چکیده:
Development of rural areas in rivers margins and flood plains, without understanding and attention to the dynamical and hydrological conditions and upstream areas of the rivers will cause to increase flood risk and loss of life and financial. Flood zoning has many applications, in floodplain management. For management of the three major branches of the Halilrood River, Rabor, Roodar and Javaran in Safarood watershed in Kerman Province, flood hazard zonation was considered in this research. For this purpose, Flood levels in 2 to 200 return periods in three mentioned reaches (72.13 km) using HEC-RAS and HEC-GeoRAS extension were determined in GIS environment. Initially, Rivers Plan was divided to 163 cross sections and in 75 of them, hydrological data were collected and roughness coefficient was determined by Manning method. Results showed that 90.26 percent of the total area affected by the 200-year flood, Susceptible to flooding by the flood under 25 years as well as study on flood depth in the floodplain showed that 68.26 percent of the average depth of floods with 200 years return period is belonged to floods with under 25 year return period. Survey on roughness coefficient in the return period of 200 years, revealed that with a doubling of the roughness coefficient, area under flood 7.15 percent increase which proves direct relationship between the return period and flood area. The result confirms accuracy of combination geographic information system and HEC-RAS software in flood zoning and river modeling.
خلاصه ماشینی:
", 2012) studied the geomorphologic effects of floods in Raeskola Watershed, after preparing some cross sections using HEC-RAS software, shear stress, river power and other needed parameters were determined and it was clear that the size of floods could be more accurately predicted for small steep mountain rivers by ancient water table and stream power indices.
They calculated the output flooding using the hydraulic method and hydrograph index and drew 44 sections along 43 km of river and achieved the maximum water surface elevation at certain levels for return periods of 5 to 100 years and calculated the area of flood hazard (Qomi Oili et al.
Considering that the first step in flood management plans is preparation of flood hazard zoning maps; as well as the results of studies conducted by researchers in Iran and other countries show that the combination of HEC-RAS hydraulic model and GIS has an acceptable accuracy for determining flood zones, which is used in the present study (Napradean and Chira, 2006).
GeoRAS extension, the layers of the central line (Rabor, Roodar and Javaran rivers), banks, boundaries determining the maximum flood V = 1 n 2 1 R 3 S2 (1)zone, flow path, cross sections with TIN maps (Figure 1) were determined, and were entered into HEC-RAS software after combining together.
063 Legend 2520 2510(View the image of this page) The results of the water surface calculation at different return periods in HEC-RAS software was transferred to GIS through HEC-GeoRAS extension and flood zones were determined for each period."