United States .- Department of

it&,,);, Agriculture The RAPID Technique: - k 5 I ’

.-_ Forest Service

Pacific Northwest A New Method for

Research Station

General Technical

Report Evaluating Downstream

PNW-GTR-220

August 1988 Effects of Forest Practices . . Y., 0!!2 on Riparian Zones

Gordon Grant
Abstract Grant, Gordon. 1988. The RAPID technique: a new method for evaluating

downstream effects of forest practices on riparian zones. Gen. Tech. Rep.

PNW-GTR-220. Portland, OR: U.S. Department of Agriculture, Forest Service,

Pacific Northwest Research Station. 36 p.

The RAPID (riparian aerial photographic inventory of disturbance) technique is a

method for using measurements made on aerial photographs of patterns of riparian

canopy disturbance to evaluate changes in channel conditions through time and to

link such changes with their possible upstream causes. The RAPID technique

provides resource specialists and managers with a relatively quick way of identifying

stream reaches that are chronically or recently disturbed by a variety of channel

processes, including increased peak flows and sedimentation from point and nonpoint sources. With examples from western Oregon, this paper describes how to

apply the RAPID technique and analyze the results to evaluate downstream or

cumulative effects of forest practices.

Keywords: Riparian zones, cumulative effects, aerial photograph interpretation,

channel changes, monitoring, geomorphology, hydrology.
Contents 1

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Introduction

Background and Theory

What Are Downstream Effects?

How Can Downstream Effects Be Assessed?

Using Aerial Photographs to Monitor Changes in Channel Conditions

Collecting Data With the RAPID Technique

Preliminary Photo Analysis

Measurement Techniques

Tabulation

Analyzing and Interpreting Results

Within-Basin Analysis

Interbasin Analysis

Conclusions

Literature Cited

APPENDIX 1

Programs for Calculations Used in the RAPID Procedure

APPENDIX 2

General References on Aerial Photograph Interpretation

APPENDIX 3

Blank Forms
Introduction Since the passage of the National Environmental Protection Act (NEPA) of 1969,

Federal resource managers have been required to assess the cumulative and longterm effects of proposed actions on the environment. Procedures and guidelines for

implementing this directive have been vague and not generally founded on scientific

grounds. This leaves managers in the unenviable position of trying to assess and

mitigate potential cumulative effects without many tools. Recently, monitoring the

effects of past and present activities has become an explicit part of forest plans,

and again, relatively few methods are available to accomplish this task.

One aspect of the problem of cumulative effects is the downstream effects from

harvest activities occurring further upstream. Downstream effects are the off-site

changes in the volume or pattern of water and sediment movement through a basin

that result from forest practices. Such changes can cause the physical structure of

channels and riparian communities to be modified. Downstream effects include a

complex and interrelated set of hydrologic, geomorphic, and biologic processes,

and researchers do not agree on how they should be measured.

This paper describes the RAPID (riparian aerial photographic inventory of disturbance) technique--a method for using aerial photographs to evaluate changes in

channel conditions through time and to link such changes with their possible upstream causes. The theory is discussed briefly below; a more detailed treatment

of the theoretical framework is given by Grant and others (1984). In the following

sections, the methods used to collect and analyze data and apply the results are

described.

As its name implies, the RAPID technique offers a relatively quick way to inventory

channel conditions. Besides providing information about how upstream activities may

affect downstream channels, it is useful for identifying channel segments with histories of instability, evaluating basinwide effects of major storms. monitoring recovery of

riparian areas following channel disturbances, and comparing the effectiveness of

different management treatments in mitigating downstream effects.

This technique was developed for analyzing geomorphic processes in the densely

forested west side of the Cascade Range, Oregon. Differences in geology, vegetation, landforms, and hydrology in other regions are likely to result in different patterns

of disturbance on aerial photos. This technique has not been tested in areas other

than the west side of the Cascades, and its application to other regions should be

considered experimental.

Background

and Theory

The RAPID technique was developed to help sort out the relative importance of

different processes producing downstream effects. It is therefore useful to consider

how downstream effects might be distinguished from each other.

What Are Downstream

Effects?

Downstream effects are one element in what I call the management-modified

disturbance system (fig. 1). This system is a cascading series of causes and effects,

with each link in the chain both an effect of preceding causes and a cause of

subsequent effects. In this model, different classes of effects are distinguished by

whether they occur at the site or away from the site of primary modification.

1
EXOGENOUS

DRIVERS

LOGGING CHANGE IN --I

~NSITE CONDITIONS

CHANGE IN w--t

ACTIVITIES -0NSITE PROCESSES

* Felling * Open canopies - Increased:

* Yarding * Compacted soils Snow accumulation

- Hauling * Reduced root strength Melt rate * Smaller. mole unstable wood Surface erosion

in channels Landsliding

Wood mobility

CHANGE IN CHANGE IN

- - - CHANGE IN - PHYSICAL STRUCTURE - STRUCTUREOF

OFFSITE PROCESSES OF STREAM CHANNELS BIOLOGICAL COMMUNITIES

* Increased: - Channel enlargement * Removal o f streamside vegetation

Peak flows * Shift in frequency of channel

Sediment lo channels units (pools, riffles, etc.)

Woody debris transport

Figure I-General model of the management-induced

disturbance system.

The disturbance system begins with a modification to the primary site for timber

harvest activities; modifications might include constructing logging roads and landings, falling and yarding timber, and preparing planting sites. These activities produce

changes in local site conditions, such as compacted soils, altered ground cover,

reduced root strength, opened canopies, and changes in the size distribution and

volume of dead and downed woody debris. Such changes in site conditions can, in

conjunction with exogenous driving events such as storms, cause changes in onsite

processes, resulting in onsite effects. In the Pacific Northwest, these effects include

reduced infiltration and subsurface flow, altered patterns of snow accumulation and

melt, expanded drainage networks, and accelerated erosion from both surface and

mass movement processes. In the disturbance system (fig.l), an external storm

event may be required for such changes to become apparent.

Onsite effects can produce changes in quantities or patterns of water, sediment,

and wood movement through the basin as a whole. The translation of onsite effects

occurs through changes in specific supply mechanisms that route water and sediment; these changes are referred to as offsite or downstream effects. Although

onsite effects are clearly linked in space and time with their management cause,

downstream effects can produce changes that are spatially removed or delayed.

Reported downstream effects include increasing peak flows, landslides, frequency

of debris flows in channels, chronic sedimentation from roads and clearcut surfaces,

and frequency of wood movement through channels.
The evidence suggests that timber harvest activities can affect the volumes, rates,

and timing of water, sediment, and wood movement through a drainage basin. Not

clearly understood is how stream channels respond to such changes in regime.

Reported channel responses include aggradation, widening and braiding, streambank

failures, increased deposition of fines, and reduction in pool volume and number.

Such physical changes may, in turn, cause biological responses, such as loss of

streamside vegetation or spawning habitat, or a change in composition of lotic

communities.

With such complex interactions, how can downstream effects be assessed? The links

between specific upstream disturbances and changes to downstream channels must

be determined. In most studies, links between upstream activities and downstream

channel changes are assumed, and the relative importance of specific water, sediment, and wood delivery mechanisms are not described. For management, distinguishing among different supply mechanisms can be important in designing improved

strategies that moderate long-term environmental damage.

The technique described here is based on two hypotheses: (I) different water,

sediment and wood delivery processes produce different types of channel response;

and (2) channel response is distinctive enough to be used as an indicator of the

delivery processes involved and, therefore, can provide a way to determine whether

specific downstream effects are active in a given basin. Preliminary tests along the

west side of the Cascade Range in Oregon suggest that these hypotheses are valid

(Grant and others 1984).

Downstream effects must be classified by the mechanisms delivering water, sediment, and wood to the channel. Table 1 presents a general framework for analyzing

channel and basin behavior resulting from management-induced disturbancesColumn 1 describes on-site effects responsible for generating downstream effects

(detailed in adjacent columns). The delivery mode classification (column 2) is

based on whether the primary causative agent is water, sediment, or wood. Where

increased sediment delivery is the primary mechanism, a further distinction is made

because different rates of sediment delivery to channels may produce different

downstream effects. The effect of material delivered over long periods from road

and clearcut surfaces may differ from the effects of an instantaneous delivery, for

example, by landslide. In this analysis, I distinguish between “chronic” and “pulse”

sedimentation. In the first case, sediment is delivered to channels by surface erosion,

creep, root throw, and small, onsite failures not entering channefways. Sediment

delivery via these mechanisms is likely to be relatively slow and prolonged. Although

delivery processes themselves may produce little adjustment within the channel,

persistent input of sediment over several years may produce channel changes.

