THE ANALYSIS OF GEOMORPHOLOGY FLOOD INDEX SENSITIVITY TO EXTREME RAINFALL VARIABILITY IN INDONESIA

• Main Author: Amanda Bintang, Jessica
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/68716
• Institution: Institut Teknologi Bandung

Floods are one of the most common natural disasters in Indonesia, but mapping flood-prone areas is still a challenge, due to the vast area and high rainfall variations. Geomorphology Flood Index (GFI) is one of the empirical methods to map flood-prone areas, Flood Hazard Mapping (FHM), which is potential to address the challenge. However, GFI only reviews the potential flooding from topographic side only and has not involved extreme rainfall that has high spatial variations in Indonesia. This research was conducted to develop the GFI method by making extreme rainfall as one of the enter. The study proposed two extreme rain indexes as inserting in Modified GFI: IP-A and IP-B. IP-A and IP-B are defined as (Px-P5)/(P100-P5) and (Px-P5)/(????????????????????????????????????????????-P5). Px is rainfall with a certain re-period, P5 and P100 are each rainfall with a 5-year and 100-year re-period, and ???????????????????????????????????????????? is the average rainfall of all regions of Indonesia for a 100-year re-period. Each of these re-periods is estimated to be the Global Precipitation Measurement (GPM) data and the Generalized Extreme Value (GEV) method. Furthermore, Ip-A and Ip-B values along with DEMNAS data are used in GFI modification calculations to get flood extent. The results of this study show that Ip-A and Ip-B methods have different results. At the time of the 100-year re-period, the modified GFI with Ip-A will produce the same flood area as conventional GFI. While GFI modification with Ip-B is more sensitive to spatial variations of extreme rainfall. For example, Ip-B in Java has different values than Maluku. The Maluku area has the highest average extreme rainfall (323.91 mm/day) and the Java area has the lowest average extreme rainfall (188.11 mm/day) in a 100-year re-term. Modified GFI with Ip-B results in a wider range of flood potential in Maluku and small in Java when compared to conventional GFI. This indicates that Ip-B produces a Modified GFI that is more sensitive to extreme spatial variations of rain. This result is expected to produce more accurate mapping of flood potential in Indonesia.