Effects of urbanization on rainfall - runoff relation: A case study in Nhieu Loc – Thi Nghe basin, Ho Chi Minh City

Abstract

Impervious surface area is one of the key parameters that profoundly affects the rainfall-runoff relation in urban basin. This study aims to assess the effects of the urbanization-induced increase in impermeable surface area on runoff characteristics for the case study in the Nhieu Loc – Thi Nghe basin (NL-TN), a high urbanization density area, located in the center of Ho Chi Minh City (HCMC). LANDSAT image data was used to determine the impervious surface area from 1985-2020. The EPA-SWMM model was used to simulate the rainfall-runoff relationship in the study basin. Remote sensing data showed that the impermeable area of the NL-TN basin gradually increased from 45,7% (1985-1990) to 75,8% (2015-2020). The simulated results of the rainfall-runoff relation for the 5- year design rainfall period showed that increasing the impervious surface area increases both the peak discharge and the total volume of runoff, but reduces the concentration-time of runoff. In the period of high urbanization (2015-2020), peak discharge and total volume at 3h after occuring rainfall increased by 52,21% and 44,92% respectively, but the concentrated time decreased by 30 minutes compared to the low urbanization period (1985-1990). The findings of the research can support flood risk management and urban planning -management in Ho Chi Minh City.