Flood encroachment in Golestan rivers with GIS

摘要

Flood is a kind of phenomenon that overwhelms the land and seacoast and lead to a great damage and loss. Flood anchorage is all the schemes and appliances that decrease the impacts and ruination of flood. Our aim of this study is to measure the rate of flood hazard of the flood plains by discharges with different return period which are located in Golestan province. After digitizing the maps and obtaining the digital elevation model (DEM), the watersheds and sub- watersheds were recognized and theirspecifications like area, slope and the length of the main canal, were obtained by using Arc View software in GIS. Then with use of land use and permeability maps, permeability specifications and the Land use of the watershed were obtained and by compiling them in HEC-GeoHMS model, The CN of the basins was obtained and HEC-HMS model was run for the specified region. According to the data which were recorded by rain gauges, the time distribution of rainfalls this region was obtained, then this time distributions was fitted to different return period of rainfalls, which were obtained based on reconstruction and completion of the recorded rainfall by rain gauges in the region. Using the recorded hydrographs in the rivers of the case study region, the specifications of the watersheds were calibrated and using them, the rainfalls by different return periods and the specifications control of the project, hydrographs was calculated and their maximum was considered as the design flood in order to flood encroachment. After that the sections geometric specifications of the canals was created in HEC-GeoRAS and then it was read with HEC-RAS. Then by using different return period flood hydrographs created in HEC-HMS zoning of the rivers was operated and flood hazard areas were recognized.