeric Target 

Approximately 50 miles of roads in Redwood Creek basin above the park are located in steep inner 

gorge areas (RNP, 1998c), and an unknown but probably significant number of roads cross 

unstable headwall areas in the basin. About 85% of these inner gorge roads had been effectively 

abandoned by 1992, and 64% were no longer drivable. Therefore, it appears likely that most of 

these inner gorge roads above the park could be decommissioned without impairing access. Most 

if not all inner gorge roads in the park have been decommissioned. The number of roads crossing 

unstable headwall areas in the park is unknown, but EPA understands that such roads have been 

targeted for decommissioning work in the past. 

14. Use of clearcut and/or tractor yarding timber harvest methods 

Timber harvesting is expected to remain the primary land use on private lands upstream of the 

park. Most futtire harvesting is expected to occur in areas of second growth forests. Reentry and 

36 
harvesting of second growth forests may cause excessive sediment loading unless more protective 

harvesting and yarding methods are used. Steep inner gorge, unstable, and streamside areas are 

most vulnerable to the effects of these more intensive harvesting and yarding methods because 

sediment from landslides and bare ground erosion is more likely to reach watercourses and cause 

adverse impacts to fish habitat. 

Studies in the lower Eel River basin suggest that landslides in recently harvested second growth 

areas underlain by Franciscan geology (similar to that found in Redwood Creek) are larger and 

more common than those in areas of unharvested second growth (PW A, 1998). In Redwood Creek 

basin, Pitlick (1982) found that slides in harvested inner gorge areas were no more common but 

were much larger than those in uncut inner gorge slopes. Clearcut logging and tractor yarding 

were by far the most common methods used in Redwood Creek basin before the 1980s. Clearcut 

logging and tractor logging are significantly more disruptive of natural watershed processes 

including soil erosion than are other logging and yarding methods which do not cause as much 

ground surface disturbance (Spence, et.al, 1996). Although alternative silvicultural methods are 

increasingly in use in Redwood Creek, use of clearcut logging and tractor yarding methods is 

expected to continue in the future. In order to minimize the erosion potential associated with use 

of these methods, the TMDL includes a numeric target which focuses on the most vulnerable 

geologically unstable areas and streamside zones. The target articulates a future desired condition 

that clearcutting and tractor methods are not used in inner gorge~ unstable or streamside areas 

except in cases where a thorough geological investigation shows that use of these methods will 

result in no increase in sediment loading to streams compared to pre-logging conditions. 

Attainment of this target is expected to reduce logging related erosion in unstable or streamside 

areas to acceptable levels. 

a. Numeric target 

The numeric target is that clearcut and/or tractor yarding harvest methods are not used in steep 

inner gorge. unstable. or streamside areas unless a detailed geological assessment is performed 

which shows there is no potential for increased sediment delivery to water courses as a result of 

using these methods. This target is selected based on recommendations from Redwood National 

Park and USGS scientists (see comments from RNP and M. Madej, USGS) and EPA's review of 

literature sources concerning the potential for minimizing logging-related erosion potential in inner 

gorge, unstable, and streamside areas (Spence, et.al., 1996, Reid, 1996 and 1998). Characteristics 

of steep inner gorge, unstable, or streamside areas generally include a combination of the 

following: 

- slopes greater than 50%, 

- located within 300 feet of a Class 1, 2, or 3 watercourse, 

- erosive or incompetent soil types or underlying geology, 

- concave slope shape, 

- convergent groundwater present, and/or 

- evidence of past movement is present. 

b. Comparison of Existing Conditions and Numeric Targets 

Past harvesting practices in Redwood Creek basin consisted almost entirely of large scale clearcuts 

using tractor yarding (RNP, 1998c). Between 1978-1995, about 30% of the area logged was 

37 
clearcut (RNP, 1998c). During this period, tractor yarding was still the preferred method for 

removing logs. The extent to which streamside forest areas were harvested and the methods used 

for such harvesting in recent years is unknown, although California Forest Practice Rules specify 

watershed and lake protection zones which must be adhered to in preparation of timber harvest 

plans. Additionally, current Forest Practice Rules require plan review by a certified geologist 

under some conditions. Attainment of this target could require modification of harvest and yarding 

methods in a significant portion of the middle and upper basin which are managed primarily for 

timber harvesting. 

Conclusion 

The numeric targets are intended to interpret and apply the narrative water quality 

objectives. They were developed to support a goal of salmonid recovery which is a conservative 

approach. A variety of instream indicators were selected because no single indicator provides a 

truly effective, discriminating measure of the relationship between sediment loading and instream 

sediment impacts. The instream numeric targets are expressed as ten year rolling average values to 

account for interannual variability. 

It should be noted that very useful monitoring information is being collected through the 

park's ongoing monitoring ofmonumented cross sections and associated thalweg (low flow 

channel) profiles. Although it was infeasible to derive specific indicators and numeric target 

values for these monitoring methods for this TMDL, researchers are currently developing 

indicators which could serve this purpose in the future. Cross section and thalweg measures 

should prove effective in the future as indicators of channel stability and change over time. Other 

new measures are also being developed (e.g., substrate permeability and turbidity measures) which 

could prove more effective than some of the indicators used in this TMDL. In future TMDL 

revisions, it may be appropriate to consider inclusion ofindicators based on these and other new 

monitoring approaches as they become available in the future. 

Hillslope indicators were also included in order to articulate desired conditions with respect 

to key land uses which are associated with future erosion potentiaL The best information available 

to EPA suggests that attainment of these targets would be an indicator that a managed watershed is 

capable of returning to an acceptable erosion regime and supporting recovery and maintenance of 

healthy instream habitat conditions. 

As additional information concerning these indicators becomes available through ongoing 

monitoring efforts by the State, Redwood National Park, landowners, and other stakeholders, these 

indicators and targets will be revisited and revised if necessary to provide the most discriminating 

set of indicators possible. 

It is recognized that no indicators were selected to address the issues of old growth 

redwood risks in the park or impairment of estuarine habitat near the mouth of Redwood Creek. 

EPA expects that if sediment reductions result in attainment of the numeric targets established in 

this TMDL, future risks to remaining streamside groves of old growth redwoods and sedimentrelated estuary impairments will be substantially reduced. However, some of the problems in the 

estuary apparently are associated with levee structures which the TMDL is not designed to address. 

38 
Section 3.3 Source Analysis 

The purpose of the Source Analysis is to demonstrate that all pollutant sources have been 

considered, and significant sources estimated, in order to help determine the degree of loading 

reductions needed to meet numeric targets and allocation of loading allowances among sources. 40 

CFR 130.2 defmes a TMDL as the sum of individual wasteload allocations, load allocations and 

natural background. The TMDL must not exceed the loading capacity of the receiving water for 

the pollutant of concern (in this case, sediment). In order to estimate the loading capacity of 

Redwood Creek and develop individual load allocations, existing and potential sources must ;first 

be characterized. This section provides three types of information: 

• an estimate of average annual sediment loads per square mile for the entire Redwood Creek 

watershed, 

• estimates of average annual sediment loads per square mile for three "reference" tributary 

watersheds within the Redwood Creek basin, and 

• estimates of historical sediment loading rates from all the significant sources of sediment in the 

Redwood Creek basin, organized by erosional process categories. 

For Redwood Creek, two general types of sediment source information are available from 

geomorphic research and monitoring programs of the National Park Service and the U.S. Geological 

Survey."" These are: 1) measurements of erosional processes within the watershed, and 2) records of 

sediment transport in Redwood Creek and some tributaries. The first type of information was used 

primarily to estimate the relative contributions of different source categories to overall sediment 

loading, and as the basis for allocating sediment source reductions and resulting TMDL load 

allocations. The second type of information was used to estimate overall sediment loading rates for 

the Redwood Creek basin and localized loading rates for three tributaries. The overall loading rate 

information provides the baseline against which TMDL-related sediment reductions are calculated. 

The localized tributary loading rate information assists in estimating the future loading capacity of 

Redwood Creek basin and the overall sediment discharge reductions heeded to protect beneficial 

uses. 

Long Term Estimates of Total Sediment Loading 

An estimate of long term annual average sediment loading per square mile was determined 

for the Redwood Creek gauging station at Orick, near the downstream end of the basin. Data 

reported in the Redwood Creek Watershed Analysis, supplemented by data furnished by Redwood 

National Park researchers, were analysed to develop long term annual average sediment output rates 

for the period 1954-1997. This is the amount of sediment which actually moves out of the basin past 

the Orick gauging station. 

During the 1954-1997 period, there was a substantial increase in instream storage of sediment 

delivered to Redwood Creek and its tributaries. Most of this increase in instream storage was the 

result of a few major discharge and flood events of which the 1964 flood was most important (RNP, 

1997). The sediment budget calculated for the Redwood Creek Watershed Analysis estimates that 

there was a net increase in the volume of sediments added to instream storage which was on the 

order of23% of the total sediment output from the basin (RNP, 1997). Most of the stored sediments 

39 
are either in the mainstem of Redwood Creek or at the bottoms of tributary streams. It has been 

estimated that stored sediments may take several decades to be remobilised, move downstream, and 

eventually discharge from the basin. This huge increase in stored sediment in Redwood Creek 

caused major adverse impacts to the stream channel and to aquatic habitat as a result The 

Watershed Analysis discusses these impacts in detaiL The long term restoration of aquatic habitat in 

·Redwood Creek depends, to a significant degree, on the ability of the system to erode and move out 

these excessive deposits of stored sediment 

For the loading estimates developed for this section, sediment storage was not included as a 

specific factor in the analysis for several reasons. It was infeasible to calculate a reliable estimate of 

changes in instream stored sediment for this period. Second, additions to stored sediment have 

caused significant damage to aquatic habitat in Redwood Creek. If instream storage were added to 

the loading estimate as a sediment sink, the overall estimate of sediment loading from 1954-1997 

would be increased substantially. By including instream storage in the analysis, it could create the 

impression that continuing increases in instream storage in the future are acceptable. This is not the 

case; to the contrary, decreases in instream stored sediment are needed. Third, the esti_mates of 

sediment reductions needed in the basin were made through comparisons with "reference" watershed 

sediment loading rates for three tributary watersheds in Redwood Creek basin. The Watershed 

Analysis indicates that 60-80% of flood-related instream sediment deposits are flushed out of 

tributary watersheds within 10 years, in contrast to the mainstem. In order to more fairly compare 

loading rates for the tributary "reference" watersheds and the loading rates for the entire Redwood 

Creek basin, it is appropriate to exclude instream storage from the loading estimates for the 

Redwood Creek mainstem. 

