Understanding Instream Flow Incremental Methodology (IFIM)

Joey Kleiner

IFIM: Instream Flow Incremental Methodology • The goal of an IFIM study is to show

the relationship between stream flows and available aquatic habitat • This Flow:Habitat relationship is

necessary for assessing potential downstream impacts on habitat resulting from upstream flow alterations

• A main product of an IFIM study is the Weighted Usable Area (WUA) table- an index showing habitat suitability for a given species over a range of flows

Steps in the IFIM Process

1) Habitat identification 2) Transect selection 3) Species selection, habitat suitability criteria (HSC) compilation 4) Collection of field hydraulic and habitat data 5) Physical Habitat Simulation System (PHABSIM) model 6) PHABSIM output of “Weighted Usable Area” (WUA)

The Formation of Fish Habitat

• Fish habitat is dependent on:• Depth • Velocity • River bottom conditions

(substrate/cover)

• Depth and velocity conditions change with increasing flow

• Example: Riffles, runs, pools

The Mapping of Fish Habitat

• The first step in an IFIM study is the identification of aquatic habitats within the study area

• The stream is divided into “study reaches” at points where significant changes in channel morphology or flow occur • The primary types of

mesohabitats within these reaches need to be identified to facilitate transect site selection

The Mapping of Fish Habitat (cont.)

• Habitat mapping is achieved through the use of existing institutional knowledge, aerial photographs, GIS, GPS, and site-specific data obtained through “float trips”

Transect Locations

• Once the river reaches and habitat types are identified and mapped, transect locations for the collection of field hydraulic data are determined • Transects are located in areas

representative of the hydraulic/habitat conditions observed in that reach

Field Data Collection

• Physical Habitat Simulation (PHABSIM) software is used to simulate the relationship between streamflow and habitat for various species and life stages of fish • Data collected in the field at each transect location is used to calibrate

PHABSIM for the study reach of interest • Data is collected at sampling stations/cells equally spaced along each

transect • Data collected at each cell include: • Water surface elevation (WSE) • Water velocity • Substrate/cover

Field Data Collection (Cont.)

• WSE and velocity data are typically collected at each transect under 3 different “target flows” (low flow, medium flow, high flow) • The target flows observed at the transects are achieved by altering dam releases upstream • Example of target flows: 50, 150, and 300 cfs (measured by a USGS gage within the study reach)

• By entering the measurements taken at 3 flows, PHABSIM is able to interpolate WSE and velocity values for flows other than the 3 observed in the field

Field Data Collection (Cont.)

• Cover/substrate measurements are taken during the lowest target flow• Codes for cover/substrate are

assigned to each cell along a transect

Species Selection and HSC

• A set of fish species needs to be selected for Flow:Habitat analysis • The species selected must be present within the

study reach

• The species chosen are usually the ones most affected by changes in flow

• Each species has corresponding Habitat Suitability Criteria (HSC) that can be gathered from existing sources• HSC quantify habitat quality for each species/life

stage based on flow velocity, depth of the water column and substrate/cover

• HSC utilize a preference index ranging from 0 (least preferred) to 1 (most preferred)

PHABSIM Development

• A hydraulic model within PHABSIM is created for each study transect • The hydraulic model consists of a water surface model and a velocity model

• The water surface and velocity models are developed and calibrated using the 3 data sets obtained in the field (1 data set from each of the 3 target flows)

• The calibrated hydraulic model is able to simulate WSE and velocity values at each cell along the transect for any flow value• The hydraulic model at each transect is

combined with the HSC to produce a WUA table showing the Flow:Habitat relationship at that transect

PHABSIM Development (Cont.)

