The Ecosystem Functions Model (EFM): A Tool for Restoration Planning

Abstract

PURPOSE: The Ecosystem Functions Model (EFM) is a planning tool that analyzes ecosystem response to changes in flow regime. The U.S. Army Corps of Engineers’ Hydrologic Engineering Center (HEC) is developing the EFM and envisions environmental planners, biologists, and engineers using the model to help determine whether proposed alternatives (e.g., reservoir operations or levee alignments) would maintain, enhance, or diminish ecosystem health. Project teams can use the EFM to visualize existing ecologic conditions, highlight promising restoration sites, and assess and rank alternatives according to the relative enhancement (or decline) of ecosystem aspects. This software is a general tool, applicable to a wide range of ecotypes and Corps projects. BACKGROUND: The EFM was developed as part of the Sacramento and San Joaquin River Basins Comprehensive Study (Comprehensive Study). The Comprehensive Study, authorized by Congress in 1998, partners the U.S. Army Corps of Engineers (USACE) and the Reclamation Board of California in an effort to explore flood damage reduction and ecosystem restoration opportunities in the Central Valley, California. Conceptually, the EFM was formulated as a diverse list of interrelated ecosystem elements of concern to Comprehensive Study restoration efforts. However, at that time, no detail was attached to how these elements would be investigated spatially, temporally, or quantitatively. As development progressed, questions were raised regarding the actual workings of the EFM. Focus began to be placed on model construct and how it would be used to assess the ecosystem elements highlighted during conceptual development. The Study Team, California Department of Water Resources, HEC, and Jones and Stokes cooperatively developed the first quantitative version of the EFM, which used statistical analyses as indicators of ecosystem elements. HEC continued EFM development and constructed a model interface that allows users to: 1) specify and perform statistical analyses designed to provide insight to ecosystem dynamics and response to changes in flow regime, and 2) use GIS software to support restoration planning. MODEL DESCRIPTION Overview. EFM analyses typically involve: 1) statistical analyses of relationships between hydrology, hydraulics, and ecology, 2) hydraulic modeling, and 3) GIS programs to display results and other relevant spatial data. The EFM is a computer model that consists of a user interface and an ArcGIS extension. The hydraulic modeling portion of the EFM process is performed by existing independent software such as HEC’s River Analysis System (HEC-RAS).