This analysis treats instream channel storage of sediment as a potentially long term, but still 

temporary sink for sediment which is associated with substantial adverse impacts to beneficial uses 

and which is generally not amenable to control after it has occurred. It is not expected that following 

the sediment loading reductions called for in the TMDL, there will be significant increases to 

instream storage except in response to very infrequent, high magnitude events. For these reasons, 

the simplifying assumption was made that in the long term, sediment inputs equal sediment outputs 

in properly functioning streams. In other words, the total sediment loading estimate does not 

separately account for instream storage as a sink or a source of sediment outputs at Orick. 

Table 7 provides summaries of annual sediment loading per square mile at Orick based on 

estimates in the Watershed Analysis for the periods 1954-1980 and 197 4-1992 along with loading 

estimates calculated for this report for the period 1981-1997 based on sediment loading data 

provided by Redwood National Park. Table 7 also provides an estimate of annual loading per square 

mile at Orick for the period 1954-1997 which is used as the baseline for calculating the TMDL and 

associated allocations. As discussed in Appendix C of the Watershed Analysis, the 1954-80 estimate 

is based on actual data collected by U.S. Geological Survey since 1971 along with an estimate of 

probable sediment yields from 1954-1971 by Knott (USGS, 1981, cited in RNP, 1997). The 1974-

1992 estimate is based on USGS and NPS data collected at Orick and is reported in RNP, 1997. The 

1981-1997 estimate is based on USGS and NPS data provided in RNP, 1997. 

For the 1981-1997 estimate, where bedload data were not reported, it was assumed that 

bedload equals 25% of total sediment transport in the Redwood Creek system. This assumption is 

based on comparison of suspended and bedload sediment loading rates from 197 4-1992 and is 

40 
consistent with the Watershed Analysis, which reports that bedload accounts for roughly 20-25% of 

total sediment load, and with findings of other researchers (e.g. Lisle and Madej, 1992, which reports 

that bedload constitutes 10-30% oftotalload). 

The 1954-1997 loading estimate was calculated as follows: 

[(54-80 av. loading rate)*(# of years 54-80) + (81-97 av. loading rate)*(# of years 81-97)] 

(number of years 1954-1997) 

which is: 

[(5995*27) + (2769*17)] = 4749 tons/square mile/year 

44 

Table 6· . Summaries of Annual Average Sediment Loading Per Square Mile at Orick 

Time Period Annual Average Load Source 

(tons/mi2

/year) 

1954-1980 5995 Redwood Creek Watershed Analysis, 

AppendixC 

1974-1992 3120 Watershed Analysis 

1981-1997 2769 calculated from Watershed Analysis and 

RNPdata 

1954-1997 4749 calculated from Watershed Analysis and 

RNPdata 

Because the TMDL is presented in terms of average annual sediment loading per square mile 

to be measured as ten year rolling averages, table 7 provides a summary of 10 year rolling average 

sediment yields at Orick, which can be compared with the TMDL of 1900 tons/square mile/year. 

Table 7: Ten Year Rolling Average Sediment Yields at Orick 

Time Period Average Sediment Yield 

(Water years) (tons/square mile) 

1980-89 2880 

1981-90 2649 

1982-91 2539 

1983-92 1955 

1984-93 1517 

1985-94 1225 

1986-95 1412 

1987-96 1481 

1988-97 2251 

41 
Figure 2 provides these 10 year rolling average data in graph form. 

Figure 2: 

Rolling 10 Year A~ Sediment Yield at Orick 

~,---------------------------------------------

zmT;~--~--~----------------------------------

1981-90 1983-92 198~4 1987.Q6 

1980-89' 1982-91 1984-93 1986-95 1988-97 

Estimates of Annual Loading for "Reference" Tributaries 

Annual average sediment loads per square mile were calculated for three tributaries of 

Redwood Creek which are believed to be in relatively good condition in terms of erosion potential 

and which, as a result, may serve as "reference streams" for purposes of comparing localized erosion 

rates with erosion rates ofthe.basin as a whole. They have received relatively little disturbance 

through timber harvesting, road building, and other land management activities in recent decades 

when compared to most of Redwood Creek watershed, and are reasonably representative of the 

major geological formations present in the basin. This type of comparison assists in evaluating 

1MDL goals or desired conditions with respect to sediment loading rates and in estimating the 

basin's loading capacity for sediment inputs. 

The first two tributary basins may be characterized as moderately vulnerable to erosion due 

to land management impacts: 

Panther Creek is located on the west side of the valley and has experienced moderate logging 

during the past decade. Most of Panther Creek basin was also harvested several decades ago, 

although increased logging has resumed in the last 2 years (personal communication with Greg 

Bundros,RNP, June, 1998). Panther Creek was selected partly because it is underlain by 

Redwood Creek schist, the most common rock type west of Redwood Creek. 

Lacks Creek is a larger tributary on the east side of the valley which has experienced relatively 

little timber harvesting during the past decade and now hosts extensive mature second growth 

forest (personal communication with Greg Bundros, RNP, June 1998). Lacks Creek is 

underlain by a combination of rock types-- principally the Coherent Unit of Lacks Creek 

(mostly less erosive sandstones) and the Incoherent Unit of Coyote Creek (more erosive silt 

and mudstones)-- and is believed to be generally representative of the geology of the east side 

of the valley. 

Sediment TMDL for Redwood Creek, CA 42 
Little Lost Man Creek is tributary to Prairie Creek, the largest tributary to Redwood Creek, and 

has experienced no significant logging or land management disturbance (personal 

communication with Randy Klein, RNP, June 1998). It is underlain by a third major rock type 

which characterizes the Prairie Creek subwatershed. Little Lost Man Creek (and Prairie Creek 

as a whole) are not representative of the rest of Redwood Creek basin because they are less 

steep, are underlain by a generally less erosive rock type, and are much less intensively 

managed. 

Note that although these three tributary watersheds are appropriate for examination as 

historical reference watersheds, they are not assumed to be appropriate as future reference streams 

for comparative analysis. It is quite possible that Panther Creek and Lacks Creek will be subject to 

intensive future management which may result in unacceptably large increases in loading rates. 

Additional work would be needed to evaluate whether they are appropriate reference streams for the 

purpose of comparing future erosion rates with erosion rates for the entire Redwood Creek 

watershed. 

Sediment transport data were collected at gauging stations near the mouths of the three 

tributaries discussed above: Panther Creek, Lacks Creek, and Little Lost Man Creek. Table 8 

presents estimates for annual average loading rates per square mile for each of these locations. 

Because bedload data were not generally available after 1992, the estimates were based on the 

assumption that bedload equals 25% of total sediment loads (see above discussion for rationale). 

In order to facilitate comparisons between loading rates for these locations and for the 

Redwood Creek watershed as a whole (as calculated for Orick from 1954-1997), Table 8 also 

presents adjusted loading rate estimates for each of these locations. The annual average loading rates 

were adjusted to account for different time periods covered by the data record in each location. The 

adjustments are based on the assumption that percentage differences in the average annual loading 

rates for the entire watershed between the 1954-1980 period and the 1981-1997 period also were 

experienced in the tributary watersheds. It is recognized that this assumption is not well validated; 

however, it is reasonable to assume that loading rates in the "reference" tributaries and for the 

watershed as a whole would vary in proportion to each other over time. 

For Panther Creek, and Lacks Creek, data were generally available for 1981-1997 (although 

data for 1989-91 were missing). For Little Lost Man Creek, data were only available for 1993-1997. 

For Redwood Creek at Orick, the annual loading rate for 1954-1997 was 172% of the loading 

rate at that location from 1981-1997. The adjusted estimated loading rates for Redwood Creek at 

Okane, Panther Creek, and Lacks Creek are equal to 172% ofthe estimated 1981-97loading rates to 

account for the higher loading rates assumed to have occurred before 1981. 

For Little Lost Man Creek, data were only available for 1993-1997. For Redwood Creek at 

Orick, the annual loading rate for 1954-1997 was 127% of the loading rate at the same location from 

1993-1997. The adjusted estimated loading rate for Little Lost Man Creek is equal to 127% of the 

estimated 1993-97 loading rates to account for the higher loading rates assumed to have occurred 

before 1993. 

43 
Table 8: Estimated Average Annual Sediment Loading For Upper Basin and Tributaries 

Location Unadjusted Average Annual Load Adjusted Average 

(area) (tons/mF1

year) Annual Load (1954-

* 

Panther Creek 1119 

(6.07 mF) (1980-97) 

Lacks Creek 1467 

(16.9 mF) (1981-97) 

Little Lost Man Creek 238 

(1993-97) 

*source: Redwood National Park and USGS Unpublished Data (RNP, 1998b) 

1 results were rounded to the nearest ten 

Specific Source Estimates 

97) 

(tons/mF'year) 1 

1930 

2520 

300 

Sediment loading associated with specific sediment source categories was estimated based 

primarily on analysis ofthe sediment budget in the Redwood Creek Watershed Analysis (RNP, 

1997, Appendix C). A sediment budget quantifies sediment sources (inputs), by each erosional 

process, as well as changes in the amount of channel stored sediment, and sediment outputs as 

measured at gauging stations over a designated time frame (Reid and Dunne, 1996). The Redwo.od 

Creek sediment budget provides rough estimates of total erosion from all the significant source 

categories (erosional processes) for the period 1954-1980 along with estimates ofinstream sediment 

storage and sediment outputs at Orick. The results are not believed to be highly accurate (RNP, 

1997). The individual source estimates for this TMDL were calculated by multiplying the 

percentage of total load associated with each individual source category by the total sediment load 

estimated above for the period 1954-1997. 

This approach assumes that future loading rates from different source categories will be 

proportional to historical loading rates for these categories. This assumption is reasonable given that 

the main erosion processes of interest (and their causes) have not changed substantially in the 

watershed. There continue to be a large number of poorly designed and maintained roads and skid 

trails in the basin, and intensive timber harvesting activities continue. What has changed is spatial 

distribution of these land management activities. Road construction and logging have decreased in 

the lower watershed and increased in the upper watershed (RNP, 1997). 

Quantifying sediment sources involves determining the volume of sediment delivered to 

stream channels by the variety of erosional processes operating within the watershed. For the 

Redwood Creek watershed, these can be divided into 2 general processes or sediment delivery 

mechanisms: 1) mass movement (of which landslides are most important) and 2) fluvial erosion 

(road and skid trail crossing failures, gullies, and surface or sheetwash erosion, and stream bank 

erosion). Erosional processes in the watershed range from the removal of individual soil particles by 

raindrops to extensive landslides that cover entire hillslopes. In general, erosion caused by obvious 

large-scale earth movement has been better documented than erosion caused by dispersed small44 
scale processes. The smaller-scale processes, however, may also be of great importance in 

generating sediment because they are more widespread. Past studies indicate that streamside 

landsliding and fluvial hillslope erosion may be the most important processes delivering sediment to 

Redwood Creek (Harden and others, 1978; 1995; Kelsey and others, 198la; 198lb, cited in RNP, 

1997). The Watershed Analysis discusses different erosional processes of interest in Redwood 

Creek in detail; a brief summary of those processes is presented here. 

