Evaluation of spatially dependent on-site detention basin policies
Date
2015
Authors
Augustine, Andrew John, author
Roesner, Larry, advisor
Niemann, Jeffrey, committee member
GironĂ¡s, Jorge, committee member
Stednick, John, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Stormwater detention basins are typically used for stormwater control in many communities across the United States. They are commonly constructed downstream of every new development to control post-development runoff, and are called "on-site" detention basins. It has been shown by multiple authors in the literature that the design of on-site detention basins with no consideration of their location (non-spatially dependent policies, or Non-SD) in the watershed can actually increase peak flows above post-development peaks that would occur in the absence of on-site detention basins. This is caused by on-site detention basins delaying the peak release of a particular subwatershed and combining with other peak flows in the watershed (McCuen 1974; McCuen 1979; Emerson et al. 2005). Strategies to combat this problem have been reported, but metrics used to judge their success are limited to the main channel of the watershed or the watershed outlet only, leaving its impact in the remaining other watershed locations unknown. In addition, some strategies have recommended increasing the storage of on-site detention basins, but this approach would increase construction and maintenance costs and reduce the amount of land available to developers. Validation of increased peak flows throughout the watershed when Non-SD policies are used to design on-site detention basins compared to no on-site detention in the watershed was investigated first. The Non-SD policies used in this study controlled the post-development 10 and 100-year peak flows to flows at or below their respective pre-development peak flows (Non-SD 1), and controlled the post-development 100-year peak flow to flows at or below the 2-year pre-development peak flow (Non-SD 2). Next, spatially dependent policies (SD policies) were created by altering the peak flow release from on-site detention basins that would have occurred under a Non-SD policy based on its location in the watershed. These peak flows were altered using a linear model and a piece-wise linear model. Results from SD policies were compared to those from Non-SD policies. Metrics used to evaluate the effectiveness of the on-site detention basin policies (both SD and Non-SD) were peak flows throughout the watershed and total watershed storage. All policies were tested on a watershed in Fort Collins, Colorado using the Urban Morpho-climatic Instantaneous Unit Hydrograph model. Results indicate that Non-SD polices effectively reduce peak flows throughout the watershed, and do not increase peak flows compared to a policy that uses no on-site detention. When compared against Non-SD 1, SD policies derived from the linear equation were successful at reducing peak flows at some 2nd and 3rd order channel and pipe intersections in the upper half of the watershed, while increasing peak flows at 2nd order channel and pipe intersections in the lower half of the watershed. The remaining intersections were not effected by this SD policy, and the total watershed storage was shown to increase. SD policies derived from the piece-wise linear model increased peak flows at 2nd order channel and pipe intersections in the lower half of the watershed. The remaining intersections were not affected by this SD policy, and watershed storage was shown to slightly decrease. When compared to Non-SD 2, SD policies had little to no effect on peak flows at any location in the watershed or on the watershed storage.
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Subject
detention basin
detention basin policy
on-site detention basin
on-site detention basin policy
policy
water resources management