Pulse sedimentation, by contrast, involves rapid transfer of large amounts of predominantly coarse sediment and organic debris directly into the stream network. It is

usually associated with mass movements, such as landslides or debris flows. High

sediment loads, coarse debris, abrupt delivery, and the shear forces generated by

mass movement within the channel all may play a role in determining channel

response. In addition, emplacement often occurs during extreme hydrologic events

when secondary mobilization and transport of deposited material is possible.

3
Table I - Predicted channel and basin behavior resulting from changes in

water and sediment delivery caused by on-site effects

On-site effects

and associated

processes

Primary

delivery

mode Supply mechanism

Channel

response

Response of basin

Qw and Qsa

Change in quantity

and timing of

hillslope runoff:

Greater

efficiency of

drainage

network

Greater snow

accumulation

and melt rates

Reduced evapotranspiration

Increased surface

erosion

Greater incidence

of shallow

landslides:

Reduced root Into

strength channel

Water High peak

flows

Sediment Chronic

sediment

input

Sediment Pulse

sediment

input to

channel

Change in

slope mass

and water

balances

Within

channel

Increased

channel

capacity,

widening

Debris dam

instability

Channel

widening

and

braiding

Accumulation of

fines

Channel

widening

and

braiding

below

sediment

source

Fluvial

texture

and

structure

of deposits

Buried

trees

Channel

scouring

and

removal of

riparian

Peak discharges for

logged basins greater

than for unlogged

basins; Qw varies as a

function of the

increase in drainage

network due to

compaction and road

drainage and the area

of management activity

in transient snow zone

Qs varies gradually as

a function of the

percentage of basin

area in bare soil that

is connected with the

drainage network

Qs varies episodically

with mass movement

events

vegetation

See footnote on page 5.
Table I-Predicted channel and basin behavior resulting from changes in

water and sediment delivery caused by on-site effects (continued)

On-site effects Primary

and associated delivery

processes mode Supply mechanism

Channel

response

Response of basin

Qw and Qsa

Change in volume

or size distribution

of woody debris

on-site and in

channels

Wood

Boulder

levees,

scarred

vegetation

Mass

movement

texture

and

structure

of deposits

High Channel widening

peak flows, and braiding

windthrow

a Qw and Qs refer to discharge of water and sediment, respectively.

Different types of mass movements may affect channels differently. Those that travel

into the channel and stop, such as landslides, may cause channel adjustment from

high quantities of sediment and debris supplied by the hillslope. In contrast, mass

movements that travel down the channel, such as debris flows, may cause channel

changes from the impact force of coarse sediment and woody debris traveling

downstream on streambanks and riparian vegetation.

Effects of changes in frequency or size distribution of wood input on channel morphology are poorly understood and difficult to separate from effects of water and sediment movement. Any decrease in the size of wood pieces left in channels after

logging may result in an increased tendency for wood to become mobile during high

flow events. Increased mobility of wood pieces may cause large unstable debris jams

to form; these in turn deflect flow laterally, thereby causing bank instability and erosion. Increased braiding may also occur as debris forms temporary blockages of main

and secondary channels.

Physical changes in channel morphology produced by these supply mechanisms are

given in table 1, column 4. Although some parameters are unique to specific supply

mechanisms, considerable overlap occurs in the ways that channels adjust. In particular, some channel widening or enlargement is predicted for all supply mechanisms.

Thus, more refined criteria are needed to distinguish between different supply processes; these are discussed in the next paragraphs. Predicted changes in basin water

and sediment yields associated with specific supply mechanisms are given in table 1,

column 5, and can be used as corroborating evidence for determining the active

mechanisms.
Using Aerial

Photographs to

Monitor Changes

in Channel Conditions

Interpretation of aerial photographs is one way to quickly inventory channel conditions over large areas. Most National Forests have aerial photo records for the last

30 to 40 years. In many cases, these photos, usually taken at 5- to lo-year intervals,

offer the best and least expensive way of reconstructing histories of channel changes

relative to management activities, and they may be the only way on some National,

Forests to review past activities, long-term trends, and cumulative effects.

Problems arise, however, in using aerial photographs. In the steep forest lands of

the Pacific Northwest, channel changes on small- to intermediate-sized (second- to

fifth-order) streams are difficult to detect because of steep hillslopes, dense riparian

cover, and shading effects. In old-growth forest stands, even seeing the channel

under the riparian canopy is often difficult. Identifiable changes in channel conditions

on these streams are limited to those that disturb the streamside canopy. Along

larger streams or streams in clearcuttings, the channel is usually visible, and shifts in

location, pattern, and geometry can often be observed directly. But even for these

channels, the small scale of photos and the shading effects of riparian vegetation

limit the usefulness of aerial photos.

Fairly broad criteria have to be used to interpret channel response from aerial photographs. The RAPID method relies on changes in the width of the riparian canopy to

indicate disturbance to the channel system (fig. 2). RAPID is able to detect only

those disturbances that disrupt streamside stands: major floods, debris flows, and

landslides. It does not detect changes in stream morphology when adjacent stands

are not affected, such as aggradation or degradation (except where these result in

mortality of streamside stands), minor shifts in channel location, or changes in

channel geometry.

Changes in the width of unvegetated streamside area or riparian canopy opening

nonetheless provide an indicator of major events of channel disturbance. Floods, for

example, are likely to result in channel widening and bank instability with consequent

opening of riparian canopies. During floods, large organic floating debris can cause

canopy opening by battering and uprooting streamside vegetation. Debris flows

similarly can scour channels and streamside areas and result in loss of canopy.

Introduction of large amounts of coarse sediment by landslides or chronic sedimentation can also induce channel widening, which leads to opened canopies. The

pattern and extent of canopy opening can thus be used as a surrogate variable for

whether the channel has experienced these types of disturbances. The width of the

canopy opening also has important implications for riparian zone processes such as

shading (hence temperature), addition of nutritional resources for aquatic communities, and delivery of large organic debris. The width ‘of the canopy opening is an

important factor influencing the health of stream ecosystems.

If, as hypothesized, the pattern and extent of canopy opening is indicative of the 

of supply mode (table l), a detailed set of diagnostic parameters sensitive enoug

register the variety of induced channel disturbances is needed. In the technique 

lined here, the critical parameters used are (1) the site conditions where the cha

first shows some opening, termed the Initiation site; (2) the degree of physical 

age or contiguity between the initiation site and open reaches further downstrea

(3) the magnitude of canopy opening, expressed in the length and area of the o

channel and the continuity of open reaches along the channel; and (4) the chan

in width of canopy opening with distance downstream (table 2).

Table 2-Physical parameters, detectable by aerial photography,

predicted to be diagnostic for specific supply mechanisms

Supply

mechanism

Mass movement Length of Continuity of Change in width

at initiation contiguous responding downstream from

Sit8 reach channels initiation site

increased peak

discharges No Variable Continuous

to patchy

Increase or

constant

Chronic

sedimentation N o Short Patchy Decrease

Pulse

sedimentation:

Into channel

Within channel

Yes

Yes

Moderate

Long

Continuous

Continuous

Decrease

Decrease

Change in wood

input or mobility Maybe Variable Continuous to

patchy

Increase or

constant

Although no one criteria is sufficient for a diagnosis (table 2), sets of parameters

allow for distinguishing among supply mechanisms. For example, the high energy 

transport and large amounts of organic and inorganic material delivered to stream

during pulse sedimentation events (debris flows and landslides) are likely to result 

a distinctive signature-a mass failure directly linked to open reaches extending

continuously down the drainage network. Longer open reaches more likely result

where input material mobilizes as a debris flow than where it stops near the site o

introduction. Distinct depositional zones may be visible in aerial photos as wide fl

bordering a channel and at the downstream end of disturbed reaches. The open

canopy might diminish with distance downstream because of dilution of sedimentcharged slurries and consequent changes in fluid dynamics or along with increasi

opportunity for deposition with decreasing gradients.
The signature of canopy opening in response to increased peak water discharges, on

the other hand, should include no mass failures at the initiation site and little continuous open reach because local channel constraints (that is, bedrock or differences in

bank stability) are likely to determine where open canopies occur. If one assumes,

moreover, that clearcuts and roads are distributed somewhat uniformly over the basin

and that increases in peak flow generated locally are additive, canopy opening might

be expected to increase or at least remain constant with distance downstream. In

general, canopy opening in response to landslides and debris flows is predicted to be

greater and more extensive than in response to either increased peak flows or

chronic supply of sediment (table 2).

