samira salmanzadeh

Rivers are known as the main sources of surface water in the world, which experience seasonal fluctuations in water level. These resources have severe damage to human societies and nature in flood conditions and have irreparable consequences in the drought seasons. Optimal utilization of these resources with maintaining the environmental conditions of the waterway and minimizing flood damage is considered one of the river engineering goals. Since the conventional methods of river management are imposed serious environmental threats on waterways and wetlands, consideration to these water resources requires attention to issues related to plant ecosystems, solving challenges of coastal bed erosion and predict the condition and management of the river in the future (Callow, 2012; Dawson and Haslam, 1983; Fan et al., 2013; Rose et al., 2010; Rowinski et al., 2018). One of the strategies that cause loss of flow energy in the river improves the hydrological system and river ecosystem is the presence of vegetation in the river banks and floodplains. Native vegetation in floodplains and coastal forests plays an important role in conserving waterway ecosystems, flood management, coastal protection in urban lands and agriculture adjacent to the river (Fathi-Moghadam, 1996). Vegetation will also control the width of the river and increase the stability of the shores by absorbing and settling suspended sediments in river banks. The plant species along rivers and waterways are composed of various vegetative components, mainly affected by the environmental conditions of their habitat, including the distance from the waterway bed, hydrological characteristics of the river, climatic and soil conditions. Obviously, the effect of each plant species in the ecosystem cycle varies and for each section of the river, a specific combination of plants will create optimal conditions.

Physical properties of tree species determine their reaction to external loads as a result of water flow. The greater the trees ability to withstand water load, the greater the amount of water energy absorption, generation of water eddies, and the acceleration of turbulence in vegetation canopies. This will increase water flow energy lost. In general, physical properties of trees include leaf density, shape, and overall flexibility of their species. In this study, an index is proposed to characterize physical properties of tree species. This will enable the application of a single momentum (or energy) equation to determine overall reaction of variety of tree species in a community. The index is derived based on the resonance frequency of the first mode of vibration of trees and a fundamental relationship for the homogeneous beams. The derived indexes for four species of coniferous trees were used in a mathematical model to estimate the drag and energy coefficients as representatives for tree reaction to water flow, and could account for the differences due to the leaf density, shape, and rigidity of the tree species.

Abstract:The ability how to predict concentration and pollution front progressing in receiving water resources is environmentally essential, especially adjacency to the water resources entrance. Hence, this study analyses the pollution progressive front and its rate of concentration affected by discharging nozzle with various convergence angles. In this research, the conduct of experiments schedule is based on geometrical and hydraulic variable effect. The main purpose of this study is to analyze the convergence angle of flow discharging nozzle. The results obtained, showed that the convergence angle of flow discharging nozzle increase from 15̊ to 90̊ degree has a remarkable impact on pollution front progressing increase. Data analysis showed that increase in dense fluid leads to 52 percent increase in concentration rate through the trajectory center line in comparison with initial concentration. Eventually, the jet flux center line concentration rate rises by 46 percent as convergence angle increases. Keywords: Progressive front of pollution, Superficial jet, convergence angle nozzle, Deep water, Final concentration of center line