Modelling the applicability of Low Impact Development (LID) technologies in a university campus in the Philippines using Storm Water Management Model (SWMM)

Abstract Progressive land development increases the imperviousness of an area which disrupts the water balance and results to the degradation of water quality, high peak flow, and excessive volume of surface runoff. One efficient approach to address this issue on water is the application of Low impact development (LID) technologies. LID helps improve the water quality and water quantity of an area to maximize its land-use. In this study, the eight LID technologies available in SWMM namely, bio retention cell, infiltration trench, rain garden, green roof, permeable pavement, rain barrel, rooftop disconnection, and vegetative swale were applied in simulating the area of the De La Salle University - Laguna Campus, a pre-developed area in Binan, Laguna which currently undergoes land-use change. This study area was simulated without the use of LID, with the use of varying LID, and capturing the 80, 90, and 95 percent of all the rainfall from 1989-2018. Digital elevation model and disaggregated rainfall data were used as input in SWMM. The ArcMap 10.4 was utilized to delineate and produce the three sub catchments with an area of 24.13 ha., 10.18 ha., and 4.34 ha., respectively while Storm Water Management Model (SWMM) software was used in analyzing these sub catchments to produce water balance values. Results showed that more than 60 percent of the disaggregated rainfall was under the one-year return period. Also, bioretention cell with 80 th percentile rainfall maximizes the reduction of runoff while infiltration trenches with 95 th percentile rainfall were the most effective in increasing the infiltration among the eight LID technologies. It was also indicated that the surface runoff in first sub catchment was reduced to more than 80% using bioretention cell, infiltration trench, rain garden, or rooftop disconnection. Finally, the area of a sub catchment has a positive correlation in its reduced runoff while a negative correlation in its infiltration when integrating the LID technologies. This research can be a resource for further studies and in to support SDGs 6, 9, and 11 to have a better water management, resilient infrastructures, and attain sustainable cities and communities.