The Application of HEC- HMS Model on the Sensitivity Analysis of the Geomorphical Variables Effective on Karvan Plain Flood

The routing of water ways and local situation of sub-basins effect of exiting flood in basin. As a result, for each flood controlling activity, the effect of them on basin should have been determined. Then, they should be classified based on their role on making exit flood. In this research, the hydrologic modeling by means of HEC- HMS software has been used in each sub-basin and its logical area to rebuild basin model and investigate the routing of flood hydrograph in and to analyze the sensitivity of flood peak of basin to the variation of three manageable geomorphologic parameters in flood water including slope, CN and area. The statistical results of this study show that the contribution of sub-basins in the are not necessarily relevant to the of flood peak sub-basins and the sub-basins which have larger flood peak are not necessarily more effective in exiting flood of a basin. Therefore by using this procedure and using Single Successive Sub watershed Elimination (SSSE) in Karvan model by means of HEC- HMS software, it has been identified that sub-basin S1 has the most effective role and S8 the least effective one in flood peak of a basin; however, S18 which has the least flood peak is in nineteenth in the contribution in the basin flood. Moreover, the sensitivity analysis of sub-basins to the manageable and controllable variants shows that by routing effect, the sub-basins have different behaviours to the variations of these variants. In the slope and CN analysis, it was observable that increasing these two parameters in their logical area had decreasing effect on the flood peak of the some sub- basins (reverse effect). However, their effect on the flood peak of a basin was direct in other sub basins. In slope sensitivity analysis, the variation of area in all sub basins were directly related to the flood peak of the whole basin; however, the sub basins with more area were not necessarily much effective to the flood peak of the whole basin in their variation. For example, sub-basin S7 having more area than basins S3, S2 which is less sensitive to the area variant.