Ecology, Environment and Conservation Paper

ANALYSIS OF MAXIMUM VELOCITY, BED SHEAR, AND SEDIMENT DISTRIBUTION TOWARDS THE EFFECT OF GROYNE PLACEMENT

Pitojo Tri Juwono, Dian Sisinggih1 and Iskandar

Abstract

Effect of river siltation caused by sediments is that the water cannot flow well that results in flooding.Sedimentation occurs due to solid particles being carried by the flow of the river. Loading mechanism of the sediment can be categorized into 3 (three) groups, namely bed load,suspended load and wash load. The goal of the analysis is to find out the maximum velocity, bed shear, and sediment distribution towards the effect of groyne placement. The method used in the study is simulation of 2-dimensional numerical model with RMA2 and SED2D methods. There are some conclusions : 1) Velocity distribution as the result of scenario III simulation in existing groynes condition when there is 34° increase in the angle of gyro and 27.50 m’ increase at both rivers confluence shows maximum velocity is larger in Scenario I and II. The maximum velocity is 1.75 m’/second as the impact of flood debit (Q50) at the 5th hour (the peak of flood hydrograph) and the total simulation time is 35 hours. 2). The largest bed shear occurs in Scenario III when there is 34° increase in the angle of gyro and 27.50 m’ increase at both rivers confluence (the bed shear is8.65 N/m2). It is bigger than the bed shears in Scenario I and II as the impact of flood debit (Q50) at the 5th hour (the peak of flood hydrograph) and the total simulation time is 35 hours.3) Sediment distribution occurs in Scenario III when there is 34° increase in the angle of gyro and 27.50 m’ increase at both rivers confluence shoes the higher sedimentation occurs at the end of groynes 1, between groynes 1 and 2, 2 and3, 3 and 4 and on the right and left side of the end of new groynes. On the other hand, erosion takes place at the direction of the dam on the right side of the cross section where sedimentation keeps taking place.Adding new groynes (scenario III) as separation zone is more effective than groynes placement in Scenario I and II, where the addition of the groynes can separate Garang and Kreo Rivers. Garang River velocity increases and causes erosion so that sedimentation taking place at the confluence between Garang and Kreo Rivers can be minimized.