Landslides 

Streamside landslides are clearly an important source of sediment in the Redwood Creek 

watershed, because of their number and volume, and because they deliver sediment directly to 

channels. Streamside landslides include debris slides, debris avalanches, and earthflows; however, 

debris slides account for most of the streamside landslide volume (Kelsey and others, 1995, cited in 

RNP, 1997). Streamside landslides may be caused in part by channel aggradation (Janda and others, 

1975, cited in RNP, 1997). Sediment deposited in the channel raises water levels during storms, 

resulting in undercutting of hillslopes that subsequently fail as debris slides. 

Most streamside landslides identified for the 1954-97 period occurred between 1962 and 

1966. Between 1970 and 1976, the number of new streamside landslides decreased in the upper 

basin, but increased in the middle and lower basins. Few streamside landslides have been initiated 

during the relatively dry period since 1975, although the 1997 storm activated a substantial number 

of new slides. 

The most aerially extensive mass movement features in the watershed are earthflows; 

however, they contribute relatively little sediment to Redwood Creek (RNP, 1997). Landslides other 

than streamside landslides include debris avalanches and debris, slumps, forested block slides, and 

some large and relatively inactive earthflows. These landslides are much less significant as 

sediment sources than are streamside landslides. 

Fluvial Hillslope Erosion 

Fluvial hillslope erosion in the Redwood Creek watershed is apparent in both natural and 

disturbed settings. On unlogged forested hillslopes, fluvial erosion is related to interactions between 

subsurface piping through root channels and gully and rill. On logged hillslopes, extensive networks 

of rills and gullies have developed from streamflow diversions and washouts at road and skid trail 

stream crossings, from ditches and cutbanks, and from interception of subsurface flow along roads 

and trails. Surface erosion of logged areas may also have increased as a result of decreased 

interception of rainfall by the forest canopy following harvest. Prairies are particularly susceptible to 

gully erosion, and road runoff has carved numerous large gullies in the Bald Hills area, near Berry 

Summit on Highway 299, and other areas within the watershed. Previous studies have documented 

large increases in fluvial erosion on lands where timber has been harvested or where roads have been 

constructed (Janda and others, 1975; Nolan and others, 1976; Walter, 1985; Hagans and Weaver, 

1987, cited in RNP, 1997). 

45 
Channel Storage 

Massive amounts of coarse sediment were deposited in tributaries and the upper and middle 

reaches of the mainstem during the flood of 1964. During subsequent floods, particularly in 1972 

and 1975, coarse sediment was scoured from tributaries and the upper mainstem and re-deposited in 

lower reaches. 

Sediment stored within the channel system continues to move in wave-like fashion 

downstream (Madej and Ozaki, 1996). As of 1990, peak aggradation was about 5 miles downstream 

from the Tall Trees Grove and about 4 miles upstream of Orick (fig. 3-5). Channel cross section 

surveys in 1995 indicated that, for the first time since measurements began in 1973, the channel bed 

between the Tall Trees Grove and Orick was scoUring. However, cross section surveys from 1996-

97 document continued channel aggradation or infilling for several miles below the Tall Trees Grove 

(public comments of Redwood National Park, November 18, 1998). It seems clear that sediment 

discharged into Redwood Creek during major storm runoff events remains in storage for decades or 

longer. High flow events can remobilize these stored sediments and cause adverse impacts through 

channel modification and sediment redeposit in downstream habitat areas: 

Sediment Budget Adjustments 

Sediment budget estimates of tributary streamside landslides were further subdivided for the 

TMD L in order to reflect different likely causative mechanisms. Pitlick' s study of landslide 

associations with pre-failure site conditions (Pitlick, 1982) provides information which can be used 

to estimate the relationship between landslides and land uses. Pitlick showed that for Redwood 

Creek tributaries, 40 percent of stream side slope failures in tributary canyons were logging related, 

and 80 percent ofthe total landslide volume came from slopes logged prior to failure. Based on 

Pitlick' s analysis, tributary streamside landslides were divided into three categories: natural 

(corresponding to Pitlick's unlogged category), road- related (corresponding to Pitlick's road-related 

failures category) and harvest-related (corresponding to Pitlick's clear cut and selection cut 

categories). Landslides were divided based on the percent of total inventoried slide mass measured 

by Pitlick for each category. This approach assumes that the distribution oflandslide volumes 

associated with roads, harvesting, and natural conditions for the basin as a whole is the same as 

measured in Pitlick' s sample of several hundred landslides. 

A 1980 study of sediment sources and sediment transport in Redwood Creek evaluated 586 

mainstem landslides. The study revealed that approximately 50 % of the slides had one or more 

associated roads (Kelsey, et. al., 1981) The evaluation ofmainstem landslides recognizes that the 

volume of each slide may be variable. However, the volume of mainstem landslides associated with 

roads, or other management activities may represent more than 50 percent of the total load. 

Table 9 reports the results of the modified sediment budget. Annual average loading rates 

were estimated by calculating the percentage of the total estimated loads associated with each source 

mechanism, then multiplying that percentage by the estimated total average annual sediment load for 

1954-1997, as discussed above. 

46 
Table 9: Sediment Source Category Estimates 

a b c 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

Source Mechanism 54-97 Average Percentage of Total 

Annual Sediment Load Estimate 

Load (t/mF/yr) 

Roads and Skid Trails 690 14.6% 

( Including silvicultural activities, 

agriculture, and public roads.) 

Gully Erosion 1020 21.4% 

(Mostly road related) 

Bare Ground Erosion 400 8.4% 

Stream Bank Erosion 590 12.4% 

Tributary Landslides: Natural 210 4.4% 

Tributary Landslides: Road Related 360 7.6% 

Tributary Landslides: Harvest Related 390 8.3% 

Mainstem Landslides 810 17.0% 

Debris Torrents 100 2.2% 

Other Mass Movements: 180 3.7% 

- earthflows 

- block slides 

TOTAL ESTIMATED LOADS 4750 100% 

Note: CalculatiOns are rounded to the nearest 10. 

Average annual loads are calculated by multiplying the percentage in column c by 4750, the total estimated 

annual loading rate for the watershed between 1954-97. 

Source: Percentages of total loads in column care derived from Redwood Creek Watershed Analysis, 1997, 

Appendix C. 

Explanation of Sediment Budget 

About 54% of the overall budget was from fluvial and surface erosion, and about 46% of the 

budget is associated with mass wasting processes. Road-related erosion processes account for 

approximately 50% of the total budget, including significant proportions of the loadings associated 

with both fluvial and mass movement processes. It is difficult to estimate the proportion of total 

loading associated with timber harvesting (road-related impacts aside), but it probably exceeds 10% 

of the total. Natural background erosion accounts for roughly 30-40% of the total loadings. As 

discussed above, it is assumed that approximately 10% of average annual sediment loads were stored 

instream during the period 1954-97. 

This sediment budget is expected to be accurate within a factor of about+/- 40%. As such, it 

should be adequate for purposes of estimating the relative share of loadings from different source 

categories and establishing a baseline loading level for purposes of calculating needed load 

reductions. EPA expects that opportunities will arise in the future to evaluate the accuracy of the 

sediment budget and associated TMDL loading allocations, and make adjustments as necessary. 

47 
Conclusion 

For the period 1954-1997, long term average annual sediment production rate for the entire 

basin is estimated to be approximately 4750 tons/mF/yr. Approximately halfwas from mass wasting 

and half from fluvial erosion sources, including surface erosion processes. About half the sediment 

production was associated with roads and skid trails and roughly 10%-20% was associated with 

timber harvesting (not including harvest related roads and skid trails). Perhaps 30%-40% of total 

loads were naturally occurring, or at least were not associated with specific land management causes. 

It is important to emphasize that average annual loading rates provide useful information for 

planning only when a long term monitoring and analysis horizon is applied. Evaluation of sediment 

loading dynamics over short time periods (e.g., less than 10 or more years) is unlikely to yield 

reliable results, given that Redwood Creek sediment loading is dominated by infrequent, high 

magnitude events. For example, the key sediment loading events of the past 40 years were believed 

to be storms expected to occur perhaps once every 25-50 years. Just as important, stream recovery 

from high magnitude sediment loading events may take decades or longer to occur. 

Although average annual sediment loading rates for the period 1981-97 were substantially 

lower than the period 1954-1980, it is not clear that the recent lower loading rates indicate that the 

sediment loading problems in the basin are a thing of the past. The 1980s and early 1990s were 

marked by lower than normal precipitation and relatively few high magnitude events. Thus sources 

on the hillslope could be triggered by future high rainfalVflow events. However, the lower loading 

rates may be also be attributable, to some extent, to improvements in timber harvest practices. This 

period coincided with a tightening of California Forest Practice Rules and the use of more protective 

harvest practices; however the amount of logging in the basin has not declined during the period 

since Redwood National Park was established. Rather, logging has been moved upstream into the 

middle and upper parts of the basin. Analysis of future loadings and associated land management 

practices will be needed to evaluate the degree to which lower loading rates for the 1980-97 period 

were associated with improvements in forest practices. 

The early analysis of the effects of the 1997 "New Year's" storm (approximately an 11 year 

storm) indicates that a large amount of unaddressed erosion potential remains (NPS 1997 and written 

comments by Redwood National Park, November 18, 1998). Over 100 large landslides were 

triggered or reactivated, and multiple road failures occurred both within the Park and on lands 

outside the park. It was estimated that over 900,000 tons of sediments were discharged into 

Redwood Creek or its tributaries, or moved into unstable hillslope positions and are perched to fail. 

The erosion response to this storm indicates that additional action is needed to prevent ongoing, 

destructive sediment loading in the basin. 

48 
Section 3.4. Loading Capacity Linkage Analysis 

In order to determine the TMDL, it is important to assess the magnitude of instream sediment 

problems and the associated levels of sediment source reductions needed to address instream 

problems. The result of this assessment is an estimate of "loading capacity" -- the amount of 

sediment the Creek can assimilate and still meet its water quality standards. This section assesses 

the degree to which sediment reductions are needed from sources in the Redwood Creek watershed 

to alleviate the instream sediment problems discussed in the Problem Statement section and 

quantified in the Numeric Targets section. The analysis is based on two methods of comparing 

existing and desired conditions for the watershed: 

1. quantitative comparison of average sediment loading rates per square mile in more highly 

impacted and relatively unimpaired areas of Redwood Creek watershed, and 

2. qualitative comparison of existing and historical conditions with target levels for the instream 

indicators selected in the numeric targets section. 

