Evaluation of a storm flow management design to contain runoff within the watershed using ponds in series

Abstract

In a closed basin, where runoff is not allowed to discharge outside the watershed, a systematic design of storm water routing with retention facility is necessary to manage the runoff. This article presents a successful design to route the excess runoff generated due to the change in land-cover from an 11.4 acre site in Tallahassee, Florida, USA. The site development involved conversion of a wooded area to an aquatics complex with pools, buildings, parking lots, and driveway access etc. creating 2.4 acre impervious area. A pond with adequate storage capacity was not feasible to construct within the site due to site constraints and high-cost. The runoff generated from the new impervious area was designed to route through the newly designed small onsite dry-detention pond and discharged to an existing offsite pond, located within a closed basin. The analysis showed successful design of an onsite pond that retains as much water as possible within the site and safely releasing excess volume downstream to the offsite pond. The results confirmed that the offsite pond in the closed basin can retain all runoff without any discharge and the two ponds in series can handle any extreme storm in an integrated manner.

Minimizing pond size using an off-site pond in a closed basin: a storm flow mitigation design and evaluation

“…The basic policy that guides the stormwater management design is the peak fl ow, after development, is required not to exceed the pre-development level for one or more design storms with a given return period and storm duration [4,5]. The guideline of many regulatory agencies for a pond located in a closed basin is even more stringent and requires retaining all runoff within the basin [6]. To meet the design standard, hydrologic models must be developed to simulate the runoff for design evaluation.…”