Using RCHARC to Evaluate Large River Restoration Alternatives

The Riverine Community Habitat Assessment and Restoration Concept (RCHARC) has been used for restoration planning and impact analysis for the main stem Missouri River and a number of rivers in the southeastern USA. The RCHARC contrasts depth and velocity distributions from a reference stream against distributions from different operational or channel alternatives in a target stream. The more nearly depth and velocity distributions of an alternative resemble distributions from the reference stream, the more highly that alternative is ranked. For the Missouri River application, the reference system was the historical river as defined by HEC-II analysis using historical (preproject) cross sections and historical mean monthly flows. For other applications, relatively unimpacted river reaches within the same basin have been used as the reference. This same approach can be employed to evaluate channel alternatives instead of flow alternatives for river restoration studies. The results of the analysis allowed the Corps of Engineers to rank operational alternatives by their ability to provide hydraulic habitat most likely to restore native warm water fishes. It was also used to develop design criteria for a major side channel restoration project on the Missouri River. The community-level perspective and whole-river descriptions used in the RCHARC facilitate assessments of ecosystem integrity of target systems.