Low Impact Development (LID) is one of the current research interests toward green infrastructures and urban flood control that have the capability to return developed watersheds to pre-development hydrological conditions, bringing numerous water quantity and quality benefits, while being cheaper than their traditional counterparts. However, there is a current research gap about LIDs within tropical regions. This study aims to evaluate the cost efficiency of LID scenarios in varying surface areas through a cost-effectiveness (C/E) analysis and to assess flow reduction and infiltration improvement of the cost-effective LID scenarios using US EPA Stormwater Management Model (SWMM) in a tropical residential catchment receiving an annual rainfall of 1780.5 mm (70.1″), under a Type 1 Philippine Climate. Results have shown that the Weibull plotting position generated the largest rainfall amounts. A total of 2112 manually simulated LID scenarios were modeled to obtain the cost-effective or optimal LID scenarios, where they can generate a maximum of 38.67% flow reduction and 29.73% peak flow reduction, all observed in the multiple LID scenarios. At high rainfall amounts, the multiple LID scenarios can also peak at a 1113% increase in total infiltration in the given sub-catchments. Determining the target capture goal, applicable LID types, and cost estimations from a pilot project are vital components in the future application of LIDs in these regions.

The widespread development in recent years has resulted in the expansion of impervious surfaces, allowing runoff to accumulate and cause flooding issues. To reduce the impacts of runoff accumulation, the concept of low impact development (LID) has been adopted to restore the hydrological balance of urbanized areas. The objective of this study was to assess the flow reduction of the LID combinations in a residential park in Cavite, Philippines using Stormwater Management Model (SWMM). The 90^th percentile of historical rainfall from the years 1975-2019 was used in the assessment. The bioretention (BR), infiltration trench (IT), and permeable pavement (PP) LID controls, which captured 43%, 42%, and 14% of the park area respectively, were selected for implementation alongside their different combinations. Results of this study have shown that most LID scenarios reached their maximum reduction capability once it takes up around 20-40% of the total available area. The highest reduction, at around 90%, was attained by the BR+IT+PP scenario. The use of the PP scenario, however, only yielded a 20% flow reduction due to its small capture area. Implementing LID controls in urbanized locations can help in reducing runoff buildup, thereby alleviating the potential impacts of flooding.