saeid roodbari shahmiri

Estuaries and bays are areas with a wide range of hydrodynamic and morphological phenomena. The existence of this diversity in environmental processes will lead to complex and sometimes unknown interactions in their structure. Understanding the behavior and environmental conditions of these beaches will improve the attitude of coastal users for better management of these areas. Many classifications have been made by researchers to understand the behavior of this coastal environment. The dimensionless VU parameter is a numerical parameter to facilitate speed, accuracy as well as cost reduction in the classification of this coastal environment. This parameter classifies the estuaries into three categories: tidal domination, wave domination, and mixed energy, based on the relative strength of the tides and the river flow relative to the wave infiltration. Each of these classes has its own behavioral characteristics. The purpose of this study is to identify the type of performance of the North Persian Gulf estuaries and sensitivity measurement The dimensionless VU parameter in the classification of morphodynamic class of Persian Gulf estuaries. Morphological classification was used as the basic criterion for validation and Hayes hydrodynamic classification was used as a comparison tool. For this purpose, data from observing the trend of changes from satellite images, wave data and tides and meteorology have been used. To classify the dimensionless parameters of the estuaries, the tidal amplitude, the area of the estuaries and the tidal prism in the estuaries have been calculated. The results of morphological classification indicate that the study area is dominated by tides and the results of Hayes hydrodynamic classification with 96% accuracy have presented similar results to morphological classification. In contrast, the dimensionless parameter VU with poor accuracy of 53% presented poor results in classification. By examining the calculation results, the error rate of the dimensionless parameter VU in small estuaries and tidal domains has been determined. By defining the ratio of wave height to tidal amplitude (H / TR), regression lines of difference intervals, the dimensionless parameter VU with morphological classification is determined. It was also found that in a constant ratio of wave height to tidal amplitude, with increasing wave height, the percentage of classification the dimensionless parameter VU error increases. And also at a constant wave height, with decreasing tidal amplitude, the percentage of the dimensionless parameter VU increases.

The aim of this study is to verify the results of numerical modeling with the available physical evidence on the Miankaleh Coast. This study was made by using MIKE 21 numerical model of (SW, HD and COUPLED MODEL FM Modules) plus field studies and sediment sampling. Wave energy and current speed decreased from west to east according to the results of numerical models of MIKE in Miankaleh coast; the wave height in the Gorgan bay inlet has shown a reduction of up to 80 percent. The average current direction out of the Bay in a year is from west to east and in the bay is counterclockwise. The overall rate of sediment transport in the Miankaleh sand spit is less than 0.00002 cubic meter per second per meter. This shows low rate of sediment transport from upstream. The east coast is more sensitive than the west coast regarding the sea level change. The results of field observations and physical complications on the coast verify the results obtained from the numerical model of MIKE in the region. The average sediments size in Miankaleh coast is 0.106 mm. Miankaleh coast is a kind of dissipative coast and dissipative effect Increases from west to east. West region is sediment deposition source and east Regions of Miankaleh is sediment destination. Numerical model of MIKE is suitable for low slope coast with dissipative characteristics.

The aim of this research was to study the stability and performance of Gorgan Bay and Miankaleh sand spit in order to find out the mechanisms of Gorgan Bay closure. According to the result of Miankaleh coasts’ numerical model (by DHI Mike21 package), wave energy and current speed reduced from west to east. Simultaneously, the sensitively of coasts to local storm surge due storm increased. The most probable storm surge at eastern coasts was about 40 centimeters and can make 15-20 cm sea level rise. Ashooradeh was a low wave energy mode region. The currents out of the bay were mostly from west to east and in the bay were counter clockwise. The total rate of sediment discharge in Gorgan inlet was 0.001 m3/sec/m that resulted in 1 cm/day bed level changes in inlet, while the rate of total sediment discharge in Miankaleh beach was less than 0.00002 m3/sec/m. Finally, the Gorgan bay inlet stability study (by Escofier popular model) showed that under the current conditions of the storm and low rate of sediment transport from upstream, it remains stable.