Hydrologic Performance of Watershed-Scale Low-Impact Development in a High-Intensity Rainfall Region

This paper evaluates watershed-scale hydrologic performance of low-impact development (LID) features at two catchments in the Houston, Texas, region. White Oak Bayou is a traditional urban watershed that is frequently plagued with flooding. In contrast, The Woodlands is a master-planned suburban community designed to preserve its natural hydrology by implementing large-scale conservation features. The objectives of this study are threefold: (1)to propose a method to simulate small-scale infiltration-based LID features over a large area by using a distributed hydrologic model; (2)to quantify the cumulative hydrologic responses of watershedwide LID implementation; and (3)to compare the flood reduction potential between two distinct LID strategies (conservation LID and retrofit LID). Conservation (master-planned) LID integrates large-scale features (e.g.,riparian buffers and swales) early in a watershed's development, whereas retrofit LID implements site-scale features (e.g.,green roofs and rain gardens) after the watershed has been fully developed. The results of this study demonstrate varying degrees of flood reduction (i.e.,peak discharge and runoff volume) at the watershed outlets with respect to different LID features and rainfall events. The results also showed that although retrofitted watersheds could not quite match the hydrologic performances of master-planned watersheds, they could still enjoy the benefit of flood reduction during smaller storms.