EFFECT OF JETTY TO THE CAPACITY OF BOGOWONTO RIVER MOUTH, KULON PROGO, DAERAH ISTIMEWA YOGYAKARTA

• Main Author: Dandy Kusuma, M
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/62775
• Institution: Institut Teknologi Bandung

Bogowonto River is the main river in the Bogowonto watershed which is included in the Serayu Bogowonto River Area, located in Wonosobo, Temanggung, Magelang, Purworejo, Central Java Province and Kulon Progo Regency, D.I. Yogyakarta Province. In the dry season, the mouth of the Bogowonto river closes because sediment deposits accumulate at the river mouth, disrupting the river flow to the sea. At high tide, sediment holds the Bogowonto river flow because it impacts the backwater downstream of the Bogowonto river, causing flooding in several locations, especially around Yogyakarta International Airport. The flow capacity of the Bogowonto river is decreasing, causing flooding problems, so this study needs to do an analysis. The purpose of this research is to analyze capacity and morphological changes in The Bogowonto river estuary before and after jetty construction from the results of the analysis of discharges, current, and tidal conditions and waves. Backwater analysis at the Bogowonto River estuary was carried out by simulating the existing and jetty in the HEC-RAS program, while the analysis of changes in river morphology was simulated with 2 jetty scenarios using the DELFT3D program. The simulation results of flood modeling in the Bogowonto Hilir River when the estuary is closed have a backwater impact up to a distance of about 3 km with a water level rise of about 1 m. When the estuary is open and there is a jetty, the change in water level rises due to backwater becoming 0.2 m so that if normalization is carried out and the construction of a jetty in the estuary can reduce the water level rise by about 0.8 m. Simulation using DELFT3D software was carried out in 2 scenarios, namely West Side Jetty (300 m) and East Side (300 m) for scenario 1, while West Side Jetty (300 m) and East Side (400 m + 300 m Southwest direction) for Scenario 2, where the results for Scenario 1 still have the potential to have an impact on sedimentation at the end of the jetty so that it can close the flow of river discharge, and while Scenario 2 it can overcome the effect of sedimentation so that Bogowonto river can be flowing into the sea. However, sedimentation on the west side of the jetty has the potential to down drift, and the east side of the jetty has the potential to up drift.