Habitat_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…