Reduction of discharge hydrograph and flood stage resulted from upstream detention ponds

The models of physiographic inundation and flood routing for channel network were used in this study to analyse the influence of the Tainan Scientific Base Industrial Park (TSBIP) and Feng-Hua detention ponds on the inundated potential, inundated volume, flood damage, and flood stage of peak flow along the Yen-Shui creek in 2-day flood for the 2-, 10- and 50-year return periods, respectively. The computed results show that the TSBIP detention ponds are able to reduce the inundated area and flood damage. However, the decrease in inundated area is not obvious for the 50-year return-period flood. Construction of the Feng-Hua detention pond resulted in a significant decrease in the flood stage along the Yen-Shui creek in the downstream reach. Moreover, the decrease in peak flow and lag of time-to-peak become increasingly evident in the downstream direction for the 2- and 10-year return-period events. For the 50-year return period, the lag of time-to-peak is not apparent, but the decrease in peak flow is still noticeable. In respect to the performance of detention ponds, the slopes of hydrographs in the rising and recession segments are smoother than those without detention ponds. Meanwhile, the shapes of peak become flatter if the detention ponds are installed. Copyright © 2007 John Wiley & Sons, Ltd.