Regional Wetland Inventory and Restoration Strategy

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Washington’s Clark County is among the fastest growing counties in the Pacific Northwest and the nation. With the demands for development, capital improvements, and infrastructure updates, Clark County determined that stronger regional coordination or a county mitigation banking program would streamline permitting and maximize mitigation benefits to wetlands.

ESA developed an atlas of potential county wetlands using a GIS-based predictive model covering approximately 200,000 acres of rapidly developing southwestern Clark County. The model encompassed 11 watersheds ranging from 5 to 90 square miles in size. We met regularly with Clark County to discuss project progress and collaborate on refining the data gathering methods and findings. Using available data, including one-foot elevation LiDAR and high-resolution aerial photography, our team performed field verification at more than 100 locations on both private and public lands in an intensive three-week effort. Field data including vegetation, GPS wetland boundaries, and wetland functions were used to modify the predictive model. Parallel to the model development, 20 reference wetlands were identified for more intensive field data collection. This additional data provided an understanding of wetland resources and their complex relationships. We incorporated the information into a GIS analysis of patterns of development and public investment in infrastructure to identify likely wetland impacts and the associated loss of functions. This information was used to geographically prioritize wetland preservation actions and to develop a wetland mitigation strategy for the County.

ESA collaborated with Clark County to produce an illustrative planning document that guides regional wetland protection and wetland mitigation activities, supplemented by an atlas of potential county wetlands and GIS shapefiles and a database.

This project received the Oregon Chapter of the American Society of Landscape Architects 2006 Merit Award for Analysis and Planning. 

Specialized Services

  • County and city regulations and mandates
  • Wetland assessments