In cooperation with the Colorado Water Conservation Board and 

Colorado River Water Conservation District

Hydraulic, Geomorphic, and Trout Habitat Characteristics 

of the Lake Fork of the Gunnison River in Hinsdale County, 

Lake City, Colorado, Water Years 2010–2011

Scientific Investigations Report 2015–5043

U.S. Department of the Interior

U.S. Geological Survey
Hydraulic, Geomorphic, and Trout Habitat 

Characteristics of the Lake Fork of the 

Gunnison River in Hinsdale County, Lake 

City, Colorado, Water Years 2010–2011

By Cory A. Williams, Rodney J. Richards, and Keelin R. Schaffrath

In cooperation with the Colorado Water Conservation Board and 

Colorado River Water Conservation District

Scientific Investigations Report 2015–5043

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod/.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Williams, C.A., Richards, R.J., and Schaffrath, K.R., 2015, Hydraulic, geomorphic, and trout habitat conditions of the 

Lake Fork of the Gunnison River in Hinsdale County, Lake City, Colorado, Water Years 2010–2011: U.S. Geological 

Survey Scientific Investigations Report 2015–5043, 28 p., http://dx.doi.org/10.3133/sir20155043.

ISSN 2328-0328 (online)
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Purpose and Scope ..............................................................................................................................2

Description of Study Area ...................................................................................................................4

Topographical Surveying Techniques ........................................................................................................4

Hydraulic Data Collection Techniques .......................................................................................................5

Streambed Sediment Characterization Techniques ................................................................................7

Riparian Canopy Characterization Techniques.........................................................................................7

Two-Dimensional Hydraulic and Habitat Modeling Techniques............................................................7

Two-Dimensional Hydraulic Model Calibration...............................................................................9

Sediment Mobility...............................................................................................................................11

Trout Habitat Suitability......................................................................................................................13

Two-Dimensional Hydraulic Model Sensitivity Analysis.......................................................................13

Hydraulic and Geomorphic Conditions ....................................................................................................17

Sediment Mobility...............................................................................................................................17

Geomorphic Channel Form................................................................................................................22

Trout Habitat Characteristics.....................................................................................................................22

Microscale Trout Habitat...................................................................................................................22

Mesoscale Trout Habitat ...................................................................................................................22

Summary........................................................................................................................................................25

References Cited..........................................................................................................................................26

Figures

1. Map of study area for the Lake Fork of the Gunnison River at Lake City, Colorado ..........3

2. Hydrograph showing daily statistics for the Lake Fork of the Gunnison River at 

U.S. Geological Survey streamflow-gaging station 09124500, water years 1938 

through 2010 ..................................................................................................................................5

3. Map of study reach with pressure transducers, grain-size sample locations, and 

cross-section locations for the Lake Fork of the Gunnison River at Lake City, 

Colorado .........................................................................................................................................6

4. Riparian canopy density assessment locations in the Lake Fork of the Gunnison 

River near Lake City, Colorado, August 2011............................................................................8

5. Map of Multidimensional Surface Water Modeling System grids of the upper 

and lower reaches......................................................................................................................10

6. Graph showing water-surface elevations for the best-fit flow simulations for 

A, 150 cubic feet per second; B, 260 cubic feet per second; and C, 1,600 cubic 

feet per second streamflows....................................................................................................11

7. Habitat suitability curves for the three life stages of brown trout and cutthroat 

trout...............................................................................................................................................14

8. Flow frequency curve for the Lake Fork of the Gunnison River at Lake City,

Colorado .......................................................................................................................................17
iv

9. Sediment-size characteristics of the five sampling sites....................................................17

10. Shear stress and water-surface elevation plots at A, cross-section 2; 

B, cross-section 3; and C, cross-section 4.............................................................................18

11. Shear stress and water-surface elevation plots at A, cross-section 5; 

B, cross-section 6; C, cross-section 7; and D, cross-section 8 ..........................................19

12. Reach-scale assessment of sediment mobility in the upper reach (A–C) and 

lower reach (D–F) of the Lake Fork of the Gunnison River at streamflows of 

400; 900; and 1,800 ft3/s, respectively.......................................................................................21

13 Plotting positions of two surveyed reaches of the Lake Fork of the Gunnison River 

near Lake City, Colorado, in comparison to thresholds for meandering and braided 

channel patterns.........................................................................................................................23

14. Weighted-usable habitat for the adult, juvenile, and fry life stages of the cutthroat 

and brown trout in the study reach of the Lake Fork of the Gunnison River ....................24

Tables

1. Summary of the lateral eddy viscosity and model diagnostics for the best-fit twodimensional hydraulic and habitat model simulations .........................................................12

2. Mesoscale-habitat suitability ranges of habitat type for cutthroat and brown trout .....15

3. Results from the analysis of the sensitivity of the lateral eddy viscosity parameter 

for three of the streamflows simulated in the multidimensional flow model for the 

upper and lower study reaches on the Lake Fork.................................................................15

4. Results from the analysis of the sensitivity of the roughness parameter (Z0) for 

three of the streamflows simulated in the two-dimensional flow model for the 

upper and lower study reaches on the Lake Fork.................................................................16

5. Sediment particle-size characteristics for the five sites sampled from August 4 to 

August 6, 2010, and August 18, 2011 (GS1-GS4 and GS-5, respectively) in the Lake 

Fork study area............................................................................................................................17

6. Results from flow-frequency curves and simulation results from the multidimensional flow model showing microscale-habitat suitability total weighteduseable habitat in a typical year for cutthroat and brown trout.........................................24

7. Mesoscale-habitat characteristics for cutthroat and brown trout during typical 

base-flow conditions in the Lake Fork near Lake City, Colorado........................................24
v

Conversion Factors

Multiply By To obtain

Length

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

meter (m) 1.094 yard (yd)

kilometer (km) 0.6214 mile (mi) 

inch (in.) 2.54 centimeter (cm)

feet (ft) 0.3048 meter (m)

miles (mi) 1.609 kilometer (km)

Area

square meter (m2

) 0.0002471 acre 

square meter (m2

) 10.76 square foot (ft2) 

Volume

cubic meter (m3

) 35.31 cubic foot (ft3)

Flow rate

cubic meter per second (m3

/s) 70.07 acre-foot per day (acre-ft/d) 

meter per second (m/s) 3.281 foot per second (ft/s) 

cubic meter per second (m3

/s) 35.31 cubic foot per second (ft3/s)

cubic meter per day (m3

/d) 35.31 cubic foot per day (ft3/d) 

cubic feet per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

Mass

kilogram (kg) 2.205 pound avoirdupois (lb)

Pressure

pascal (Pa) 1 Newton per square meter

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as 

°F = (1.8 × °C) + 32.

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as 

°C = (°F – 32) / 1.8.

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88) and Geoid 2003 (US Conus). Horizontal coordinate information was referenced to the 

North American Horizontal Datum of 1983 (NAD83). 

Water Year (WY) is defined as beginning October 1 and continuing through September 30 of the 

following year.
vi

Acronyms and Abbreviations

CDOT Colorado Department of Transportation

ft3/s cubic feet per second

RTK-GPS Real-Time Kinematic mode Global Positioning System

TIN Triangulated Irregular Network

USGS U.S. Geological Survey
Abstract

Channel rehabilitation, or reconfiguration, to mitigate a 

variety of riverine problems has become a common practice in 

the western United States. However, additional work to monitor and assess the channel response to, and the effectiveness of, 

these modifications over longer periods of time (decadal or longer) is still needed. The Lake Fork of the Gunnison River has 

been an area of active channel modification to accommodate 

the needs of the Lake City community since the 1950s. The 

Lake Fork Valley Conservancy District began a planning process to assess restoration options for a reach of the Lake Fork 

in Lake City to enhance hydraulic and ecologic characteristics 

of the reach. Geomorphic channel form is affected by landuse changes within the basin and geologic controls within the 

reach. The historic channel was defined as a dynamic, braided 

channel with an active flood plain. This can result in a natural 

tendency for the channel to braid. A braided channel can affect 

channel stability of reconfigured reaches when a single-thread 

meandering channel is imposed on the stream. The U.S. Geological Survey, in cooperation with the Colorado Water Conservation Board and Colorado River Water Conservation District, 

began a study in 2010 to quantify existing hydraulic and habitat 

conditions for a reach of the Lake Fork of the Gunnison River 

in Lake City, Colorado. The purpose of this report is to quantify existing Lake Fork hydraulic and habitat conditions and 

establish a baseline against which post-reconfiguration conditions can be compared. This report (1) quantifies the existing 

hydraulic and geomorphic conditions in a 1.1-kilometer section 

of the Lake Fork at Lake City that has been proposed as a location for future channel-rehabilitation efforts, (2) characterizes 

the habitat suitability of the reach for two trout species based 

on physical conditions within the stream, and (3) characterizes 

the current riparian canopy density. 

The FaSTMECH computational flow-model within 

MD_SWMS was selected to characterize the effects of streamflow on hydraulic and habitat-suitability conditions for a study 

reach of the Lake Fork. Habitat suitability was evaluated for 

cutthroat (Oncorhynchus clarkii) and brown trout (Salmo 

trutta morpha fario) fry, juveniles, and adults. Microscale 

(point locations) and mesoscale (reach features) habitats 

were assessed using the combination of field observations, 

measurements, and hydraulic simulations within the study 

reach of the Lake Fork. Microscale trout habitat, presented 

as weighted usable area, generally increased as streamflow 

increased for both trout species and all life stages. Areas of 

suitable microscale habitat occur along the banks for flows of 

900 cubic feet per second (ft3

/s) and less. Out-of-bank areas 

became more substantial contributors to overall habitat availability for flows of 1,300 ft3

/s or more when compared to other 

features. Adult habitat, for both trout species, was the most 

abundant habitat type for nearly all streamflows. In general, 

the upper reach provided 2–3 times more available habitat 

than the lower reach for both trout species.

Mesoscale trout habitat of the Lake Fork was assessed 

based on the conditions present in the 150 ft3

/s flow simulation 

as well as field observation. Both the upper and lower reach is 

primarily characterized as riffle/run habitat. The presence of 

pool habitat was limited throughout both reaches and occurred 

along the channel margins. For both reaches, the pool habitat 

was less than 5 percent of the total wetted area, a percentage that is substantially lower than the recommendations for 

sustainable populations of 40–70 percent. Areas of cover were 

adjacent to potential drift feeding areas in the lower reach, and 

often occurred within the same pool habitat. This may favor 

energy expenditure ratios of both fish species, wherein little 

energy is needed to acquire adequate food sources.

Sediment mobility is an important process for flushing 

fine sediments from within the gravel frameworks. Evaluations 

of channel and flow characteristics at cross-section locations 

2–8 show a range of streambed mobility. In general, boundary 

shear stress and streambed mobility increase with increases in 

streamflow. Within the cross sections, the greatest boundary 

shear stress occurs towards the center of the channel. Reachscale assessment of sediment mobility in the lower reach 

shows increased streambed mobility. This is due in part to 

smaller grain sizes in the lower reach, but may also reflect the 

greater extent of channel alterations, specifically the temporary berms constructed by CDOT in the late 1980s and 1990s, 

present in this reach.

Hydraulic, Geomorphic, and Trout Habitat Characteristics 

of the Lake Fork of the Gunnison River in Hinsdale County, 

Lake City, Colorado, Water Years 2010–2011

By Cory A. Williams, Rodney J. Richards, and Keelin R. Schaffrath
2 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

Introduction

The Lake Fork of the Gunnison River (hereafter, Lake 

Fork) has been an area of active channel modification since 

the 1950s to accommodate the needs of the Lake City community (Lake Fork Valley Conservancy, 2010). Historically, 

the Lake Fork was characterized by its braided channel which 

frequently overtopped its banks and created an active and 

dynamic flood plain (Lake Fork Valley Conservancy, 2010). 

However, beginning in the 1950s, increased rates of land-use 

change within Lake City resulted in the straightening and 

channelization of the Lake Fork to promote channel stability 

and development of riverfront properties (Lake Fork Valley 

Conservancy, 2010).

