An Emperical Equation for the determination of the Displacement of the Gilan Estuaries

The objective of this study is to find empirical equation for the determination of the estuaries displacements of Gilan Province’s Rivers، Iran. For this purpose، first، the displacement of estuary of each river was determined using the Geographical Information Systems (GIS). Remote sensing data and topographical maps of four different years were used in this study and the displacement of estuary of the rivers were determined by providing the estuaries map in those periods. On the other hand، the sediment transport rate of the rivers was calculated in different periods using observed sediment data. Correlation between the sediment concentration indices and displacement of the estuaries indices in Gilan Province’s Rivers were studied. Results show that the ratio of maximum sediment concentration to average sediment concentration of each river has high correlation with the transversal average displacement of the estuaries in each period. Examination of results show that variation of transversal displacement of rivers’ estuaries with sediment index can be investigated in three intervals. In the first interval، sediment index was 0-50، in the second interval 50-100 and in the third interval 100-150. The average transversal displacement of rivers estuaries in three intervals are about 15 m، 87 m، 286 m per year، respectively. This research shows that erosion and sedimentation management of watersheds، debris flood control and limiting the up-stream dams’ flushing play crucial role in estabilization of the morphology of Gilan’s estuaries.