Providing faultless proceeding of the engineer in order to protect the rivers, requires understanding the morphological behavior of the river and studying the hydrodynamic phenomena of the area. The intersection of the Karun rivers as the largest and longest river in Iran with the Arvand border river is of considerable importance due to its strategic location. In this paper, using field measurement and numerical modeling, the hydrodynamic processes of this area have been investigated. Measurement of marine parameters related to the border area with hard access at the intersection of Karun to Arvand and it includes water level and current velocity, hydrography, sediment granulation, and hydrodynamic modeling of current and sediment. Current velocity measurements show that the prevailing flow velocity in this area is towards Arvand and Arvand tide can only reduce the flow velocities of this river locally. Hydrographic changes also indicate flood currents in Karun, which act like water jets, causing significant changes in the bed of the intersection of Karun and Arvand rivers and shifting the Talweg line to Iraq. At the intersection of rivers due to sharp changes in depth, sediments are coarser than other points and also the concentration of sediments increases with movement at depth. The results of the numerical model are consistent with field measurements and indicate that sediment flow in the Arvand River is carried out by the Karun River and the effects of sediment flow in the Arvand River on Karun are very small. Also, the intersection of these two rivers has a high potential for sedimentation and increase the thickness of the bed.