Watershed Analysis1 

Alan Gallegos2 

Abstract 

Watershed analyses and assessments for the Kings River Sustainable Forest Ecosystems 

Project were done on about 33,000 acres of the 45,500-acre Big Creek watershed and 

32,000 acres of the 85,100-acre Dinkey Creek watershed. Following procedures developed 

for analysis of cumulative watershed effects (CWE) in the Pacific Northwest Region of 

the USDA Forest Service, the present project is comparing the Equivalent Roaded Area 

(ERA) method used widely in the Pacific Southwest Region of the Forest Service, a 

method that has several inherent weaknesses. Selected stream reaches have been 

described in terms of Rosgen channel types, Phankuch stream stability, and V-star 

ratings. Preliminary results from the ERA method indicate that 4 of 15 subwatersheds in 

the Big Creek watershed and 7 of 33 subwatersheds in the Dinkey Creek watershed are at 

or above the threshold of concern. Results from the ERA method indicate that several 

subwatersheds, but no stream reaches, are of concern. By contrast, results from more 

specific stream surveys, an inventory of fish habitat conditions, and data on sediment 

delivery attributable to roads indicate concern for several stream reaches as well. 

The Kings River Sustainable Forest Ecosystems Project area is located in 

Fresno County, approximately 32 air miles northeast of Clovis, California (fig. 1). 

About 33,000 acres of the 45,500-acre Big Creek watershed and 32,000 acres of the 

85,100-acre Dinkey Creek watershed are included within the Project’s 

boundaries. Both watersheds drain into the Kings River above Pine Flat 

Reservoir. Most of the two watersheds are within the Sierra National Forest, 

although 6,896 acres are on private land. 

The Big Creek watershed ranges in elevation from about 1,000 to 6,400 ft, and 

the Dinkey Creek watershed ranges from about 1,250 to 10,000 ft. Each watershed 

is subdivided into several subwatersheds—15 for Big Creek and 33 for Dinkey 

Creek—within the Project’s boundaries. These subwatersheds range in size from 

about 190 to 2,760 acres and average about 1,500 acres. Precipitation, mostly 

during fall, winter, and spring, ranges from 20 to 80 inches, occurring primarily 

as snow above 6,000 ft. Rain on snow is common. Summers are dry with low 

humidity. Air temperature averages from 42 to 60o F. Vegetation types are mixed 

chaparral, ponderosa pine (Pinus ponderosa) forest, mixed-conifer forest, and red 

fir (Abies magnifica) forest. 

Cumulative watershed effects (CWEs) are impacts to the environment 

resulting from the incremental accumulation of impacts of actions, past, present, 

and in the foreseeable future, regardless of what agency (Federal or nonfederal) 

or person undertakes these actions. CWEs can result from individually minor 

but collectively significant actions occuring over a period of time. 

The current model used to analyze CWEs—the Equivalent Roaded Area 

(ERA) method (McGurk and Fong 1995, USDA 1988)—has several inherent 

1	 An abbreviated version of this 

paper was presented at the 

Symposium on the Kings River 

Sustainable Forest Ecosystems 

Project: Progress and Current 

Status, January 26, 1998, Clovis, 

California. 

2 Assistant Forest Geologist, 

Southern Sierra Province; 

Stanislaus, Sierra, and Sequoia 

National Forests; USDA Forest 

Service, 1600 Tollhouse Road, 

Clovis, CA 93611. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 55 
Gallegos 

Figure 1—The Kings River 

administrative study area in the Sierra 

National Forest in central California 

includes the 64,000-acre Big Creek 

and Dinkey Creek watersheds 

(indicated by shading). 

Watershed Analysis 

�

Sierra National Forest 

Sierra National Forest 

Study Area 

Dinkey Creek Watershed 

Big Creek Watershed 

weaknesses, including equal coefficients for disturbances regardless of their 

distance from stream channels, a lack of sensitivity to sediment yields, and the 

scale at which the model applies. Current USDA Forest Service direction for 

ecosystem management requires the development of better methods and models 

for assessing cumulative watershed effects. 

The various processes and interactions occurring within a watershed are 

integral to any project that endeavors to apply science-based concepts of 

ecosystem managment at a watershed scale. The watershed analysis briefly 

described here was undertaken to help understand these processes and 

interactions in the two watersheds in the Project area. Additional objectives 

are to characterize current watershed conditions and to develop and test an 

improved method or model to assess cumulative effects of management 

activities on watersheds. 

Methods 

Selected stream reaches can be described in terms of Rosgen channel types 

(Rosgen 1994), Phankuch stream stability (Phankuch 1975), and V-star ratings. 

