Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 26, 2006
Publication Date: N/A
We demonstrate an approach to reduce the anticipated increase in stormwater runoff from development under conventional subdivision design by incorporating hydrologic factors into a land suitability analysis and a low-impact subdivision design. A typical land suitability analysis assesses attributes such as slope, soil, aquifer recharge areas, floodplains, scenic areas, and wildlife habitats. These factors are then weighted to reflect their relative importance in determining the suitability of a particular land use in a given area (Wang 2004). Formal site analysis procedures incorporating impacts on stormwater runoff remain poorly-defined, yet offer good prospects for improving the effectiveness of suitability analysis. As a contrast to the conventional subdivision design, the tenets of open-space conservation design emphasize the management of residential growth within a framework of protected natural areas and green space for communal use (Arendt 1996, 1999; see also Felson and Pickett 2005). The study site is a 3 hectare experimental watershed located within the North Appalachian Experimental Watershed (NAEW) in Ohio, which is a part of a network of experimental watersheds operated by the United States Department of Agriculture (USDA). Volume and peak runoff values were calculated with TR-55. Three scenarios were compared – pre-development, conventional residential subdivision design and low-impact residential subdivision design with the same number of dwellings. The pre-development land use is in a maintained hay meadow. The conventional design follows a typical checkerboard layout of dwellings arranged in a circular pattern about a cul-de-sac, which is accessed by a wide street. For the low-impact development scenario, a land suitability analysis was conducted to determine the areas that would yield minimal departure from natural conditions in terms of runoff response. We selected suitability factors that would contribute to the minimization of post-development runoff volume and peak discharge - slope and soil drainage represented by a qualitative hydrologic soil group classification. The most suitable areas were subsequently subdivided based on the open space conservation design concepts.
For the most frequent storm recurrence interval (1 year) conventional development increased runoff depth by 70 percent and over 100 percent for peak discharge, from the pre-development condition. The increases of runoff depth and peak discharge for a 2-yr storm (a popular design standard for municipal stormwater infrastructure), were 56 and 70 percent, respectively. For the low-impact development, the increase of runoff relative to the pre-development condition is less than that of the conventional development scenario. We estimated that for the most frequent storms, runoff depth and peak discharge were increased by 20 and 33 percent, respectively. Runoff response of the low-impact scenario declines to a relatively uniform level for a storm recurrence interval greater than 10 years, compared to the overall higher runoff response to conventional development throughout the continuum of storms. Through the open-space conservation design, the low-impact scenario retained a greater amount of open-space and therefore enhanced opportunities for infiltration and more lengthy runoff flow paths. In addition to the hydrological improvement, the low impact design also can achieve economic benefits of reducing infrastructure construction and maintenance cost and social benefits by promoting livelier neighborhood. The increased potential for informal social interactions can be important components in the formation of neighborhood social ties, which strengthens sense of community among residents. Our approach and promising simulation results call for more widespread implementation of practical tests of landscape hydrologic response to creative, low-impact designs that are based on an enhanced suitability analysis.