HYDROLOGICAL MODELLING AND EVALUATION OF DETENTION PONDS TRANSFORMED FROM ROUNDABOUT TO MITIGATE URBAN FLOODING

Kuok, King Kuok and Chiu, Po Chan (2022) HYDROLOGICAL MODELLING AND EVALUATION OF DETENTION PONDS TRANSFORMED FROM ROUNDABOUT TO MITIGATE URBAN FLOODING. Journal of Engineering Science and Technology, 17 (6). pp. 4398-4409. ISSN 1823-4690

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Abstract

Kota Samarahan, Sarawak, Malaysia has emerged from a fishing village into an education hub and urban society within 30 years. The changes in land use increased the peak and volume of surface runoff. However, the non-upgrading of the existing stormwater drainage system and the impact of climate change caused Kota Samarahan to be plagued with multiple flood events in recent years. One of the efficient flood mitigation methods is to construct a detention pond that requires enormous land, which is difficult to fulfil in a developed township. It is proposed in this study to convert the large roundabout in front of University Malaysia Sarawak, Kota Samarahan into a detention pond. Different scenarios were investigated, including rainfall intensity 2, 10 and 100 years average recurrence intervals (ARIs), different orifice sizes ranging from 1.5 m × 1.5 m to 4.5 m × 4.5 m using Storm Water Management Model (SWMM). Results proved that transforming the roundabout into detention pond is an effective way to manage excess stormwater and reducing the peak runoff significantly. The ideal detention pond geometry is circular, 134 m bottom diameter, 150 m top diameter, and 2 m depth with a side slope of 4:1 (H:V). Results also revealed that orifice size 4.0 m × 4.0 m is sufficient for mitigating the 100 years ARI flooding problem. Therefore, building a stormwater detention pond within a roundabout is advantageous because it helps with stormwater runoff management and saves space for pond construction.

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