STUDY OF THE EFFECT OF LAND COVER CHANGES ON FLOOD HAZARD IN CILIWUNG WATERSHED

• Main Author: Inri Pratama, Maryo
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/50942
• Institution: Institut Teknologi Bandung

Jakarta is the city with the highest population density and population growth in Indonesia. At present, the development of an increasing population along with the depletion of land that can be converted into residential land is driving growth towards locations with lower densities, namely the upstream areas of Jakarta, such as Depok city and Bogor Regency. The increase in population in the upstream area of Jakarta coincides with the increasing frequency and the impact of flooding that has occurred in the last 20 years. It is indicated that the floods have worsened due to the increasingly damaged land in the upstream area. This research intends to conduct a study on the danger of flooding in the Ciliwung River Basin due to changes in land cover, especially in the Special Capital Region of Jakarta. The purpose of this research is to analyze the relationship between changes in land cover and flood events in the Ciliwung watershed and to predict their effects on future flood hazards. This research were carried out in 4 process stages, namely hydrological analysis, hydraulic analysis, flood hazard mapping and flood sensitivity analysis on land cover in which there is also an analysis of land cover interventions to minimize the impact of flooding. This study models the impact of land cover change on the magnitude of flooding that may occur in 2030, where the projected land cover uses the Bogor Regency Spatial Plan (RTRW) and the results of the analysis of land cover change trends. Calibration and validation were carried out using flood events in 2015, 2016, 2017 and 2018 at Depok water post, M. T. Haryono water probe post and Manggarai floodgate for hydrological analysis and using historical flood maps for hydraulic analysis. The maximum capacity of the Ciliwung river flood storage is obtained at 208.8 m3 / s, which will then begin to overflow and cause flooding at a distance of 8.5 kilometers from the Manggarai Water Gate. The likelihood of flooding in 2030 will increase twofold if the current trend of land cover change is not changed / does not follow the RTRW. The hydrological calibration process gave the best results with a lag time parameter of 330 minutes in the Depok sub-watershed and 280 minutes in the M. T. Haryono subwatershed with an NSE value of more than 68%. Hydrological analysis shows that there is an increase in projected flood events caused by a decrease in infiltration capacity upstream, with an increase in peak discharge of 5.1% and an increase in runoff volume of 4.3% occurring in the projected RTRW land cover and an increase in peak discharge by 25.2% and an increase in runoff volume by 21.15 % on land cover projections according to trend growth. Research shows that with an increase in 1 CN value, there is a decrease in infiltration by 4.2%, an increase in discharge and runoff volume by 3.6% and 2.9%, respectively. The hydrological calibration process gave the best results with the Manning channel roughness coefficient parameter value of 0.04 and 0.07 in the flood plain. An increase in inundation area by 15.85% occurred in the RTRW land cover projection and 91.1% in the land cover projection according to the trend growth, while there was an increase in inundation volume by 18.2% and 101.7% in the projected land cover respectively. Through the analysis of flood hazard reduction, it was found that efforts to improve infiltration through lowering CN value could not provide maximum results, so it needs to be combined with other flood hazard reduction methods, including the construction of water absorption areas in residential areas and public facility areas and by increasing river capacity.