Loading...
HomeMy WebLinkAboutHabitat_Modeling_(Payne)THE PROS AND CONS OF HABITAT MODELING AS A PLANNING TOOL PRESENTED TO: NORTH CAROLINA DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES DIVISION OF WATER RESOURCES ECOLOGICAL FLOWS SCIENCE ADVISORY BOARD OCTOBER 23, 2012 CHAPEL HILL, NORTH CAROLINA Presented by: Thomas R. Payne Certified Fisheries Scientist Normandeau Associates, Inc. WHAT’S AN AQUATIC HABITAT MODEL? In general, an aquatic habitat model for the  purpose of determining ecological flows is a tool  that creates an index relationship between flow  and some measure of hydraulic habitat. All aquatic habitat models assume a correlation  between target species abundance or biomass  and the hydraulic habitat index. Different models use different methods,  variables, and degrees of complexity. EXAMPLE OF PHYSICAL HABITAT INDEX •MesoHABSIM •Expert Habitat Mapping •Demonstration Flow Assessment •Hydraulic Habitat Modeling –PHABSIM –RHABSIM –RHYHABSIM –CASiMiR –River2D –EVHA –PHABSIM WIN 2002 –RSS –SEFA WHAT TOOLS ARE OUT THERE? MesoHABSIM (Parasiewicz 2001) MesoHABSIM (Parasiewicz 2001) EXPERT HABITAT MAPPING (McBain & Trush Habitat at 150 cfs Habitat at 200 cfs (Photo at 150 cfs) DEMONSTRATION FLOW ASSESSMENT (Railsback and Kadvany 2008) •Step 1 – Frame the Decision –Clearly define the instream flow decision process •Step 2 – Develop Conceptual Models of Flow Effects –Develop a shared understanding of important flow mechanisms •Step 3 – Select Habitat Metrics –Define the specific measures to be observed and quantified •Step 4 –Design and Conduct Field Observations –Observe and quantify or rate the selected habitat metrics •Step 5 –Analyze Results –Rank alternative flows by the quantity or value of the metrics •Step 6 –Negotiate Instream Flows DEMONSTRATION FLOW ASSESSMENT (Railsback and Kadvany 2008) INSTREAM FLOW INCREMENTAL METHODOLOGY (Bovee et al. 1998) PHABSIM!(Bovee and Milhous 1978) Hydraulics Microhabitat area per unit length of stream Channel structure Microhabitat suitability criteria 1-D HYDRAULIC HABITAT XSEC 1 XSEC 2Hydraulic Model Velocity: v i Depth: d i Substrate: s i Biological Model Velocity Cv Sv i Sd i Ss i Substrate Cs Hydraulic Habitat Index Flow AW S 2-D HYDRAULIC HABITAT 1-D HABITAT REPRESENTATION O O O O OO OOO OOO O Data points O O O O O OO O O O O O O O Data points O 2-D HABITAT REPRESENTATION DVASW @150 01234 VELOCITY IN FEET PER SECOND 0 1 2 3 DE P T H I N F E E T Cover 4 5 6 T1 = 15% T2 = 35% T3 = 35% T4 = 15% T2 T3 T4 T1 Scaled & weighted data points, 3‐axis frequency analysis N=132 Data Points Scaled by Suitability and Weight ALL METHODS GIVE HABITAT INDEXES SO WE HAVE A CURVE… •The Usual Options: –Peak of the Curve –Percentage of Peak of the Curve –Habitat Time Series –Habitat Duration –Rule Making –Negotiation –Settlement/Order/Litigation THE QUESTIONS THEN… •Do these habitat models have any validity? •What are the pros of habitat models? •What are the cons of habitat models? AQUATIC SPECIES USE DIFFERENT HABITAT TYPES •Most validation studies show that velocity,  depth, and substrate or cover variables do  correlate with biomass •The existence of empirical models argues  that habitat suitability varies with flow •The common experience of practitioners is  that habitat index curves do describe  observed habitat conditions POSITIVE EVALUATIONS OF MODELS THE PROS FOR HABITAT MODELING… •Longevity –Still here after 35 years of experience •Popularity –Most common method in U.S. and worldwide •Defensibility –No court challenge has been successful •Reviewability –Results can be independently reviewed THE CONS FOR HABITAT MODELING… •Insufficient validation for many species –Only trout and smallmouth bass studied •Costly and time consuming –Cost: $10K‐500K+   Time: 1 month‐2 years •Intensive field data requirements –Channel topography, suitability criteria •High technical knowledge –You  need to know what you’re doing CRITIQUES ARE GENERALLY OFF-BASE •Focus often on: –Lack of validation studies –Lack of instantaneous responses –Non‐statistical sampling strategies –Details instead of big picture •Few reviewers understand the models •No reviewer has ever said the results are  ecologically inaccurate THE BOTTOM LINE •“There is a there there.” •Proper understanding and use of habitat  models is critical. •Habitat models are not fish position  models, they are frequency analyses. MODELS AS FREQUENCY ANALYSIS QUALIFIERS •Suitability criteria (HSC) drive the models  – hydraulics are minor in comparison •Site‐specific HSC are much better than  generic HSC •Validation procedures for HSC rarely work •Professional judgment HSC can work if  done with expert knowledge •Results must make sense! APPLICATION TO STREAM CLASSIFICATION •There is an additional relationship between  habitat suitability and physical stream  characteristics than only to hydrologic  patterns or characteristics •Evidence: –Washington Toe ‐of‐Bank Method –Hatfield and Bruce Meta‐Analysis –Payne AFS BioEngineering Meta‐Analysis RECOMMENDATION •Continue with hydrologic classification  process •Supplement with physical characteristics –Channel width –Channel gradient –Channel elevation –Pool/riffle ratio –Predominant substrate type –Others? QUESTIONS AND DISCUSSION…