Together, these data sources can be combined to describe stream channels as 

aquatic ecological units. The Rosgen stream channel classification divides stream 

reaches into seven major types that differ in entrenchment, gradient, ratio of 

width to depth, and sinuosity. Each major stream type is further described by 

dominant channel material along a continuum from bedrock to silt/clay. 

Determination of Phankuch stream stability is a procedure to systematize 

measurements and describe the resistive capacity of mountain stream channels 

to the detachment of bed and bank materials and to provide information about 

the capacity of streams to adjust and recover from potential changes in flow, 

increases in sediment production, or both. 

56 USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 
Watershed Analysis 

The V-star rating provides a cross-sectional sample of the depth of fine 

sediment at the bottom of a stream. It is obtained by pushing a slender, steel bar 

vertically through the sediment to bedrock or bed load at regular intervals 

perpendicular to the stream’s course and recording the depth of sediment at each 

point. These data then permit estimation of the fraction of a pool’s volume that is 

filled with fine sediment—an index of sediment supply, water quality, and 

stream habitat (Lisle and Hilton 1992) (fig. 2). 

The watershed analysis identified several issues, the most important being 

CWEs. These can be evaluated in part by determining the sources of high 

sediment loads in Big Creek and the condition of aquatic habitat in both 

watersheds. Ecological indicators selected to establish baseline conditions and 

monitor watershed conditions are ground cover, rates of erosion and sediment 

delivery, and landslide frequency. ERA is the indicator of CWEs for the ERA 

method. V-star ratings and the number of benthic macro-invertebrates have been 

selected as indicators of the quality of fish habitat. 

All subwatersheds in both watersheds were mapped and delineated in 1991 

to ensure consistent analysis of CWEs. Watershed analyses followed procedures 

developed for use in the Forest Service’s Pacific Northwest Region, as described 

by Furniss and McCammon (1993): 

• Identify issues, describe desired conditions, and formulate key questions. 

• Identify key process, functions, and conditions 

• Stratify the watershed. 

• Assemble analytic information needed to address the key questions. 

• Describe past and current conditions. 

• Describe condition trends and predict effects of future land management. 

• Integrate, interpret, and present findings. 

• Manage information, monitor, and revise. 

CWE analyses were done for Big Creek and Dinkey Creek using the ERA 

model, a decision-based model that attempts to equate impacts of projects to the 

impacts of a given acreage of road disturbance. The ERA model has three steps: 

1. Determine the threshold of concern (TOC) 

2. Determine existing and potential ERAs 

3. Determine the potential for CWEs. 

Step 1—Determine the Threshold of Concern 

The TOC is determined for each subwatershed, based on its natural sensitivity. 

Subwatersheds have higher TOCs when they have high percentages of sensitive 

landforms (steep ground, landslide potential), highly erodible soils, and highly 

Gallegos 

Figure 2—Schematic cross 

section of a pool along its 

longitudinal profile, showing fine 

sediment and residual pool. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 57 
Gallegos Watershed Analysis 

bifurcated networks of stream channels. The Sierra National Forest uses low, 

moderate, and high sensitivity levels, ranging from 3.5 to 6.0 ERAs, to reflect 

TOCs. These values have been corroborated with field data: watersheds with 

sensitive landforms, highly erodible soils, and a high bifurcation ratio responded 

to disturbance with compacted soils, high amounts of sediment in stream 

channels, and less than optimum fish habitat. 

Step 2—Determine Existing and Potential ERAs 

The management history of affected subwatersheds is determined, and each 

ground disturbance is rated and assigned an ERA coefficient according to the 

nature and age of the disturbance. Hydrologic recover is considered when 

determining the ERA for any given disturbance, assuming that a disturbance 

could recover to an ERA value of nearly zero if enough time has passed. Values 

for various existing disturbance areas are then summed to estimate the total 

existing percent ERA value for the subwatershed. Values for proposed activities 

are then assigned an ERA coefficient using those established for the Sierra 

National Forest, and these are summed with the existing ERA values to estimate 

a total ERA value for the subwatershed if the activities were to occur. 

Step 3—Determine Potential for CWEs 

If the total ERA for a given subwatershed exceeds the TOC, it is determined to 

have a higher risk for CWEs. In addition, qualitative field data may be collected 

to determine whether CWEs are occurring. These field data could include stream 

condition inventories, soil quality, and condition of fish habitat. In some cases, 

activities have been postponed to allow natural recover, or watershed restoration 

has been undertaken to speed recover. In other cases, the proposed activity was 

implemented after site investigations found healthy soils and streams. 

A Model for Watershed Condition 

The model for assessing watershed condition is a process-based model that can 

be applied at several scales and considers natural disturbances to determine 

whether a watershed is degraded. The model evaluates conditions and 

interrelations of upland watershed areas and riparian areas. It can be used for 

any of the aforementioned ecological indicators (for example, ground cover and 

sediment delivery rates). The model has five steps that can be done concurrently 

or consecutively. I use rates of erosion and sediment delivery as examples to 

describe the model. 

