Flood risk reduction based on The Green Infrastructure implementation plan in South Central Business of Jakarta

Infiltration well is the only mandatory green infrastructure to reduce the risk of pluvial flood in Jakarta in the last decade. This study aims to assess the impact of the performance of infiltration wells implementation in drainage scale to reduce the pluvial flood in one of the major business center of South Jakarta named Kemang raya. The study utilizes an integrated approach, combining hydrological and hydraulic models with the rational method and flood analysis through HEC-RAS-1D2D and illustrating the findings using ArcGIS software. Model calibration results, based on flood depth data, yielded a Nash-Sutcliffe Efficiency (NSE) value of 0.86, indicating strong model performance. Flood risk assessment was conducted based on the Neighbourhood Association (NA), using parameters of hazard, vulnerability, and capacity indexes. This study used several scenarios of flood risk assessment including existing condition, intervention with infiltration wells, combining with storage and drainage normalization. The findings indicate that the inclusion of interventions involving infiltration wells, reservoirs, and the normalization of the drainage network effectively decreased the flood risk from 56% high, 25% medium, and 19% low categories to an acceptable level over the whole NA region. Therefore, we conclude that relying solely on mandatory infiltration wells cannot sufficiently lower the flood risk in Kemang to a low level. Furthermore, it is found that the implementation of infiltration well could only effectively decrease the pluvial flood risk to the allowable level when it combined with other types of Green Infrastructure (GI) and Sustainable Urban Drainage System (SuDS). The findings of this study provide essential insights for the Jakarta Water Resources and City Spatial Planning Agency to reformulate effective and adaptable strategies aimed at reducing the risk of pluvial flooding in the Kemang area, based on a five-year rainfall return period.