Library of Habitat Models to Evaluate Benefits of Aquatic Restoration Projects on Fishes

Habitat models are used to evaluate impacts of water resource development activities such as flood control and navigation projects, and environmental benefits of restoration or mitigation projects. These models generally take the form of an index ranging from 0.0 (poor habitat) to 1.0 (optimum habitat), referred to as a Habitat Suitability Index (HSI). HSI's are used to weight acres of affected habitat, a method compatible with the commonly used Habitat Evaluation Procedure (www.fws.gov/policy/hbindex.cfm) or Instream Flow Incremental Methodology (www.fort.usgs.gov/Products/Software/IFIM/). Both of these methods multiply quality (i.e., HSI) and quantity (e.g., acres) to determine habitat conditions. HSI s represent the biological components of the evaluation (e.g., number of species, relative abundance) and their responses to changes in habitat conditions. The multiplicative product of HSI and acres of habitat is a unit (e.g., Habitat Unit, Weighted Usable Area) that can be compared among project alternatives and averaged over the life of the project (e.g., Average Annual Habitat Unit). The U.S. Army Engineer Research and Development Center (ERDC) continues to evaluate consequences of flood control, water supply, and navigation projects on fish assemblages, as well as benefits of aquatic restoration. Many of these projects have been completed through leveraged funds from Corps of Engineers Districts (primarily Vicksburg and Memphis Districts) and the Ecosystem Management and Restoration Research Program at ERDC. HSI models are based on field-derived correlations between biotic-abiotic variables, resulting in a library of regression equations developed over the past 10 years. The purpose of this technical note is to summarize the HSI models and describe their development and applicability as assessment tools in similar aquatic systems.