SPATIAL ANALYSIS OF FLOODING HAZARD AND IT'S IMPLICATION TO WATERSHED ECOSYSTEM RESILIENCE (A CASE STUDY FROM WANGGU WATERSHED EASTERN INDONESIA)

The combination of climate change and deforestation in the upstream of the Wanggu Watershed has led to an increase in the intensity and scale of flood disasters. This study aims to: (1) analyze the spatial distribution of the potential flood hazards; (2) analyzing driven factors forming potential flood hazards; (3) formulating policy implications to increase watershed resilience to flood hazards. The results of this study indicate that the potential for flood hazards was dominated by medium classes of 14394 ha (47.04%), followed by low and high hazard classes respectively 10148.13 ha (33.16%) and 6057.31 ha (19, 80%). The combination of land-use change and extreme rain was thought to be the main trigger for the Wanggu River overflow event in 2017. The results of land-use changes over the past 20 years showed that the average change in forest covers an area of 329.84 ha per year (1.08%), at the same time there was an increase in bush area, dryland agriculture, settlement, and bare land, respectively 0.41%, 0.36%, 0.13%, and 0.23%. Furthermore, climatic data showed that during 2017 the average annual and monthly rainfalls were 1050.6 and 35.0 mm respectively, with an average of and 23 rain days. During the flood events on 11-13 May 2017, the average daily rainfall had reached 70 mm. The reduced protection of vegetation and high rainfall intensity had resulted in a decrease in infiltration capacity and cause a drastic increase in surface flow. This condition had triggered the river flood discharge. The policy implications that can be carried out by local governments to increase the resilience of watersheds are upstream land use regulation, increasing the size of river green open space and conservation of water catchment areas as well as encouraging the implementation of urban green infrastructure approaches.