Comparing Stormwater Impacts and Costs on Three Neighborhood Plan Types

Abstract

This paper summarizes a comparison of three alternative plans for a demonstration development site for environmental impacts, particularly stormwater quantity and quality, and costs of development. Two of the three alternatives are representative of neighborhood plan types in many areas of the United States—a conventional low density pattern typical of many subdivision developments, and a more dense, mixed use new urbanist-influenced pattern. A third less common but lower environmental impact plan represents similar density and land use mixes to the mixed use plan with greater open space, urban forest and stormwater features. Each plan preserves different amounts of open space and pursues different approaches to infrastructure, urban forests and stormwater management. Comparing neighborhood development patterns from a stormwater perspective, the findings suggest that the higher densities, mixed uses and greater vehicular and pedestrian connectivity now encouraged in Oregon and elsewhere in the nation can either compete with or complement goals of water resource protection and stormwater runoff reduction. To become both complementary and cost-effective, strategic tradeoffs must be made between land dedicated to roads and parking and land dedicated to open space, urban forest and stormwater.