Step 1—Stratify the Watershed 

Watersheds in the Kings River Project area were stratified using data from the 

Forest Service’s existing Ecological Unit Inventory (EUI), which can be used to 

classify and delineate areas of similar ecological form and function (fig. 3). 

Components of an ecological unit include bedrock or unconsolidated deposits, 

geomorphic processes and landform, soil type, and potential natural vegetation. 

Step 2—Describe the Reference (“Normal”) Variability for 

Rates of Erosion and Sediment Delivery 

Earlier studies estimated mean rates of sediment delivery at 110 tons/mi2/year 

for the North Fork of the Kings River (Breazeale 1972) and 43 tons/mi2

/year for 

small basins in the Teakettle Experimental Watershed (Dunne and Reid 1985). 

These estimates are mean, long-term rates for watersheds with heterogeneous 

geology, geomorphology, soils, and vegetation. The studies did not consider 

natural disturbance regimes or the range of variation among areas as they 

recovered from disturbances. 

58 USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 
Watershed Analysis 

The reference variability for rates of erosion and sediment delivery, in 

tons/mi2

/year for each major ecological map unit of the two watersheds, will 

be determined by modeling fire and high precipitation events as the major 

disturbances. For example, rates of erosion and sediment delivery are at their 

highest in the first year after a fire, decreasing over time as vegetation recovers. 

Eventually these rates would be expected to fluctuate mainly in response to 

variation in precipitation events, then characterizing the “reference variability.” 

Step 3—Describe Existing Rates of Erosion and 

Sediment Delivery 

Most erosion and sediment delivery in the Sierra Nevada are assumed to be a 

result of roads and stream channels. Landslides are not believed to be a major 

source of sediment. Data have been collected from 50 mi of roads in the Project 

area to use in the Watershed Erosion Prediction Project (WEPP) model (Elliot 

and Hall 1997). This is a process-based model with several output options 

including runoff, soil erosion, and sediment delivery. These data will quantify 

rates of erosion and sediment delivery for different types of roads (native surface, 

aggregate surfaced, asphalt surfaced) in different ecological units (major strata). 

Step 4—Describe the Conditions of the Aquatic System 

Existing data allow description of selected stream reaches in terms of Rosgen 

stream channel types, Phankuch stream stability, and V-star ratings. Initial 

Gallegos 

Figure 3—Ecological landscape 

units stratifying the Kings River 

Project area by geology, soils, 

geomorphology, and potential 

vegetation: 1 = Granodiorite; deep 

to moderately deep thermic 

(Auberry-Ahwahnee, Tollhouse 

complex); mass wasting, fluvial; 

chaparral. 2 = Granodiorite; deep 

mesic (Holland-Shaver complex); 

fluvial, mass wasting; ponderosa 

pine. 3 = Granodiorite; shallow, 

mesic (Chawanakee-Tollhouse 

complex); mass wasting, fluvial 

erosion; ponderosa pine. 4 = 

Granodiorite; deep mesic (Holland 

family); fluvial erosion, mass wasting; 

ponderosa pine. 5 = Glacial deposits, 

Granodioarite; deep, frigid (Sirretta 

family; mass wasting, fluvial, relic 

glacial depositional; mixed conifer. 6 

= Granodiorite; deep, mesic 

(Shaver-Holland complex); fluvial, 

mass wasting; mixed conifer. 7 = 

Granodiorite; moderately deep to 

deep, frigid (Ledford-Gerle-CannelCagwin complex); fluvial; mixed 

conifer. 8 = Granodiorite; 

moderately deep, frigid (Cagwin 

family); mass wasting, fluvial; mixed 

conifer. 9 = Metamorphic; deep, 

frigid (Ledford-Gerle complex); 

fluvial; mixed conifer. 10 = 

Metasedimentary; moderately deep 

to deep, frigid (Cagwin-Cannel 

complex); fluvial; red fir. 11 = Mixed 

lithology; moderately deep to deep, 

frigid (Cagwin-Sirretta complex); 

fluvial, relic glacial; red fir. 12 = 

Granodiorite; moderately deep to 

shallow, frigid (Cagwin-Rock 

Outcrop complex); fluvial, mass 

wasting; Jeffrey pine. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 59 
Gallegos 

Figure 4—Section of Big Creek 

showing desired condition of a 

cobble/gravel-controlled, pool-riffle 

reach. Notice lack of fine sediment. 

Watershed Analysis 

analysis of 33 V-star reaches showed that 30 percent had high sediment loads (fig. 

