Evaluation of Spatial Planning in Cisadane Watershed and Its Relationship to Flood.

Abstract

Flood disaster in Cisadane river have resulted substantial consequences in Jakarta and Banten (Tangerang) regions anually. To cope with the problem, flood assessment in the watershed should be conducted to establish disaster mitigation strategy constructed in spatial planning. This research aims (1) to refine land cover and landform map in the watershed; (2) to estimate Cisadane peak discharge; (3) to analyze flood hazard and the associated risk; and (4) to evaluate current spatial planning based on established land cover, flood hazard, and flood risk. Geographic information systems (GIS) coupled with multiple criteria evaluation (MCE) is demonstrated to assess flood hazard considering several parameters, including landforms and recorded flood events. In this research, flood risk is modeled as a function of flood hazard and its vulnerability and comprises of several variables such as social, economic, demographic, and physical properties. It was found that spatial distribution of flood hazard is influenced by flat landform and shaped by fluvial processes and fluvio-marine landforms. Flood is affected by upstream precipitation and downstream water fluctuation (tidal). Flood hazard and risk is classified into low, moderate, and high level. This research found that areas having low, moderate and high-level flood hazard are about 37.124 ha, 15.564 ha, and 1.587 ha respectively. Majority of research area are low risk (41.415 ha), while about 10.972 ha areas are categorized in moderate level. Only about 1.891 ha regions are at high-level risk. Largest flood is contributed by downstream Cisadane region, which has the highest peak discharge (1.833 m3 sec-1). Analysis of spatial planning indicates that flood mitigation is urgent, especially through drainage and dyke development.