ANALYSIS OF BED LEVEL CHANGE DUE TO SEDIMENT MOVEMENT

• Main Author: TRES WIDYANTORO (NIM : 25014309), FRENKI
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/22215
• Institution: Institut Teknologi Bandung

River is one of water source for human. River can also be utilised as transportation infrastructure. However, in addition to the benefits of the river there are also losses caused by the river. That is due to changes in planform / morphology of the river that can affect the safety and stability of the cliffs around the river which in some locations there are building, rice fields, plantation, or bridges. In further investigation we can know from some references that changes in planform / morphology of the river is caused by several factors, including the distribution of speed, secondary flow, agradation and sediment degradation. In relation to these conditions, it is necessary to identify the problems and river bank protection building planning including the numerical model of the hydraulic building to know the characteristics of river bank protection and sedimentation. <br /> <br /> <br /> Hydraulic physical modeling of this research has been conducted by Agung Wiyono (ITB, 2005). At this stage of the research, in the hydraulic model, the simplification is as follows: the channel has a regular curve, ie, cornering 180o and 90o, the wall is vertikal and not eroded. At this research the bed is mobile bed. Bed material that used in is Galunggung sand that has been filtered, so it is classified as an uniform materials. Then the physical modeling result data is used as calibration data for modeling on MIKE 21 Curvilinear program. <br /> <br /> <br /> This research use MIKE 21 Curvilinear, with the channel data is similar to research that conducted by Agung (ITB, 2005). Sedimen grain size (D50) = 1.1 mm. Inner bend radius is 100 cm and outer bend radius is 150 cm. Channel width is 50 cm. Channel discharge is 7,35 lt/s, Froude number = 0.497, average water level = 4,47 cm and average water velocity = 32,92 cm/s. In this modeling the groyne is impermeable with submerged and not submerged condition. Groyne length is 10% dan 20% channel width, distance between each groyne is 3O dan 6O. <br /> <br /> <br /> Based on the result of R2 and discrepancy ratio, the result of the model that closest to the physical model result is kb (bed load factor) = 0.9 and ks (suspended load factor) = 0,1. The flow velocity pattern on the outer bend is faster than in the inner side, and the water level on the outer side is higher than the inside corner. The scouring pattern on the outer bend is degradation and on the inside side there is aggradation. The groyne begins at 12o when the scour is 1 cm in the model, equal to 25 cm in prototype. Submerged groyne can reduce the vortex, especially in the earliest groyne so can reduce the scours that can affect the stability of groyne foundation. Groyne with L=20%B can reduce more agradation in inner bend. The coefficient 1,8 of akikusa formula is need correction become 0,445 – 1,033. In the Ripley Equation, coefficient K=17,52 become 13,636-1030. Correction in the transverse slope equation is coefficient nm = 0,012 become 0,023-0,811. <br />