Differences between sediment delivery and transport by mass movement processes,

as opposed to nonmass movement processes, may be particularly apparent at tributary junctions where changes in channel gradient and width are likely to cause debris

flows to stop. This is especially true where the junction angle between tributary and

mainstem is sharp (Benda 1985). An abrupt downstream terminus to the reach exhibiting open canopy might be expected at a tributary junction. Where higher peak flows

or chronic sedimentation is the cause of open canopies, open reaches will likely

extend downstream of tributary junctions and have less abrupt downstream boundaries. They may even show an increase in width of canopy opening below junctions

as a result of the addition of water and sediment from other sources and increased

opportunity for deposition in lower gradient reaches.

It is generally more difficult to ascribe channel changes directly to a wood supply

mechanism because the effects tend to mimic those caused by increased water and

sediment delivery (table 2). The RAPID procedure is not sensitive enough to evaluate whether channel changes are caused by wood movement alone. Wood should

be considered as a contributing factor for all classes of downstream effects.

Open canopies do not necessarily indicate locations of channel instability. Some

channels may be naturally open as the result of site factors, such as soil type or

moisture availability, that limit establishment of riparian species. It is also fairly

common to find channels with open canopies in areas not affected by basinwide

disturbances, such as floods or extensive landslides. In some cases, open canopies

may result solely from channel reworking of alluvial deposits, such as where a

stream flows through an alluviated valley with a floor of glaciofluvial outwash

deposits. Canopy opening is only an indicator of potential sites of channel instability.

Field examination is often required to clearly identify the processes involved.

Collecting Data

With the RAPID

Technique

The three steps in collecting data with the RAPID technique-preliminary photo

analysis, measurement, and tabulation-will be discussed separately. Before

applying this technique, users may wish to study the general techniques of aerial

photo interpretation (for references see appendix 2).

Preliminary

Photo Analysis

Preliminary photo analysis involves selection and preliminary analysis of aerial

photos to identify stream reaches for measurement, determine location and type of

initiation sites, and classify stream reaches by type of and contiguity with initiation

site. Figure 3 gives an example for part of the area shown in figure 2B.

9
- Open reach, contiguous

--- Open reach, discontiguous

-a= - Clearcut boundary

----- Road

AL- Axial landslide

RL - Riparian landslide

f -- landslide from forest

r - landslide from road

F -Forest initiation site

M - - Multiple initiation sites

LCR - Length of contiguous reach

LDR - Length of discontiguous reach

LDO - Length of discontiguous opening

Figure 3- Initiation sites and stream reaches were classified

for the area shown in figure 2B.

Selecting aerial photos--Aerial photos of the basin(s) of interest need to be

collected. Photos selected for analysis ideally are high-resolution, large-scale photos

with minimal shading and distortion and were taken directly over the stream. In

reality, selection of photos will be governed by availability. The stream channel of

interest should be as close to the center of each photograph as possible; successive

and overlapping photos along the same flight line should be used to restrict to the

center of the photograph measurements made on any one photo; this will minimize

edge distortion. The RAPID technique was developed on photographs with scales of

1:12,000 and 1:15,840. Larger scale photographs make identification of individual

features easier; photos with scales smaller than 1 : 24,000 will be only marginally

useful. Either color or black-and-white photos can be used, although color photos

make deliniation of the unvegetated channel area somewhat easier.

1 0
The nominal photo scale, which is the scale commonly printed on the photos, 

inaccurate because of differences in topography, flight elevation, and camera 

length. To accurately determine the scale of the photos being used, it is nece

measure a known distance on the photos. This is best done by measuring the 

tance between two points that can be clearly identified on both the photos and 

U.S. Geological Survey or USDA Forest Service map at a similar (though no

sarily the same) scale. Such points might include road intersections, clearcut 

aries, bridges, or tributary junctions; measured points should lie as close as 

to the channel being measured. The photo scale can then be calculated acco

the following formula:

PS = (PD x MS)/ MD ;

where PS is the photo scale, MS is the map scale, and PD and MD are the m

ured photo and map distances, respectively, in the same units. For a more ind

treatment of photo scale determination, see Ward and Dawson (1986, chapter 

Identifying open reaches--Aerial photos of the entire drainage basin of inte

should be laid out and examined to identify initiation sites and open channel 

Examining photos in stereo or under low-power magnification may be required

Identifying open reaches is fairly straightforward. In areas with dense riparian 

open reaches are identified by bare streamside areas with few, if any, trees (fig

Open reaches are identified by light-colored trimlines in clearcuttings and othe

of sparse vegetation (fig. 2B). The color or tone of open reaches will vary ac

to the photography and nature of vegetation, soil, and parent materials. Open

reaches will not necessarily appear white. Small, discontiguous openings (ex

below) in dense canopy areas appear as breaks in the streamside canopy. T

openings may be difficult to distinguish because of shading; comparison with 

photos along the same flightline or with earlier photos may assist in determini

whether openings are present. Closed canopy reaches, on the other hand, ha

woody riparian vegetation adjacent to the active channel; a small border of unv

tated streamside area may mark the location of the high-water channel in clos

canopy reaches.

Classifying initiation sites--The point furthest upstream where a canopy ope

along any tributary is observed is designated “the initiation site” for that tributa

Initiation sites are classed by whether open canopy begins at a landslide (L) in 

forest (F) or clearcut (C), or near a road (R) without a landslide. Ambiguous sit

conditions (for example, failures in clearcut units immediately downslope from 

should be noted. For landslide sites, the type of landslide is further classed as 

axial or riparian: axial landslides (AL) are those that failed essentially parallel 

within the axis of the creek, drainage depression, or zero-order basin; riparian

landslides (RL) are those that failed more or less perpendicular to the axis of 

creek. Both types of landslides can be seen in figure 2B. For landslide initiatio

the site condition (forest, clearcut, or road) is also noted with a subscript (fig. 3

Initiation sites correspond to the supply mechanisms shown in table 2.
WCR

. tl LDO ---

tT---

4)

0

WDO

\

o Basin Mouth

- Open reach, contiguous

--A Open reach, discontiguous

LCR - Length of contiguous reach

LDR - Length of discontiguous reach

LDO - Length of discontiguous opening

WCF? - Width of contiguous reach

WDO - Width of discontiguous opening

Figure 4-Measurements of lerigth and width are made on

aerial photographs of contiguous and discontiguous reaches.

Classifying stream reaches--The next step in characterizing the condition of the

channels involves the degree of linkage between the initiation site and affected or

open channel reaches. If a section of channel immediately downstream from an

initiation site exhibits continuous canopy opening along its course and incorporates

no sections of closed canopy reaches, it is termed a contiguous reach (CR) (fig. 4).

The section of channel from the first visible canopy closure downstream is termed a

discontiguous reach (DR). Channel openings that occur along a discontiguous

reach are termed discontiguous openings (DO) (fig. 4).

Both contiguous and discontiguous stream reaches are classified according to their

initiation site(s) (fig. 3). To tabulate data for basins with multiple open reaches, the

longest contiguous reach is defined as the main stem. The locations where other

open reaches, either contiguous or discontiguous, join the mainstem are noted, as

are the locations of riparian landslides next to the channel (fig. 3). Where two

reaches with different classes of initiation sites join, the channel below the junction is

classified as having multiple initiation sites. Where two tributaries of the same class

of initiation site join, the classification of the downstream channel does not change

and is tabulated as a continuation of the tributary having the longer contiguous reach

(fig. 3).

12
Measurement

Techniques

The location and classification of initiation sites and open reaches should be ma

from the photos onto a drainage network map of about the same scale. If no map 

available, the stream network can be traced directly from the photos by using a 

table. Each stream segment exhibiting open reaches, beginning with the mainst

(as previously defined), should be numbered to assist in tabulation.

