Spatial Modeling of Flood Inundation to Evaluate Drainage Channel, Case Study of East Banjarmasin South Kalimantan, Indonesia

Abstract

January 2021 Floods hit South Kalimantan in 10 cities, and floodwaters inundated at least 24,379 houses. The government of South Kalimantan announced Emergency Status for Flood Disasters a day after water washed that region on January 15, 2021. Given the data of the phenomenon, Banjarmasin's Public Works and Spatial Planning Department has submerged 90% of East Banjarmasin and 40% of South Banjarmasin. The runoff ratio to rivers' carrying capacity in East Banjarmasin is ± 7 (seven) times greater than its capacity, including narrowing, silting, and blockages in the channels and rivers.

This study intends to model the distribution of high inundation that occurs using the Storm Water Management Model (SWMM) and also aims to obtain a Priority Analysis based on the impact of inundation that occurs by referring to the Procedure of Compiling a Master Plan for Urban Drainage Systems from the Directorate General of Human Settlements, Ministry of Public Works and Housing. The research location is in the SimpangLayang and Veteran Flood Control Area (FCAs), East Banjarmasin, with an area of 2,078,740 ha.

From the nine modeled Sub-Systems, the average flood inundation height in the Simpang Layang FCA is about 0.886 m. The average inundation height for the Veterans FCA is about 0.838 m from the eight modeled Sub-Systems. This modeling obtained 195 points of inundation that occur in both FCA. Recommendations will be made for Priority Analysis of the Control Flood Inundation to validate the data on the distribution of inundation points. This study took five validation points: Jl Ayani, Komplek Kenanga, Komplek Smanda III, Jl Mahat Kasan, and Jl. Pramuka. Jl. Pramuka is the location with the highest priority, assessed based on inundation parameters, economic losses, social disturbances, government facilities, transportation disturbance losses, housing losses, and personal/household property rights losses. The area with this highest priority number requires forward mitigation because this area has been most severely affected and inundated for a long time. This area is also one of the centers of government, economic commodities, various companies, health center facilities, residential and public transportation centers in Banjarmasin, and other public facilities.