MULTI-SCALE ANALYSES ON FLASH FLOOD SUSCEPTIBILITY ASSESSMENT BY USING GEOMORPHOLOGICAL APPROACH AND HYDROLOGICAL MODEL IN JUWANA CATCHMENT, CENTRAL JAVA PROVINCE
PRIMANDA KIKY W., DR. M. ANGGRI SETIAWAN, M.Si.
2014 | Tesis | S2 Ilmu Lingkungan-
Flash flood has become one of the most exposed hazards in Juwana Catchment. It causes destruction to houses and bridges, paddy fields, and even casualties. It becomes important to know the susceptible area of flash flood. Flash flood occurence is mainly controlled by two main factors, i.e. rough topography and heavy rainfall. Therefore, two methods were used to assess the flash flood: by using geomorphological approach and hydrological model. Geomorphological approach includes the quantitative parameters: Relative Height Differences – Slope – Drainage Density; which are to represent the components of morphographic, morphogenesis, morphometry, and morphoprocess. On the other hand, hydrological model provides detailed flash flood process computing complex parameters such as DEM, land cover, channel, vegetation and house cover as its input. Main objective of the research is to provide a stepwise assessment of flash flood susceptibility by using geomorphological approach and hydrological model. The specific objectives of this research are: 1) To identify the flash flood susceptible area based on geomorphological approach, 2) To simulate the flash flood by using hydrological model, and 3) To analyze flash flood susceptibility based on the result of geomorphological approach and hydrological model. The geomorphological approach was mainly based on quantitative method by using weighted scoring of Relative Height Differences (RHD), Drainage Density, Slope. Hydrological model was using openLisem model. The main input maps are DEM, channel, road, land cover, and vegetation cover. The advantage of using openLisem in the hydrological model is that it may provides 1D/2D model of flash flood, although it needs many detailed data. The model can be functional in Indonesia to accomodate the variation in catchment condition because openLisem can be adjusted to fit with various assumptions. The result of geomorphological analysis shows the location of flash flood prone area that highly controlled by the slope and drainage density. Based on the medium scale analysis, it was found that 20 sub-catchments in Juwana Catchment are prone to flash flood. On large scale and field survey, the dominant factors affecting flash flood are slope and the surface morphology. Meanwhile, the hydrological model shows flow dynamic and the effect of catchment properties. The spatial distribution of flash flood is generally accumulate near the meeting of channels and in the flat terrain in the middle of the catchment. As conclusion, the combination between geomorphological approach and hydrological model in flash flood assessment is quite effective in large scale; although still using many assumption and limitation. The geomorphological approach in the medium scale may provide the prone area of flash flood, and may be used as consideration to determine the location which needs extra attention. Larger scale provides insight analyses of the morphology condition. The hydrological model shows the choke points and flat area where the flash flood accumulate. Keywords: Flash Flood, Multi-scale Analyses, Geomorphological Approach, Hydrological Model
Kata Kunci : Flash Flood, Multi-scale Analyses, Geomorphological Approach, Hydrological Model
