Florida Fish and Wildlife Conservation Commission

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Florida Fish and Wildlife Conservation Commission
Eric Nagid and Gary Warren
PHABSIM
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Physical HABitat SIMulation System

• Combines hydrological and biological models
• to predict changes in habitat area over a
  range
• of discharges.

• Is a component of the Instream Flow
• Incremental Methodology (IFIM).

• Is the most widely used model for deductive
• estimation of biological effects of stream
  flow
• alteration.

• Has been successfully defended in court.

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Primary Components of PHABSIM

• Hydrological

• Field measurements of physical habitat conditions
• along transects.

• velocity
• depth
• substrate / cover

2. Hydrological modeling of flow / stage
relationships.
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PHABSIM Flowchart
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PHABSIM Output

Weighted Usable Area

• The usable area of habitat available, in a
• stream reach, to a given species at
• a given discharge.

• The product of velocity, depth, and
• substrate/cover preferences multiplied
• by cell size.

• WUAs are summed over an entire reach
• and used as an index of habitat quality
• and availability.

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Biological Suspectsfor the Suwannee River Basin
Suwannee bass (Micropterus notius)
Net-spinning caddisflies (Hydropsychidae), Mayflie
s (Baetidae)

• Limited range SSC
• Recreationally important
• Easily sampled

• Flow sensitive
• Sessile
• Easily sampled

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Criticisms of PHABSIM

General
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Evaluation of Stream Flow Models Selecting and
Modifying the Most Appropriate Model for Florida
Streams

• PHABSIM / IFIM

• River 2D

• Channel Units / Channel Types (CU / CT)

• Indicators of Hydrologic Alteration (IHA)

• System Impact Assessment Model (SIAM)

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