Constructed Wetland Suitability Analysis in Oregon

Abstract

Communities across Oregon have begun to take an interest in non-traditional approaches to stormwater management. Of these approaches, those designated as “Green Infrastructure” have begun taking a major role. Green Infrastructure is a blanket term to denote natural or semi-natural systems which perform a valuable service for human communities. Stormwater Green Infrastructure aims to capture, store, infiltrate, or slow down precipitation and runoff at the site level. Green Infrastructure has a number of benefits, including lower capital and operational costs versus traditional systems, flexibility in terms of scale, carbon sequestration dividends, and resilience to natural hazard events. Of particular note, constructed wetlands or extended wet ponds are a Green Infrastructure strategy successful in treating large volumes of stormwater and providing natural habitat for wildlife communities. According to the Environmental Protection Agency, these projects are defined as “treatment systems that use natural processes involving wetland vegetation, soils, and their associated microbial assemblages to improve water quality.” Many successful examples of constructed wetlands lie within small and mid-sized communities in places such as Arcata, California, Houghton Lake, Michigan, and Cannon Beach, Oregon. However, despite their realization in many places, constructed wetlands have yet to see widespread application across Oregon. Along with institutional resistance to change and maintenance concerns, a primary reason for this lack of investment is missing information on areas suitable for constructed wetland projects. Smaller communities in particular often lack the time, formal knowledge, and appropriate tools to perform a rigorous assessment of which locations in their community may be suitable. To address this shortfall, this report presents an automated Geographic Information System (GIS) suitability analysis tool for constructed wetland projects in Oregon. Rather than serving as a detailed “site selection” tool, this program is intended as a “site search” tool to identify the boundaries of suitable project areas and associated characteristics. The analysis itself is performed using a range of geographic data sets related to a variety of accepted constructed wetland practices and design techniques. To maintain the largest possible assortment of potential users, all datasets and the tool programming language within this program were gathered from open source locations such as the State of Oregon’s Spatial Data Library. To illustrate the applicability of this tool, a sample suitability analysis was performed in Cottage Grove, Oregon. This analysis was evaluated along with relevant local planning documents and case studies of successful constructed wetlands projects in various land use situations. These results have been presented to give greater direction in how this analysis tool might be utilized and applied by other Oregon communities.