Lengths and widths of contiguous and discontiguous reaches and discontiguous

openings are measured and recorded on the data form (table 3) after initial data

preparation. Measurement is best done under low-power magnification by using 

analytical stereoplotter, stereoscope, or a dissecting microscope. A hand lens or 

loupe with a graduated scale can also be used. Aerial photos should be taped to 

light table for easy viewing.

Length measurements--The channel length is measured on the photos along t

channel axis of each tributary with open reaches, beginning at the upstream init

site and extending downstream to either the basin mouth or a previously measur

channel, whichever comes first. Points along the channel where width measure

will be made are also identified at this time, as described below. To provide a co

mon location on successive photos for width measurements, channel lengths are

measured in uniform increments, termed the “photo measurement interval”. The

photo measurement interval (in centimeters) is a function of a predetermined gro

increment distance (in meters) according to the following formula:

photo measurement interval = (ground increment distance /photo scale reciprocal) x 100

The photo scale reciprocal is the inverse of the photo scale; for example, if the

photos are at a scale of 1:15,840, the photo scale reciprocal is 15,840. At this sc

the photo measurement interval corresponding to a ground increment distance of 

meters (330 ft) is (100/15,840) x 100 or 0.63 centimeters (0.25 in).

Selection of a ground increment distance depends on the inherent variability of

widths of opening along the channel and the objectives of the study. Generally, a

smaller ground increment distance means more accurate results but greater time

required to make measurements.

Where widths of openings are highly variable or where the purpose of the study is 

detect small changes in width of canopy opening, a ground increment distance of

100 meters (330 ft) is used. Longer increments of 200-300 meters can be used

where the width of openings is less variable or where a less detailed view of cha

conditions is desired.
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-- _- -- -- -- _- -- -_ -- -_ -_ -_ -_ -- -- -- -- -- -- __ -- __ -- -- -- -- -

- -.

14
Channel lengths and the locations for width measurements can be measured and

marked off at intervals corresponding to the ground increment distance by using a

wheel or electronic planimeter, if available. Otherwise, a strip of clear or frosted

Mylar’ can be used. To do this, a line corresponding to the calculated photo measurement interval is drawn on the Mylar. The Mylar is laid on the channel with one

end of this line at the initiation site. The channel length is then measured by following the channel along the line, rotating the Mylar strip around a pin placed wherever

the channel course deviates from the line until the line intersects the channel again

(fig. 5). When the end of the tine is reached, the pin is used to make a small hole in

the photograph, the Mylar strip is rotated 180°, and the process is repeated until the

entire channel length downstream from the initiation site to the basin mouth has been

measured and marked. The locations of the pin holes are numbered with a grease

pencil to correspond with their ground distances, and the lengths of contiguous and

discontiguous reaches are read directly from the photos. Lengths between pin holes

can be interpolated where necessary. Lengths of contiguous and discontiguous

reaches for each class of initiation site are tabulated separately (table 3).

Figure 5 - How a clear Mylar strip can be used to measure

sinuous channel lengths.

Width measurements--Widths of canopy openings in both contiguous and discontiguous reaches are measured and recorded at intervals corresponding to the chosen

ground increment distance as marked by the pin holes. An analytical stereoplotter is

the ideal tool for making these measurements. If not available, an eye loupe with a

scale in O.l-millimeter increments or electronic planimeter set to point-to-point mode

can be used; a ruler with a scale readable to +O.l millimeters can also be used. If an

electronic planimeter is used, measurements should be repeated until at least two

measurements agree, then all should be averaged.

’ Use of a trade name does not imply endorsement or

approval of any product by the U.S. Department of

Agriculture to the exclusion of others that may be suitable.

1 5
Tabulation

The width of canopy opening is measured perpendicular to the channel axis to the

nearest 0.1 millimeter (0.004 in). Photo distances are converted to ground distances

in meters by the following formula:

ground distance in meters = photo distance in millimeters x photo scale reciprocal/1000.

Calculated ground distances should be rounded off to the number of significant digits

in the calculated photo scale; for example, a nominal photo scale of 1:12,000 has

two significant digits. A measurement of 1.6 millimeters (0.06 in) on these photos

would therefore be rounded off to 19 meters (62 ft).

Accurate determination of width of canopy opening may be difficult along some

channel sections because of shading or camera angle. Sequential photos taken

along the same flight path should be examined to reduce the effects of the fatter;

however, in some cases it may be necessary to extrapolate widths at measurement

sites from adjacent stream reaches where shading is not a factor.

Widths are measured along all contiguous reaches and discontiguous openings

beginning at the initiation site (fig. 4). Widths normally are not measured for closed

canopy reaches because the unvegetated area cannot be easily seen. Widths of

discontiguous openings should be made at the beginning and end of the opening if

the opening is shorter than the photo measurement interval and at photo distances

corresponding to the photo measurement interval for larger openings.

The site condition (forest, clearcut, partial cut, or road) for each streambank should

be recorded at each measurement site (table 3); this makes it possible to determine

whether streamside management activities affect the extent of canopy opening. The

locations where other open- or closed-canopy tributaries join should also be noted

(table 3).

One of the major advantages of the RAPID technique is its flexibility. Depending on

the type of analysis desired, the data can be used to examine the pattern of canopy

openings extending downstream from a specific initiation site to analyze the extent of

canopy opening resulting from a class of initiation sites in a particular basin (that is,

all road-related landslides), or to compare the total canopy opening resulting from a

storm in two basins with different histories or management treatments (that is, logged

and unlogged).

Data summaries--The raw data provide information on patterns of canopy openings

associated with specific initiation sites. A summary of lengths and average widths for

contiguous and discontiguous reaches and discontiguous openings should be made

for each initiation site (table 3). Average width of canopy opening is calculated for

each contiguous reach and discontiguous opening and widths of discontiguous openings, respectively, by averaging individual width measurements weighted by the proportion of total reach length corresponding to that width measurement. A program for

the Hewlett-Packard (HP) 41 series calculators that computes weighted averages is

given in appendix 1. For discontiguous reaches, the number and sum of the length of

discontiguous openings are also calculated, along with the total length of discontiguous reach (table 3).

1 6
By summing measurements made on individual initiation sites over an entire basin,

summary statistics for the basin as a whole can be developed (table 4). These summaries are useful for comparing basins with different treatments or for analyzing time

trends in an individual basin. The widths of contiguous openings and widths of discontiguous openings for the basin are determined by averaging the weighted means

from individual reaches weighted by the total contiguous or discontiguous reach

length.

The data can also be summarized by initiation site class so that the effectiveness

of specific types of initiation sites in producing canopy openings can be analyzed

(table 5). This is particularly useful for evaluating the relative importance of specific

downstream effects operating in a basin.

Computation of canopy opening indices--To quantify relations between patterns of

canopy openings and initiation site types, indices are developed from the measurements outlined above (table 6). These indices are used to evaluate the extent and

type of canopy opening associated with particular initiation site classes and to test

hypotheses about the relative importance of different mechanisms for producing

canopy openings in a given basin or among a population of basins. Computation of

indices is simplified by using a program for HP-41 calculators (appendix 1) or a

computer spreadsheet program.

Indices can be generated for (1) individual, responding channel reaches; (2) all

reaches in a particular basin; and (3) all reaches in a basin having a particular

initiation site class. Methods for calculating each of these types of indices is discussed below; interpretation of indices is discussed in the section “Analyzing and

Interpreting Results.”

Individual responding reaches--Indices are calculated from the data summaries for

individual reaches (table 3). Mean widths used in these calculations are averages of

individual measurements weighted by the proportion of total reach length associated

with each measurement. For channel segments without discontiguous openings, the

discontiguity index is undefined, not zero. Indices derived in this manner are used to

compare the effectiveness of specific initiation sites in producing open canopies.

All reaches in a basin -- These indices are developed from the data summary for the

entire basin (table 4) and are used to describe basin response as a whole. Indices

are calculated using column totals from table 4. In particular, the area of canopy

opening index (table 6) should be calculated by summing the area of canopy opening

values for the individual reaches, rather than by multiplying the total reach length by

the average width for the basin as a whole; because of the weighted averaging

procedure, some discrepancy between these two methods is likely.

All reaches having a particular class of initiation site -- Indices can also be

calculated for all reaches having specific classes of initiation sites by using the data

summary table (table 5). Such indices are useful in comparing the relative importance of specific types of initiation sites for producing canopy opening. Column totals

are used to calculate indices, and average widths are weight averaged.

