Benefit–cost analysis of a low-impact development design

The urban development increase in the built-up areas leads to more impervious areas with the consequence of larger runoff. Undeniably, this excess water has many benefits. Low-impact development (LID) is one of the innovations to conserve wasted runoff water. The two LID scenarios (water storage – WS; infiltration – I) under different rainfall depths (20, 25, 30, 35 mm) are assessed using Storm Water Management Model (SWMM) and analyzed based on their benefit–cost. This study aims to evaluate the hydrological performance and the benefit–cost ratio to identify the optimal LID design. The benefit calculation is not only projected by runoff reduction aspects, but also the other opportunities aspects. Based on the hydrological performance, scenario I shows a higher runoff reduction performance than scenario WS. Based on the benefits aspects studied, scenario I provides greater benefits with more cost than the WS scenario. Rainfall depth influenced the life cycle cost with 20-mm WS scenario experiencing faster payback period than other scenarios. HIGHLIGHTS Scenario infiltration excels in reducing runoff, particularly in low rainfall conditions.; Scenario water storage with 20-mm rainfall depth offers the best cost-effectiveness, but sensitivity to costs and discount rate emphasized.;