Study on Rainfall Correlation and Development of Design Rainfall Curves for Drainage Capacity Assessment in Data-Scarce Areas

Abstract

Upgrading and improving urban drainage systems to prevent and mitigate urban flooding under the impacts of climate change and rapid urbanization has become an urgent priority. However, the design of drainage systems must be based on appropriate design standards. This study aims to develop design rainfall hyetographs using the Intensity–Duration–Frequency (IDF) approach and the Alternating Block Method (ABM), combined with the EPA Storm Water Management Model (EPA-SWMM), to evaluate the drainage capacity of an urban catchment. While key urban areas generally have sufficient and reliable hydrometeorological data for drainage design, newly developed urban areas often lack both comprehensive drainage infrastructure and long-term rainfall observations. Therefore, this study investigates the correlation between daily rainfall and short-duration rainfall for a data-scarce area, namely the Thu Duc Canal catchment. The correlation analysis between the Tan Son Hoa rainfall station and the Xi Mang Ha Tien station, which represents the data-scarce study area, yielded a strong relationship with a correlation coefficient of R > 0.9. Based on this relationship, IDF curves were developed for the Thu Duc Canal catchment, and the resulting design rainfall hyetographs were applied to simulate hydraulic flows within the main drainage network using EPA-SWMM. The simulated flooding results were subsequently compared with observed flood conditions to verify the reliability of the rainfall correlation analysis and the proposed design rainfall development method.