4). It is not clear, however, whether this has resulted from management 

disturbances, from natural events, or both. Quantifying sediment sources and 

estimating rates of sediment transport should help to answer this question. 

Step 5—Synthesize Available Data 

Synthesis of available data should establish whether rates of erosion and 

sediment delivery are within the reference variability. If not, then channel reaches 

that have high sediment loads and degraded conditions will be assessed to 

determine which subwatersheds are the sources of sediment. These sources 

could include native-surfaced roads, other disturbances (for example, gullies) on 

highly sensitive soils, and extensively in-sloped roads adjacent to channel and 

road crossings. 

Final Step—Identify Opportunities for Watershed 

Improvement 

Opportunities for watershed improvement could include surfacing nativesurfaced roads with gravel or asphalt, redesigning roads from an in-sloped to an 

out-sloped road prism, obliterating roads in highly sensitive areas, tilling highly 

compacted soils, and stabilizing gully systems that have developed from past 

management. 

Preliminary Results 

A strategy to collect additional data and address the key questions identified in 

the watershed analysis has been approved and is being implemented. Results of 

our efforts to develop the conceptual model have resulted in completion of Step 

1 and some progress with the remaining steps. A more detailed, landtype-level 

(1:24,000) EUI has been completed to stratify the watershed by geology, soils, 

land-forming processes, and potential natural vegetation. Interpretations 

have been made to describe sensitive landforms, erodible soils, and potential 

wildlife habitat. This inventory aided in the delineation of boundaries for 

riparian management zones in the Big Creek watershed, where those 

60 USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 
Watershed Analysis 

boundaries are set according to guidelines in the Sierra National Forest’s 

Land Management Plan. Some data have been collected and analyzed to 

determine the reference variability for erosion and sediment delivery rates. 

These data are being compared with data from other areas in the Sierra 

Nevada to establish long-term rates for erosion and sediment delivery. 

Preliminary work has been done to develop a landscape model using these 

data. Some of this work includes erosion and fire-spread modeling. The next 

phase is to integrate results from these models. 

More than 50 miles of road data have been collected, including road design 

(width, insloped with ditch or outsloped, slope gradient), surface type, soil type, 

rill and gully erosion, and percent vegetation on the road cut and fill. These data 

are being analyzed to determine mean rates of erosion and sediment delivery for 

road types that occur in unique ecological units. 

Stream-condition surveys, including Rosgen Channel typing, have been 

completed on several of the main tributaries to Dinkey Creek and the main stem 

of Big Creek. Macroinvertebrate data have been collected from 16 first- and 

second-order streams in the two watersheds. A final determination about 

watershed health, however, will not be made until all data are collected and an 

improved model is developed to analyze watershed condition. 

Acknowledgments 

I have benefited from constructive comments on a draft of this paper by Neil 

Berg and Jerome V. DeGraaf. 

References 

Breazeale, Robert E. 1972. An estimation of the natural geologic sedimentation rate of the North 

Fork Kings River. Open-File Report. Clovis, CA: Sierra National Forest, Forest Service, U.S. 

Department of Agriculture; 61 p. 

Dunne, Thomas; Reid, Leslie. 1985. Effects of the Haas-Kings River Project on sediment transport 

and sedimentation. Seattle, WA: R.W. Beck Engineering Co.; 166 p. 

Elliot, William J.; Hall, David H. 1997. Watershed Erosion Prediction Project (WEPP): forest 

applications. Gen. Tech. Rep. INT-GTR-365. Ogden, UT: Intermountain Research Station, Forest 

Service, U.S. Department of Agriculture; 11 p. 

Furniss, Mike; McCammon, Bruce. 1993. A federal agency guide for pilot watershed analysis, 

version 1.2. Portland, OR: Pacific Northwest Region, Forest Service, U.S. Department of 

Agriculture; 201 p. 

Lisle, Thomas E; Hilton, Sue. 1992. The volume of fine sediment in pools: an index of sediment 

supply in gravel-bed streams. Water Resources Bulletin 28: 371-383. 

McGurk, Bruce J.; Fong, Darren R. 1995. Equivalent roaded area as a measure of cumulative effect 

of logging. Environmental Management 19: 609-621. 

Phankuch, Dale J. 1975. Stream reach inventory and channel stability evaluation. U.S. Department 

of Agriculture, Forest Service, R1-75-002. Government Printing Office #696-260/200, Washington, 

D.C.; 26 p. 

Rosgen, David L. 1994. A classification of natural rivers. Catena 22: 169-199. 

USDA [USDA Forest Service]. 1988. Cumulative off-site watershed effects analysis. Forest Service 

Handbook (Section 2509.22, Ch. 20, July 1988). San Francisco, CA: Region 5 Regional Office, 

Forest Service, U.S. Department of Agriculture; 32 p. 

Gallegos 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 61 
62