Reduced channel width, sinuosity, and riparian habitat 

have been noted in the Lake Fork as well as Henson Creek, a 

smaller tributary located upstream from Lake City (Lake Fork 

Valley Conservancy, 2010) (fig. 1). Failures of sediment-retention structures (cribbing piles) on Henson Creek in the 1960s 

and 1970s have contributed large volumes of sediment into the 

fluvial system. In the late 1980s and early 1990s, the Colorado 

Department of Transportation (CDOT) constructed temporary 

berm structures along the river on the north side of town to 

protect the highway from channel migration until permanent 

structures could be completed (Lake Fork Valley Conservancy, 

2010). The constructed berms may be a potential source of 

channel instability and sediment inputs, because they were not 

designed to withstand high-flow conditions. Additional areas 

along the north side of town were also straightened by CDOT 

and U.S. Army Corps of Engineers in the 1980s (Lake Fork 

Valley Conservancy, 2010).

The Lake Fork Valley Conservancy District began a 

planning process to assess restoration options for a reach of 

the Lake Fork in Lake City to enhance hydraulic and ecologic 

characteristics of the reach (Lake Fork Valley Conservancy, 

2010). In part, candidacy for the proposed channel-restoration 

efforts is based on the effects of similar efforts in other areas 

of the Lake Fork. Beginning in the last few decades, several groups have completed channel reconfiguration efforts 

downstream from the study area on the Lake Fork to improve 

aquatic habitat and channel stability. In 1997, 35 kilometers 

(km) downstream from Lake City, a 3-km reach of the Lake 

Fork was reconfigured. The objectives of these earlier efforts 

were to improve habitat for brown and rainbow trout (Lake 

Fork Valley Conservancy, 2010).

Reshaping the downstream channel banks and river pools 

during this earlier effort was done to improve riparian habitat, vegetation, and streambank stability and to reduce sediment sources that were believed to be impairing the fisheries 

(Lake Fork Valley Conservancy, 2010). Reconfigured channel 

efforts carried out by the Colorado Division of Wildlife and 

the Bureau of Land Management included reshaping of the 

channel and placing large boulders to improve fish habitat 

and increasing channel stability (Lake Fork Valley Conservancy, 2010). Additional planting of riparian vegetation was 

expanded in areas where the channel widths were decreased 

during channel reshaping. Following reconfigured channel efforts, the total fish biomass (weight of fish across all 

age classes per acre of stream, in pounds per acre [lbs/acre]) 

increased from approximately 40 to 100 lbs/acre, an indication 

that the reconfiguration efforts improved fish habitat (Lake 

Fork Valley Conservancy, 2010).

Channel rehabilitation, or reconfiguration, to mitigate a 

variety of riverine problems has become a common practice in 

the western United States. Reasons for channel rehabilitation 

include restoration to more natural or historical conditions, 

improved water conveyance in flood-prone areas, mitigation 

of unstable streambeds and streambanks, increased sediment transport, enhancement of aquatic and riparian habitat, 

improved water quality, and recreation. Numerous private 

entities and resource-management agencies have attempted 

to modify stream channels by using designs based on different geomorphic philosophies and classification schemes. 

However, additional work to monitor and assess the channel response to, and the effectiveness of, these modifications 

over longer periods of time (decadal or longer) is still needed. 

To address this need, the U.S. Geological Survey (USGS) is 

engaged in a program designed to monitor and assess selected 

river reaches that have undergone reconfiguration (Elliott and 

Parker, 1999).

The basis for determining the “success” of a channelreconfiguration project is often not made through analysis of 

quantifiable metrics, leaving little information for resource 

managers, planners, and designers to use to determine the 

effectiveness and durability of channel restoration techniques 

used for stream rehabilitation (including biological response) 

and channel stability. The U.S. Geological Survey, in cooperation with the Colorado Water Conservation Board and Colorado River Water Conservation District, began a study in 2010 

to quantify existing hydraulic and habitat conditions for a 

reach of the Lake Fork in Lake City, Colorado (Colo.).

Purpose and Scope

The purpose of this report is to quantify existing Lake 

Fork hydraulic and habitat conditions and establish a baseline 

against which post-reconfiguration conditions can be compared. This report (1) quantifies the existing hydraulic and 

geomorphic conditions in a 1.1-kilometer (km) section of the 

Lake Fork at Lake City that has been proposed as a location 

for future channel-rehabilitation efforts, (2) characterizes the 

habitat suitability of the reach for two trout species based 

on physical conditions within the stream, and (3) characterizes the current riparian canopy density. This characterization describes existing channel conditions and establishes a 

baseline for post-reconfiguration comparisons for resource 

managers to evaluate restoration project success.

Figure 1. Map of study area for the Lake Fork of the Gunnison

River at Lake City, Colorado.—Following page
Introduction 3

#

^

LAKE SAN CRISTOBAL

Slumgullian Landolide Slumgullion Landslide

Hensen Creek Lake City

Lake Fork of the Gunnison River

Lake Fork of the Gunnison River

Lake Fork of the Gunnison River

Handies Peak

09124500

107°30’ 107°15'

38°15'

38°00'

0 2 4 8 MILES

0 2 4 8 KILOMETERS

Base from U.S. Geological Survey National Elevation 

Dataset 30 meter elevation model showing land surface

elevations shaded at 2-meter intervals scale 1:265,000

^

HINSDALE

COUNTY

Study Reach

COLORADO

San Juan Mountains

EXPLANATION

# U.S. Geological Survey

 streamflow-gaging station 09124500

General study reach location

Study reach drainage area

Continental divide

^

A
4 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

This report does not aim to determine limiting conditions 

for these species. Instead, this report quantifies the availability 

of trout habitat characteristics based on physical conditions 

within the stream. No considerations were made related to 

inter-species interactions.

Description of Study Area

The study reach is located in the town of Lake City, 

Colo., along the Lake Fork. Lake City is a small mountain 

town with a population of 375 year-round residents (U.S. Census Bureau, 2011). The Lake Fork originates in the northern 

portion of the San Juan Mountain Range and flows in a northern direction (fig. 1). The study reach is located at an elevation 

of 2,643 meters (m) and the drainage area upstream from the 

study reach encompasses 544 square kilometers (km2) of the 

1,144-km2 Lake Fork Basin (U.S. Geological Survey, 2010b). 

Most of the land in the Lake Fork Basin is federally owned 

and managed by the Bureau of Land Management and U.S. 

Department of Agriculture Forest Service. The remainder of 

land is privately owned except for Lake San Cristobal, which 

is owned and managed by the local government.

Land cover in the basin varies with elevation (Homer and 

others, 2004) and the highest elevations include barren and 

grassland classifications. Tree line in Colorado occurs at an 

elevation of approximately 3,500 m (Pielke and others, 2003). 

Both deciduous and coniferous forests are found throughout 

the basin and along stream margins (Homer and others, 2004).

Local climate is typical of other mountainous areas of 

western Colorado. Precipitation tends to increase with elevation while temperatures decrease with elevation (Pielke and 

others, 2003). The majority of precipitation falls as snow and 

is stored as snowpack through the winter months. The average 

annual precipitation in Lake City is 14.1 inches (in.) of water, 

and the average annual snowfall accumulation is 82.8 in. 

(based on data from August 1, 1948 through December 21, 

2008 from the Western Regional Climate Center, 2011). Average annual maximum temperature in Lake City is 55.7 °F, and 

the average annual minimum is 22.4 °F (Western Regional 

Climate Center, 2011).

The hydrology of the Lake Fork is governed by snowpack accumulations and spring temperatures which drive 

snowmelt-runoff. The annual streamflow pattern is characterized by streamflow increases that begin in April, peak in May 

and June, and finally decrease in July and August (U.S. Geological Survey, 2010a). The Lake Fork of the Gunnison River 

is monitored at USGS streamflow-gaging station 09124500, 

Lake Fork at Gateview, Colo. (hereafter, Gateview). The 

drainage area of Gateview is 964 km2

, and it is located 

approximately 35 river km downstream from the study reach. 

No major tributaries or diversions occur in the Lake Fork 

between the study reach and the streamflowgaging station. A 

summary of daily streamflow conditions is shown in figure 2

including: maximum, 75th percentile, mean, 25th percentile, 

and minimum. The highest recorded streamflow was 2,720 

cubic feet per second (ft3

/s), July 10, 1983, with the lowest 

daily mean streamflow of 21 ft3/s, recorded January 3, 2002 

(U.S. Geological Survey, 2010a). Additional water-quality and 

streamflow data are available from the USGS National Water 

Information System (NWIS) website at http://waterdata.usgs.

gov/co/nwis. 

The dominating geology in and around Lake City is 

Tertiary volcanic deposits (Tweto, 1979). The extensive 

volcanic activity, along with intrusions and mineralization, 

created widespread distributions of ore bodies in the San Juan 

Mountains that were deposited during the late-Tertiary period 

(Tweto and Sims, 1963; Burbank and others, 1947). Historical 

mining activities in the region were driven by the discovery of 

gold and silver deposits near Lake City. Relic mining cribbing 

piles have introduced sediment into Henson Creek, which 

transported it into the study reach (Lake Fork Valley Conservancy, 2010). This sediment may affect channel form, habitat, 

and toxicity.

Instabilities associated with geologic formation 

sequences have resulted in the unique history of the Lake Fork 

Valley and a history of large landslides (Tweto, 1979). Most 

notably, the Slumgullion landslide which occurred roughly 

700 years (yr) ago was large enough to dam the Lake Fork. 

This landslide deposit resulted in the creation and persistence 

of Lake San Cristobal, the second largest natural lake in Colorado (Guzzi and Parise, 1992).

Topographical Surveying Techniques

Topographical surveying was used to map water-surface 

and stream channel elevations for a 1.1-km reach at Lake 

Fork at Lake City (figs. 1 and 3). The majority of the surveying occurred August 2–6, 2010, with additional flood-plain 

surveying on May 24, 2011. Topographical surveying of 

water-surface elevations includes conditions present during 

each day of surveying as well as preserved high-flow conditions (high-water marks) from spring 2010 and 2011 identified 

through interpretation of sediment deposits and debris lines. 

Eight monumented cross sections were established in the study 

reach for long-term channel monitoring (fig. 3).

Surveying was completed using survey-grade Global 

Positioning System (GPS) equipment, operated in Real-Time 

Kinematic mode (RTK-GPS) to determine the elevation and 

coordinate locations of each surveyed point (Trimble Navigation Limited, 2009). The RTK-GPS used a stationary GPS 

receiver (base station) positioned over a reference benchmark and roving GPS receivers (rovers) operated by separate 

hand-held computers (data collectors). The RTK-GPS system 

calculates the locations of the rovers in real time, using the 

positions of orbiting NAVigation Signal Timing And Ranging 

(NAVSTAR) GPS satellites and a known base-station location.

All surveyed elevations (RTK-GPS) were output to a 

spreadsheet program in metric Northing, Easting, and Elevation 

format using a Universal Transverse Mercator coordinate system (UTM, Zone 12 North). Horizontal coordinate information 

was referenced to the North American Horizontal Datum of 
Hydraulic Data Collection Techniques 5

1983 (NAD83). Vertical coordinate information was referenced 

to the North American Vertical Datum of 1988 (NAVD 88) and 

Geoid 2003 (US Conus). Elevation values were visually examined for relative accuracy graphically and through inspection of 

GPS positional precision and diagnostic parameters.

Hydraulic Data Collection Techniques

Streamflow was measured using a FlowTracker® Handheld Acoustic Doppler Velocimeter (ADV) for wadable stream 

conditions and followed standard techniques outlined in 

Turnipseed and Sauer (2010). For unwadable flows, an Acoustic Doppler Current Profiler (ADCP) was used to measure 

streamflow from the 5th Street pedestrian bridge (near GS1, 

fig. 3) using a tethered boat, following standard techniques 

outlined in Mueller and Wagner (2009). Streamflow measurements were made at 40; 150; 270; 760; and 1,400 ft3

/s between 

August 5, 2010 and August 1, 2011.

