an investigation into the effects of tidal barrier operation on the tidal asymmetry in the arvand estuary

The arvand river forms the border between iran and iraq and is the only permanent river discharging into the persian gulf(pg). it is a tidal river adversely affected by sedimentation,which is more likely resulted from tidal asymmetry. the tidal barrier(tb) has remarkable effects on the tidal regime. to assess these effects on the tidal waves asymmetry,it is critical to study the two main factors of closure percentage(cp) and closure duration(cd). this manuscript aims to investigate the tidal barrier effect on the asymmetry of the tidal waves propagating through the estuary. to evaluate tidal asymmetry,tidal asymmetry index(tai) is introduced based on the relative phase angle of the m2 and m4 components through the river. a two-dimensional delft3d hydrodynamic model is utilized. the tidal wave is flood dominant, and its relative phase angle increased slightly, from 90 to 135 degrees in km 40 and then decreased to just under 90 degrees near the abadan(65km) and constant along the abadan to khorramshahr. the tidal barrier has changed the tidal regime in the river which leads to relatively constant tidal asymmetry during the 45km upward. to reach the highest tai, a closure percentage and duration of 55% and 180 minutes are estimated. the tidal barrier operation also adversely affects the amplitude of the m2 and m4 components. m4 component amplitude increases before reaching the tb and then decreases. the decrease is more elaborated from kilometer 45 onward. increasing the closure percentage amplifies the changes described above,but it has little effect on the general trends.