Deriving short-duration design rainfall from daily rainfall for urban drainage assessment in a data-scarce area

Tóm tắt

Upgrading and improving urban drainage systems to prevent and mitigate urban flooding under the impacts of climate change and urbanization has become an urgent priority. The design of drainage systems should be based on appropriate design standards. Accordingly, this study develops design rainfall hyetographs based on intensity-duration-frequency (IDF) curves and the Alternating Block Method (ABM), combined with the Storm Water Management Model (EPA-SWMM), to assess the drainage capacity of an urban catchment. While typical urban areas generally have sufficient rainfall monitoring stations providing short-duration rainfall observations for drainage system design, newly developed urban areas often lack such data. Therefore, this study focuses on analyzing the correlation between daily and short-duration rainfall, using Tan Son Hoa (TSH) station as the reference station and Xi Mang Ha Tien (XMHT) station as the representative station for the data-scarce Thu Duc Canal catchment. The results show a strong correlation in maximum daily rainfall between the two stations, with R2=0.996, while the relationships between daily and short-duration rainfall exhibit R2 values ranging from 0.9047 to 0.9813, all of which are statistically significant at the 5% significance level. Based on the regression equations between ZdayP and ZdurationP, IDF curves and design rainfall hyetographs were developed for return periods of N=2-50 years, using a peak position coefficient of r=0.45. The subsequent EPA-SWMM simulations provide a preliminary assessment indicating that the drainage capacity of the Thu Duc Canal catchment is limited, with several drainage pipes and manholes exceeding their design capacity thresholds in areas including Kha Van Can Street, Vo Van Ngan Street, and the Thu Duc Post Office area.