7 7
Table 4 - Data form for basin summary by segment, Bohemia Creek

RAPID PROCEDURE: BASIN SUMMARY BY SEGMENT

BASIN Bohemia Ck

PHOTOS USED:

YEAR /4;6 7

SCALE . 

MEASUREMENT UNITS: ft, in, @ cm (Circle one)

SUMMARY VARIABLES BY SEGMENT RESPONSE INDICES

CONTIGUOUS I DISCONTIGUOUS

I4 , ' ---- ' SEGMEN T OPEN REACH : AVG : AVG I I

NUMBER CLASSIFICATION : LCR WCO : LDR NDO SUM LOO WDO I LRC ACD RCO CI DI PI I

LCR WCO LDR NDO SUM LDO WDO LRC ACD RCO CI DI PI

CODING LEGEND

OPEN REACH CLASSIFICATION SUMMARY VARIABLE ABBREVIATIONS

(Based o n initiation site type) RESPONSE INDICES

AXIAL LANDSLIDE A L LCR Length o f contiguous reach LRC A x1i al landslide from forest ALF LDR

Length of responding channel

Length of discontlguous reach ACO al landslide from clearcut ALc

Area of canopy opening

Axi AUG WCO RCO A x1i al landslide From road ALr AUG WDO

Average width of contiguous opening Responding channel opening

CI

RIPARIAN LANDSLIDE RL

Average width of discontlguous opening Contiguity index

SUM LDO Sum of the lengths of discontiguous DI

Riparian landslide from Forest RLF

Discontinuity index

openings PI Patchiness index

Riparian landslide From clearcut RLc NDO

Riparian landslide From road RLr

Number of discontiguous openings

FOREST (No landslide) F

CLEARCUT (No landslide) c ROAD (No landslide) R

MULTIPLE (Below junctions of M

tributaries having different

classes of initiation sites1
Table 5 - Data form for basin summary by Initiation site type, Bohemia Creek

RAPID PROCEDURE: BASIN SUMMARY BY INITIATION SITE CLASS

BASIN Bohemia Ck

SHEET 1 OF 1

PHOTOS USED:

YEAR

SCALE

MEASUREMENT (Circle one)

SUMMARY VARIABLES BY INITIATION SITE RESPONSE INDICES

: CONTIGUOUS I DISCONTIGUOUS 1t , * 1 , 0 I

OPEN REACH SEGMENT : AUG : AUG : ,

CLASSIFICATION NUMBER : LCR WCO

0

I LDR NDO SUM LDO WDO : LRC ACD RCD CI DI PI :

TOTALS BY INITIATION SITE

LCR WCO LDR NDO sun LDO WDD LRC A C D RCD CI DI PI

AXIAL LANDSLIDES (AL)

AL-forest

AL-clearcut

AL-road

RIPARIAN LANDSLIDES (RL) : RL-Forest 8

RL-clearcut 1I

RL-road

FOREST

CLEARCUT

ROAD

MULTIPLE

SUMMARY VARIABLE ABBREVIATIONS RESPONSE INDICES

LCR Length of contiguous reach LRC

LDR Length of discontiguous reach ACO

Length of responding channel

AVG WCO Average width of contiguous opening RCO

Area of canopy opening

AVG WDO Average width of discontiguous opening CI

Responding channel opening

SUM LDO Sum of the lengths of discontiguous Contiguity index

D I

openings PI

Discontinuity index

ND0 Number of discontiguous openings Patchiness index
Table 6 - Quantitative indices for measuring degree of channel opening’

Index Description Formula

Length of responding

channel (LRC) The total length of responding

channel measured downstream from

an initiation site to basin mouth

or junction with main stream (m)

LCR + LDR

Responding channel

opening (RCO) A measure of opening for channels

showing some response expressed

as a percentage of channel

responding

Contiguity index (C I) The degree to which response

can be directly related in

space to a particular initiation

site

Absolute channel opening

(ACO)

An approximation of total area

of open channel (m*)

Relative basin channel

opening (RBCO)

An approximation of the

proportion of a basin in open

condition, treated as a

percentage

Discontinuity index (DI) The degree of discontinuity

in a discontiguous reach. High

values indicate relatively low

degree of opening within the

reach while low values indicate

a high degree of opening.

n

LCR ; $LDOj x 100%

LRC

where n = ND0

LCR

LRC

(LCR x WCR) + (LDO x WDR)

ACO x 100%

total basin area

LDR x ND0

CLDO

Patchiness index (PI) The frequency of opening per

linear kilometer of

discontiguous channel

NDO x 1000

LDR

a Abbreviations are as follows: LCR = length of continuous response; LDF? = length of discontiguous response; LDO = length of discontiguous

openings; WCR = average width of contiguous response; WDR = average width of discontiguous response; and NDO = number of

discontiguous openings. Example of measurements used to derive indices is shown in figure 3.

2 0
Analyzing and Several different types of analyses can be performed by using the RAPID technique.

Interpreting Results These range from relatively rapid assessment of riparian canopy conditions for an

individual stream or group of streams to time-trend analyses for a channel or basin

and quantification of the degree of canopy opening associated with specific initiation

sites. From these analyses, the relative importance of different mechanisms for

producing downstream effects can be interpreted. Analysis procedures differ depending on the questions being asked. In this section, use of the data summaries and

indices for both within-basin and interbasin analyses are discussed; analysis procedures are summarized in table 7.

Table 7-Suggested approaches for different types of analysis using the RAPID technique

Analysis type Objective Suggested approaches

Within-basin:

At a given

point in time Analyze pattern

of canopy opening

along individual

channels

Plot width of canopy opening as a point in time of canopy opening

function of distance downstream from along individual initiation site,

location of tributary channels junctions, road crossings, and so forth

Time trend

Cumulative

effects

analysis

I nterbasin

analysis

Compare patterns

of canopy opening

among different

channels within

same basin at a

single point in time

Compare patterns 1. Successive plots of width of of canopy opening canopy opening

of canopy opening for the same stream within same basin reach through time

within same basin showing location over a period of landslides, roads, tributaries,

over a period of time and time so forth

Interpretation of

causative factors

contributing to

open canopies,

channel changes

Analyze effects of

different geologic,

hydrologic, climatic,

or management

conditions on

degree of canopy

opening

1. Order streams by ACO, Cl, or RBCO of canopy opening

indices to compare magnitude of opening among different on

different streams

2. Plot ACO, RCO, and number or type single point in of initiation

site as a function of time drainage area or stream order

2. Plot ACO, Cl, and PI as functions of time, percentage of basin

in cutover condition, and miles of road

1. Calculate frequency distributions ACO, LRC, Cl, or PI by type

of initiation site

2. Compare composite response indices for each initiation

site class

Calculate and compare composite indices of basin response,

notably RBCO and Cl, as a function of management intensity

(percentage of basin harvested or roaded); intrinsic geomorphic

stability (proportion of basin in unstable geologic or soil units);

or storm history

21
Within-Basin

Analysis

Within-basin analysis includes patterns of canopy opening for both individual and

multiple stream reaches, time-trends, and interpretation of factors producing canopy

openings on a basin scale.

Individual stream reaches--Patterns of canopy openings for a specific stream reach

can be analyzed by plotting the width of the canopy opening as a function of distance

downstream from the initiation site. An example from Bohemia Creek, a tributary to

the Middle Fork of the Willamette River, is shown (fig. 6). A plot of this kind is useful

for interpreting causal mechanisms of canopy openings. According to table 2, the

width of canopy opening should decrease away from mass movement initiation sites

and increase or remain constant where increases in the peak flow are the primary

cause. The decreasing trend of width of canopy opening with distance downstream

on Bohemia Creek suggests that, in this case, the former mechanism is the dominant

one (fig. 6).

/T\I Closed tributary

T Open tributary

Landslide

400 800 1200 1600 2000 2400 2800

Distance from first initiation site (m)

Figure 6 - Change in width of canopy opening, Bohemia

Creek, relative to sites of sediment and water introduction to

the channel, as measured from aerial photographs.

Plotting the locations of other factors that may influence the extent of canopy

opening, such as landslides, roads, clearcuts, and open and closed tributary

junctions, directly on the graph may also be useful (fig. 6). In this way, it is possible

to determine whether other processes (for example, runoff from road surfaces or

point introduction of sediment from landslides) contribute to canopy opening.

