Effect of Rainwater Gardens as Flood Mitigation using Storm Water Management Model

Flooding is a perennial problem in the Philippines, particularly in its capital city of Manila. Sampaloc is one of the barangays in Manila vulnerable to flooding according to the Flood Risk Map of Metro Manila. The researchers considered España Boulevard as the area of study since it is one of the most flood prone roads in Manila, according to Metro Manila Development Authority (MMDA). The study is focused on the analysis of Rainwater Gardens as an additional flood mitigation in España Boulevard using Storm Water Management Model (SWMM) simulation. Studies have proven that rainwater garden is considered as one of the most effective, simplest, and low-cost methods to address abrupt flooding. Moreover, it is easy to install, maintain and has a lot of advantages such as removing nutrient-based pollutants such as nitrogen and phosphorus, improving air quality, money saving and water conservation and improving environmental aesthetics. The data was collected through online surveys. The gathered data was calibrated and simulated using SWMM. As per the results, the rainwater garden is effective as an additional flood mitigation system since it can reduce the flood depth up to 19.42% and 14.78% for 25-year return period and 50-year return period storm, respectively. The delay of abrupt flooding is beneficial to the residents of flood prone areas. In real life scenario, the 0.15 m difference in flood depth for a 25-year return period storm and 0.17 m difference in flood depth for a 50-year return period storm will serve as longer time for evacuation of the residents when excessive flooding occurs. Moreover, rescuers will have more time to respond to affected areas and save more people.