Urban growth generally alters land cover and hydrology of a watershed, increasing runoff and flood events. Low impact development (LID) practices are commonly used stormwater management techniques for controlling runoff. Although LID practices has been shown to decrease runoff at lot level, their effectiveness for reducing flood risk reduction at the watershed scale is not well documented. This study examined the impact of urbanization on storm runoff and flood risk to evaluate the effectiveness of LID practices in reducing flooding in an urbanized watershed in central Illinois. The Personal Computer Storm Water Management Model (PCSWMM) was used to simulate long-term runoff and downstream flood risk related to urban land use change from 1992 to 2030 in the City of Normal-Sugar Creek Watershed. The effectiveness of three LID practices – porous pavement, rain barrel, and rain garden – for reducing flooding in the watershed was simulated using various scenarios from 25% to 100% implementation level for individual practices and 50% implementation level for combined practices. The model was successfully calibrated and validated for daily runoff using daily precipitation and 2006 land cover (base map) with NSE and R2 of 0.501 and 0.506 for the calibration period (2006-2013), and 0.512 and 0.63 for the validation period (1997-2003). The baseline condition was derived with 2006 land use for a period of 30-years (1984-2013) for daily precipitation, and 26-years (1987-2012) for hourly precipitation. The model was further validated for the baseline condition for average annual runoff calculated with hourly precipitation, with a deviation of 2%. Two metrics were developed to define direct runoff events that produced 'flooding requiring action' – a discharge of 43 m3/s and a stage above 7 feet – and 'extreme flooding' – a 95 m3/s discharge and a stage above 11 feet. The effect of urbanization on average annual runoff and flood risk was modeled with both daily and hourly precipitation while the effectiveness of LID was modeled with hourly precipitation. Increase in urban land use from 50% to 94% between 1992 and 2030, increased average annual runoff by 50% (155.6 to 232.4 mm) and one-hour flood events by 67% (from 99 events to 165 events) during this period, indicating that flood risk increased due to land use change. The implementation of LID practices reduced the amount of runoff, ranging from 3.4% to 50%, for various implementation levels. Runoff events that would cause `extreme flooding' and 'flooding requiring action' were also reduced by 55% and 40%, respectively, indicating that LID practices can be used to reduce flood risk in urban watersheds.
|Commitee:||Morgan, Susan, Zhou, Jianpeng|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 54/03M(E), Masters Abstracts International|
|Subjects:||Hydrologic sciences, Geomorphology, Water Resource Management|
|Keywords:||Flood, Land use, Low impact development, Stormwater management, Watershed|
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