Assessment of the sub-urban drainage system resilience on the increased flooding scenario using Storm Water Management Model (SWMM)

Abstract

This study aims to provide technical support for decision-makers by presenting an evaluation of flood in Tanjung Bundong, Kota Samarahan, Sarawak, Malaysia. Storm Water Management Model was utilized to simulate the existing drainage network until it reached the main outlet of Sabang River. The hydrological and hydraulic parameters which included rainfall and tidal effects of Sabang river were determined to assess the cause of flooding series since 2015. The mapping of the drainage network was carried out to evaluate the existing drainage. The site investigations showed about 31% of the earthen canals and 5% of concrete drains were obstructed due to the trash accumulation, overgrown vegetation along the drain, and accumulation of soil sediments. Therefore, these occurrences shallowed the invert levels of the drain. This had resulted in 15 nodes flooded when simulated with 2-year average recurrence interval design rainfall and rose to 29 nodes with 50-year average recurrence interval design rainfall. With the combination of high tidal levels, the flood volumes reached 241,579 m3, especially during intense rainfall. The results showed the importance of periodic maintenance on the drainage network to ensure its resilience against nuisance flooding.