# Presentation: 093649

## Florida Fish and Wildlife Conservation Commission

**Florida Fish and Wildlife Conservation Commission**

- PHABSIM:

**Eric Nagid and Gary Warren**

## Physical HABitat SIMulation System

- _P_hysical _HAB_itat _SIM_ulation System

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

-   Has been successfully defended in court.

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

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

**Notes:**
Amount of habitat is the decision variable, not abundance, biomass, production, or predation.

PHABSIM is the scientific modelling component of the IFIM, developed by USGS fisheries biologists in the late 70s – early 80s as a system to equitably manage streamflows for the good of all involved parties.  IFIM combines the modeling component with social science components, such as stakeholder inclusion and negotiation. 

## Primary Components of PHABSIM

-   **Hydrological**

- Field measurements of physical habitat conditions
-       along transects.

- velocity
- depth
- substrate / cover

- 2.  Hydrological modeling of flow / stage relationships.

## PHABSIM Flowchart

**PHABSIM Flowchart**

## PHABSIM Output

**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.

**Notes:**
Output of the PHABSIM model is the weighted usable area of habitat for a selected species.
The model expressed as a simple equation looks more complicated than it really is.
Weighted usable area is simply the sum of the surface areas of the identified cells at a given flow rate (which is the hydrological portion of the model) times the composite suitability of the identified cells at the same given flow (which is the biological component of the model).

## Biological Suspectsfor the Suwannee River Basin

- Limited range – SSC
- Recreationally important
- Easily sampled

- Flow sensitive
- Sessile
- Easily sampled

**Suwannee bass**
- (*Micropterus notius*)

**Net-spinning caddisflies**
- (Hydropsychidae)**,**
**Mayflies **(Baetidae)

## Criticisms of PHABSIM

**Criticisms of PHABSIM**

**General:**

## Evaluation of Stream Flow Models

- Selecting and Modifying the Most Appropriate Model for Florida Streams

-   PHABSIM / IFIM

-  River 2D

-  System Impact Assessment Model (SIAM)

-  Channel Units / Channel Types (CU / CT)

-  Indicators of Hydrologic Alteration (IHA)

**Notes:**
A model that we are strongly considering is PHABSIM, which is a component of a decision support system called the instream flow incremental methodology, developed by the USGS at their Ft. Collins Science Center. 

River 2D newest of models; incorporates a second, lateral, flow dimension.

CU/CT an approach under development by USGS Co-op unit for GA

IHA developed by Nature Conservancy; focuses on impact of high water events.

SIAM integrates water quantity, water quality, and biological models. 

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