عنوان مقاله [English]
نویسنده [English]چکیده [English]
Meanders are among beautiful landscapes as well as hazardous geomorphologic - hydrological forms on floods plain in mountainous areas. River meanders are major factors responsible for creation, development and or on the surface of the Earth and have long fascinated people by their apparent regularity. They play a major role in floodplain construction and evolution and are major components of the fluvial landscape. Thay can be highly dynamic features and so pose practical problems associated with channel movement. Many movement meanders and lateral movement of rivers channel. The floods and the excess of energy on rivers bed are main causes for creation of these phenomenons. Meanders are the signs of flood hazards in occurrence area. Shor river (from 36° 05' to 37 °20' N and from 46 °43 to 47° 15' E) have many curvatures on length of channel rivers. This river have typical meander in many parts of the channel.
Materials and methods
In the present study, changes in channel morphology along the Shor River floodplain were investigated using areal and satellite photographs. And then rate of sinuosity of channel is calculated by index of sinuosity. In this article, in order to investigate the meanders and with aim of study on rate of flood hazard, LFH index has been used. In this study some parameters of meander, for example, wide of channels and belts of meanders have been used too, … In order to investigation on flooding risk on all lengths of channel of Shor River, the channel is shared to 21 segments. All accessory calculations are made in these segments. For investigation on flooding potential of river channel, the parameters of channel curvatures and meandering of course river flow have been used.
Also for calculating of flood potential, because of lack data and information by using of different index and coefficients, we explain the situation of flooding in different part of region. Indexes that use in this research are basin relief, drainage density, roughness number, constant of channel maintenance, stream frequency, texture ratio, form factor, elongation ratio. for calculation of flood potential on meandering course of river, we use different experimental equation such as Villiams equation and flood way reduction by using of actual meander amplitude (Aact) and The possible largest meander (Amax). Local flood hazard (LFH) is very important index for calculating risk of flood hazard in meandering river. equilibrium between FR and CA calculate for access to local flood hazard (LFH). in this research by using of meander length, average of debit calculated. For calculating of meander length we use satellite images. Also by using of meander arc and arc angle and width of channel, relation between them calculated. For measuring of parameters mentioned above, we use aerial photos on 21 segments of Shor river.
Results and Discussion
The results of this study suggested that LFH in length of river channel is very varying. The average of LFH is 0.77. This means that the potential of flood hazard in many parts of channel meandering on Shor river is high. Movement of curvature of meander to lateral of flood plain is cause of increase the bank erosion in length of Shor river and increase of hazards in flood plain. The results suggested also, Rn in Shor basin is high. These results show that the Shor basin treated by flood. Curvature of meanders experiment flooding and since flood Crossed on curvature, channel of river lateral movement. Lateral movements cut the banks and are amang the major causes of the increased sediment. The structures are located near the banks, due to the curvature movement, so the risk of this structure is too high, because flooding and lateral erosion. Also the result show that the first order of drainage network in Shor river is higher than other order or steps. For this reason more tributary reach to higher order and can discharg more runoff to higehr order.
Many parts of meandering of Shor River have high potential flooding. The results of the study show that this river experiments floods every years. When flood is occurred, curvature of courses is movement. These movements are widening the floodplain. This widening is made by cutting of bank. These movements are very hazardous for the structures which are located near the river channel. The lateral erosion increases when the curvature moves into the bank of channel.