• HSC for water depths, water velocities and substrate/cover are used to rank the suitability of each model cell in a transect• This uses a multiplicative approach where suitability indexes (on a scale from 0.0 to 1.0) for a single

cell in a transect are multiplied together (depth*velocity*substrate) to produce a composite suitability score for that cell (0.0 to 1.0)

• The suitability score of a cell is used to weight the area of that cell to produce a “Weighted usable area” (WUA) value for that cell

• The weighted values for all cells in a transect are summed to produce a total WUA for that transect

WUA = suitability-weighted samples of area • WUA is an index to the microhabitat availability

WUA Development within PHABSIM

• By repeating this process for multiple species/lifestages over an entire range of flows, a WUA table can be produced for each transect displaying the flow:habitat relationship for each species/lifestage of interest

• The WUA tables from each transect in a reach can be averaged together using weighting factors to produce a single WUA table representative of the entire reach • WUA tables from each transect are weighted so that each transect's

contribution to the reach-WUA is indicative of the amount of each habitat type (% area) present in the reach • Area weighting factors are determined during the development of the habitat

maps

WUA Development within PHABSIM (Cont.) • Weighting transect-WUAs to produce a single reach-WUA table:

% of each habitat type present in a single reach

Weighting factors for each transect in the reach

WUA Example

WUA ExampleRedBSun

Juvenile Adult Spawning Adult Spawning Spawning Slow Fast Slow Fast10 8,650 4,062 18,545 1,585 112 19,431 8,020 288 17,310 1,17220 13,381 8,447 18,820 2,071 176 19,960 4,740 693 18,889 2,53640 22,200 16,204 18,799 3,537 293 19,972 2,488 1,137 21,407 5,26160 28,774 20,791 18,726 5,323 394 19,880 1,643 1,964 23,420 7,96980 32,940 22,872 18,496 7,642 482 19,876 1,532 2,631 25,292 10,168

100 36,522 24,433 17,592 10,083 574 19,626 1,479 2,807 26,489 12,558120 39,761 25,291 16,474 13,036 684 19,183 1,644 3,136 27,450 15,079160 44,456 26,838 13,635 19,659 893 16,465 1,062 3,354 28,132 20,133200 47,555 27,499 9,493 26,700 1,096 13,042 667 2,065 27,429 24,033250 49,959 28,079 7,368 33,427 1,247 11,139 615 1,564 26,722 27,576300 51,581 28,710 6,000 39,508 1,379 9,454 430 1,071 25,607 30,227350 52,257 28,869 4,792 44,866 1,456 7,854 486 737 24,197 30,935400 51,643 28,429 3,887 49,235 1,498 6,617 546 611 22,672 30,704450 50,249 27,458 3,261 52,640 1,477 5,411 645 517 20,851 29,608500 48,364 26,438 2,821 55,144 1,407 4,514 484 413 19,294 28,123550 46,047 25,640 2,554 56,623 1,322 3,889 334 333 17,737 26,710600 44,087 24,248 2,144 57,514 1,201 3,229 189 279 16,570 25,499650 42,233 23,011 1,925 58,020 1,099 2,898 155 197 15,305 23,741700 40,196 22,018 1,769 58,065 976 2,565 173 154 14,093 22,428750 38,186 20,711 1,503 57,884 831 2,121 196 125 12,972 20,835800 36,218 19,469 1,392 57,521 661 1,875 216 84 12,034 19,426900 33,366 17,012 1,114 56,349 469 1,557 186 51 10,274 16,857

1,000 29,379 14,898 962 54,663 329 1,339 122 31 8,706 14,5191,100 26,655 13,299 793 52,923 197 1,178 89 24 7,588 12,331

Smallmouth Bass N Hogsucker Shallow Guild Deep GuildWUA (ft²/1,000 ft stream)

Flow(cfs)

WUA ExampleRedBSun

Juvenile Adult Spawning Adult Spawning Spawning Slow Fast Slow Fast10 8,650 4,062 18,545 1,585 112 19,431 8,020 288 17,310 1,17220 13,381 8,447 18,820 2,071 176 19,960 4,740 693 18,889 2,53640 22,200 16,204 18,799 3,537 293 19,972 2,488 1,137 21,407 5,26160 28,774 20,791 18,726 5,323 394 19,880 1,643 1,964 23,420 7,96980 32,940 22,872 18,496 7,642 482 19,876 1,532 2,631 25,292 10,168

