Experimental investigation the effect of submersible Bandal like and normal type of spur dike on bed elevation changes at 90 degree mild bend

Background and Objectives:
Rivers are source of any civilization formation and also any societies. As a result of many factors like human interferences, earthquake, flood and sand removing from river margins the dynamic balance of rivers changes. The consequences of these undesired phenomena's are erosion of river banks and lateral migration. On the other hand, these derbies could fill dam reservoirs. Decreasing useful life of dams and also producing operation difficulties are other two side effects of erosion. Hence bank erosion and lateral migration creates a lot of economic and social problems. Noticing above mentioned notes we conclude that investigation about hydraulic of rivers and also understanding dike hydraulic and characteristics is necessary and important. One of the common and simplest method of coastal protection is using spur dike that are useful structure to improve the flow pattern and used for control and reduce the coastal erosion of rivers.
Bandal like structure is new type of spur dike that is compound from a submersible and no submersible spur dike.

Materials and Methods:
In this research we focus on Bandal-like dikes. Explicitly we investigate the effect of dike submersion on erosion and sediment formation around a 90 degree mild bend. Experimental tests are performed under various hydraulic characteristics. Three types of dike are provided. Heights of dike are 6.5,8.5 and 12 centimeters and the width of dike is 20 percent of flood width. Also three discharge 25,27,30 and 33 liters per second for two type (submersible and no submersible) of spur dikes were tested. In this study used a 90 degree bend flume with 0.7m width
Results:
The result of this study show that the maximum of scouring rate, occur for submersible theme test and the minimum is for Bandal – like with 12cm height. Also the result show that depth of scouring with Bandal like spur is reduce than no submersible theme structure and with increased the height of structure depth of scouring will be reducing. The result show that with increased the discharge, the Thalweg divert to middle of canal.
Conclusion:
The results of this study can be summarized as:
1) The maximum of scouring is for theme submersible test.
2) The minimum of scouring is for Bandal like with 12cm height.
3) Between Bandal like spurs, the maximum of scouring is for structure with 6.5 cm height.
4) Increasing the height of structure reduce the depth of scouring.