Onset Hobo water level loggers (model U20-001-01, 

unvented, pressure transducer) were used in conjunction with 

local vertical elevation reference markers (staff-plates) to 

monitor water-surface elevation at selected locations within 

the study reach. Pressure transducers were deployed at the 

upstream study-reach boundary, at approximately halfway 

through the study reach, and at the downstream study-reach 

boundary (fig. 3). Pressure transducers were placed in protective polyvinyl chloride (PVC) casings and attached to 

T-posts which were secured to the river bed. A fourth pressure 

transducer was located outside the stream at cross-section 

8 (fig. 3) to record barometric-pressures changes for postprocessing corrections of the unvented, pressure-transducer 

readings (Freeman and others, 2004). This process resulted 

in a continuous record (30-minute intervals) of water-surface 

elevations at these three locations from August 2 to October 

28, 2010; and from March 24 to August 1, 2011.

A stage-discharge rating curve based on the relation 

between the measured streamflow and water-surface elevation 

pairs was determined for the upstream study-reach boundary at 

cross-section 1 through least-squares regression techniques, as 

described by Rantz and others (1982) (fig. 3). At the remaining pressure-transducer locations, water-surface elevations 

corresponding to 50; 150; 260; 400; 900; 1,300; 1,600; and 

Figure 2. Hydrograph showing daily statistics for the Lake Fork of the Gunnison River at U.S. Geological Survey 

streamflow-gaging station 09124500, water years 1938 through 2010.

1

10

100

1,000

10,000

Maximum

75th percentile

25th percentile

Minimum

Mean Simulated streamflows

EXPLANATION

Streamflow, in cubic feet per second

Date

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
6 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

5

5

5

5 5

5

5

5

5

5 5

5

5

5

5

5

#

##

#

107°19’ 107°18’ 

38°02’ 

38°01’ 

1

2

3

4

5

6 7

8

0 150 300 600 METERS

0 150 300 600 YARDS

EXPLANATION

# Pressure transducers

Grain-size sample locations

Lake City boundary

Area of figures 4 and 5

Survey cross-section 

Base from U.S. Department of Agriculutre

National Agriculture Imagery Program (NAIP)

Universal Transverse Mercator Projection Zone 13 North

GS1

GS2

GS3

GS4

GS5

GS5

1

Figure 3.
Two-Dimensional Hydraulic and Habitat Modeling Techniques 7

1,800 ft3/s were determined based upon the date and time of 

the estimated streamflow at the upstream boundary. Based 

on field observations, it was assumed that the streamflow at 

the downstream boundary was equal to the streamflow at the 

upstream boundary, because there were no large inflows or 

diversions within the reach.

High-water marks from the water year 2010 (October 1, 

2009, through September 30, 2010) peak flow were identified 

and surveyed within the study reach; however, streamflow 

data were unavailable within the study reach to relate these 

water-surface elevations to discharge. The Gateview dataset 

was used to estimate the corresponding streamflow through 

a Maintenance of Variance 1 (hereafter, MOVE.1) equation 

analysis (Hirsch, 1982). The MOVE.1 equation uses data 

from an adjacent site (downstream in this instance) to predict 

streamflow for the site of interest. This methodology uses an 

algorithm to relate the streamflow values between sites while 

maintaining the natural variations in each dataset. 

To determine how often a specific flow occurs each year, 

flow-duration curves were used to determine flow frequencies as percent of year. The flow frequency for cross-section 1 

was calculated using 30 arithmetic bins following the regionalized-duration curve method for estimating flow-durations 

for ungaged sites (U.S. Department of Agriculture, 2009). 

The regionalized flow-duration curve method relates flow 

between two sites (a gaged site and an ungaged site of interest) 

by transferring a nondimensional flow-duration curve. This 

technique preserves the shape of the flow-duration curve and 

allows the magnitude of the streamflows to be scaled appropriately between sites based on standardized peak-flow values 

between sites. Peak-flow magnitudes (2-, 5-, 10-yr floods) 

were estimated based on regional regression analysis (Capesius and Stephens, 2009; U.S. Geological Survey, 2010b). 

The 2-yr recurrence interval peak streamflow was selected for 

use in this technique for consistency in methodology between 

the two sites (Capesius and Stephens, 2009; U.S. Geological 

Survey, 2010b).

Streambed Sediment Characterization 

Techniques

Sediment particles were measured from August 4 to 

August 6, 2010, and August 18, 2011 (GS1-GS4 and GS-5, 

respectively) at five locations in the study reach (fig. 3) to 

characterize the grain size of different geomorphic surfaces 

and to estimate channel roughness. Bars and channel margins 

were chosen because these areas are inundated most of the year 

and represent the coarser material transported within the river 

channel. Grain size was determined in the field using areal 

techniques (pebble-counts) as described by Wolman (1954). 

A minimum of 100 clasts were measured during each pebble 

count, and sampling was performed parallel to the direction of 

streamflow at one- or two-pace intervals along the streambed 

or alluvial bars. The intermediate, or “b-axis,” of each sediment 

particle was measured to the nearest millimeter for gravel and 

small cobbles, and to the nearest 5 millimeters for large cobbles 

and small boulders. Grain-size statistics (d50, size at the 50th 

percentile, and d84, size at the 84th percentile; dn is the size 

at the nth percentile) were determined from the cumulativefrequency distribution function of b-axis measurements.

Riparian Canopy Characterization 

Techniques

Canopy density was characterized during a low-flow 

period (August 17–18, 2011) at multiple locations within the 

study area using a spherical densiometer (Model A) (Lemmon, 1956). Differences in canopy density can affect habitat 

cover as well as water temperatures, terrestrial insect inputs, 

and leafy organic inputs into the aquatic system (Lindsey and 

others, 1998). Four measurements were taken at each location from the center of the stream with the operator facing: 

upstream, downstream, towards left bank, and towards right 

bank (Lemmon, 1956). The percentage of the densiometer 

view field that was obstructed was recorded for each measurement. This provides a standardized methodology to characterize the canopy density within the stream reach. Observations 

are presented as rose diagrams within the study reach (fig. 4).

Two-Dimensional Hydraulic and 

Habitat Modeling Techniques

The Multidimensional Surface Water Modeling System 

(MD_SWMS) is a graphical user interface that was developed by the USGS to aid in pre- and post-processing twodimensional streamflow analysis (McDonald and others, 2001; 

2005; 2006). The FaSTMECH computational flow-model 

within MD_SWMS was selected to characterize the effects of 

streamflow on hydraulic and habitat-suitability conditions for 

the 1.1-km study reach of the Lake Fork (Nelson and McDonald, 1997; Thompson and others, 1998; Lisle and others, 2000; 

Nelson and others, 2003; McDonald and others, 2005; 2006).

The FaSTMECH model uses a curvilinear orthogonal 

grid built upon a user-defined centerline and width that fits 

the path of the modeled reach. FaSTMECH is a vertically 

averaged two-dimensional model that simulates spatially 

distributed values of depth, velocity, and total bed shear stress. 

The resolution of the grid was defined such that there were 

no fewer than 10 locations along any cross-section within the 

wetted-channel area at the lowest simulated flow (or a spatial 

Figure 3. Map of study reach with pressure transducers, grainsize sample locations, and cross-section locations for the Lake 

Fork of the Gunnison River at Lake City, Colorado.—Previous page
8 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

5

5

5

5 5

5

5

5

5

5 5

5

5

5

5

5

1

2

3

4

5

6 7 8

US

US

US

US

LB

80 100

60 40

EXPLANATION

Riparian vegetation canopy density sites,

shown as percent coverage

20

Upstream

Downstream

Right bank Left bank

107°18'40" 107°18'30"

38°02'10"

38°02'

38°01'50"

LF-1A

0 37.5 75 150 YARDS

0 37.5 75 150 METERS

LF-1A

LF-1B

LF-1C

LF-1D

LF-1E

LF-4A

LF-4B

LF-4C

LF-4D

LF-4E

LF-3A

LF-3B

LF-3C

LF-3D

LF-3E

LF-2A

LF-2B

LF-2C

LF-2D

LF-2E

LF-1A

LF-1B

LF-1C

LF-1D

LF-1E

LF-4A

LF-4B

LF-4C

LF-4D

LF-4E

LF-3A

LF-3B

LF-3C

LF-3D

LF-3E

LF-2A

LF-2B

LF-2C

LF-2D

LF-2E

N

Base from U.S. Department of Agriculutre

National Agriculture Imagery Program (NAIP)

Universal Transverse Mercator Projection Zone 13 North
Two-Dimensional Hydraulic and Habitat Modeling Techniques 9

resolution of 1.0- by 1.0-m grid). Additional information on 

the interface and the model can be found in McDonald and 

others (2001; 2006), Nelson and McDonald (1997), and Nelson and others (2003).

Channel geometry was obtained from the topographical 

survey of the channel. Interpolation between measured data 

points was completed within the model interface elevation data 

to generate a suitable dataset. Aerial images were obtained 

from the U.S. Department of Agriculture National Agricultural 

Imagery Program (2011) and were used in conjunction with the 

survey data to best define the channel topography. Elevation 

data within the stream channel were interpolated in a streamwise direction between surveyed cross sections. Otherwise, 

interpolation of elevation data was in a cross-sectional direction. The final elevation dataset was a densely spaced set 

of topographic data from which a final dataset for channel 

geometry was created using the Triangulated Irregular Network 

(TIN) method (Environmental Systems Research Institute, Inc., 

2010). For computational efficiency, the FastMECH model 

grid, derived from the final elevation dataset, was divided into 

upper and lower reaches (fig. 5). The grid cells in the computational grids for both reaches approximated 1.0- by 1.0-m. The 

grid in the upper reach was approximately 455 m long and 60 

m wide (fig. 5). The grid in the lower reach was approximately 

411 m long and 100 m wide (fig. 5).

Two-Dimensional Hydraulic Model Calibration

FaSTMECH model calibration was achieved through 

iterative adjustments of the roughness until the root mean 

squared error (RMSE) between the observed and simulated 

water-surface elevations was minimized. The RMSE was 

calculated following standard techniques (Helsel and Hirsch, 

2002). Multiple techniques are available to the user for selection of the roughness parameter within the model interface. 

The Z0 parameter was selected to calculate roughness, where 

Z0 is defined as the distance above the streambed at which the 

velocity is zero (Julien, 2010). 

The Z0 parameter is calculated as the quotient of the grain 

roughness height and 30 (Julien, 2010). The grain roughness 

height in gravel bed rivers has been characterized as a function of grain size in a variety of ways including: 3.5 × d84 and 

6.8 × d50 (Bray, 1982) and 1.25 × d35 and 3.5 × d90 (Millar and 

Quick, 1994). The d84 was calculated from the five grain-size 

samples (three samples in the upper reach and two samples 

in the lower reach) which are discussed in the “Streambed 

Sediment Characterization Techniques” section. The average 

Z0, calculated from the d84 of the five grain-size samples, was 

0.013 m, and the same average resulted when the two reaches 

were considered separately.

FaSTMECH uses a constant Z0

 to calculate a variable 

drag coefficient as a function of depth for the study reach 

(Rich McDonald, U.S. Geological Survey, oral commun., 

September 2011), where the drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance 

of an object in a fluid. The Z0

 parameter was chosen to 

determine channel roughness because it is based on the grain 

size of the streambed (a persistent condition within gravel 

streams for moderate time steps); Z0

 is also advantageous 

because it is less subjective than other roughness estimates 

(Manning’s n or Darcy-Weisbach friction factor) that are 

made based on visual comparisons to reference values which 

integrate roughness sources along the entire cross section or 

reach (Barnes, 1977). Another benefit to using Z0

 over other 

roughness estimates is that it does not change with stream 

depth and so requires a single characterization for the entire 

range of flow conditions (Julien, 2010). However, when 

using Z0

, the characteristic roughness height for a channel is 

a function of scales that range from as large as the channel 

form to as small as the characteristic grain size of the channel, and the streambed is discretized onto a grid that may be 

coarser than some of the roughness scales of the channel. 

The model is therefore calibrated by varying the roughness 

height as described above. 

