Impacts of River Morphology Changes on Floodplain Zoning: A Case Study

Flood is a natural event which depends on numerous parameters, and affects floodplain land use planning based on an acceptable level of risk. In order to predict the extent of the floodplain, it is necessary to consider flood characteristics including flood return periods. One of the most important parameters in floodplain studies is how to deal with the variability of river cross sections and considering their effects on the uncertainties of river engineering studies, which has not been emphasized much in previous works. Because of the variation in river morphology due to erosion and sedimentation during major floods, hydraulic routing of the flood is affected by the variations in cross sections. The HEC-RAS simulation model is used to investigate the flood plain variations. In this paper, floodplain zoning at the Pirsohrab plain located in the south-eastern part of Iran is investigated. Sensitivity analysis on river cross sections is done for predicting the critical reaches of the river. Based on the results of this study, recommendations are given to reanalyze the placement of a pressure irrigation network supported by levee construction.