Low Impact Development Modeling to Assess Localized Flood Reduction in Thailand

Abstract

The causes and impacts of, and emergency responses to, the recent catastrophic flooding in northern and central Thailand, including Bangkok, are reviewed. A number of short term and long term engineering solutions have been proposed to avoid or minimize future flooding impacts. Low impact development (LID) technologies might be one reasonable, sustainable, approach to solving urban drainage and water quality problems in Bangkok, but the local urban approaches should be integrated with watershed wide planning efforts. PCSWMM was used to model single and multiple LID technologies in a case study of a peri-urban village near Bangkok as a preliminary exploration of LID benefits in terms of stormwater quantity and quality. A 2 y design storm for Thailand was used in the modeling. The design plans of LID technologies , using either CAD or Google SketchUp, were visualized through Google Earth, and were costed using local information. All LID scenarios reduced combined sewer overflow (CSO) volume, CSO pollutant loadings and the durations of surface flooding, although single rain barrels installed at all houses had a relatively small (4% to 9% reduction) impact. This may be related in part to the fact that a 2 y storm in Thailand is more similar to a 50 y or 100 y storm in northeastern North America. The combined rain barrel and bioretention cell scenarios offered the greatest control in reducing CSO discharges, but the costs may be prohibitive in Thailand at present.