Flood Analysis in Kali Lamong Watershed

Abstract

Sub-watershed of Kali Lamong is includes in parts of downstream Bengawan Solo Watershed that flooded every year. The risk of flood lead to the disadvantage of various aspects of life, e.g. properties, facilities and infrastructure, socio-economy factors, decreased land productivity and environmental quality. The aims of this study were: (1) to determine the integrated spatial model of land use with river hydrodynamic model towards the flood potential by GIS method; (2) to know the watershed responses for the flood risk valuation; (3) to determine the flood risk analysis model regards to controlling land functions in the area of Kali Lamong Watershed. First, we used problem identification method, continued by area assessment and model development. Area assessment consisted of demands, data collection and data processing. Data development includes Hydrology Integrated Model and Dynamic GIS. Data processed by model testing and model application and result the Decision Support System (DSS) Model. Results obtained the total flooded area in Q5 is 15,805.284 ha, Q10 16,632.930 ha, Q5-50 17,359.265 ha, and Q100 17,956.701 ha. The flood (input debit 300 m³/s) expands along the Districts of Sambeng to Mantup, Balongpanggang to the north Benjeng, Kebomas, Menganti, and Benowo which passed by Kali Lamong. The land use areas which affected most are rainfed paddy field and ponds for all distance period. Thus we concluded that if the average rainfall on Kali Lamong is more than 100 mm/s, then the area surround Kali Lamong will be overflooded.