Eight streamflow conditions were simulated: 50; 150; 

260; 400; 900; 1,300; 1,600; and 1,800 ft3

/s. Five of the simulated streamflows had one measured water-surface elevation 

available located at the upstream boundary of each reach. For 

streamflow conditions of 150; 260; and 1,600 ft3

/s, multiple 

measured water-surface elevations distributed throughout 

the reach allowed for more rigorous calibration of these flow 

simulations (fig. 6). There were 183 surveyed water-surface 

elevations (data points) for the 150 ft3

/s simulation; 110 data 

points for the 260 ft3

/s simulation; and 40 data points for the 

1,600 ft3/s simulation (the data points used for the 1,600 ft3/s 

simulation were 2010 high-water marks).

For all of the flow simulations except 1,600 ft3

/s (in the 

lower reach), the root mean squared error of the water-surface 

elevation was 0.09 m or less. The 1,600 ft3

/s flow simulation in 

the upper reach had a root mean squared error of 0.24 m, and 

the predictions of water-surface elevation were consistently 

higher than the data points. The largest differences between 

the predictions and data points for this simulation occurred in 

the middle of the study reach (maximum was 0.58 m), while 

the up- and downstream boundaries had smaller differences 

(0.11 m or less) (fig. 6C). This may indicate additional streamflow within that section of the reach that occurs outside of the 

simulated flow area or over estimation of channel roughness 

based on estimates of Z0

.

Within the hydraulic model calibration procedure, the 

RMSE in streamflow is used to aid in the assessment of flow 

simulation convergence. The RMSE in streamflow compares 

the observed and mean simulated streamflow for each flow 

condition along the computational grids. For most flow simulations, the RMSE in streamflow was less than 1.0 percent 

(table 1). The 50 ft3

/ssimulation had the largest RMSE in both 

Figure 4. Riparian canopy density assessment locations in the 

Lake Fork of the Gunnison River near Lake City, Colorado, August 

2011.—Previous page
10 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

Figure 5. Map of Multidimensional Surface Water Modeling System grids of the upper and lower reaches.

107°18'50" 107°18'40" 107°18'30" 107°18'20"

38°02'10"

38°02'

38°01'50"

0 37.5 75 150 YARDS

0 37.5 75 150 METERS

Base from U.S. Department of Agriculutre

National Agriculture Imagery Program (NAIP)

Universal Transverse Mercator Projection Zone 13 North

Figure 5.

EXPLANATION

Lower reach grid

Upper reach grid
Two-Dimensional Hydraulic and Habitat Modeling Techniques 11

Sediment Mobility

Fluvial transport of sediment particles is an important 

component of the assessment of channel stability. In general, 

sediment transport occurs within a stream when the forces 

acting to move a particle exceed the resisting forces of the 

particle. Analysis of each particle within a stream is unfeasible 

and dependent on the relative positioning of other particles 

within the stream, so a more generalized assessment of sediment mobility is presented in this report as a function of the 

median grain size (d50).

In natural river systems, the portion of the boundary 

shear stress available to move sediment particles (grains) 

can be referred to as the grain shear stress (Julien, 2010). In 

wide, straight streams the boundary shear stress is equal to the 

grain shear stress. In other instances, additional energy losses 

reduce the shear stress available to move sediment particles. 

Substantial losses of energy in coarse-bed streams (gravelsized particles and larger) can be the result of turbulent eddy 

formation, bedforms, vegetation, and changes in channel 

geometry (channel expansions and contractions, alluvial bars, 

and meander bends). The equations within FaSTMECH, in 

conjunction with the computational grid density used for this 

analysis, inherently account for these energy losses (except 

those induced by vegetation). Therefore, within this analysis, 

the boundary shear stress estimates within the wetted channel 

(free of vegetation) are equal to the grain shear stress of those 

areas. FaSTMECH calculates boundary shear stress based on 

the following equation (Nelson and McDonald, 1997):

τ ρ b = + Cd ( ) u v 2 2

(1)

where

	 τb is the total boundary shear stress, in Newtons 

per square meter;

	 ρ is the fluid density, in kilograms per cubic 

meter;

Cd is the non-dimensional drag coefficient;

u is the vertically averaged stream-wise 

velocity, in meters per second; and

v is the vertically averaged cross-stream 

velocity, in meters per second. 

In order to determine the precise conditions that will 

result in the initiation of motion for more than one particle 

of interest, reasonable generalizations of the particle shape, 

orientation, submerged weight, and protrusion into flow must 

be assessed. The critical shear stress (τc) for a particle is the 

minimum shear stress needed for general movement of the 

particle to begin. Critical shear stress should be considered 

the minimum value for motion of the streambed because only 

a small fraction of the sediments will be in motion over short 

time periods (Milhous, 1982). Substantial mobilization of 

sediments has been shown to occur at roughly two times the 

critical shear stress (Wilcock and McArdell, 1993).

Within this report, a comparison of the boundary shear 

stress to critical shear stress of the median grain size (d50) 

is used to determine when sediments within the channel are 

Figure 6. Graph showing water-surface elevations for the bestfit flow simulations for A, 150 cubic feet per second; B, 260 cubic 

feet per second; and C, 1,600 cubic feet per second streamflows.

C. 1,600 cubic feet per second

2,628

2,629

2,630

2,631

2,632

2,633

2,634

2,635

2,636

2,637

2,638

Water-surface elevation, in meters

0 100 200 300 400 500 600 700 800 900 1,000

Streamwise distance, in meters

Figure 6.

B. 260 cubic feet per second

2,628

2,629

2,630

2,631

2,632

2,633

2,634

2,635

2,636

2,637

2,638

Water-surface elevation, in meters

0 100 200 300 400 500 600 700 800 900 1,000

Streamwise distance, in meters

A. 150 cubic feet per second

Observed

EXPLANATION

Predicted

Observed

EXPLANATION

Predicted

Observed

EXPLANATION

Predicted

2,628

2,629

2,630

2,631

2,632

2,633

2,634

2,635

2,636

2,637

2,638

Water-surface elevation, in meters

0 100 200 300 400 500 600 700 800 900 1,000

Streamwise distance, in meters

study reaches. Roughness (Z0) was varied over a range until 

the smallest RMSE was achieved for each flow simulation. 

The final value fit within the bounds of the literature values 

mentioned previously in this section.
12 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

Table 1. Summary of the lateral eddy viscosity and model diagnostics for the best-fit two-dimensional hydraulic and habitat model 

simulations.

[RMSE, root mean squared error; --, insufficient data]

Observed streamflow, 

in cubic feet per 

second

Lateral eddy viscosity, 

in square meters per 

second

RMSE for streamflow, 

in percent

RMSE for watersurface elevation,

in meters

Minimum percent

deviation from 

observed streamflow

Maximum percent 

deviation from 

observed streamflow

Upper reach

50 0.003 3.3 -- –9.0 12.0

150 0.005 0.8 0.07 –5.0 3.0

260 0.005 0.7 0.06 –3.0 1.0

400 0.005 1.1 0.00 –5.0 3.0

900 0.010 0.8 0.01 –5.0 4.0

1,300 0.006 0.8 0.02 –2.5 2.0

1,600 0.007 0.8 0.08 –3.5 2.5

1,800 0.007 0.8 0.02 –3.0 3.0

Lower reach

50 0.003 1.1 0.04 –3.0 8.0

150 0.002 0.3 0.04 –1.6 1.0

260 0.005 0.7 0.04 –1.5 2.5

400 0.008 0.4 0.01 –2.0 0.8

900 0.009 0.4 0.05 –0.7 1.2

1,300 0.015 0.2 0.09 –0.4 0.7

1,600 0.015 0.2 0.24 –0.3 0.6

1,800 0.015 0.4 0.06 –1.5 0.6

mobile. This accounts for the continuum of possible interactions of particles including hiding (conditions when mixtures 

of coarse and fine particles are positioned such that the finer 

material is sheltered by larger particles, thereby decreasing 

sediment mobility of the finer particles) or increased mobility (when larger particles are surrounded in a matrix of finer 

material, thereby increasing sediment mobility of the larger 

particles) (Julien, 2010).

Multiple dimensionless critical shear-stress values were 

selected for the sediment mobility analyses to cover the range 

of conditions within the reach. Based on the d50, the dimensionless critical shear stress was 0.047 using equations 2 and 3 

from Julien (2010)

τ φ * . . tan * *

c

d d

≈ + e e − 



 





− −

03 006 1 3 20

(2)

where

τ*c is the dimensionless critical shear stress;

φ is the sediment particle angle of repose 

(assumed to be 38 degrees); and 

d d G g

v s

m

*

( ) =  −



 



 1

2

1

3

(3)

where

d* is the dimensionless sediment particle diameter;

ds is the median grain size (d50), in meters;

G is the specific gravity of sediment (2.65, 

dimensionless);

g is gravitational acceleration (9.81 meters per 

second per second); and

vm is the kinematic viscosity at 20 degrees 

Celsius (1.0 × 10-6 square meters per 

second).

A dimensionless critical shear value of 0.060 was selected to 

represent areas where the streambed was tightly structured 

or where the particles were strongly imbricated (Parker and 

others, 1982; Andrews, 1983; Komar, 1987; Powell and 

Ashworth, 1995). These two values cover a range of potential 

transport conditions within the stream based on field observations of streambed conditions. These values were used to 

estimate sediment mobility at the surveyed cross-sections.

The dimensional critical shear stress needed to initiate 

motion of the streambed was calculated relative to the d50 

using equation 4. In this report, comparisons are made to the 

d50 within each reach. As previously mentioned, this method 

represents the general condition of sediment motion within the 

channel by accounting for occurrence of particle hiding and 

increased mobility of differently-sized particles.

τ τ γ γ c c s s = − ( ) d * (4)

τc is the critical shear stress, in Newtons per 

square meter (pascal); 

τ*c is the dimensionless critical shear stress or 

Shields parameter;

γs is the specific weight of sediment (25,996.5 

Newtons per cubic meter);
Two-Dimensional Hydraulic Model Sensitivity Analysis 13

γ is the specific weight of water (9,810 Newtons 

per cubic meter); and

ds is the particle size of interest (d50), in meters. 

An assessment of sediment mobility was done through 

an assessment of transport strength using FaSTMECH. This 

method is most sensitive to the potential for sediment mobility 

because it uses the lowest threshold value for motion (dimensionless critical shear stress value of 0.03). This is a reasonable threshold accounting for conditions possibly present that 

were not observed in the cross-section locations. Sediment 

mobility is reported using equation 5 to calculate the transport 

strength (T), where T=0 is the threshold of motion and T=1 is 

the threshold for substantial motion for the d50:

T = −b c c ( ) τ τ /τ (5)

where

T is the transport strength, dimensionless, τb is the boundary shear stress or grain shear 

stress, in pascals; and

τc is the critical shear stress, in pascals.

Trout Habitat Suitability

Habitat suitability was evaluated for cutthroat (Oncorhynchus clarkii) and brown trout (Salmo trutta morpha fario) fry, 

juveniles, and adults. These species were chosen because they 

represent the two extremes of trout found in Colorado mountain streams and also because they represent a comparison 

between native (cutthroat trout) and introduced (brown trout) 

salmonids in Colorado. A longitudinal stratification of these 

species often occurs in stream systems where multiple species 

of trout are present. Typically, cutthroat trout are found in 

headwater areas with cooler water temperatures, lower sediment concentrations, and less biological production (Hickman and Raleigh, 1982). Brown trout are usually found at 

the lowest reaches, where warmer water temperatures, higher 

sediment concentration, and higher biological production are 

typical (Raleigh and others, 1986).

Microscale (point locations) and mesoscale (reach 

features) habitat was assessed using the combination of field 

observations, measurements, and hydraulic simulations within 

the study reach of the Lake Fork. This provides resource managers with tools to assess the effects of hydrologic conditions 

(wet, average, and dry years) and flow alterations on habitat 

availability for specific streamflows or over annual timescales. 

To assess how habitat availability changes with streamflow, 

microscale-habitat quantification was done for each simulated 

streamflow and was also reported as a time-weighted annual 

total (based on typical flow frequencies).