It is recognized that inferring linkages between prospective hills lope erosion sources and 

instream impacts based on these methods will produce uncertain results. However, it is necessary to 

estimate the level of sediment reductions needed in the future to meet water quality standards. 

Because there are no reliable direct linkages to evaluate (i.e., the sediment-impact relationships tend 

to be separated in time and space) and no reliable methods for modeling those linkages, it is 

necessary to rely on these less certain inferential methods. EPA believes that through future 

monitoring and evaluation, it will prove more feasible to evaluate these cause-effect linkages with 

greater certainty than was feasible for this TMDL. 

Comparison of Sediment Loads in Redwood Creek to Reference Streams 

As discussed in the preceding sections, Lacks Creek, Panther Creek, and Little Lost Man 

Creek provide the best local candidates for estimating historical reference watershed loading rates. 

Adjusted average annual loading rates were estimated for each of these tributaries (see Source 

Analysis chapter for details), and the results are reported along with the average annual loading rates 

estimated for Redwood Creek at Orick. 

To allow a comparison of historical loading rates for the Redwood Creek watershed as a 

whole with "reference watershed" loading rates, it was necessary to weight the loading rates for the 

reference watersheds in accordance with how representative their underlying geologies are of the 

entire basin. For this adjustment, it was assumed that Panther Creek loading rates would be 

representative of"reference" loading rates for all ofthe basin area underlain by schist-- about 42% of 

the basin. It was further assumed that Little Lost Man Creek loading rates were representative of 

"reference" loading rates for the Prairie Creek area-- about 14% of the basin. Finally, it was 

assumed that Lacks Creek loading rates were representative of "reference" loading rates for the 

remainder of the basin-- about 44% of the basin. The Lacks Creek assumption is reasonable because 

that tributary is underlain by both of the most common remaining geologic types present in the basin, 

a combination of resistant sandstones and less resistant mudstones and siltstones. 

49 
The weightings were calculated as follows to yield a single estimated reference loading rate 

for the entire Redwood Creek basin (see table 1 0). First, the sediment loading rates for each 

reference stream (column b) were multiplied by the corresponding percentage (expressed as a 

decimal, i.e., 42% becomes 0.42) of the whole basin underlain by the reference stream geologic type 

(column c) to yield loading rate factors for each reference. The three loading rate factors were added 

together to yield the overall estimated loading for the entire basin. The weighting of the "reference" 

loadings yields an overall composite estimate of loadings associated with reasonably well 

functioning watersheds which are not experiencing excessive human-caused erosion. This 

calculation yields an estimate for a basin-wide reference loading rate of 1962 tons/square mile, 

which is 59% lower than the estimated basin loading rate for 1954-1997 of 4750 tons/square mile. 

While considering the assumptions made on calculating the reference loading rate, the result 

suggests that a reduction of approximately 60-% might be needed in order to achieve "reference 

watershed" conditions over a long time horizon. 

Table 10: Reference Stream Comparison Loading Information 

a b c 

I 

2 

3 

4 

5 

Reference Stream 

Panther Creek 

Lacks Creek 

Little Lost Man Creek 

Estimated Reference 

Loading Rate for 

Redwood Creek Basin 

Estimated Sediment 

Loading Rate (t/sq milyr) 

* 

1925 

2520 

301 

(weighted loading value= 

1960) 

*Redwood Creek Watershed Analysis, RNP,1997 

% of Watershed Representative 

of Reference Stream Geology 

42% 

44% 

14% 

100% 

Although some land management activity was occurring in Panther Creek and Lacks Creek 

several decades ago, this average annual loading estimate (1960 t/sq milyr) based upon reference 

streams is considered conservative because it includes the use of Little Lost Man Creek- a nearly 

pristine tributary -- as a reference stream for 14% of the basin. EPA does not expect that it would be 

necessary to attain the near pristine levels of sediment loading associated with Little Lost Man Creek 

in order to restore a functioning aquatic habitat in the watershed as a whole. 

Qualitative Analysis of Instream and Hills lope Conditions 

Linkages between sediment sources in the watershed and instream conditions are generally 

indirect and highly variable. However, over the long term, reductions in sediment inputs to the 

stream system are expected to result in reduction in sediment distributions in the channel. Over 

time, the instream indicators identified in the Numeric Targets section should reflect changes in 

response to reduced sediment loading and transport. Because of historical data limitations, it was 

infeasible to prepare a quantitative comparison between historical and target conditions for instream 

indicators. However, Table 11 summarizes the qualitative comparisons reported in the Numeric 

Targets section. This qualitative comparison appears to indicate that instream conditions remain 

inadequate to support healthy habitat, but that conditions may be improving. Recently observed 

50 
improvements in conditions may be associated with improved land management or with lower 

sediment loading rates during a relatively dry period. Significant continued sediment loading 

reductions appear to be necessary to address the instream problems associated with sediment. Large 

storm events of the magnitude seen prior to 1980 have not occurred since. When such events occur, 

higher sediment loading rates may result and consequently reveal deterioration of instream target 

conditions. 

Table 11· . Comparison of Existing/Historical Levels for lnstream Indicators with Target Levels 

Indicator Qualitative Comparison 

Fines <0.85mm historical levels may exceed target levels to 

moderate extent; may be improving in upper 

watershed 

Fines <6.5mm historical levels may exceed target levels to 

moderate extent; may be improving in upper 

watershed 

Median surface particle size historical levels appear lower than target 

(d50) levels indicate elevated fine sediment; some 

improvement in upper basin 

Surface fines <2 mm may be approaching target range, but no data 

post-1984 available 

Percent Riffles riffle percentage exceeds target in many 

locations but appears to be improving 

Pool Depth possibly nearing target levels in mainstem 

Conclusion: Estimate of Sediment Loading Capacity in Redwood Creek 

Both the reference stream analysis and instream indicator analysis indicate that some 

sediment reductions and reductions in future erosion potential are necessary. In EPA's judgement, 

reductions should be based primarily on the quantitative results of the reference stream analysis as 

this provides a more rigorous basis for estimating loading capacity. EPA estimates that reductions of 

about 60% are needed in order for Redwood Creek to meet water quality standards for sediment in 

the future. This suggests that allowable loading capacity is on the order of 40% ofhistoricalloading 

rates. This figure also compares with the estimation from the sediment budget that natural 

background erosion accounts for roughly 30-40% of the total estimated load for the period 1954-

1997. By multiplying the historical average annual loading rate (4750 tons/square mile) by the 40% 

allowable annual loadings, it yields an overall loading capacity estimate at Orick of 1900 tons/square 

mile/year. 

The Loading Capacity meets the regulatory definition at 40 CFR 130.2(f) which states that 

the loading capacity is "the greatest amount of loading that a water can receive without violating 

water quality standards." In addition, the Load Allocations meet the regulatory requirements at 40 

CFR 130.2(g) in that they are "best estimates of the loading, which may range from reasonably 

accurate estimates to gross allotments ... " 

51 
Section 3.5. Total Maximum Daily Loads and Allocations 

The requirements of a TMDL are described in 40 CFR 130.2 and 130.7 and Section 303( d) of 

the Clean Water Act, as well as in various guidance documents. A TMDL is defined as the sum of 

the individual wasteload allocations for point sources, and load allocations for nonpoint sources and 

natural background pollutants, such that the loading capacity of the receiving water is not exceeded. 

The allocations indicate the amount of pollutant reduction from individual source categories that is 

required to attain water quality objectives. Allocations may be assigned based on land use, land 

'area, or erosional process. In addition, the regulations at 40 CFR 130.2(g) state that "Load 

allocations are best estimates of the loading, which may range from reasonably accurate estimates to 

gross allotments, depending on the availability of data and appropnate techniques for predicting the 

loading." The Redwood Creek allocations have been developed for erosion processes (associated 

with land use activities where feasible) based on the source analysis of the various erosional 

processes. The load allocations have been developed as long term annual average loads per square 

mile at the basin-wide scale. As discussed in the source analysis chapter, sediment storage was not 

factored into the TMDL, loading capacity, and allocation calculations. 

Total Maximum Daily Load Calculation 

The TMDL for Redwood Creek is being expressed as long term annual average sediment 

loading per square mile, as applied at the Orick gauging station at the downstream end of the 

watershed. This meets the regulatory definition that "TMDLs can be expressed in terms of either 

mass per time, toxicity, or other appropriate measure." (40 CFR 130.2) This annual TMDL could be 

converted into daily loads, but expressing the TMDL as an annual average yield better reflects the 

dynamic nature of sediment movement throughout a watershed over time. The annual average 

loading rate for this TMDL will be measured in terms of 10 year rolling annual averages. The longer 

term annual average timestep is an appropriate approach to account for the large interannual 

variability in sediment loading and the long term timeframe in which beneficial use impacts occur 

and change. This annual average loading per square mile will be referred to as the TMDL for 

Redwood Creek. The TMDL is calculated by applying the loading capacity range from the previous 

section, which was estimated at 1900 tons/square mile/year (rounded). The TMDL for Redwood 

Creek is therefore estimated to be 1900 tons/square mile/year. expressed as 10 year rolling 

annual averages. 

Load Allocations and Wasteload Allocations 

The following are the load allocations (column e in Table 12 on the following page). The 

waste load allocation for Redwood Creek is zero as there are no permitted point sources of sediment 

discharge to the watershed. Explanation is provided below under Explanation of Allocations and 

Calculations. 

52 
Table 12: Summary of TMDL and Allocations for the Redwood Creek watershed. 

a b c d e 

Historic Percent Controllable Remaining Load 

Source Mechanism Sediment Load1 Controllable2 Load3 (Allocationt 

(t/mi2

/yr) (t/mi2

/yr) (t/mi2

/yr) 

Roads, Landings and Skid 690 85% 580 llO 

Trails erosion 

Gully Erosion 1020 85% 870 150 

( ~90% road related) 

Bare Ground Erosion 400 85% 340 60 

Stream Bank Erosion 590 35% 210 380 

Tributary Landslides: 210 0% 0 210 

Naturally Occurring 

Tributary Landslides: 360 80% 290 70 

Road Related 

Tributary Landslides: 390 50% 190 200 

Harvest Related 

Mainstem Landslides 810 40% 320 490 

(Human Induced and 

Naturally Occurring) 

Debris Torrents 100 50% 50 50 

Other Mass Movements 180 0% 0 180 

(Naturally Occurring): 

-earthflows 

- block slides 

Totals 4750 2850 1900 

1 The estimated historic sediment load for each source. 2 The percent of that historic load that is estimated as controllable. Controllable discharges are those discharges resulting 

from human activities that can influence the quality of the waters of the State and that can be reasonably controlled. 3 The load that is estimated as controllable (the percent controllable multiplied by the historic load), rounded to the 

nearest 10. 4 The difference between the historic load estimate and the controllable load estimate, rounded to the nearest 10. This is 

the estimated load at which sahnonids in the Redwood Creek watershed would no longer be limited by sediment 

Explanation of Allocations 

The Allocations divide the TMDL among key source categories, including natural 

background sources. (The method for addressing natural background is discussed below.) The 

allocations are derived from the adjusted sediment budget presented in the source analysis section, 

which was based primarily on the sediment budget in the Redwood Creek watershed analysis. 

