STUDY OF THE EFFECT OF LAND COVER CHANGES ON FLOOD HAZARDS IN THE CIKERUH RIVER BASIN

• Main Author: Marshal Syuhada, Muhammad
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/76286
• Institution: Institut Teknologi Bandung

Flood is one of the natural disasters that frequently occur in Indonesia due to high rainfall. Floods happen when the volume of water overflows and inundates the surrounding areas due to inadequate drainage systems or lack of river capacity to contain the runoff. One area in Indonesia that is often affected by floods is the Cikeruh River Basin which is part of the Bandung Basin region. Flood hotspots in the Cikeruh River Basin, especially in the Sapan and Rancaekek areas, have been a concern for the government to address. However, the implemented measures have not been effective, and one suspected factor is the land cover changes in the Cikeruh River Basin. Land cover changes, such as land conversion to urban and industrial areas, have an impact on increasing the runoff discharge. Previous studies have also shown that the Cikeruh River Basin has undergone land cover changes with a decrease in the area of paddy fields, forests, grasslands, and fallow lands. The recurring floods in the Cikeruh River Basin disrupt activities in the Bandung Metropolitan Area, which is the provincial government center with the largest population in Indonesia as a province. Therefore, an integrated solution is needed to mitigate floods and reduce their impacts. One aspect that needs to be considered is the change in flood hazard levels due to land cover changes. iv This research aims to analyze land cover changes and their impacts on flood hazard levels in the Cikeruh River Basin. The study utilizes a flood simulation method using the Rainfall-Runoff-Inundation (RRI) model to generate flood hazard maps based on land cover changes with certain return periods of rainfall. The methods employed in this research include literature review, data collection, hydrological analysis, land cover change analysis, model parameter calibration, verification of calibration results, flood inundation modeling, development of flood hazard map, and correlation analysis between land changes and flood hazard levels. The research utilizes the Rainfall-Runoff-Inundation model as a tool for calibration, verification, and flood modeling. This model can simulate 2D runoff and inundation simultaneously, as well as lateral subsurface flow and infiltration. The results of this research show that the calibration of the Rainfall-Runoff-Inundation Model produces valid Manning roughness values with high accuracy. The MAPE test results for calibration against observed discharge yield a deviation of 4.25%, while verification results show 14.17%. The flood simulation using a 25-year return period rainfall indicates an increase in the extent and depth of inundation due to land cover changes between 2000 and 2020. In 2000, the flooded area was 42.7 km2 with an average depth of 1.45 m, whereas in 2020, the flooded area was 3.2 km2 with an average depth of 1.52 m. Although the majority of threat levels remained at H2 or Low from 2000 to 2020, with depths ranging from 0.5 to 1 m, the flood hazard map shows an increase in flood threat in certain areas, particularly in regions with low Manning roughness coefficients and infiltration, especially at H2 and H3 levels due to the increased average inundation depth. The observed changes in flood threat are strongly correlated with land cover changes in the Cikeruh River Basin. This is indicated by the examination of threat levels based on administrative locations and land cover, both of which demonstrate correlations between flooded area, inundation depth, threat levels, and the presence of specific land cover types such as settlements and paddy fields. The generated flood hazard maps can serve as a reference for the development of integrated solutions to reduce flood risk in the Cikeruh River Basin. This research provides a better understanding of the relationship between land cover changes and flood threats, as well as the utilization of the Rainfall-Runoff-Inundation model, which can be used as a basis for policymaking in the management of flood-prone river basins.