Effects of gradually constructed levees on the flood characteristics in Maen Village, North Sulawesi, Indonesia

Abstract

The flood occurring in 2015 in the Maen Village, North Sulawesi, was caused by high-intensity rainfall, which exceeded the capacity of the Maen River to accommodate and convey the water to the sea. Therefore, to prevent the occurrence of extreme flood events, it is necessary to construct levees along the Maen river. In this regard, 2D hydrodynamic simulation was conducted using HECRAS 6.1 to investigate the effects of gradually constructed levees (upstream-downstream or downstream-upstream) on the flood characteristics (depth and velocity) in the Maen village. The purpose of this study is to provide an overview of whether the upstream or downstream locations should be prioritized for the levee construction, which was done based on the analysis of flood hazard index. First, 2D simulation was carried out with the levees entirely constructed along the river (approximately 2.8 km). It was shown that the levees were able to anticipate the flood with 25- year return period. Afterwards, the 2D hydrodynamic analysis was performed with the levees partially constructed upstream or downstream of the river. The results suggest that the levees should be constructed from upstream to downstream of the river showing a lower value of flood hazard index. The finding of this study is expected to provide a new perspective for the planning of levee construction especially when gradual construction must be accounted for.