53 
The individual load allocations are based on EPA's assessment of the degree to which 

loadings from different source categories can actually be controlled or prevented. The controllable 

fraction of total loads from each source category was estimated, and the remaining loads by category 

were summed and compared with the TMDL. This analysis found that application of reasonable 

practices to control and prevent future loading would result in reductions adequate to meet the 

TMDL. 

"Controllable" sources of sediment are defined as those which are associated with human 

activity and will respond to mitigation, altered land management, or restoration. The percentages are 

based on an understanding of the available mitigation, land management and/or restoration measures 

which have been developed for a variety of situations. The percentages reflect professional 

judgment of how successful the various best management practices (BMPs) generally are in 

controlling these sources. These assessments of source control potential are generally consistent 

with those used for the Garcia River sediment TMDL established in 1998. 

Estimates of controllable percentage of loads for road-related sources are derived from field 

work in basin and nearby basins by Weaver and Hagans (see, e.g., Weaver and Hagans, 1994). The 

estimate that about 90% of gully erosion is road-related comes from Hagans, et al., 1986 and RNP, 

1997). 

Estimates of controllable percentage of loads from bare ground were derived from a 

conservative reading of results of bare ground sediment control practices in Redwood Creek basin 

documented in Kveton, et al. (1983) and Hagens, et.al. (1986). 

Estimates of controllable percentage for streambank erosion were based on EPA's judgment 

summarized as follows: A significant portion ofbank erosion is believed to be associated with 

higher flow elevations caused by changes in channel shape, which in turn are associated with 

sediment loads which exceed the stream's natural transport capacity (Rosgen, 1996). As sediment 

loading is reduced in the future, it is assumed that the frequency and magnitude of bank erosion will 

decline, and that the volume of eroded bank sediments will decline as well. In addition, it is 

expected that some streambank erosion will be addressed through stream restoration projects in some 

parts ofthe basin. Finally, it is expected that some reduction in bank erosion will occur in response 

to improvements in livestock management practices and, potentially, timber harvesting practices in 

riparian zones. 

Estimates of controllable percentage of harvest related mass wasting are based on Pitlick, 

1982, EPA and Regional Board staff judgment and experience, and are consistent with control rates 

estimated for the Garcia River sediment TMDL. 

The available analysis concerning associations between landslides and roaded, harvested, or 

unlogged areas focused upon landslides in tributaries (Pitlick, 1982). Because the patterns and 

causes, and associated ability to prevent landslides along the mainstem of Redwood Creek are not 

well understood, this analysis assumed that mainstem landslides would not be as amenable to control 

as tributary landslides. Following this reasoning, it is estimated that about 40% of loads from 

mainstem landslides could be prevented, about half the amount of load prevention which could be 

expected for tributary landslides which are road related. 

54 
The sediment budget description inferred that most debris torrents are road-related. Because 

road-related debris torrents can usually be avoided through proper road siting and maintenance (e.g., 

through avoidance of side-casting), the estimated 50% control level is realistic. 

Natural background is addressed in the allocations in two ways. First, explicit estimates of 

natural background loading levels are provided for different mass wasting processes, and it was 

assumed these sources are not controllable. Second, it is inferred that a portion of fluvial erosion 

would be naturally occurring, although the proportion of uncontrollable loads for the fluvial erosion 

categories which are related to natural sources versus uncontrollable anthropogenic sources is not 

distinguished. Control percentages for these sources are more modest as a result. 

Allocations for road-related sediment applies to all land use activities including roads for 

timber, agricultural, residential, and park management activities as well as state and county roads. 

Calculations 

Table 12 summarizes the information used to calculate the individual allocations. The total 

historical loads estimated for each category (column a) are provided in column b. Column c 

provides data on the percent of the total loads for informational purposes. The estimate of 

controllable load in column d was calculated by multiplying the loads from column b by the 

controllable percentages in column c. Column e is the remaining load, calculated by subtracting the 

controllable load (column d) from the historical load (column b). Thus column e becomes the load 

allocation. There are no point sources in the watershed; nor are any expected to be proposed in the 

near future. Therefore, the wasteload allocation for point sources is zero. 

AI¢ culture 

As noted above, the allocation for road related sediment applies to all land use activities 

including agriculture (principally ranching in Redwood Creek basin). In addition, the allocations for 

the following categories also apply to agricultural activity: gully erosion, bare ground. erosion, 

streambank erosion, mainstem landslides, and debris torrents. The sediment budget prepared by 

Redwood National Park does not separately estimate erosion associated with agriculture, although 

the existing categories account for agriculture related erosion to some degree. Overall, this approach 

is acceptable because agriculture-related erosion is not believed to be a major source in Redwood 

Creek watershed. Separate Load allocations are only required for significant source categories. If 

subsequent erosion source inventories find that agriculture-related sources are significant, it may be 

appropriate to revise the allocations accordingly in the future. 

Conclusion 

The Loading Capacity and Allocations of Loads are developed for all major sources of 

sediment in Redwood Creek. As part of the supporting documentation, all sources were considered. 

Certain sources were not quantified including sediment related to certain agricultural activities. 

These were accounted for in the margin of safety. The sum of the load allocations plus the natural 

background is less than or equal to the estimated loading capacity and associated TMDL. 

55 
Section 3.6. Margin of Safety 

Section 303(d) of the Clean Water Act and the regulations at 40 CFR 130.7 require that 

TMDLs shall be established at levels necessary to attain and maintain the applicable narrative and 

numerical water quality standards with seasonal variations and a margin of safety which takes into 

account any lack of knowledge concerning the relationship between effluent limitations and water 

quality. The margin of safety can either be incorporated into conservative assumptions used to 

develop the TMDL or added as a separate component of the TMDL (EPA, 1991}. In every one of 

the components used to develop the TMDL, assumptions were made where sufficient data was 

lacking. Conservative assumptions have generally been made in each case as a way of addressing 

the uncertainty associated with the data. 

EPA has identified these conservative assumptions more specifically to fully account for 

the implicit margin of safety. 

Selection of Instream Numeric Target Levels 

The relationship between physical measures of cold water aquatic habitat characteristics 

and the actual future health of salmonid populations is poorly understood. Available research 

results, which provide the information base from which target values are selected, vary widely 

with respect to the physical characteristics believed to be associated with well-functioning cold 

water aquatic habitats. No specific information concerning the relationship between physical 

measures of aquatic habitat and aquatic ecosystem health was available for Redwood Creek 

watershed. 

Instream numeric targets were selected for the Redwood Creek TMDL based on a review 

of available literature sources which evaluate the relationship between salmonid health and various 

physical habitat measures. Target values for each measure were generally established at levels 

which were associated with successful salmonid reproduction and survival in carefully designed 

research settings, or which were associated with actual stream ecosystems which support healthy 

cold water aquatic habitat. Where available research results report a range of possibly acceptable 

levels of different physical habitat characteristics, values were selected for numeric target levels 

for the TMDL which were associated with higher salmonid survival rates or with stream 

conditions more favorable for healthy cold water ecosystem function. 

In the case of measures of fine sediment in stream riffles, target values were set at levels 

associated with high levels of salmonid reproductive success in streams in the Pacific Northwest. 

Salmonids in California may have adapted to be able to thrive in settings where fme sediment 

levels are higher than found in comparable settings in Washington, Oregon, Alaska, or British 

Columbia. However, because this possibility has not been fully verified through reliable research 

results based on work in California streams, the target levels for fine sediments used in the TMDL 

were set at lower levels associated with research results from other locations in the Pacific 

Northwest. This is a conservative assumption because the numeric targets for fine sediments were 

set closer to the low end of the range of "acceptable" fine sediment levels reported in the 

literature. 

56 
Use of HillslQPe Targets 

It will take a substantial period of time (at least 10 years) before it will be appropriate to 

assess whether instream targets and associated water quality standards are being attained. During 

the period before this assessment can be conducted, significant uncertainty will remain concerngint 

the effectiveness of the TMDL and associated implementation actions. In addition to instream 

targets, the TMDL includes hillslope targets which identify desired conditions with respect to key 

. land use management practices which could contribute to unacceptable increases in sediment 

loading rates. It will be possible to monitor whether these hills lope targets are being attained over 

short periods of time (i.e., less than 10 years). If it is determined that the hillslope targets are not 

being attained, it will be possible to evaluate whether the TMDL and/or implementation plan 

require immediate revision. Provision of hillslope factors provides an additional margin of safety 

to account for the lag time between establishment and implementation of the TMDL and 

evaluation of its effectivness. 

Proportion of Bedload in Total Sediment Load 

Total sediment load is comprised of suspended load and bedload. Much of the sediment 

data for Redwood Creek in recent years is available for suspended sediment only. It was 

important to used these data in the TMDL analysis to evaluate recent trends in sediment loading. 

In order to make recent data comparable with historical data for total sediment loading, it was 

necessary to assume the bedload fraction of total sediment loading in Redwood Creek. The 

loading analysis assumes a bedload proportion at the high end of the range (25%) estimated for the 

basin in available literature sources. (10-30%). 

Sediment Storage in Mainstem of Redwood Creek 

After sediment is discharged into North Coast California streams, it may be deposited in 

the stream bottom or floodplain, causing stream aggradation. It may take decades for excessive 

sediment loads deposited in the stream to be remobilized and transported out of the basin. The 

stream itself may therefore act as both a sink for sediments (a temporary storage location) and a 

source for sediment (through resuspension and transport of previously discharged sediments). 

Streams may have some capaCity to absorb excess sediment loadings without impairing beneficial 

uses under some circumstances; however, this "buffering" effect is poorly understood. 

Moreover, in streams such as Redwood Creek which experienced massive discharges of sediment 

following major stoims over the past 40 years, the stream may be unable to absorb temporary 

discharges of excessive sediment in this manner. Therefore, the TMDL was developed through a 

conservative approach which gives no "credit" for instream storage as a consideration in TMDL 

determination since current excessive levels of instream stored sediment are significantly 

impairing beneficial uses. The TMDL is approximately 10-25% lower than would be the case if 

instream storage credit were provided. 