Habitat builder in MD_SWMS was used to quantify 

microscale habitat availability following methodologies 

similar to the Habitat Suitability Index method (Hickman and 

Raleigh, 1982; Raleigh and others, 1986). Suitability criteria 

were defined based on published values for three life stages 

of the two fish species: (1) adult, (2) juvenile, and (3) fry, 

based on depth and velocity ranges (fig. 7). Habitat suitability 

curves, scaled from 0 to 1, were developed for each of the 

three life stages based on depth and velocity conditions. A 

value of zero indicates that the velocity or depth condition is 

not acceptable; whereas a value of 1 indicates that the condition is optimal. Between 0 and 1, habitat suitability values 

were interpolated linearly to indicate increasing or decreasing 

acceptability of the condition. For each streamflow and life 

stage, the habitat builder provides a map of the calculated geometric mean of the suitability curves and total weighted usable 

area as the sum of the area of each grid cell multiplied by the 

geometric mean of the grid node.

Mesoscale habitat quantification was done through the 

separation of each reach into features of specific habitat type 

(pool or riffle/run habitat) based on the geomorphology and 

hydraulic characteristics of larger, continuous features within 

each reach. Separation of these habitat types was done in a 

geographic information system based on velocity, depth, and 

visual inspection of morphological form. Separation of the 

reaches into two habitat types provides a comparison between 

the observed proportions of habitat and general guidelines 

derived from observations of reaches with sustained populations of each species (Hickman and Raleigh, 1982; Raleigh 

and others, 1986) (table 2).

A vital component of habitat for fish includes available 

cover. Fishes use different cover types depending on what 

types are available, the location of cover relative to other 

important habitat features (such as feeding habitat or refuge), 

time of year, and life stage. Cover can vary from rubble bed 

substrate, aquatic vegetation or plant debris, or deep pools 

and surface disturbances that obscure visibility from terrestrial or avian predators. Cover estimates were limited to adult 

life stages in this analysis. Cover estimates were quantified 

as a function of the distance to cover from drift feeding areas 

within each reach. Feeding areas were selected as areas that 

could provide access to food sources while requiring little 

exertion. These were typically lower-velocity areas adjacent 

to or downstream from higher velocity areas that could funnel 

benthic invertebrates and terrestrial insects to these fish from 

the current. Cover was identified as pool areas or vegetated 

channel banks within each reach.

Two-Dimensional Hydraulic Model 

Sensitivity Analysis

FaSTMECH model sensitivity was analyzed for two 

parameters: the lateral eddy viscosity and channel roughness 

based on Z0, for 150; 260; and 1,600 ft3/s flow simulations, 

because water-surface elevation data were available along the 

entire length of each reach for these flows. Sensitivity of the 

two parameters was evaluated by holding all parameters constant in best-fit flow simulations and then individually adjusting the lateral eddy viscosity and Z0

 by –25 and +25 percent. 

Model results from the sensitivity analysis were compared to 

original best-fit flow simulations (tables 3 and 4). Water-surface 
14 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

Figure 7. Habitat suitability curves for the three life stages of brown trout and cutthroat trout. A, habitat suitability for brown trout 

based on depth; B, habitat suitability for brown trout based on velocity; C, habitat suitability for cutthroat trout based on depth; D, habitat 

suitability for cutthroat trout based on velocity.

1

A B

0

0.2

0.4

0.6

0.8

1

Suitability Index

0

0.2

0.4

0.6

0.8

1

Suitability Index

0

0.2

0.4

0.6

0.8

1

Suitability Index

0

0.2

0.4

0.6

0.8

1

Suitability Index

Depth, in meters

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Velocity , in meters per second

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Depth, in meters

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Velocity , in meters per second

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Figure 7.

C D

Cutthroat

Adult

Juvenile

Fry

EXPLANATION

Cutthroat

Adult

Juvenile

Fry

EXPLANATION

Brown Brown

Adult

Juvenile

Fry

EXPLANATION

Adult

Juvenile

Fry

EXPLANATION

elevations, velocity, and shear stress are calculated from 

means of all wetted nodes in each flow simulation. Differences 

between the two flow simulations were reported from means of 

the differences in values between wetted node-pairs from each 

flow simulation. Percent difference was calculated as the mean 

difference between the two flow simulations, relative to the 

mean value of the best-fit flow simulation. Larger differences 

indicate greater sensitivity of the model parameter.

None of the flow simulations showed substantial sensitivity to changes in lateral eddy viscosity (table 3). The percent 

difference between flow simulations ranged from –0.3 percent 

to +0.5 percent. The extremes occurred in boundary shear 

stress in the lower reach for the 1,600 ft3

/s simulation and 

the upper reach for the 1,600 ft3/s simulation, and in mean 

water-surface elevation in the upper reach for the 260 ft3/s 

simulation. In the 1,600 ft3/s simulation at the upper reach, the 

+0.5 percent for mean boundary shear stress corresponded to 

+0.20 pascal. The largest change in mean velocity was +0.01 

meters per second and the largest change in mean depth (and 

mean water-surface elevation) was +0.01 m (table 3).

Flow simulations showed increased sensitivity to changes 

in Z0 (table 4). Most model outputs changed by less than 

10 percent. Shear stress was generally the most sensitive of 

model outputs, where the difference from the mean boundary shear stress ranged from –59.4 percent to +8.0 percent. 

Percent difference from mean velocity ranged from –1.6 to 

+19.5 percent; whereas, the percent difference of mean watersurface elevation ranged from –24.2 to +5.6 percent (table 4).
Two-Dimensional Hydraulic Model Sensitivity Analysis 15

Table 2. Mesoscale-habitat suitability ranges of habitat type 

for cutthroat and brown trout (from Hickman and Raleigh, 1982; 

Raleigh and others, 1986).

Trout species Mesoscale habitat suitability

Pool, percent Riffle/Run, percent

Brown 50–70 30–50

Cutthroat 40–60 40–60

Table 3. Results from the analysis of the sensitivity of the lateral eddy viscosity parameter for three of the streamflows simulated in 

the multidimensional flow model for the upper and lower study reaches on the Lake Fork.

[Sensitivity analysis of the lateral eddy viscosity parameter were made at 75 (italicized values) and 125 (bolded values) percent of the calibrated lateral eddy 

viscosity value. Percent differences are relative to the mean of the calibrated model and percent difference in water-surface elevation is relative to the mean 

depth. The mean values are based on all of the wet nodes in the model. RMSE, root mean squared error; -- insufficient data]

Observed 

streamflow, 

in cubic 

feet per 

second1

Lateral eddy 

viscosity, 

in square 

meters per 

second

Model output Percent difference from the mean

Mean 

depth, 

in

meters

Mean watersurface 

elevation, 

in meters

Mean

velocity, 

in meters

per second

Mean

boundaryshear stress,

in Pascals

RMSE for 

watersurface 

elevation, 

in meters

Watersurface 

elevation, 

in

percent

Velocity, 

in

percent

Boundary 

shear stress, 

in percent

Upper Reach

150 0.010 0.31 2,635.82 0.76 13.81 0.07 0.2 0.0 0.2

150 0.008 0.31 2,635.82 0.76 13.77 0.07 -- -- --

150 0.006 0.31 2,635.82 0.76 13.77 0.07 0.3 –0.0 –0.0

260 0.007 0.38 2,635.92 0.95 18.27 0.06 0.5 0.1 0.3

260 0.006 0.37 2,635.92 0.95 18.20 0.06 -- -- --

260 0.004 0.37 2,635.92 0.95 18.19 0.06 0.1 –0.0 –0.1

1,600 0.006 0.66 2,636.52 1.52 32.29 0.08 –0.1 0.1 0.5

1,600 0.005 0.66 2,636.52 1.51 32.09 0.08 -- -- --

1,600 0.003 0.66 2,636.52 1.52 32.20 0.08 0.0 0.1 0.3

Lower Reach

150 0.002 0.30 2,629.96 0.78 17.52 0.04 –0.0 –0.0 –0.0

150 0.002 0.30 2,629.96 0.78 17.52 0.04 -- -- --

150 0.003 0.30 2,629.96 0.78 17.51 0.04 0.0 –0.0 –0.1

260 0.004 0.38 2,630.06 0.99 21.87 0.04 –0.1 –0.0 –0.1

260 0.005 0.38 2,630.06 0.99 21.89 0.04 -- -- --

260 0.006 0.38 2,630.06 0.99 21.85 0.04 0.0 –0.0 –0.2

1,600 0.011 0.94 2,630.74 1.93 54.69 0.24 –0.0 0.0 0.1

1,600 0.015 0.94 2,630.74 1.93 54.61 0.24 -- -- --

1,600 0.019 0.94 2,630.75 1.92 54.48 0.24 0.1 –0.0 –0.3

1

To convert from cubic feet per second to cubic meters per second divide by 35.31.
16 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

Table 4. Results from the analysis of the sensitivity of the roughness parameter (Z0) for three of the streamflows simulated in the twodimensional flow model for the upper and lower study reaches on the Lake Fork.

[Sensitivity analysis of the roughness parameter (Z0) were made at 75 (italicized values) and 125 (bolded values) percent of the calibrated Z0 value. Percent 

differences are relative to the mean of the calibrated model and percent difference in water surface elevation is relative to the mean depth. The mean values are 

based on all of the wet nodes in the model. RMSE, root mean squared error; -- insufficient data]

Observed 

streamflow, 

in cubic 

feet per 

second1

Z0,

in

meters

Model output Percent difference from the mean

Mean 

depth,

in

meters

Mean watersurface 

elevation,

in meters

Mean 

velocity,

in meters 

per second

Mean 

boundaryshear 

stress,

in Pascals

RMSE for 

watersurface 

elevation, 

in meters

Watersurface 

elevation, 

in

percent

Velocity,

in

percent

Boundary 

shear stress,

in percent

Upper Reach

150 0.010 0.30 2,635.80 0.81 12.65 0.07 –5.0 1.6 –9.5

150 0.013 0.31 2,635.82 0.76 13.77 0.07 -- -- --

150 0.016 0.30 2,635.84 0.71 14.25 0.08 2.4 –0.8 7.5

260 0.010 0.36 2,635.91 1.00 16.52 0.06 –4.0 1.4 –10.0

260 0.013 0.37 2,635.92 0.95 18.20 0.06 -- -- --

260 0.016 0.38 2,635.93 0.92 19.35 0.06 3.1 –0.8 7.2

1,600 0.010 0.64 2,636.37 2.10 20.17 0.16 –24.2 19.5 –59.4

1,600 0.013 0.66 2,636.52 1.51 32.09 0.08 -- -- --

1,600 0.016 0.67 2,636.54 1.47 33.42 0.08 2.9 –1.6 5.9

Lower Reach

150 0.010 0.31 2,629.98 0.75 18.92 0.04 5.6 –1.4 8.0

150 0.013 0.30 2,629.96 0.78 17.52 0.04 -- -- --

150 0.016 0.28 2,629.94 0.84 16.22 0.06 –6.2 1.7 –9.0

260 0.010 0.39 2,630.07 0.96 23.27 0.04 4.1 –1.1 6.3

260 0.013 0.38 2,630.06 0.99 21.89 0.04 -- -- --

260 0.016 0.37 2,630.03 1.06 20.24 0.05 –5.8 1.7 –9.2

1,600 0.010 0.98 2,630.78 1.86 58.06 0.27 4.3 –1.1 6.3

1,600 0.013 0.94 2,630.74 1.93 54.61 0.24 -- -- --

1,600 0.016 0.90 2,630.70 2.02 51.02 0.20 –4.9 1.4 –7.1

1

To convert from cubic feet per second to cubic meters per second divide by 35.31.
Hydraulic and Geomorphic Conditions 17

Hydraulic and Geomorphic Conditions

The existing hydraulic and geomorphic conditions for 

a 1.1-km section of the Lake Fork at Lake City are summarized as a function of the current streamflow regime based on 

model simulations for eight streamflows that cover the range 

of streamflow conditions typically observed at the site (figs. 2

and 8). Comparisons and evaluation of differences in sediment 

mobility and habitat suitability will provide resource managers with information to evaluate existing channel stability and 

habitat conditions of the reach as well as provide a baseline to 

compare with future conditions.

Within these systems, limiting fine-sediment deposition 

and removal of fine sediments (sizes less than 2 millimeters 

[mm]) within framework grain interstitial spaces enhances 

habitat suitability for both fish and invertebrates. Gravel substrates used for spawning redds (spawning habitat) are most 

suitable when free of finer sediments (Hickman and Raleigh, 

1982; Raleigh and others, 1986). Benthic invertebrates 

productivity and abundance, as well as larval and fry refugia, 

are optimized when fine sediments are limited to less than 

5 percent (Hickman and Raleigh, 1982; Raleigh and others, 

1986). Sediment mobility is an important process for flushing 

fine sediments from within the gravel frameworks.