100 36,522 24,433 17,592 10,083 574 19,626 1,479 2,807 26,489 12,558120 39,761 25,291 16,474 13,036 684 19,183 1,644 3,136 27,450 15,079160 44,456 26,838 13,635 19,659 893 16,465 1,062 3,354 28,132 20,133200 47,555 27,499 9,493 26,700 1,096 13,042 667 2,065 27,429 24,033250 49,959 28,079 7,368 33,427 1,247 11,139 615 1,564 26,722 27,576300 51,581 28,710 6,000 39,508 1,379 9,454 430 1,071 25,607 30,227350 52,257 28,869 4,792 44,866 1,456 7,854 486 737 24,197 30,935400 51,643 28,429 3,887 49,235 1,498 6,617 546 611 22,672 30,704450 50,249 27,458 3,261 52,640 1,477 5,411 645 517 20,851 29,608500 48,364 26,438 2,821 55,144 1,407 4,514 484 413 19,294 28,123550 46,047 25,640 2,554 56,623 1,322 3,889 334 333 17,737 26,710600 44,087 24,248 2,144 57,514 1,201 3,229 189 279 16,570 25,499650 42,233 23,011 1,925 58,020 1,099 2,898 155 197 15,305 23,741700 40,196 22,018 1,769 58,065 976 2,565 173 154 14,093 22,428750 38,186 20,711 1,503 57,884 831 2,121 196 125 12,972 20,835800 36,218 19,469 1,392 57,521 661 1,875 216 84 12,034 19,426900 33,366 17,012 1,114 56,349 469 1,557 186 51 10,274 16,857

1,000 29,379 14,898 962 54,663 329 1,339 122 31 8,706 14,5191,100 26,655 13,299 793 52,923 197 1,178 89 24 7,588 12,331

Smallmouth Bass N Hogsucker Shallow Guild Deep GuildWUA (ft²/1,000 ft stream)

Flow(cfs)

Sources:Appomattox River Instream Flow (IFIM) Study: George F. Brasfield Dam to Harvell Dam, Final Report. Hunt Valley, MD: EA Engineering, Science, and Technology, Inc., 2012 http://deq2.bse.vt.edu/sifnwiki/images/4/4f/G_Appomattox_River_Instream_Flow_IFIM_Study.pdf

Averett et. al. Stream Habitat Modeling to Support Water Management Decisions for the North Fork Shenandoah River, Virginia, Final Report. Blacksburg, VA: Virginia Tech Dept. of Fisheries & Wildlife Sciences, 2004 http://deq3.bse.vt.edu/sifnwiki/images/f/fc/Ifim_nf_shen_doc.pdf

Bovee, K. D. et al. Stream Habitat Analysis Using the Instream Flow Incremental Methodology. Fort Collins, CO: U.S. Geological Survey, 1998 http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA361209

Instream Flow Incremental Methodology (IFIM) Studies on the North Anna and Pamunkey Rivers, Virginia, Final Report. Sparks, MD: EA Engineering, Science, and Technology, Inc., 2009 http://deq3.bse.vt.edu/misc/ifim_northanna_notebook.pdf

Krstolic, J.L., and Ramey, R.C. South Fork Shenandoah River habitat-flow modeling to determine ecological and recreational characteristics during low-flow periods: U.S. Geological Survey Scientific Investigations Report 2012–5081, 64 p. 2012 http://pubs.usgs.gov/sir/2012/5081/pdf/sir2012-5081.pdf

Payne, T. et. al. Appalachian Power Company Claytor Hydroelectric Project No. 793-018, Instream Flow Needs Study, Final Report. Arcata, California: Thomas R. Payne & Associates, 2008. http://www.claytorhydro.com/documents/studyReportsDocs/ClaytorIFNStudy-FinalReport12-30- 08.pdf

Schreiner et. al. Habitat Assessment of the Potomac River From Little Falls to Seneca Pool, Final Report. Columbia, MD: Versar, Inc., 2003 http://esm.versar.com/PPRP/potomac/2002report.htm

Stalnaker, C. et al. The Instream Flow Incremental Methodology, A Primer for IFIM. U.S. Dept. of the Interior Report 29, 1995. https://www.fort.usgs.gov/sites/default/files/products/publications/2422/2422.pdf