Comparison of Sediment Loading from Reference Streams with Redwood Creek as a Whole 

The analysis of loading rates from three "reference" tributaries found that historical 

sediment loading rates were about 59% lower than for the Redwood Creek watershed as a whole. 

Some researchers and commenters have observed that, other factors being equal, sediment loading 

57 
rates per unit of area appear to increase as watershed size increases. In comparing the loading 

rates from the smaller reference tributaries to the whole watershed, EPA made the conservative 

assumption that the loading rates could be compared directly, without attempting to compensate 

for scale differences which could explain (to some degree) why sediment loading rates from the 

watershed as a whole were much higher than for the reference tributaries. The Redwood Creek 

TMDL contains no compensating corrections to account for this phenomenon because it is poorly 

understood and because it was infeasible to evaluate the extent to which it actually exists in 

Redwood Creek watershed. This is a conservative assumption which may result in an 

overestimate of amount of sediment loading reductions needed to address sediment problems in 

Redwood Creek as a whole. 

Association of HillslQPe Sources With Human Causes 

Where possible, the source analysis distinguishes human-caused sediment discharge 

sources from naturally occurring sources. Available research provides information on several 

types ofhillslope sediment sources which are "associated" with land management activities. The 

TMDL source analysis makes the conservative assumption that hillslope sources identified as 

"associated" with land management activities are caused by the associated land management 

activities. This assumption results a higher estimate of human-caused discharges which are 

amenable to some degree of control or avoidance, and lower TMDL and associated load 

allocations as a result. 

Estimation of Loadin~ Capacity 

The estimate of sediment loading capacity in the TMDL was based on a quantitative 

comparison of historical sediment loading rates in "reference" tributaries with the watershed as a 

whole, and a qualitative comparison of observed values for instream habitat indicators with the 

target values for those indicators. The quantitative comparison indicated that "reference" loading 

rates were about 40% of the loading rates for the watershed as a whole (suggesting that significant 

load reductions would be needed in the watershed as a whole). The qualitative comparison of 

instream parameters indicated that instream conditions may be improving, particularly in the upper 

watershed (implying that the system is recovering and may not require significant sediment 

discharge reductions. However, rather than raising the loading capacity estimate to account for 

the possible improvements in instream conditions, the TMDL makes the conservative assumption 

that the potential improvements in instream conditions have not been verified by adequate 

monitoring over an adequate monitoring period. This assumption results in the establishment of a 

lower loading capacity estimate which is more protective of aquatic habitat. 

Conclusion 

As the margin of safety discussion points out, there are a number of uncertainties 

associated with the supporting documentation, most notably in the source analysis and linkage 

analysis to estimate loading capacity. Given these uncertainties, conservative assumptions have 

been made regarding the amount of loading reductions that are needed to attain water quality 

objectives . This approach is warranted and meets the statutory requirements that a margin of 

safety take into account any lack of knowledge concerning the relationship between the effluent 

limitations and water quality. 

58 
Collection of site-specific data in the future will help to reduce the uncertainty associated 

with the current assessment and will therefore allow for a reduction in the degree of conservatism 

associated with the current assumptions. Thus, it is possible, depending on the quality and 

quantity of the site-specific data which is collected over time, that adjustments to the TMDL in the 

future will result in less stringent allocations as the margin of safety is reduced. 

Section 3. 7. Seasonal Variation 

There is inherent annual and seasonal variation in the delivery of sediment to stream systems. 

Surface erosion occurs on an annual basis, but primarily as a result of winter rains. Fluvial erosion 

and mass wasting, on the other hand, occur as a result of big storms and thus may not be 

significantly active processes every year. For this reason, the allocations are designed to apply to the 

sources of sediment, themselves, not the movement of sediment across the landscape or delivery of 

sediment directly to the stream channel. If implemented as envisioned, potential and existing 

sediment delivery sites will be identified and the quantity of sediment associated with each site 

measured or estimated. Then, as a result of mitigation or altered land management, the amount of 

potential sediment saved from delivery to receiving water State will be measured or estimated. The 

relationship between the original measurement or estimate of potential sediment delivery and the 

amount saved by mitigation will indicate the degree to which the allocation has been achieved. 

It is difficult to accurately predict specific impacts of sediment loading at particular times and 

places on particular salmonid life stages given spatial and temporal lag time between sediment 

delivery and the occurrence of sediment related impacts on beneficial uses. In addition, it is 

infeasible to predict or control sources at fine spatial and temporal scales in many cases. Therefore, 

the approach in this TMDL is to select indicators to interpret narrative water quality objectives 

which are believed to provide a good composite picture of instream sediment-related conditions and 

changes over time. Then, targets and associated TMDLs are set at levels believed to be protective of 

beneficial uses at key life stages taking into account the lag time effects. In addition, the numeric 

targets generally represent summer flow conditions. This TMDL accounts for seasonal variation 

through the careful articulation of likely cause and effect relationships between sediment loadings 

and effects on salmonid habitat at different key life stages, and its consideration of lag time effects. 

Normal winter rains and larger storms will nonetheless have an effect on the assessment of 

allocations. Storm events which occur after mitigations have been achieved will provide a test of the 

success of the mitigation. For this reason, the monitoring plan will propose follow-up inventories of 

hillslope sources which will help assess post-mitigation success. 

Section 3.8. Critical Conditions 

The regulations at 40 CFR 130.7 state that TMDLs shall take into account critical conditions 

for stream flow, loading and water quality parameters. This TMDL does not explicitly estimate 

critical flow conditions for several reasons. First, unlike many pollutants (e.g. acutely toxic 

chemicals) sediment impacts on beneficial uses may occur long after sediment is discharged, often at 

locations far downstream from the point of discharge. Second, sediment impacts are rarely 

correlated closely with flow over short time periods. Third, it is impractical to accurately measure 

sediment loading, transport, and short term effects during high magnitude flow events which usually 

59 

/' 
produce most sediment loading and channel modification in systems such as Redwood Creek. 

Therefore, the approach used in this TMDL to account for critical conditions is to use indicators 

which are reflective of the net long term effects of sediment loading, transport, deposition, and 

associated receivil).g water flows. These indicators may be effectively measured at lower flow 

conditions at roughly annual intervals. Inclusion of a large margin of safety helps to ensure that the 

TMDL will result in beneficial use protection during and after critical flow periods associated with 

maximum sedimentation events. 

Critical conditions concerning stream habitat status and recovery may change substantially 

following major storms (e.g., storms with a recurrence interval of approximately 50 years or more). 

Such storms and the associated floods and huge sediment loads can have the effect of 

"recallibrating" the stream channel morphology for decades to follow. It may be appropriate to 

reconsider the TMDL and associated allocations following such an event. 

Se<;tion 4. Public Participation 

Federal regulations require that TMDLs be subject to public review (40 CFR 130.7). The 

State and EPA have provided for public participation through several mechanisms. The State has 

held several formal and informal public workshops during 1998 to discuss the State's TMDL and 

implementation plan proposals. EPA has participated in two of these workshops. The State and 

EPA have worked together to assure that the EPA TMDL for Redwood Creek is very similar to the 

TMDL proposed by the State. 

EPA invited public comment on the EPA draft TMDL in a public notice dated October 19, 

1998. That public notice was published in several North Coast newspapers and was mailed out to a 

mailing list of interested parties provided to EPA by the RWQCB. EPA hosted a public hearing on 

the Redwood Creek and South Fork Trinity River TMDLs in Eureka, CA on November 19, 1998. 

EPA reviewed public comments received in writing during the comment period as well as oral 

comments made at the public hearing in reaching its final decision on the TMDL. EPA has prepared 

a comment responsiveness summary which shows how EPA considered public comments in its final 

decision. The fmal TMDL incorporates changes in the following areas: 

- clarification of instream numeric targets 

- addition of hillslope numeric targets 

-minor clarifications of the source analysis, linkage analysis, TMDL, and allocations 

- restructuring of the margin of safety discussion, and 

- additional detail in the implementation and monitoring recommendations. 

Section 5. Implementation and Monitoring Recommendations 

Federal regulations require the State to identifY measures needed to implement TMDLs in the 

state water quality management plan ( 40 CPR 130.6). EPA has established policies whiCh 

emphasized the importance of timely implementation of measures to implement TMDLs which 

address nonpoint source discharges ( EPA, 1997b ). EPA expects the State to promptly develop 

implementation measures and ensure the implementation of source control and erosion prevention 

measures which are adequate to achieve the allocations in the TMDL. 

• 

60 
EPA expects that the State will incorporate the TMDL and associated implementation 

measures in the State water quality management plan (in California, the RWQCB Basin Plan) upon 

approval by EPA , as required 40 CFR 130.6. This requirement may be met through EPA's approval 

of the TMDL and implementation plans already added to the Basin Plan by the State, or through 

incorporation of an EPA-established TMDL and State-adopted implementation measures in the 

Basin Plan following EPA's establishment of the TMDL. 

Implementation Plan Recommendations 

Concurrent with its effort to develop the Redwood Creek TMDL, the RWQCB has drafted an 

Implementation Plan (Plan) for the TMDL (November 10, 1998) and is continuing to refine the Plan 

in consultation with interested stakeholders. EPA strongly supports the draft Implementation Plan 

and offers the following recommendations to further strengthen that Plan: 

L Promote and facilitate cooperative public-private implementation and monitoring efforts. The 

draft Plan recognizes that measures developed under the auspices of other planning mechanisms may 

be recognized by the Regional Board if they contain all the required elements of the erosion control 

plans. An MOU between the park and interested private landowners provides a potential existing 

mechanism for planning implementation actions and monitoring programs at a scale broader than 

individual ownerships. The Regional Board Plan would be improved if it more actively promoted 

cooperative efforts by Redwood National Park and interested private landowners to inventory roads 

and other potential erosion sites, plan erosion control and prevention actions, carry out those actions, 

and conduct instream and hillslope monitoring activities. The Plan should urge agencies and private 

landowners to share all data concerning instream water quality and hillslope practices with the State 

to assist in future review of the TMDL. 

The Plan should also note that significant funding for implementation planning and action as well as 

monitoring may be available from outside sources (e.g., President's Forest Plan funds, Clean Water 

Act Section 319 nonpoint source and Clean Water Action Plan grant funds, NRCS cost share funds, 

and possibly state funding sources). If the park and local landowners are interested in obtaining such 

funds, the Regional Board should actively facilitate efforts to do so. EPA recommends that if 

outside funding is obtained to support implementation activities in the basin, preference for spending 

these funds should be targeted to smaller landowners who may be less able to carry out the necessary 

planning and implementation activities. 