0

10

20

30

40

50

60

0 500 1,000 1,500 2,000 2,500 3,000

Percent of year

Average flow, in cubic feet per second

Figure 8. Figure 8. Flow frequency curve for the Lake Fork of the Gunnison 

River at Lake City, Colorado.

Sediment Mobility

Boundary shear stress calculated from each flow simulation was compared to the critical shear stress of mean d50

in each reach to determine streambed mobility (fig. 9 and 

table 5). In this report, where boundary shear stress was equal 

to critical shear, sediment transport conditions are reported as 

potentially mobile; where the boundary shear stress exceeded 

two times the critical shear stress, sediment transport conditions are reported as substantially mobile.

0

10

20

30

40

50

60

70

80

90

100

0.1 1.0 10 100 1,000

Cumulative percent finer

Sediment size, in millimeters

GS1 (103 millimeters)

GS2 (51 millimeters)

GS3 (80 millimeters)

GS4 (54 millimeters)

EXPLANATION

Sediment sample locations

(Median particle size)

GS5 (80 millimeters)

Figure 9. Figure 9. Sediment-size characteristics of the five sampling sites.

Table 5. Sediment particle-size characteristics for the five sites 

sampled from August 4 to August 6, 2010, and August 18, 2011 

(GS1-GS4 and GS-5, respectively) in the Lake Fork study area. 

(Grain-size sample locations [GS1–GS5] are shown in fig. 3.)

[Easting and Northing datum is Universal Transverse Mercator Zone 13 

North American Datum 1983; d50, median (50th percentile) particle diameter; d84, 84th percentile particle diameter]

Site short 

name

Easting, 

in meters

Northing,

in meters

d50,

in

millimeters

d84,

in

millimeters

GS1 296,993 4,211,721 103 155

GS2 297,083 4,211,874 51 113

GS3 297,172 4,212,064 80 135

Upper reach average 78 134

GS4 297,358 4,212,262 54 123

GS5 297,476 4,212,329 80 132

Lower reach average 67 128

Evaluations of channel and flow characteristics at crosssection locations 2–8, presented in downstream order, show 

a range of streambed mobility (figs. 10 and 11). In general, 

boundary shear stress and streambed mobility increase with 

increases in streamflow. At streamflows of 50, 150, and 260 

ft3/sthe streambed is not mobile (figs. 10 and 11). However, 

the streambed is potentially mobile for the 400 ft3/s streamflow at cross-sections 4–8 depending on which dimensionless 

critical-shear stress value is referenced (0.03, 0.047, or 0.06) 

(figs. 10 and 11). At cross sections 2–8, sediment is potentially 

mobile at streamflows of 900 ft3/s. The streambed is substantially mobile at cross sections 4–8 at streamflows of 1,300 to 

1,600 ft3/s with all cross sections being substantially mobile at 

1,800 ft3/s (figs. 10–11). Within the cross sections, the greatest 

boundary shear stress occurs towards the center of the channel. 

Sediments are generally less mobile near the channel margins 

for all flow simulations.
18 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

Figure 10. Shear stress and water-surface elevation plots at A, cross-section 2; B, cross-section 3; and C, cross-section 4.

2,635

2,636

2,637

2,638

2,639 0

20

40

60

80

100

0 10 20 30 40 50 60

Elevation, in meters Elevation, in meters Elevation, in meters

Shear stress, in pascals

Horizontal distance, in meters

Horizontal distance, in meters

Horizontal distance, in meters

0 10 20 30 40 50 60

0 10 20 30 40 50 60

2,635

2,637

2,636

2,638

2,639 0

20

40

60

80

Shear stress, in pascals100

2,634

2,635

2,637

2,636

2,638

2,639

2,634

0

20

40

60

80

100

Shear stress, in pascals

0.06

0.047

0.03

0.06

0.047

Figure 10.

0.06

0.047

0.03

0.03

50

0.047 (dimensionless)

0.03 (dimensionless)

0.06 (dimensionless)

150

260

400

900

1,300

1,600

1,800

Land surface 

EXPLANATION

Shear stress profile

(streamflow in cubic feet per second)

Water-surface elevation profile

(streamflow in cubic feet per second)

Critical shear stress

50

150

260

400

900

1,300

1,600

1,800

A

B

C
Hydraulic and Geomorphic Conditions 19

Figure 11. Shear stress and water-surface elevation plots at A, cross-section 5; B, cross-section 6; C, cross-section 7; 

and D, cross-section 8. 

50

0.047 (dimensionless)

0.03 (dimensionless)

0.06 (dimensionless)

150

260

400

900

1,300

1,600

1,800

Land surface 

EXPLANATION

Shear stress profile

(streamflow in cubic feet per second)

Water-surface elevation profile

(streamflow in cubic feet per second)

Critical shear stress

50

150

260

400

900

1,300

1,600

1,800

0.06

0.047

0.03

Figure 11.

Elevation, in meters

2,630

2,632

2,631

2,633

2,629

Horizontal distance, in meters

55 65 75 85 105 125 145 165 95 115 135 155 175 185

0

20

40

60

80

Shear stress, in pascals

100

B

Elevation, in meters

Horizontal distance, in meters

0 5 10 15 25 35 45 55 20 30 40 50 60

2,631

2,633

2,632

0 2,634

20

40

60

80

Shear stress, in pascals

100

2,630

0.06

0.047

0.03

A
20 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

Reach-scale assessment of sediment mobility in the upper 

reach shows that there are areas where the streambed is potentially mobile for all streamflow simulations and that boundary 

shear stress and streambed mobility increase as streamflow 

increases (fig. 12A–C). For streamflows of 400 ft3/s or less, the 

streambed is potentially mobile in some areas. Areas where 

the streambed is substantially mobile began to appear in flow 

simulations of 900 ft3/s and greater, and the size of these areas 

increase as streamflow increases. At streamflows of 1,300 ft3/s 

or greater, the majority of the channel is potentially mobile 

except areas along the channel margins. 

Reach-scale assessment of sediment mobility in the 

lower reach shows increased streambed mobility (fig. 12D–F). 

This is due in part to smaller grain sizes in the lower reach 

(mean d50 is 11 mm smaller than the upper reach mean d50, 

[table 5]) but may also reflect the greater extent of channel 

50

0.047 (dimensionless)

0.03 (dimensionless)

0.06 (dimensionless)

150

260

400

900

1,300

1,600

1,800

Land surface 

EXPLANATION

Shear stress profile

(streamflow in cubic feet per second)

Water-surface elevation profile

(streamflow in cubic feet per second)

Critical shear stress

50

150

260

400

900

1,300

1,600

1,800

0.047

0.03

0.06

10 30 50 70 90 110 130 150 170 190

D

Horizontal distance, in meters

Figure 11.

0.06

0.047

0.03

10 30 50 70 90 110 130 150 170 190

Elevation, in meters

2,629

2,631

2,630

2,632

2,628

0

20

40

60

80

Shear stress, in pascals

100

C

Horizontal distance, in meters

Elevation, in meters

2,629

2,631

2,630

2,632

2,628

0

20

40

60

80

Shear stress, in pascals

100

Figure 11. Shear stress and water-surface elevation plots at A, cross-section 5; B, cross-section 6; C, cross-section 7; 

and D, cross-section 8.—Continued

Figure 12. Reach-scale assessment of sediment mobility in 

the upper reach (A–C) and lower reach (D–F) of the Lake Fork 

of the Gunnison River at streamflows of 400; 900; and 1,800 ft3

/s, 

respectively.—Following page
Hydraulic and Geomorphic Conditions 21

107°18'30" 107°18'20"

38°02'10"

38°02'5"

38°2'15"

5

6

7

8

5

Base from U.S. Department of Agriculutre

National Agriculture Imagery Program (NAIP)

Universal Transverse Mercator Projection Zone 13 North

F

107°18'30" 107°18'20"

38°02'10"

38°02'5"

38°02'15"

5

6

7

8

5

E

107°18'30" 107°18'20"

38°02'10"

38°02'5"

38°02'15"

5

6

7

8

5

D

EXPLANATION

Potentially mobile

Substantially mobile

Streambed mobility

Cross-section location

 and number

Not mobile

2

107°18'50" 107°18'40"

38°02'

38°01'50"

3

4

2

C

107°18'50" 107°18'40"

38°02'

38°01'50"

3

4

2

B

107°18'50" 107°18'40"

38°02'

38°01'50"

3

4

2

Figure 12.

A
22 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

alterations, specifically the temporary berms constructed by 

CDOT in the late 1980s and early 1990s, present in this reach. 

In the 400 ft3/s flow simulation, some areas within the channel 

become substantially mobile with additional areas of potential mobility appearing downstream throughout the reach. In 

the 900 ft3/s flow simulation, the entire length of the channel 

becomes potentially mobile with small patches of the streambed that are substantially mobile. In the 1,800 ft3

/s flow simulation, the majority of the channel along its entire length is 

substantially mobile except along the channel margins which 

are potentially mobile.

Geomorphic Channel Form

Geomorphic channel form is affected by land-use 

changes within the basin and geologic controls within the 

reach (Lake Fork Valley Conservancy, 2010). The historic 

channel was defined as a dynamic, braided channel (multiple, 

bifurcating channels) with an active flood plain (Lake Fork 

Valley Conservancy, 2010). Comparisons of the channel 

slope, high-flow conditions, or floods (Capesius and Stephens, 

2009; U.S. Geological Survey, 2010b), and d50 of each reach 

to channel-form thresholds (meandering and braided channel) indicated that current channel characteristics may favor a 

braided channel form (fig. 13) (Leopold and Wolman, 1957; 

Richards, 1982). This can result in a natural tendency for the 

channel to braid, which can affect channel stability of reconfigured reaches when a single-thread meandering channel is 

imposed on the stream (Elliott and Capesius, 2009). The similarities of channel slope, total stream power index (streamflow 

times channel slope), and median bed-material size for the 

upper and lower reaches and at Gateview, which was historically a braided reach and is considered a reference reach for 

this report, support a natural tendency for the channels to braid 

in both reaches (fig. 13). 

Additional constraints on channel form include natural 

and artificial impingement of the active channel occurring 

from placement of boulder revetments, cobble-boulder berms, 

and bedrock outcrops along the channel margins. Boulder 

revetments are common between cross-sections 1 and 5 along 

the left bank of the river, with limited use along the right bank. 

Cobble-boulder berms occur between cross-sections 4 and 8 

along both banks. Bedrock constraints occur along both banks 

for much of the channel between cross-sections 4 and 5, and 

along the left bank between cross-sections 6 and 8. These features constrain the channel from lateral migration and channel 

adjustments and potentially limit the capability of geomorphic 

channel response to alterations in this area.

Trout Habitat Characteristics

Habitat suitability analysis can include an evaluation 

of several inter-related stream conditions (Bovee, 1982). 

Dissolved oxygen, water temperature, pH, and other waterchemistry constituents (nutrients, metals, and total dissolved 

solids) are important to overall aquatic habitat suitability; 

however, this analysis will focus on the physical habitat elements of the reach such as depth, velocity, and distance to 

cover. Model output for each streamflow was used to quantify 

trout habitat abundance.

Microscale Trout Habitat

Microscale trout habitat, defined as weighted-usable area, 

generally increased as streamflow increased for both trout species and all life stages (fig. 14). Areas of suitable microscale 

habitat occur along the banks for flows of 900 ft3/s and less. 

Out-of-bank areas contributed more substantially to overall 

habitat availability for flows of 1,300 ft3/s or more when compared to other features. Adult habitat, for both trout species, 

was the most abundant habitat type for nearly all streamflows. 

Habitat for juvenile cutthroat trout and brown trout fry was the 

least abundant in both reaches. In general, the upper reach provided 2–3 times more available habitat than the lower reach 

for both trout species.

