Document Type

Thesis

Abstract

Urbanization can lead to the disruption of the natural flow patterns of streams in a watershed. The changes in the natural flow regime that are brought about by urbanization may result in problems such as an increase in the frequency and magnitude of flooding events as well as an overall reduction in groundwater recharge. The focus of this study is to analyze the changes in stream flow, which occur due the changing watershed conditions. Two similarly sized basins that are at differing stages of development in the Williamsburg, Virginia area were selected for study in an attempt to quantify the impact of local urbanization on the flow of the streams in these basins. By analyzing the hydrographs of the two streams in these basins, we are able to compare how the subsequent stream flows have been altered given the varying stages of development. It has been found that in the more heavily developed basin, the lag time between precipitation events and peak discharge was less than that of the basin which was only lightly developed. The average lag time for the more developed basin was found to be 4.22 hours, while the average lag time for the less developed basin was found to be 5.63 hours. This is directly related to the increased speed of delivery of water to the stream in the more developed basin due to an increase in area of impervious surfaces and thus generation of more runoff. Additionally, when the peak discharge of the more heavily developed basin exceeded that of the less developed basin, it was greater by an average of 2.01 times. However, the more developed basin did not consistently display greater peak discharge values. As such, it would appear that the intensity, volume and duration of storm events influence which of the two basins will have the higher peak discharge. These findings are in agreement with the previous studies, which have been undertaken by other William and Mary students and faculty and suggest that continued development, which is planned for this area, will further affect the watershed conditions. As such, this information may prove to be useful to town planners and builders in assisting them to understand the extent of development which can be sustained in this area or in the very least the need to reduce the impacts of said development.

Date Awarded

2002

Department

Geology

Advisor 1

Gregory S. Hancock

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