2. Clarify focus on potential erosion sites as well as existing sites. Although the text of the Plan 

indicates that landowner inventories should address both potential and active erosion sites, the Plan 

should be clarified to place greater focus on detection of potential erosion sites and implementation 

of measures to prevent activation of erosion from these sites. It is often cost-prohibitive to address 

erosion sites which have already begun to erode. In addition, if initial erosion site inventories are 

designed to identify all sites with future erosion potential based on the presence of characteristics 

indicating instability or vulnerability, it may prove unnecessary to conduct repeated detailed 

inventories every few years as proposed. If done well the first time, it may be necessary to follow-up 

these detailed initial inventories only with periodic cursory inspections of potential erosion sites and 

erosion control practices and structures. 

61 
3. ClarifY the 10 year implementation timeframe and urge quicker implementation. The Plan calls 

for implementation of needed erosion prevention and control measures within 10 years after the 

baseline inventory is developed. The baseline inventory is scheduled for submission by 2003. EPA 

supports the 10 year implementation timeframe. However, the State should consider requiring 

submission of the baseline inventory and initiation of the 10 year implementation timeframe sooner 

than 2003. It should not have to take landowners 5 years to complete the inventory. EPA 

recommends a tighter timeframe for submission of the baseline inventory-- perhaps 2-3 years from 

the date ofTMDL adoption. If the 2003 submission schedule is retained, the Plan should strongly 

encourage the implementation of erosion prevention and control measures as soon as is practicable, 

beginning now. 

4. Improve protection of Class 3 watercourses. Existing forest practice rules appear to provide 

inadequate measures to protect Class 3 watercourses from disturbances which can trigger significant 

erosion and sediment delivery to Class 1 and 2 watercourses. The Regional Board plan should 

explicitly require inventories and action plans to address potential erosion sites near Class 3 

watercourses. 

Monitoring Recommendations 

EPA guidance concerning the development ofTMDLs through the phased approach 

emphasizes the importance of establishing rigorous monitoring and evaluation plans and associated 

schedules which will guide the review and potential revision of the TMDLs and implementation 

activities (EPA, 1991 ). The State should establish a monitoring and evaluation plan which identifies 

parties responsible for implementation and timeframes for RWQCB review of monitoring results. 

The monitoring plan should describe how and when monitoring results will be reviewed to evaluate 

the need for TMDL or implementation plan revisions. Finally, the monitoring plan should provide 

for data sharing among landowners, agencies, and interested stakeholders. 

The Regional Board Plan should describe a more detailed approach to developing a 

comprehensive monitoring plan. EPA recommends the following monitoring provisions: 

1. Actively lead the development of a comprehensive monitoring plan. EPA commends the State 

for its. plan to work with other agencies and landowners to develop the monitoring plan, we suggest 

that the Regional Board develop a specific agreement with Redwood National Park (and perhaps 

with other agencies) to jointly lead the development of this plan. The Plan should recognize the 

opportunities to dovetail TMDL monitoring activities with ongoing monitoring conducted by 

Redwood National Park, USGS, other agencies, and private landowners. The Regional Board and 

Redwood National Park should describe a specific mechanism through which interested agencies and 

landowners can work together to develop and implement this monitoring plan. As discussed above, 

it may be appropriate for the Regional Board to facilitate acquisition of outside funds to support 

future monitoring efforts. 

2. Distinguish monitoring needs in different stream types and hillslope locations. Different 

monitoring approaches will be appropriate in different locations. With respect to instream 

monitoring, it would be appropriate to establish monumented monitoring sites distributed throughout 

the mainstem and lower portions of key tributary watersheds. Priorities for monitoring tributaries 

and mainstem reaches which include potential spawning/rearing habitat include (in priority order): 

62 
- pebble counts at riffle crests, 

- large woody debris inventories, 

- thalweg and cross section measures which facilitate measurement of pool indicators, 

- suspended sediment and possibly bedload sediment at mouths of key tributaries, including 

Lacks Creek, Prairie Creek, Panther Creek, Coyote Creek, Bridge Creek, and Little Lost Man 

Creek, and 

- bulk sampling of substrate composition at riffle crests in a subset of established monitoring 

sites. 

Priorities for monitoring in the larger portions of Redwood Creek should include the following: 

- thalweg profiles and cross sections, 

- large woody debris inventories, 

- suspended and bedload sediment loads at Orick and Okane. 

Additional indicators which should be considered for addition to monitoring programs include: 

-substrate permeability, 

- turbidity, and 

-bed mobility measures (e.g. scour chains) 

Hillslope monitoring will also be an important component of the monitoring plan. In 

addition to the implementation monitoring and reporting requirements in the Plan, the hillslope 

monitoring plan should provide for information collection adequate to update the sediment budget 

about once every 10-15 years. EPA recommends the use of rapid sediment budgeting methods 

described in Reid and Dunne (1996). 

All monitoring plans should include specific descriptions of the monitoring protocols and 

data management efforts to be followed in adequate detail to guide monitoring and data recording by 

different field workers. Agreement at the outset on monitoring protocols and data management 

methods is crucial to ensure that data collected at different times and locations by different parties 

will be comparable in the future. If feasible, provision should be made to record and report data in 

electronic formats. 

63 
Section 6. Glossary 

Aggradation: To fill and raise the elevation of the stream channel by deposition of sediment. 

Agricultural facility: Any building, corral, pen, pasture, field, trail, or other feature on the landscape 

which is attributable to or associated with agricultural operations 

Anadromous: Refers to aquatic species which migrate up rivers from the sea to breed in fresh water. 

Areas of instability: Locations on the landscape where land forms are present which ·have the 

ability to discharge sediment to a watercourse. 

Baseline data: Data derived from field based monitoring or inventories used to characterize existing 

conditions and used to establish a database for planning or future comparisons. 

Beneficial Use: Uses of waters of the state that may be protected against quality degradation 

including, but not limited to, domestic, municipal, agricultural and industrial supply; power 

generation; recreation; aesthetic enjoyment; navigation; and the preservation and enhancement of 

fish~ wildlife and other aquatic resources or preserves. 

Class I: Watercourses which contain domestic water supplies, including springs, on site 

and/or within 100 feet downstream of the operation area and/or have fish always or seasonally 

present onsite, including habitat to sustain fish migration and spawning. Class I streams include 

historically fish-bearing streams. 

Class II: Watercourses which have fish always or seasonally present offsite within 1000 feet 

downstream; and/or contain aquatic habitat for non-fish aquatic species. Class II waters do not 

include Class III waters that are directly tributary to Class I waters. 

Class III: Watercourses which do not have aquatic life present, but show evidence of being 

capable of sediment transport to Class I and II waters under normal high flow conditions during and 

after completion of land management activities. 

Class IV: Human-made watercourses, which usually supply downstream established domestic, 

agricultural, hydroelectric supply or other beneficial uses. 

Controllable source: Any soti.rce of sediment with the potential to enter a water of the State which 

is caused by human activity and will respond to mitigation, restoration, or altered land management. 

Debris torrents: Long stretches of bare, generally unstable stream channel banks scoured and 

eroded by the extremely rapid movement ofwater-ladened debris, commonly caused by debris 

sliding or road stream crossing failure in the upper part of a drainage during an intense storm. 

Deep seated landslide: Landslides involving deep regolith, weathered rock, and/or bedrock, as 

well as surficial soil. Deep seated landslides commonly include large (acres to hundreds of acres) 

slope features and are associated with geologic materials and structures. 

64 
Drainage structure: A structure or facility constructed to control road runoff. These structures 

include but are not limited to fords, inside ditches, water bars, outsloping, rolling dips, culverts or 

ditch drains. 

Flood event: Flood frequency analysis defines the event which can be expected once every "Y" 

years, on the average. This does not imply that a "Y -year event" will occur regularly every "Y" 

years. Return periods, as well as flood magnitudes, are subject to analysis. For example, there is a 

two percent chance that a 50-year event will occur I any one year. 

Flooding: The overflowing of water onto land that is normally dry. 

Fry: A young juvenile salmon after it has absorbed its egg sac and emerged from the redd. 

Headwater swale: The swale or dip in the natural topography that is upslope from a stream, at its 

headwater. There may or may not be evidence of overland or surface flow of water in the headwater 

swale. 

Interstices: The space between particles (e.g. space between sand grains). 

Inner gorge: A geomorphic feature formed by coalescing scars originating from mass wasting and 

erosional process caused by active stream erosion. The feature is identified as that area of stream 

bank situated immediately adjacent to the stream, having a slope generally over 65% and being 

situated below the first break in slope above the channeL 

Inside ditch: The ditch on the inside of the road, usually at the foot of the cutbank. 

Landslide: Any mass movement process characterized by downslope transport of soil and rock, 

under gravitational stress by sliding over a discrete failure surface-- or the resultant landform. 

Large woody debris: A piece of woody material having a diameter greater than 30 em (12 inches) 

and a length greater than 2m (6 feet) that is located in a position where it may enter the watercourse 

channel. 

Mass wasting: Downslope movement of soil mass under force of gravity-- often used synonymously 

with "landslide." Common types if mass soil movement include rock falls, soil creep, slumps, 

earthflows, debris avalanches, debris slides and debris torrents. 

Numeric targets: A numerical expression of the desired instream environment. For each 

stressor or pollutant addressed in the problem statement of the Strategy, a numeric target is 

developed based on the numeric or narrative State water quality standards which are needed to 

recovered the impaired beneficial use. 

Permanent drainage: A road drainage structure designed and constructed to remain in place 

following active structure land management activities while allowing year round access on a road. 

Planning Watershed: The uniform designation and boundaries of sub basins within a larger 

watershed (designated by the California Department of Forestry as Cal Water Watersheds). 

65 
Redd: A gravel nest or depression in the stream substrate formed by a female salmonid in which 

eggs are laid, fertilized and incubated. 

Sediment: Fragmented material that originates from weathering of rocks and decomposed 

organic material that is transported by, suspended in, and eventually deposited by water or air. 

Sediment budget: An accounting of the sources, movement, storage and deposition of sediment 

produced by a variety of erosional processes, from its origin to its exit from a basin. 

Sediment delivery: Material (usually referring to sediment) which is delivered to a watercourse 

channel by wind, water or direct placement. 

Sediment discharge: The mass or volume of sediment passing a point in the stream in a unit of 

time. 

Sediment erosion: The group of processes whereby sediment (earthen or rock material) is 

loosened, dissolved and removed from the landscape surface. It includes weathering, solubilization 

and transportation. 

Sediment source: The physical location on the landscape where earthen material resides which 

has or may have the ability to discharge into a watercourse. 

Sediment yield: The sediment yield consists of dissolved, suspended and bed loads of a 

watercourse channel through a given cross-section in a given period oftime. 