Multiple stream reaches--One of the simplest uses of the RAPID technique is to

quickly evaluate riparian canopy conditions among several streams. This approach

might be called for when the objective is to identify the location of stream reaches

that have in the pas? or are now exhibiting open canopies. Different streams or

stream segments can be ordered by their area of canopy opening index (table 6),

2 2
a measure of the total area of canopy opening. This measure is somewhat biased,

however, in favor of larger streams. A less biased measure is the relative basin

channel opening index (table 6) because this is the total area of canopy opening

divided by the basin (or subbasin) drainage area. Stream segments can also be

ordered by their contiguity index, which is the ratio of length of contiguous opening

to total length of downstream channel; this can be used as a measure of the amount

of a channel in open condition (table 6).

Identifying which parts of a drainage basin are particularly susceptible to canopy

opening may be useful. Two different approaches can be followed: The first is to plot

the location of initiation sites, perhaps stratified by type of site (landslide or nonlandslide) on a drainage network map, compute the drainage area for each initiation site

(using an areal planimeter), and plot the number of initiation sites in different drainage area classes. A second approach is to determine the stream order of all open

reaches by using a Horton-Strahler analysis (see Dunne and Leopold 1978, p. 498-

499) and plot the percentage of total length of stream order in open condition for

each stream-order class; an example of this latter approach is shown (fig. 7). Either

method is useful for analyzing where open reaches are within a basin, and each can

provide corroborating evidence for interpretation of causes of canopy opening. Open

reaches located along higher order streams, for example, are more likely to be the

result of fluvial factors rather than mass movement factors because debris flows and

torrents are usually limited to steeper, lower order drainages.

Length contiguous

opening

4 0 I’l’l’l’,

- 10

, ,,, Length discontiguous q+; opening

E

- 1

0”& 3 0

Q

1 2 3 4

Stream order

Figure 7-Percentage of channel length in different stream

orders exhibiting canopy opening on 1967 photos, tributaries

to Middle Fork of the Willamette River.

2 3
Time trend analysis--Changes through time in riparian conditions for either an individual channel or an entire basin can also be evaluated. From aerial photos taken in

successive years, the width of riparian canopy opening along a channel can be plotted as a function of distance downstream from a fixed location. Plots for successive

years allow time trends in magnitude of canopy opening to be analyzed. Channel,

conditions along the Breitenbush River, Willamette National Forest, were analyzed

from aerial photos at a scale of 1 :12,000 in 1959 and at 1 :15,840 for 1967, 1972, and

1979 (fig. 8). The upper channel of the Breitenbush is in a Wilderness Area, and the

lower channel was subjected to intensive salvage logging operations in the riparian

corridor from 1960 to 1985; the most intensive salvaging occurred downstream of the

bridge (see fig. 8). Width of the canopy opening in the upper (wilderness) channel of

the Breitenbush was about twice that of the lower channel under natural conditions in

1959 (fig. 8a). Between 1959 and 1967, the width of the canopy opening increased

over the entire channel, most markedly in the reach below the bridge (fig. 8b). Much

of this can be attributed to a major storm in December 1964. Comparison of width of

canopy opening between 1972 and 1979 shows a general decrease presumably

caused by new riparian vegetation in flood- affected areas (fig. 8c). Major salvage

operations in the lowest reaches of the stream coupled with a major storm in 1977

appear to have been responsible for the dramatic increase in width of canopy

opening seen in the 1979 photos in the section below the bridge (fig. 8d).

To accurately superimpose plots of widths of canopy openings from different photo

series, the locations of several clearly identifiable points visible on all photos should

be used as references for orienting the plots. The plots may have to be aligned by

hand to achieve the best fit between successive years.

Time-trend analysis for a basin as a whole is accomplished by using indices of basin

response. The basin’s length of responding channel, area of canopy opening, contiguity index, or patchiness index can be plotted for successive years, thereby providing a measure of how basin riparian conditions have changed over time. For this kind

of analysis, it is helpful to also plot management and natural disturbance factors of

interest, such as the percentage of the basin in cutover condition, the miles of road in

the basin, the timing of large storms, and the number of landslides visible on photos,

if such information is available. In this way, relations among management activities,

storm history, and basin response indices can be explored.

2 4
A.

90,

70 -

z

-

5 60- --Wtldrrnrsss 50-

0’ 40-

is

3 30-

g 20-

= IO-

: 0- , , , ‘ , , , , ,

0 2000

,

4000 6000 8000 10.000

DISTANCE DOWNSTREAM FROM DATUM (m)

o!. ,..,,,,,, I 0 2000 4000 SOW 0000 10.000

DISTANC E DOWNSTREAM FROM DATU M (m)

80

P

- 70

z"

f 60 m Increase in width

0” 0 Decrease in width

0 5 0

:

0 4 0

5

tJ 3 0

IL

O 2 0 I

k 1 0

5

0 - . . . . , , , , , 0 2000 4000 6000 8000 10.000

DISTANCE OOWNSTAEAM FROM DATUM (m)

D.

90 , I

0 2000 4000 6000 8000 10,000

DISTANCE DOWNSTREAM FROM DATUM (m)

Figure 8 - Change in width of riparian canopy from 1959 to

1979, Breitenbush River, Oregon.

25
Interpretation of causative factors--The RAPID technique was originally developed

to distinguish among potential causes of downstream or cumulative effects. Interpretation of factors contributing to downstream effects in a given basin is aided by using

response indices (table 6) calculated for all reaches having a particular class of

initiation site (table 5). Two approaches are used. First, statistics for the entire population of reaches having a particular class of initiation site are generated and compared with those having a different type of initiation site; for example, the frequency

distribution of lengths of contiguous reaches for reaches with and without mass

movement initiation sites can be compared to examine the relative effectiveness of

different classes of initiation sites in producing canopy openings (fig. 9). It is clear

from figure 9 that the length of contiguous reach for sites with mass movements is

greater than the length of contiguous reach for sites without mass movements. Mean

length of contiguous reach for mass movement sites is 430 meters (1,410 ft) compared to 130 meters (430 ft) for sites without mass movements; this indicates that

processes associated with mass movement initiation sites are more effective in

producing open canopies. In a similar fashion, one could look at the frequency

distribution of contiguity index, area of canopy opening, or patchiness index for all

reaches in a basin, stratified by type of initiation site. These indices can be used to

compare patterns of canopy openings associated with landslide initiation sites from

forests, clearcuts, and roads to determine if certain classes of landslides are more

effective in producing open canopies.

I Multiple

2- 0

:

l - n n RR n A

3 I . 1 I I

c

*

z

Q Chronic

C

- 3- f 2-

.c lii I 1 I I I I I I

0

L

5 Pulse

I I I , I I n u-j

0 100 200 300 400 500 600 700 800 v 2800

Figure 9 -Distribution of lengths of open reaches contiguous

with their initiation sites for different supply mechanisms.

Pulse sites include all axial and riparian landslide initiation

sites; chronic sites include all other initiation sites; and multiple sites include two or more initiation sites of different types.

2 6
Composite-response indices can also be calculated and compared for each type of

initiation site (that is, axial landslides, riparian landslides, or forest, clearcuts, and

roads without landslides). For this purpose, data summaries, such as table 5, are

used. In a study (Grant 1986, p. 73) of fourth- and fifth-order streams draining into

the Middle Fork Willamette River in Oregon, it was found that the composite contiguity index for all mass movement initiation sites (0.87) was over twice that for

initiation sites without mass movements (0.41). Because both length of contiguous

reach and contiguity index measure the amount of canopy opening spatially linked

to the initiation site, the results seem to confirm that a canopy opening downstream

from a mass failure initiation site is likely to be more continuously open for longer

distances than when no mass movements are present. In this sense, landsliderelated sedimentation events appear to be more effective in producing canopy

opening, as predicted (table 2).

lnterbasin Analysis Interbasin analysis is used to compare patterns of canopy openings among several

basins, In this way, effects of differing geologic, hydrologic, or management conditions can be assessed. Comparing amounts of canopy opening across several basins

subjected to the same storm may help identify those basins that are particularly

susceptible to canopy opening and those basins that are relatively resistant.

