Cosumnes River Mitigation Bank: A Case Study in the Approach and Challenge of Developing and Crediting a Mitigation Bank in a Dynamic Riverine System; Matthew Gause

 

¹Ecological Resources and Land Stewardship Director – Westervelt Ecological Services

 

 

Wetland mitigation projects and mitigation banks often focus on the “in-kind” replacement of lost wetland and/or species habitat functions and values.  To this end, the “in-kind” approach has often resulted in mitigation that restores specific quantifiable terrestrial and aquatic habitat features under the assumption that these features have a high degree of spatial and temporal stability and will exist perpetually with minimal human intervention.  In dynamic riverine systems, these features and their functional capacities can vary from year to year or be completely altered during a significant flood or drought. This dynamic nature can result in significant spatial and/or temporal variability in resource function across the landscape. Traditionally, wetland and stream mitigation banks have approached mitigation crediting on a specific habitat element acreage and/or linear measurement basis to arrive at a crediting valuation.  These crediting methods typically fail to accommodate the very dynamic nature of many of the riverine and floodplain systems of the western United States.  In California’s Central Valley, the Cosumnes Floodplain Mitigation Bank on the Cosumnes River offers a case study on successfully accommodating the dynamic nature of natural riverine processes within the highly regulated framework of mitigation banking in California.  The presentation will focus on the interplay among performance criteria, crediting method, ecological processes, and site durability elements (e.g., conservation easement, long-term management plan and long-term stewardship fund).