Shallow seated landslide: A landslide produced by the failure of the soil mantle (typically to a depth 

of 1-2 meters, sometimes includes some weathered bedrock), on a steep slope. It includes debris 

slides, soil slips and failure of road cut-slopes and sidecast. The debris moves quickly (commonly 

breaking up and developing into a debris flow) leaving an elongated, concave scar. 

Skid trail: Constructed trails or established paths used by tractors or other vehicles for skidding 

logs. Also known as tractor roads. 

Smolt: A young salmon at the stage at which it migrates from fresh water to the sea. 

Steep slope: A hillslope, generally greater than 50% that leads without a significant break in slope 

to a watercourse. A significant break in slope is one that is wide enough to allow the deposition of 

sediment carried by runoff prior to reaching the downslope watercourse. 

Stream: See watercourse. 

Stream class: The classification of waters of the state, based on beneficial uses, as required by the 

Department of Forestry in Timber Harvest Plan development. See definitions for Class I, Class II, 

Class III, and Class IV for more specific definitions. 

Stream order: The designation (1,2,3, etc.) ofthe relative position of stream segments in the 

drainage basin network. For example, a first order stream is the smallest, unbranched, perennial 

66 
tributary which terminates at the upper point. A second order stream is formed when two first order 

streams join, and so forth. 

Sub basin: A subset or division of a watershed into smaller hydrologically meaningful 

Watersheds. For example, the North Fork Redwood Creek is a sub basin of the larger Redwood 

Creek watershed. 

Swale: A channel-like linear depression or low spot on a hillslope which rarely carries runoff except 

during extreme rainfall events. Some swales may no longer carry surface flow under the present 

climatic conditions. 

Thalweg: The deepest part of a stream channel at any given cross section. 

Thalweg profile: Change in elevation of the thalweg as surveyed in an upstream-downstream 

direction against a fixed elevation. 

Unstable areas: Characterized by slide areas, gullies, eroding stream banks, or unstable soils. 

Slide areas include shallow and deep seated landslides, debris flows, debris slides, debris torrents, 

earthflows and inner gorges and hummocky ground. Unstable soils include unconsolidated, noncohesive soils and colluvial debris. 

Watercourse: Any well-defined channel with a distinguishable bed and bank showing evidence of 

having contained flowing water indicated by deposit of rock, sand, gravel, or soiL 

Watershed: Total land area draining to any point in a watercourse, as measured on a map, aerial 

photo or other horizontal plane. Also called a basin, drainage area, or catchment area. 

Water quality objective: Limits on or level of water quality constituents or characteristics which 

are established for the reasonable protection of beneficial uses of water or the prevention of nuisance 

within a specific area. 

Water quality standard: Consist of the beneficial uses of water and the water quality objectives 

as described in the Water Quality Control Plan for the North Coast Region. 

67 
Section 7. References 

Bilby, R.E. and J.W. Ward. 1989. Changes in characteristics and function of woody debris with 

increasing size of streams in western Washington. Transactions of the American Fisheries Society. 

118:363-3 78. 

Burns, J. W. 1970. Spawning bed sedimentation studies in north California streams. Pages 253-279 

in California Fish and Game 56(4). 

Cederholm, C.J., L.M. Reid, and E.O. Salo. 1980. Cumulative Effects of Logging Road Sediment 

on Salmonid Populations in the Clearwater River, Jefferson County, Washington. In SalmonSpawning Gravel Conference Procedings, 1980. 

Chapman, D. W. 1988. Critical review of variables used to define effects of fines in reds of large 

salmonids. In: Transactions of the American Fisheries Society 117. Pages 1-25 

Chapman, D.W. and K.P. McLeod. 1987. Development of Criteria for Fine Sediment in the North 

American Rockies Ecoregion. EPA 910/9-87-162, April, 1987. 

Flosi, G. And F.L. Reynolds. 1994. California salmonid stream habitat restoration manuaL Inland 

Fisheries Division, California Department ofFish and Game, The Resources Agency. 

Hagans, D. K., W. E. Weaver and M.A. Madej. 1986. Long-term on-site and off-site effects of 

logging and erosion in the Redwood Creek basin, northern California. In: Papers presented at Amer. 

Geophys. Union meeting on cumulative effects (9-13 Dec. 1985, San Francisco, Ca.). Tech. Bull. 

490, pp. 38-66, National Council ofthe Paper Industry (NCASI), New York, New York. 

Hagans, D.K. and W.E. Weaver. 1987. Magnitude, cause and basin response to fluvial erosion, 

Redwood Creek basin, northern California. Erosion and Sedimentation in the Pacific Rim 

(Proceedings ofthe Corvallis Symposium, August 1987). 

Keller, E. A., and W. N. Melhorn. 1995. Rhythmic spacing and origin of pools and riffles. In: 

Geological Society of America Bulletin, v. 89. Doc. no. 80509. Pages 723-730 

Kelsey, H., et. al. 1981. Sediment Sources and Sediment Transport in the Redwood Creek Basin: A 

Progress Report, National Park Service, Redwood National Park, Arcata, California. 

Knopp, C. 1993. Testing indices for cold water fish habitat. Final Report for the North Coast 

Regional Water Quality Control Board. 

Kondolf, G. Mathias, M. J. Sale, M.G. Wolman. 1993. Modification of Fluvial Gravel Size by 

Spawning Salmonids. Water Resources Research, Vol. 29, No.7, 2265-2274, July 1993. 

68 
Kveton, K.J., et aL 1983. Comparison of Slope Treatments for Reducing Surface Erosion of 

Disturbed Sites at Redwood National Park. Redwood National Park. In Proceedings of the first 

biennial conference of research in California's National Parks. September 9-10, 1982, University of 

California, Davis. 

Lisle, T. E. and M.A. Madej. 1992. Spatial Variation in Armoring in a Channel with High Sediment 

Supply. Dynamics of Gravel Bed Rivers. John Wiley and Sons Ltd., 1992. 

Madej, Mary Ann and Vicki Ozaki. 1996. Channel Response to Sediment Wave Propagation and 

Movement, Redwood Creek, California USA. Earth Surface Processes and Landforms, Vol. 21, 

911-927 (1996). 

National Marine Fisheries Service. 1997. Aquatic Properly Functioning Condition Matrix. NMFS, 

Southwest Region, March 20, 1997. 

Peterson, N.P., A. Hendry, and T.P. Quinn. 1992. Assessment of cumulative effects on salmonid 

habitat; some suggested parameters and targets conditions. Timber, Fish and Wildlife. TFW-F3-92-

00l. 

Pitlick, John. 1982. Sediment routing in tributaries of Redwood Creek basin, Northwestern 

California, Redwood National Park, Arcata, California. 

Redwood National and State Parks, 1995. Draft Redwood Creek Watershed Analysis. June 2, 1995. 

Redwood National and State Parks, 1997. Draft Redwood Creek Watershed Analysis. March, 1997. 

Redwood National and State Parks, 1998a. Draft Redwood National and State Park General 

Management Plan/General Plan and Draft EIS/EIR, 1998 • 

. Redwood National and State Parks, 1998b. Unpublished Sediment Data For Redwood Creek and 

Tributaries, 1998. 

Redwood National and State Parks, 1998c. Redwood Creek Watershed Information. 1998. 

Regional Water Quality Control Board. 1994. Water Quality Control Plan for the North Coast 

Region, Santa Rosa, CA. 

Regional Water Quality Control Board. 1998. Staff Report for the Proposed Redwood Creek Water 

Quality Attainment Strategy for Sediment (Total Maximum Daily Loads and Implementation Plan), 

November 10, 1998. 

Reid, L.M. 1996. Evaluating Timber Management Effects on Land Uses and Values in Northwest 

California. Draft, December 3, 1996. 

Reid, L.M. 1998. Review of the Sustained Yield Plan/Habitat Conservation Plan for the properties 

of the Pacific Lumber Company, Scotia Pacific Holding Company, and Salmon Creek Corporation. 

69 
Reid, L.M. and T. Dunne. 1996. Rapid Evaluation of Sediment Budgets. CATENA VERLAG 

GMBH, 35447 Reiskirchen, Germany. 

Rosgen, D. 1996. Applied River Morphology. Wildland Hydrology, Pagosa Springs, Colorado. 

Spence, B.C., G.A. Lornnicky, R.M. Hughes, and R.P. Novitzki. 1996. An ecosystem approach to 

salmonid conservation. TR-4501-96-6057. ManTech Environmental Research Services Corp., 

Corvalis OR. 

Tappe!, P.D. and T.C. Bjomn. 1983. A new method of relating size of spawning gravel to salmonid 

embryo survival. North American Journal of Fisheries Management 3:123-135. 

U.S. Environmental Protection Agency. 1991. Guidance for Water Quality-based Decisions: The 

TMDL Process, EPA 440/4-91-001. 

U.S. Environmental Protection Agency. 1997a. National Clarifying Guidance for 1998 State and 

Territory Section 303(d) Listing Decisions. Memo from Robert Wayland to Water Division 

Directors, August 27, 1997. 

U.S. Environmental Protection Agency. 1997b. New Policies for Establishing and Implementing 

Total Maximum Daily Loads (TMDLs). Memo from Robert Perciasepe to Regional Administrators 

and Regional Water Division Directors, August 8, 1997. 

U.S. Environmental Protection Agency. 1998a. Records of Telephone Communications With R. 

Klein, M.A. Madej, G. Bundros, and V. Ozaki. · 

U.S. Environmental Protection Agency. 1998b. Description of Basis for Sediment Source Estimates 

in Redwood Creek TMDL. E-Mail message from David Smith, USEPA to Bruce Gwynne, North 

Coast Regional Water Quality Control Board, August 20, 1998. 

U.S. Environmental Protection Agency. 1998c. Total Maximum Daily Loads for SedimentRedwood Creek, California. Public Review Draft, October 19, 1998. 

Weaver W. E. and D. K. Hagans. 1994. Handbook for Forest and Ranch Roads: a guide for 

planning, designing, constructing, reconstructing, maintaining and closing wildland roads. Prepared 

for the Mendocino County Resource Conservation District, Ukiah, CA in cooperation with the 

California Department of Forestry and Fire Protection and the USDA Soil Conservation Setvice. 

149 pages + appendices. 

Weaver, W. and D. Hagans. 1996. Sediment Treatments and Road Restoration: Protecting and 

Restoring Watersheds and Restoring Watersheds from Sediment-Related Impacts. In Healing the 

Watershed: A Guide to the Restoration of Watersheds and Native Fish in the West. Pacific Rivers 

Council, Inc., July, 1996. 

Young, Michael K., W.A. Hubert, and T.A. Wesche.1991. Selection ofMeasures of Substrate 

Composition to Estimate Survival to Emergence of Salmonids and to Detect Changes in Stream 

Substrates. North American Journal of Fisheries Management 11:339-346. 

70