The approach for comparing basins is straightforward: data summaries for basins

(table 4) are used to generate composite indices of channel response for the entire

basin. These indices are plotted against basin parameters of interest, such as the

percentage of basin harvested or proportion of basin area in unstable terrain. The

relative basin channel opening index for eight basins in and near the Middle Fork

Willamette River area was plotted against area of basin harvested by using 1967

photos (fig. 10) (Grant 1986). Results suggest an increase in the proportion of total

channel area open with increasing area harvested. One creek (Bohemia) was plotted

as an outlier to this general trend, though, and exhibited a much higher proportion of

open channel area. Subsequent analysis revealed that the Bohemia Creek basin had

the highest proportion of unstable terrain as defined by Soil Resource Inventory units

(Legard and Meyer 1973). This technique thus makes it possible to identify basins

particularly sensitive to canopy opening because of intrinsic geological factors.

2 7
Conclusions

3.2 - 0 BOH

: 0 l-6- SIM

u

c

0

0

2 0.8- 0 BUC

o WIN

[’ FPC 0 GLD OWlL

0.0 1 I o I

CFP

I I I 1

0 2 4 6

Area harvested (km*)

Figure l&Relation of the relative basin canopy opening

index, computed as the percentage of basin area in open condition, to area harvested in 1964. Individual basins are BOH =

Bohemia Creek, SIM = Simpson Creek, WIN = Windfall

Creek, GLD = Gold Creek, BUC = Buck Creek, WIL = Willow

Creek, CFP = Coffeepot Creek, and FPC = French Pete

Creek.

Through measurements made on aerial photographs of riparian canopy conditions,

the RAPID technique allows resource specialists and managers to identify stream

reaches chronically or recently disturbed by a variety of channel processes- Patterns

of disturbed canopy are used as indicators of specific processes involved. This

technique can be used to both inventory channel conditions and assess causes of

channel changes.

The RAPID technique offers a quick, inexpensive, yet quantitative approach for

evaluating changes in riparian canopy conditions through time and space. Changes in

riparian conditions can be assessed over periods ranging from years to decades,

time scales over which land management histories and techniques may have

changed and the forest may have experienced storms of various magnitudes.

The technique also offers ways to rapidly assess streamside conditions across a

large area. It is useful for scoping or identifying sensitive stream reaches and basins.

Flexibility in calculating response indices allows for evaluation of individual stream

reaches, entire channels, entire basins, or multiple basins.

2 8
Finally, the RAPID technique provides a tool for assessing the relative importance of

different processes producing effects downstream. It can provide only one type of

evidence, however. Corroborating evidence, such as ground surveys, are required to

confirm interpretations made from aerial photographs. The RAPID techniques can

help the resource specialist decide where to look and what to look for to determine if

downstream effects are present. The most useful application may be framing and

testing hypotheses about the location and prevalence of and processes responsible

for disturbances in riparian areas.

Literature Cited Benda, L.E. 1985. Delineation of channels susceptible to debris flows and debris

floods. In: International symposium on erosion, debris flow, and disaster

prevention; 1985 September 3-5; Tsukuba, Japan. [City unknown], Japan: The

Erosion Control Engineering Society: 195-201.

Dunne, T.; Leopold, LB. 1978. Water in environmental planning. San Francisco:

W.H. Freeman and Co. 818 p.

Grant, GE. 1986. Downstream effects of timber harvest activities on the channel and

valley floor morphology of western Cascade streams. Baltimore, MD: Johns

Hopkins University. 364 p. Ph.D. dissertation.

Grant, G.E.; Crorier, M.J.; Swanson, F.J. 1984. An approach to evaluating off-site

effects of timber harvest activities on channel morphology. In: Proceedings of the

symposium on the effects of forest and land use on erosion and slope stability;

1984 May 7-l 1, Honolulu. Honolulu: East-West Center of Hawaii: 177-186.

Legard, H.A.; Meyer, L.C. 1973. Willamette National Forest soil resource inventory.

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

Region. 167 p.

National Environmental Policy Act of 1969, Public Law 91-190; 42 U.S.C.

4321-4347.

Ward, J.F.; Dawson, R.O. 1986. Aerial photograph interpretation techniques:

Region 6 basic training manual. Portland, OR: U.S. Department of Agriculture,

Forest Service, Pacific Northwest Region. 230 p.

APPENDIX 1 The following two programs (figs. 11 and 12) were written for Hewlett-Packard

Programs for (HP)-41 series calculators to expedite calculations used in the RAPID procedure.

Calculations Used They can also be used with the HP-97 desktop calculator. Program lines should be

in the RAPID Procedure keyed into the calculator exactly as written. The owners handbook should be

consulted for more explanation of the key codes and abbreviations.

2 9


1. INDCALC program: This program (fig. 11) calculates response indices shown in

table 6 after being prompted for measured parameters. It can be used to calculate

response indices for individual sites, entire basins, or particular classes of initiation

sites, as explained in the text. Measurements can be entered in feet or meters; units

of indices will vary depending on the measurement system used. See table 6 for

definitions and formulas of variables. Abbreviations for variables used in the program

are as follows:

Input variables

Units of

measurement

LCR, length of contiguous reach

WCO, average width of contiguous opening

LDR, length of discontiguous reach

NDO, number of discontiguous openings

LDO, sum of the length of discontiguous openings

WDO, average width of discontiguous openings

m or f t

m or f t

m or f t

morft

m or f t

Output variables

LRC, length of responding channel

ACO, area of canopy opening

RCO, responding canopy opening

Cl, contiguity index

DI, discontinuity index

PI, patchiness index

ft

m

m or f t

m* or ft*

Percent

m/m or ft/ft

m/m or ft/ft

Openings/km or

openings/mile

Feet

Meters

Running the program: After keying in the program, press the SHIFT key followed by

the RTN key. Then execute SIZE (XEQ SIZE). When prompted for the size, key in

015. To begin the program, press the R/S key. The program will first prompt for the

measurement units used (feet or meters) and then prompt for the input variables.

Appropriately labeled output data will then follow. The PI and DI are calculated only

when discontiguous reaches are present; they are undefined otherwise. After running

through the calculations, the program will loop back; it is then ready for another set

of measurements. To terminate the program, press CLX.

2. WTAVRG program: This program (fig. 12) computes the average width of an open

reach, which is calculated by averaging individual width measurements weighted by

the proportion of total reach length associated with each measurement. The total

reach length must be determined before the program is run and be entered at the

prompt. The program then prompts for lengths and corresponding widths of individual

measurements. It checks for whether the sum of individual length measurements

entered equals the total reach length. If so, it calculates the weight-averaged width

for the reach; if not, it prompts for the next pair of measurements. An error message

is printed if the sum of input lengths exceeds the total reach length.

3 2
Input variable Description

LENGTH

LENGTH (N)

WIDTH (N)

Total reach length over which widths are

to be averaged

Length and measured width at each

measurement site, where N = 1, 2 . . . total

number of sites

Output variable

AVGWIDTH Average weight-averaged width for the reach

Running the program: After keying in the program, press the SHIFT key followed by

the RTN key. To begin the program, press the R/S key. The program will first prompt

for the total reach length. It will then prompt for pairs of length and width measurements. The average width will automatically be calculated when the sum of the individual length measurements equals the total reach length. If the sum of individual

length measurements exceeds total reach length, the message ERROR-CHK LNGTH

will appear; it indicates that either the total reach length or the individual measurement lengths were improperly entered.

APPENDIX 2

General References

on Aerial Photograph

Interpretation

Caylor, Jule A. 1984. Basic aerial photograph utilization techniques course

workbook and manual. San Francisco: U.S. Department of Agriculture, Forest

Service, Pacific Southwest Region, Engineering Office.

Paine, D.P. 1981. Aerial photography and image interpretation for resource

management. New York: John Wiley and Sons.

Ray, R.G. 1960. Aerial photographs in geologic interpretation and mapping. U.S.

G.S. Prof. Pap. 373. Washington, DC: U.S. Government Printing Office.

Ward, J.F.; Dawson, R.O. 1986. Aerial photograph interpretation techniques: Region

6 basic training manual. Portland, OR: U.S. Department of Agriculture, Forest

Service, Pacific Northwest Region. 230 p.

