Milburnie Dam: A case study for management implications of dam removal mitigation banks

Abstract

Dam removal is a commonly used method for restoring rivers and is being widely considered for mitigation banks, generating compensatory mitigation credits to offset unavoidable aquatic ecosystem impacts. The U.S. Army Corps of Engineers regulates such projects, and must develop and implement guidance for selection or requirement of success criteria and associated metrics, including consideration of alternative metrics and acceptable measurement techniques. Our evaluation of two alternative metrics-wetland extent via remote sensing and dissolved oxygen via in situ sensors-following removal of the Milburnie Dam suggests that these metrics were insensitive to removal and/or that available data for use by project managers did not sufficiently capture ecosystem response to dam removal. To meet the goals of evaluating mitigation to ensure positive ecosystem response, alternative metrics or measurement techniques are needed for dam removal.