HYDRODYNAMIC STUDY OF PAMARAYAN WEIR DUE TO THE POTENTIAL OF SEDIMENTATION IN THE UPSTREAM AND SCOUR IN THE DOWNSTREAM WEIR, BANTEN

• Main Author: Miartix, Lezi
• Format: Theses
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/70805
• Institution: Institut Teknologi Bandung

Pamarayan Weir is a sluice weir located in Ciujung River. Pamarayan Weir located in Panyabrangan, Cikeusal, Serang. It is one of the most important weir of Ciujung River as it serves for irrigation of 21,350 ha of rice fields. The capacity of Paramayan weir is reduced not only for irrigation but also for flood control. Furthermore, during the rainy season as the peak discharge of flood hydrograph is trend to increase and the weir capacity is trend to decrease. In the dry season, sedimentation occurs at the Pamarayan weir. Sedimentation on the left side of the weir. Therefore, these sediments can cover the scours downstream of the weir. The purpose of this study to assess the potential sedimentation and bed erosion pattern around the weir. The assessment scheme using mathematical model HEC-RAS 6.1 of 1D and 2D Unsteady Flow. The upstream boundary conditions of the study will use a flood discharge of 2 years, 50 years, 100 years return periods and a daily discharge of 1 year. Flood discharge using the results of HECHMS 4.9 software analysis with the Snyder method. Flood discharge for 2 years return periods is 576.62 m3/s, flood discharge for 50 years return periods is 1523.25 m3/s, and flood discharge for 100 years return periods is 1707.27 m3/s. The downstream boundary conditions of the study will use a normal depth is 0.00221. Sedimentation analysis will use bed sediment grain size D50 is 0.425 mm and the analysis will use the Meyer Peter Muller method. This study will use four scenarios for sedimentation analysis, the existing conditions; upstream cutoff condition; upstream cutoff condition with digging 150 m; and the condition of the maximum opening gate weir is 3 meters. The analysis will be carried out at 2 locations, cross 906 in the upstream and cross 2046 in the downstream of the weir. At cross 906 which is downstream of the weir, the 2-year flood discharge results in degradation with flooding events for 48 hours if using the existing operating pattern. The supply of sediment from upstream is insufficient to cover the scour that occurs downstream. However, if the gate is opened a maximum of 3 meters for 48 hours, aggradation occurs at cross 906. In the event of a flood with a flood discharge of Q 50 and 100 years for 48 hours, agradation occurs downstream of the weir, with sediment supply from upstream to cover the degradation that occurs in downstream weir. At cross 2046 which is at the upstream of the weir, the flood discharges of 2, 50 and 100 years will result in degradation of the river bed. When the discharge is greater, the velocity and degradation are also greater. In the daily discharge, it can be seen that the degradation that occurs is also greater when compared to the flood discharge that occurs. The height of the gate opening will affect the amount of degradation in the upstream weir and agradation in the downstream of the weir. When the height of the gate opening is greater, the sediment transport is also greater.