APPENDIX 3 ,

Blank Forms

3 3
RAPID PROCEDURE: PRIMARY DATA FORM

SEGMENT

SHEET _ OF _ STREAM

BASIN

PHOTOS USED:

YEAR

SERIES

NUMBERS

SCALE

MEASUREMEN T UNITS: ft, in, m, cm (Circle one)

CONTIGUOUS DISCONTIGUOUS 1I

OPEN DISCONTIG

REACH :INFLUENCES REACH

CLASSIFICATION DISTANCE WIDTH R L

INFLUENCES

NUMBER DISTANCE WIDTH R L , I I I IP-PI I 1 I ----- , I 4 , 0 I I I , 8 , 8 I I , 4 I 0 --- ----- I , I I I I , I 0 I ---0 - - I 1 8

1 1 I , 8 I I , , I , , I I --- --- , I

CODING LEGEND

OPEN REACH CLASSIFICATION

(Based on initiation site type)

 AXIAL LANDSLIDE AL

Axial landslide from forest

Axial landslide from clearcut

ALF

Axial landslide from road ALc

ALr

 RIPARIAN LANDSLIDE RL

Riparian landslide from forest

Riparian landslide from clearcut

RLF

Riparian landslide from road

RLc

RLr

FOREST (No landslide) F

CLEARCUT (No landslide) C

ROAD (No landslide) R

MULTIPLE (Below junctions of

tributaries having different M

classes of initiation sites)

INFLUENCES

OPEN TRIBUTARY

(where n - segment number)

CLOSED TRIBUTARY

CLEARCUT

ROAD CROSSING

MARGINAL ROAD

OT(n)

CT

cc

RX

R M

SUMMARY

t CONTIGUOUS : DISCONTIGUOUS II

1 SUMMARY VARIABLE ABBREVIATIONSI

REACH ,VVVI I AVG AVG :

CLASSIFICATION :LCR WCO :LDR NDO SUM L D O WDO II

1 1 I 0 , I I --- I

8 I 8 I I I I --- I t , : I I : I , I I - - I 1

TOTFILS I I 4 : I I ,--P1 I

LCR

LDR

Length OF contiguous reach

AUG WC0

Length OF discontlguous reach

AUG WDO

Average width OF contiguous opening

sun LDD

nverage width of discontlguous opening

Sum of the lengths OF discontiguous

openings

ND0 Number of discontiuuaus openings
RQPIJJ PROCEDURE: BASIN SUMMARY BY INITIATION SITE CLASS

BASIN

SHEET __ of _ PHOTOS USED:

YEAR

SCALE

MEASUREMENT UNITS: ft, in, m, cm (Circle one)

SUMMARY VARIABLES BY INITIATION SITE RESPONSE INDICES

: CONTIGUOUS I DISCONTIGUOUS i 0

: I I1 ,, OPEN REACH SEGMENT : AVG : AVG : ,I

CLASSIFICATION NUMBER I LCR WCO I LDR ND0 sun LDO WDO I LRC ACO RCO CI DI PI : ,

TOTALS BY INITIATION SITE

LCR WC0 LDR NDO SUM LDO WDO LRC ACO RCO CI DI PI

SUMMARY VARIABLE ABBREVIATIONS RESPONSE INDICES

LCR

LDR

AVG WCO

AVG WDO

SUM LDO

Length of contiguous reach LRC Length of responding channel

Length of discontiguous reach ACO

Average width of contiguous opening RCO

Area o f canopy opening

Average width of discontiguous opening CI Responding channel opening

Sum of the lengths of discontiguous

Contiguity index

DI Discontinuity index

w

WI
W

(J,

RAPID PROCEDURE: BASIN SUMMARY BY SEGMENT

BASIN

PHOTOS USED:

YEAR

SCALE

MEASUREMENT UNITS: ft, in, m, cm (Circle one)

SUMMARY VARIABLES B Y SEGMENT RESPONSE INDICES

: CONTIGUOUS I DISCONTIGUOUS 8I

I 1 I 0 I I

SEGMENT OPEN REACH : AVG I AUG I

NUMBER CLASSIFICATION : LCR WCO : LDR NDO SUM LDO WDO I LRC ACO RCD CI D I PI :

: : II

I - I I I I ---- I : I , I I I --- , I - - I I I

I I : I t I ---- I 1 I I I I I I t t I --- I I ------ I , I I , I I * ‘-I- - 1 I I I - - : I , , I 1 ---- 0 t I I 0 I I I I 8 --- I 1 , I I , --p--mI I I

I 0 I I I 4 I I I : I ! I I I 1 , I --P I I * , , I 1 ----- 1 )-I-I- : I I 8 , I I - - -_I__--: : I I I I I 1 , I I I --P: I 1 I I - - I : I : , 1 I I 0 I 1 I -L___-- --- I : I I I - - : I I ---- , I I I , 4 # I : t : I 1 I --- I I I I I : ,

I 1 I I , I ------

I I ,--P’ I I -‘-

0 ,

,-I-I I --’ I ,

I 1 I 0 I I 1 , I , I I , I I , I : I I I I --- * I I I 1 I - - , 6 I ---- I 9 8 I I --- , l I I I , I I 8 1 I I - - ---- 1 , -1-I -’ : I I - - :v-I I I I I t I I I I I I I - - I , I I I I --- , I I t t I - - I

0 0 I --- I l ,I - - I, t ----I

I I I ,

I I , I I I 1 8 I I I -1_1_-- I I --- , I

, I I I I I I I I , 1 I , I -__- I 8 :---4-;--I -‘-‘-I- ! - -

LCR WC0 LDR ND0 SUfl LDO WDO LRC AC0 RCD CI D I P I

BASIN TOTALS 0 I I , I 9 I I I 8 I 1 I I I --- I I --------‘- , , : 1

CODING LEGEND

OPEN REACH CLASSIFICATION SUf-VlARY UARIQBLE f4BBREUI~TIDNS

(Based on initiation site type) RESPONSE INDICES

AXIAL LANDSLIDE A L LCR Length of contiguous reach

Axial landslide from forest ALf LDR LRC Length of discontiguous reach

Length of responding channel

ACO Axial landslide from clearcut ALc AUG WCO Area of canopy opening

RCO Axial landslide from road ALL- AUG WDO

Average width of contiguous opening Responding channel opening

CI RIPARIAN LANDSLIDE RL SUM LDO

Average width of discontiguous opening Contiguity index

Riparian landslide from forest RLf

Sum of the lengths of discontiguous D I

openings

Discontinuity index P I Riparian landslide from clearcut RLc NDo

RLr

Number of disontiguous openings

Patchiness index

Riparian landslide From road

FOREST (No landslide) F

CLEARCUT (No landslide) C

ROAD (No landslide) R

MULTIPLE (Below junctions of M

tributaries having different

classes of initiation sites)
Grant, Gordon. 1988. The RAPID technique: a new method for evaluating

downstream effects of forest practices on riparian zones. Gen. Tech. Rep.

PNW-GTR-220. Portland, OR: U.S. Department of Agriculture, Forest Service,

Pacific Northwest Research Station. 36 p.

The RAPID (riparian aerial photographic inventory of disturbance) technique is a

method for using measurements made on aerial photographs of patterns of riparian

canopy disturbance to evaluate changes in channel conditions through time and to

link such changes with their possible upstream causes. The RAPID technique

provides resource specialists and managers with a relatively quick way of identifying

stream reaches that are chronically or recently disturbed by a variety of channel

processes, including increased peak flows and sedimentation from point and nonpoint sources. With examples from western Oregon, this paper describes how to

apply the RAPID technique and analyze the results to evaluate downstream or

cumulative effects of forest practices.

Keywords: Riparian zones, cumulative effects, aerial photograph interpretation,

channel changes, monitoring, geomorphology, hydrology.

The Forest Service of the U.S. Department of

Agriculture is dedicated to the principle of multiple

use management of the Nation’s forest resources

for sustained yields of wood, water, forage, wildlife,

and recreation. Through forestry research,

cooperation with the States and private forest

owners, and management of the National Forests

and National Grasslands, it strives - as directed by

Congress - to provide increasingly greater service

to a growing Nation.

The U.S. Department of Agriculture is an Equal

Opportunity Employer. Applicants for all Department

programs will be given equal consideration without

regard to age, race, color, sex, religion, of national

ofigi n.

Pacific Northwest Research Station

319 S.W. Pine St.

P.O. Box 3890

Portland, Oregon 97208