A GIS MODELLING APPROACH FOR FLOOD HAZARD ASSESSMENT IN PART OF SURAKARTA CITY, INDONESIA

Floods are the most frequent hazard in the world. In Indonesia floods become routine events, especially in rainy season. Surakarta city is one of the area in Indonesia that frequently struck by floods events in recent years The local authority has implemented both of structural and non structural mitigation measure to reduce the flood risk. However, flooding remains to handle in Surakarta. Developing an understanding of the characteristic of the flood behavior may be used by the local authority to reduce the flood problem. To better understand which areas might be at risk or being flooded, a prediction tool is needed to simulate the flood. In this study, a hydrodynamic model using Flo2D was constructed and applied in part of Surakarta City, Indonesia to simulate the flood scenario for return period 10, 25 and 100 years. The modelling result output are the two parameter of flood: maximum water depth and maximum flow velocity. In addition, the flood inundation extent during 2007 flood event was used in flood model validation. The model result gives 74% agreement with the inundation extent. In hazard assessment, there are two ways to generate the hazard map: single parameter and multi parameter. All of the hazard maps were categories into four classes, i.e extreme, high, medium and low. A 62% decrease in extreme zone was observed in the multi parameters hazard map compared to that of conventional hazard map which was only use water depth parameter. A multi parameter flood impact assessment was propose to integrates water depth and velocity and categorize the flood impact according to different interest, such as human safety and property damage. Furthermore, the building affected by flood is calculated