In order to determine the interaction of flow frequency 

and habitat abundance within the current flow regime, a combination of the available habitat was related to the probability 

of that flow occurring each year. This relation provides a measure of the overall habitat for each life stage over the course of 

an average flow year. The results are summarized by species 

and life stage in table 6.

There are seasonal differences between the two species 

when fry are present in the stream (Hickman and Raleigh, 

1982; Raleigh and others, 1986). Both species construct redds 

when spawning in small gravelly areas with good hyporheic 

flows and minimal fine sediments. However, cutthroat trout do 

so in early spring (February or later, based on water temperatures) and the larvae typically hatch within 28–49 days 

depending on water temperatures (Hickman and Raleigh, 

1982). Brown trout construct redds in late summer to early 

fall; this makes the redds more susceptible to over-wintering 

conditions within the gravels and possible smothering due to 

fine sediment deposition (Raleigh and others, 1986). However, 

when brown trout emerge in the spring they are larger and 

typically better able to out-compete cutthroat fry if resources 

are limited (Raleigh and others, 1986). The flows that typically 

occur during these two different time periods were used to 

calculate the total weighted-usable habitat in a typical year for 

the fry of both species (table 6).

Mesoscale Trout Habitat

Mesoscale trout habitat assessment of the Lake Fork was 

done based on the conditions present in the 150 ft3/s flow simulation as well as field observation. Both the upper and lower 

reaches are primarily characterized as riffle/run habitat; however, in the upper reach, the total available pool habitat (total 

wetted area) is greater (table 7). The presence of pool habitat 

was limited throughout both reaches and occurred along the 

channel margins. For both reaches, the pool habitat was less 
Trout Habitat Characteristics 23

Figure 13

0.001

0.01

0.1

1 10 100 1,000

Channel slope, in meters per meter 

Estimated 2-year flood, in cubic meters per second

Upper reach

2-year flood

5-year flood

10-year flood

2-year flood

2-year flood

5-year flood

10-year flood

Lower reach

Reference reach

EXPLANATION

Threshold lines from Leopold and 

 Wolman (1957) and Richards (1982)

0.01

0.1

1

10 100

Total stream power index, in cubic meters per second

Median bed-material size, in millimeters

Braided channels

Meandering channels

Multi-thread

channels

Single-thread

channels

A

B

Gateview

Gateview

Figure 13. Plotting positions of two surveyed reaches of the Lake Fork of the Gunnison River near Lake City, 

Colorado, in comparison to thresholds for meandering and braided channel patterns based on findings from 

A, Leopold and Wolman (1957) and B, Richards (1982).
24 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

0

500

1,000

0 500 1,000 1,500

Adult

Juvenile

Fry

Fish species Life stages

Streamflow, in cubic feet per second

Weighted-useable area, in square meters

EXPLANATION

Brown Trout

Cutthroat Trout

Figure 14.

Figure 14. Weighted-usable habitat for the adult, juvenile, and fry life stages of the cutthroat and 

brown trout in the study reach of the Lake Fork of the Gunnison River.

Table 6. Results from flow-frequency curves and simulation 

results from the multidimensional flow model showing 

microscale-habitat suitability total weighted-useable habitat in a 

typical year for cutthroat and brown trout.

Trout species

Life stage

Adult

square meters

Juvenile

square meters

Fry

square meters

Brown 358 249 96

Cutthroat 332 19 279

Table 7. Mesoscale-habitat characteristics for cutthroat and brown trout during typical baseflow conditions in the Lake Fork near Lake City, Colorado.

Reach Total wetted area,

in square meters

Pool area,

in square meters

Pool,

in percent

Riffle/Run,

in percent

Distance to cover 

from feeding areas,

in meters

Upper 7,126 315 4.4 95.6 15

Lower 6,231 47 0.7 99.3 less than 1
Summary 25

than 5 percent of the total wetted area. This percentage is 

substantially lower than the recommendations for sustainable 

populations of 40–70 percent (tables 2 and 7) (Hickman and 

Raleigh, 1982; Raleigh and others, 1986). An exception to this 

is an isolated scour pool located outside of the modeled area 

(between the two reaches) below a waterfall which was not 

quantified in this analysis.

Riparian canopy study results show differences between 

the upper and lower reaches. Riparian canopy density measurements were consistent in the upper reach, with approximately 20 percent coverage occurring along both banks 

throughout (fig. 4). Vegetation patterns in the lower reach were 

less consistent and demonstrate local effects of topography. 

The large hillslope along the left bank between cross-sections 

7 and 8 produced greater canopy density and shading than 

other areas (fig. 4).

Assessment of the distance of various in-stream habitats to cover (pool areas or vegetated channel banks within 

each reach) from potential feeding areas shows differences 

between the characteristics of the two reaches. Areas of cover 

were adjacent to potential drift feeding areas in the lower 

reach, and often occurred within the same pool habitat (distance to cover from feeding areas were less than 1 m). This 

condition may favor energy expenditure ratios of both fish 

species, wherein little energy is needed to acquire adequate 

food sources (table 7). In the upper reach, distances from drift 

feeding areas to cover were much greater (15 m), a condition 

that is less conducive to cutthroat trout which tend to occupy 

drift feeding areas where cover is located nearby (Hickman 

and Raleigh, 1982).

Summary

Since the 1950s, the Lake Fork of the Gunnison River has 

been an area of active channel modification to accommodate 

the needs of the Lake City community. The Lake Fork Valley 

Conservancy District began a planning process to assess restoration options for a reach of the Lake Fork in Lake City to 

enhance hydraulic and ecologic characteristics of the reach. 

Channel rehabilitation, or reconfiguration, to mitigate a 

variety of riverine problems has become a common practice in 

the western United States. Reasons for channel rehabilitation 

include restoration to more natural or historical conditions, 

improved water conveyance in flood-prone areas, mitigation 

of unstable streambeds and streambanks, increased sediment transport, enhancement of aquatic and riparian habitat, 

improved water quality, and recreation. Numerous private 

entities and resource-management agencies have attempted 

to modify stream channels by using designs based on different geomorphic philosophies and classification schemes. 

However, additional work to monitor and assess the channel 

response to, and the effectiveness of, these modifications over 

longer periods of time (decadal or longer) is still needed. To 

address this need, the U.S. Geological Survey is engaged in a 

program designed to monitor and assess selected river reaches 

that have undergone reconfiguration. The U.S. Geological 

Survey, in cooperation with the Colorado Water Conservation 

Board and Colorado River Water Conservation District, began 

a study in 2010 to quantify existing hydraulic and habitat 

conditions for a reach of the Lake Fork of the Gunnison River 

in Lake City, Colorado.

The purpose of this report is to quantify existing Lake 

Fork hydraulic and habitat conditions and establish a baseline 

against which post-reconfiguration conditions can be compared. This report (1) quantifies the existing hydraulic and 

geomorphic conditions in a 1.1-km section of the Lake Fork 

at Lake City that has been proposed as a location for future 

channel-rehabilitation efforts, (2) characterizes the habitat 

suitability of the reach for two trout species based on physical 

conditions within the stream, and (3) characterizes the current 

riparian canopy density. This characterization describes existing channel conditions and establishes a baseline for postreconfiguration comparisons for resource managers to evaluate 

restoration project success.

Sediment particles were measured at five locations in 

the study reach to characterize the grain size of different 

geomorphic surfaces and to estimate channel roughness. Bars 

and channel margins were chosen because these areas are 

inundated most of the year and represent the coarser material 

transported within the river channel.

Canopy density was characterized during a low-flow 

period at multiple locations within the study area using a 

spherical densiometer. Differences in canopy density can 

affect water temperatures, terrestrial insect and leafy organic 

inputs into the aquatic system, and habitat cover. Four 

measurements were taken at each location from the center of 

the stream with the operator facing: upstream, downstream, 

towards left bank, and towards right bank.

The FaSTMECH computational flow-model within 

MD_SWMS was selected to characterize the effects of streamflow on hydraulic and habitat-suitability conditions for the 

1.1-km study reach of the Lake Fork. Channel geometry was 

obtained from the topographical survey of the channel. Model 

calibration was achieved through iterative adjustments of 

the roughness until the root mean squared error between the 

observed and simulated water-surface elevations was minimized.

Within this report, a comparison of the boundary shear 

stress to critical shear stress of the median grain size (d50) 

is used to determine when sediments within the channel are 

mobile. Multiple dimensionless critical shear-stress values 

were selected for the sediment mobility analyses to cover the 

range of conditions within the reach (dimensionless critical 

shear-stress values of 0.047 and 0.060). An assessment of sediment mobility was done through an assessment of transport 

strength using FaSTMECH.

Habitat suitability was evaluated for cutthroat (Oncorhynchus clarkii) and brown trout (Salmo trutta morpha fario) 

fry, juveniles, and adults. These species were chosen because 

they represent the two extremes of trout found in Colorado 

mountain streams and also because they represent a comparison between native (cutthroat trout) and introduced (brown 
26 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

trout) salmonids in Colorado. Microscale (point locations) and 

mesoscale (reach features) habitat was assessed using the combination of field observations, measurements, and hydraulic 

simulations within the study reach of the Lake Fork. 

FaSTMECH model sensitivity was analyzed for two 

parameters: the lateral eddy viscosity and channel roughness 

based on Z0

, for 150; 260; and 1,600 ft3/s flow simulations, 

because water-surface elevation data were available along 

the entire length of each reach for these flows. Shear stress 

was generally the most sensitive of model outputs, where the 

difference from the mean boundary shear stress ranged from 

–59.4 percent to +8.0 percent. Percent difference from mean 

velocity ranged from –1.6 to +19.5 percent, whereas the percent difference of mean water-surface elevation ranged from 

–24.2 to +5.6 percent.

The existing hydraulic and geomorphic conditions for a 

1.1-km section of the Lake Fork at Lake City are summarized 

as a function of the current streamflow regime based on model 

simulations for eight streamflows that cover the range of 

streamflow conditions typically observed at the site. Comparisons and evaluation of differences in sediment mobility 

and habitat suitability will provide resource managers with 

information to evaluate existing channel stability and habitat 

conditions of the reach as well as provide a baseline to compare with future conditions.

Within these systems, limiting fine sediment deposition 

and removal of fine sediments (sizes less than 2 mm) within 

framework grain interstitial spaces enhances habitat suitability 

for both fish and invertebrates. Sediment mobility is an important process for flushing fine sediments from within the gravel 

frameworks. Evaluations of channel and flow characteristics at 

cross-section locations 2–8 show a range of streambed mobility. In general, boundary shear stress and streambed mobility 

increase with increases in streamflow. At cross sections 2–8, 

sediment is potentially mobile at streamflows of 900 ft3

/s. 

The streambed is substantially mobile at cross sections 4–8 

at streamflows of 1,300 to 1,600 ft3

/s with all cross sections 

being substantially mobile at 1,800 ft3

/s. Within the cross 

sections, the greatest boundary shear stress occurs towards 

the center of the channel. Reach-scale assessment of sediment 

mobility in the lower reach shows increased streambed mobility. This is due in part to smaller grain sizes in the lower reach 

but may also reflect the greater extent of channel alterations, 

specifically the temporary berms constructed by CDOT in the 

late 1980s and early 1990s, present in this reach.

Geomorphic channel form is affected by land-use changes 

within the basin and geologic controls within the reach. The 

historic channel was defined as a dynamic, braided channel with 

an active flood plain. Comparisons of the channel characteristics 

to channel-form thresholds indicated that current channel characteristics may favor a braided channel form. This can result 

in a natural tendency for the channel to braid, which can affect 

channel stability of reconfigured reaches when a single-thread 

meandering channel is imposed on the stream. 

Microscale trout habitat, presented as weighted usable 

area, generally increased as streamflow increased for both 

trout species and all life stages. Areas of suitable microscale 

habitat occur along the banks for flows of 900 ft3

/s and 

less. Out-of-bank areas become more substantial contributors to overall habitat availability for flows of 1,300 ft3

/s or 

more when compared to other features. Adult habitat, for 

both trout species, was the most abundant habitat type for 

nearly all streamflows. In general, the upper reach provided 

2–3 times more available habitat than the lower reach for 

both trout species.

