Document Type
Thesis
Abstract
Urbanization of landscapes produces a greater area of land covered by impervious surfaces, causing stormwater to move through faster runoff pathways and contribute more directly to streams. Streams are affected by this decrease of retention time and increased volume by channel incision due to larger flows. To mitigate the effects on streams, retention ponds are the most widely used management practice. Retention ponds are constructed to return post-development stormwater runoff flows into streams to predevelopment stormwater runoff flows. This study’s purpose was to evaluate the effectiveness of a retention pond mitigating stormwater runoff by studying the Kensington Woods Subdivision’s retention pond in detail. This was accomplished by taking data from field measurements of pond elevation through time. The elevation measurements from the field were translated through engineering equations and models given in the engineering design to obtain peak inflow, peak outflow, retention duration, and runoff coefficient. By comparing the calculated values for each storm event from the field data to the predicted models in the design documents, which were used for the approval and construction of the retention pond, I was able to compare the predicted mitigation of stormwater to the actual mitigation of stormwater. Through monitoring 21 storms over 9 months, I assessed the peak outflow, peak inflow, retention duration, and runoff coefficient for a series of different storm intensities. I found that no retention duration was held for the mandated 24 hour retention duration time period, and almost none were held for longer then 10 hours. Also, two thirds of the runoff coefficients monitored were larger then the predicted runoff coefficient from the design documents. This meant more stormwater was inflowing into the pond then predicted. Based on the data, I concluded that the retention pond is not controlling stormwater as predicted from the design documents. Furthermore, I believe this incorrect operation of the retention pond is caused from the lack of accurate equations and modeling used in the design process.
Date Awarded
2006
Department
Geology
Advisor 1
Gregory S. Hancock
Recommended Citation
Grenz, Michael, "Effectiveness of a Retention Pond in James City County, Virginia: A Comparisn of As-built Pond Performance to Design for Kensington Woods Subdivision" (2006). Geology Senior Theses. William & Mary. Paper 160.
https://scholarworks.wm.edu/geologyseniors/160
