Resumen
GIS (Geographic Information System) can be used to combine multiple hydrologic data and geographic data for FIA (Flood Impact Assessment). For a developing country like China, a lot of geographic data is in the CAD (Computer Aided Design) format. The commonly used method for converting CAD into DEM may result in data loss. This paper introduces a solution for the conversion between CAD data and DEM data. The method has been applied to the FIA based on the topographic map of CAD in Hanjiang River. When compared with the other method, the new method solves the data loss problem. Besides, the paper use GIS to simulate the inundation range, area, and the depth distribution of flood backwater. Based on the analysis, the author concludes: (1) the differences of the inundation areas between the flood of HQ100 and the flood of HQ50 are small. (2) The inundation depth shows a decreasing trend along the upstream of the river. (3) The inundation area less than 4 m in flood of HQ50 is larger than that in flood of HQ100, the result is opposite when the inundation depth is greater than 4 m. (4) The flood loss is 392.32 million RMB for flood of HQ50 and 610.02 million RMB for flood of HQ100. The method can be applied to FIA.