Regional Wetland Inventory and Restoration Strategy
Clark County Public Works
(Merit Award for Planning and Analysis, American Society of Landscape Architects, Oregon Chapter, 2006)

Vigil-Agrimis, Inc. (VAI) worked with Clark County Public Works to:
(1) Create an atlas of potential wetlands using a GIS based predictive model; (2) Conduct field research to verify the model and identify reference wetlands; and (3) Develop a mitigation banking strategy for the County. The project covered approximately 200,000 acres of rapidly developing land in southwest Clark County. The area included 11 watersheds that ranged from 5 to 90 square miles in size.

The GIS predictive wetlands model used available data including 1-foot elevation LiDAR data and high resolution aerial photography. VAI teamed with a subconsultant to perform field verification at over 100 locations on both private and public land. Four field teams completed the work in an intensive three-week field effort. Teams collected vegetation data, using GPS to locate wetland boundaries, and assessed wetland functions using Washington State Wetland Rating System for Western Washington. Field data was used to modify the wetland model before it was published as the Clark County Atlas of Potential Wetlands. Approximately 20 reference wetlands were identified parallel to the model development. Field data collection at these sites was similar, but more intensive than that collection at the field verification sites. The GIS modeling and reference wetland components of the project allowed the team to locate wetland resources, and describe the relationship between landscape position, hydrogeomorphic classification, size, condition and functions. This understanding of wetlands in the County was incorporated 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.

Deliverables for this project included GIS shapefiles and database with NGDC compliant metadata, an illustrative report written for lay audiences and County staff, and the Clark County Atlas of Potential Wetlands.