Mesoscale trout habitat assessment of the Lake Fork 

was done based on the conditions present in the 150 ft3/s 

flow simulation as well as field observation. Both the upper 

and lower reaches are primarily characterized as riffle/run 

habitat. The presence of pool habitat was limited throughout both reaches and occurred along the channel margins. 

For both reaches, the pool habitat was less than 5 percent 

of the total wetted area, a percentage that is substantially 

lower than the recommendations for sustainable populations of 40–70 percent. An exception to this is an isolated 

scour pool located outside of the modeled area (between the 

two reaches) below a waterfall which was not quantified in 

this analysis. Areas of cover were adjacent to potential drift 

feeding areas in the lower reach, and often occurred within 

the same pool habitat. This may favor energy expenditure 

ratios of both fish species, wherein little energy is needed to 

acquire adequate food sources.

References Cited

Andrews, E.D., 1983, Entrainment of gravel from naturally 

sorted riverbed material: Geological Society of America 

Bulletin, v. 94, p. 1225–1231.

Barnes, H.H. Jr., 1977, Roughness characteristics of natural 

channels: U.S. Geological Survey Water-Supply Paper 

1849, 213 p.

Bovee, K.D., 1982, A guide to stream habitat analysis using 

the Instream Flow Incremental Methodology—Instream 

flow information Paper 12: U.S. Fish and Wildlife Service, 

Office of Biological Services, FS/OBS-82/26, 249 p.

Bray, D.I., 1982, Flow resistance in gravel-bed rivers, in Hey, 

R.D., Bathurst, J.C., and Thorne, C.R., Gravel-bed rivers, 

fluvial processes, engineering and management: New York, 

Wiley, p. 109–137. 

Burbank, W.S., Eckel, E.B., and Varnes, D.J., 1947, The 

San Juan region, in Vandenvilt, J.W., Mineral resources 

of Colorado: Denver, Colo., Mineral Research Board, 

p. 396–446. 

Capesius, J.P., and Stephens, V.C., 2009, Regional regression 

equations for estimation of natural streamflow statistics in 

Colorado: U.S. Geological Survey Scientific Investigations 

Report 2009–5136, 46 p.
References Cited 27

Elliott, J.G., and Capesius, J.P., 2009, Geomorphic changes 

resulting from floods in reconfigured gravel-bed river channels in Colorado, USA, in James, L.A., Rathburn, S.L., and 

Whittecar, G.R., eds., Management and restoration of fluvial 

systems with broad historical changes and human impacts: 

Boulder, Colo., Geological Society of America Special 

Paper 451, p. 173–198.

Elliott, J.G., and Parker, R.S., 1999, Reconfigured-channel 

monitoring and assessment program: U.S. Geological Survey Water-Resources Investigations Report 99–4111, 6 p.

Environmental Systems Research Institute, Inc., 2010, 

ArcGIS—A complete integrated system: Redlands, Calif., 

Environmental Systems Research Institute, Inc., accessed 

Oct. 17, 2011, from http://www.esri.com/software/arcgis/.

Freeman, L.A., Carpenter, M.C., Rosenberry, D.O., Rousseau, 

J.P., Unger, R., and McLean, J.S., 2004, Use of submersible 

pressure transducers in water-resources investigations: U.S. 

Geological Survey Techniques of Water-Resources Investigations, book 8, chap. A, 65 p.

Guzzi, Raffaela, and Parise, Mario, 1992, Surface features 

and kinematics of the Slumgullion landslide, near Lake 

City, Colorado: U.S. Geological Survey Open-File Report 

92–252, 45 p. 

Helsel, D.R., and Hirsch, R.M., 2002, Statistical methods in 

water resources: U.S. Geological Survey Techniques of 

Water-Resources Investigation, book 4, chap. A3, 523 p.

Hickman, Terry, and Raleigh, R.F., 1982, Habitat suitability 

index models—Cutthroat trout: U.S. Fish and Wildlife Service Biology Report, vol. 82, no. 10.5, 38 p.

Hirsch, R.M., 1982, A comparison of four streamflow record 

extension techniques: Water Resources Research, v. 18, 

no. 4, p. 1081–1088.

Homer, Collin, Huang, Chengquan, Yang, Limin, Wylie, B.K., 

and Coan, Michael, 2004, Development of a 2001 National 

Land Cover database for the United States: Photogrammetric 

Engineering and Remote Sensing, v. 70, no. 7, p. 829–840.

Julien, P.Y., 2010, Erosion and sedimentation second edition: 

Cambridge, United Kingdom, The Cambridge University 

Press, 371 p.

Komar, P.D., 1987, Selective gravel entrainment and the 

empirical evaluation of flow competence: Sedimentology, 

v. 34, p. 1165–1176.

Lake Fork Valley Conservancy, 2010, Lake Fork River restoration project: Lake City, Colo. ,Lake Fork Valley Conservancy, 4 p. 

Lemmon, P.E., 1956, A spherical denisometer for estimating 

forest overstory density: Forest Service Science, v. 2, no. 4, 

314–320 p.

Leopold, L.B., and Wolman, M.G., 1957, River channel 

patterns—Braided, meandering and straight: U.S. Geological Survey Professional Paper 282-B, p. 39–84. 

Lindsey, B.D., Breen, K.J., Bilger, M.D., and Brightbill, R.A., 

1998, Water quality in the lower Susquehanna River Basin, 

Pennsylvania and Maryland, 1992–95: U.S. Geological Survey Circular 1168, accessed April 10, 2012, at http://pubs.

er.usgs.gov/publication/cir1168. 

Lisle, T.E., Nelson, J.M., Pitlick, John, Madej, M.A., and 

Barkett, B.L., 2000, Variability of bed mobility in natural, 

gravel-bed channels and adjustments to sediment load at 

local and reach scales: Water Resources Research, v. 26, 

no. 12, p. 3743–3755.

McDonald, R.R., Bennett, J.P., and Nelson, J.M., 2001, The 

USGS Multi-Dimensional Surface Water Modeling System, in Seventh Federal Interagency Sedimentation Conference, March 25–29, 2001, Reno, Nev., Proceedings: 

SEDHYD, p. I161–I-167, accessed April 5, 2011, at http://

pubs.usgs.gov/misc/FISC_1947-2006/pdf/1st-7thFISCsCD/7thFISC/7Fisc-V1/7FISC1-1.pdf. 

McDonald, R.R., Nelson, J.M., and Bennett, J.P., 2005, Multidimensional surface-water modeling system user’s guide: 

U.S. Geological Survey Techniques and Methods, book 6, 

chap. B2, 156 p.

McDonald, R.R., Nelson, J.M., Kinzel, P.J., and Conaway, J., 

2006, Modeling surface-water flow and sediment mobility with the Multi-Dimensional Surface Water Modeling 

System (MD_SWMS): U.S. Geological Survey Fact Sheet 

2005–3078, 6 p.

Milhous, R.T., 1982, Effect of sediment transport and flow 

regulation on the ecology of gravel-bed rivers, in Hey, R.D., 

Bathhurst, J.C., and Thorne, C.R., eds., Gravel-bed rivers: 

Chichester, England, Wiley, p. 819–842.

Millar, R.G., and Quick, M.C., 1994, Flow resistance of highgradient gravel channels, in Cotroneo, G.V., and Rumer. 

R.R. (eds.), Hydraulic engineering ‘94: American Society of 

Civil Engineers, Buffalo, N.Y., p. 717–721.

Mueller, D.S., and Wagner, C.R., 2009, Measuring discharge 

with acoustic Doppler current profilers from a moving boat: 

U.S. Geological Survey Techniques and Methods 3A–22, 

72 p.

Nelson, J.M., Bennett, J.P., and Wiele, S.M., 2003, Flow and 

sediment-transport modeling, in Kondolf, G.M., and Piegay, 

H., eds., Tools in fluvial geomorphology: Chichester, England, Wiley, p. 539–576.

Nelson, J.M., and McDonald, R.R., 1997, Mechanics and 

modeling of flow and bed evolution in lateral separation 

eddies: Bureau of Reclamation, Glen Canyon Environmental Studies Report, 69 p.
28 Hydraulic, Geomorphic, and Trout Habitat Characteristics, Lake City, Colorado, Water Years 2010–2011 

Parker, Gary, Klingman, P.C., and McLean, D.G., 1982, 

Bedload and size distribution in paved gravel-bed streams: 

American Society of Civil Engineers, Journal of the 

Hydraulics Division 108(HY4), p. 544–571.

Pielke, R.A., Sr., Doesken, N., and Bliss, O., 2003, Climate of 

Colorado—Climatology report 60: Fort Collins, Colo., Colorado State University, Department of Atmospheric Science.

Powell, D.M., and Ashworth, P.J., 1995, Spatial pattern of flow 

competence in bed load transport in a divided gravel bed 

river: Water Resources Research, v. 31, no. 3, p. 741–752.

Raleigh, R.F., Zuckerman, L.D., and Nelson, P.C., 1986, Habitat suitability index models and in stream flow suitability 

curves—Brown trout, revised: U.S. Fish Wildlife Service 

Biology Report, vol. 82, no. 10.124, 65 p.

Rantz, S.E., and others, 1982, Measurement and computation 

of streamflow—Volume 1, Measurement of stage and discharge: U.S. Geological Survey Water-Supply Paper 2175, 

v. 1, p. 1–284.

Richards, Keith, 1982, Rivers—Form and process in alluvial 

channels: London, Methuen, 358 p.

Thompson, D.M., Nelson, J.M., and Wohl, E.E., 1998, 

Interactions between pool geometry and hydraulics: Water 

Resources Research, v. 34, no. 12, p. 3673–3681. 

Trimble Navigation Limited, 2009, Trimble® R8 GNSS 

receiver user guide, version 4.11, revision A: Dayton, Ohio, 

Trimble Navigation Limited, 50 p., accessed Nov. 4, 2011, 

at http://www.al-top.com/sites/default/files/0Trimble_

R8-R6-R4-5800M3_ENG.pdf.

Turnipseed, D.P., and Sauer, V.B., 2010, Discharge measurements at gaging stations: U.S. Geological Survey Techniques and Methods, book 3, chap. A8, 87 p.

Tweto, Ogden, comp., 1979, Geologic map of Colorado: U.S. 

Geological Survey Map, scale 1:500,000.

Tweto, Ogden, and Sims, P.K., 1963, Precambrian ancestry of 

the Colorado Mineral Belt: Geological Society of America 

Bulletin, v. 74, p. 991–1014.

U.S. Census Bureau, 2011, Population finder: U.S. Census 

Bureau, accessed June 26, 2011, http://www.census.gov/.

U.S. Department of Agriculture, 2009, Part 654—Stream restoration design: U.S. Department of Agriculture, National 

Engineering Handbook, 714 p. 

U.S. Geological Survey, 2010a, 09124500 Lake Fork at 

Gateview, CO: U.S. Geological Survey Water Data Report, 

accessed August 9, 2011, http://wdr.water.usgs.gov/wy2010/

pdfs/09124500.2010.pdf.

U.S. Geological Survey, 2010b, StreamStats—Colorado: U.S. 

Geological Survey, accessed August 9, 2011, http://water.

usgs.gov/osw/streamstats/colorado.html.

Western Regional Climate Center, 2011, Colorado climate 

summaries: Western Regional Climate Center, accessed 

June 26, 2011, http://www.wrcc.dri.edu/climate-summaries/.

Wilcock, P.R., and McArdell, B.W., 1993, Surface-based 

fractional transport rates—Mobilization thresholds and 

partial transport of a sand-gravel sediment: Water Resources 

Research, v. 29, no. 4, p. 1297–1312.

Wolman, M.G., 1954, A method of sampling coarse river-bed 

material: American Geophysical Union Transactions, v. 35, 

p. 951–956.

Publishing support provided by:

Denver Publishing Service Center, Denver, Colorado

For more information concerning this publication, contact:

Director, USGS Colorado Water Science Center

Box 25046, Mail Stop 415

Denver, CO 80225

(303) 236-4882

Or visit the Colorado Water Science Center Web site at:

http://co.water.usgs.gov/
Williams and others—Hydraulic, Geomorphic, and Trout Habitat Characteristics, Hinsdale County, Lake City, Colo, Water Years 2010–2011—SIR 2015–5043

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20155043