Investigation lands use changes and its role on floodwater zones in GIS and RS environment, case study: NekaRood

Neka watershed is associated with a large number of floods from the past, and had irrecoverable damages. Land use and its changes is one of the most important factors in country planning and policy making. In this research, land use map of year 2000 was prepared for Neka watershed by ETM+ images of 2000 and IRS 1D images of 2011 based on digital processing of maximum probability in ENVI environment. Then, 2 km path upstream to Neka city was entered to GIS environment by 1:1000 scale plane maps and creating regional TIN and HEC-geo-RAS attachment. Finally, all data were imported to HEC-RAS software and flooding zonation was determined based on determination of roughness coefficient for two, three, five, 10, 20, 50, 100 and 200 return periods with Cown method. Results demonstrated that agricultural lands, Useless lands and municipal lands have been increased by 2.27, 7.31 and 1.91 percent, and forest and rangelands have been decreased by 10.22 and 1.27 percent respectively. These changes caused an increase of 13.14 percent of flooding zone in year 2011 compared to year 2000.