Simulating future trends in stormwater runoff at a university campus related to climate and land use changes

Abstract

Stormwater management is essential for the management of sewerage and stormwater systems as insufficient drainage can result in flood damage and impact public health. During the planning of new infrastructure at Campus I of the Royal University of Phnom Penh, it was observed that a hydrological assessment had not yet been completed. Without such an assessment, climate change and poor land-use planning may result in more frequent flood events in the future. Thus, this study aims to quantify the potential impacts of changes to stormwater runoff related to climate change and an increase in the area of impervious surfaces on campus. PCSWMM modeling software was employed to simulate surface runoff volumes flowing to the catchment of the Building D pond. Three different scenarios for rainfall intensity (2, 5, and 10-year return period) and five scenarios for changes to impervious area (10%, 30%, 50%, 70% and 100%) were used in the simulation. A baseline was also established by analysing rainfall intensity, land use characteristics, and topography in the catchment area. Under present conditions the volume of the Building D pond is about 18,933 m3 with a surface area of 6,173 m2. The average permanent water volume of the pond is about 9,916 m3, with a remaining storage capacity of 9,016 m3. It is estimated that the pond will flood within one hour of intense rainfall (63.70 mm/h) under these conditions. The surface runoff volume for the Building D catchment was estimated for a range of scenarios. It was found that even under intense rainfall (63.70 mm/h); the pond would not flood if measures were implemented to reduce the impervious area on campus by 10%. This shows that preserving permeable surfaces in the catchment is likely to reduce the frequency of flood events on campus over a range of climate change scenarios.