Distributed Flood Model For Urbanization Assessment In A Limited-gauged River Basin
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M. Farid, A. Mano & K. Udo
A distributed model is commonly used to investigate the effects of land cover change on flood discharge due to urbanization. The model should have adequate spatial data parameters in order to resemble actual condition and to achieve good accuracy. Unfortunately, most of developing countries have limited and insufficient datasets. The circumstances can be a problem in distributed flood model simulation. The objective of this study is to develop a distributed flood model for simulating runoff-response change due to urbanization in a river basin by using limited available datasets which correspond to the availability of datasets in developing countries. A 2D shallow water equation is used to simulate surface runoff while hydrologic parameters are simulated based on a nearly calibration free (NCF) tank model. The infiltration rate in the urban area is accommodated by applying a spatial distributed urban density. The model is applied to the upstream of the Ciliwung River basin, located in West Java Province, Indonesia. This domain, with an area of 234 km2 and a 46 km length of river, has contributed to flooding in its downstream area, Jakarta, the capital city of Indonesia. The urban area in this basin has increased by 183% while the forest area has declined by 52% from 1972 to 2002. The limitation of hourly rainfall data causes difficulty in producing spatial distributed hourly rainfall which is significant in flood simulations. Therefore, a method using simple linear interpolation is developed to solve this problem. Calibration and validation, conducted using events in 2002, showed good agreement to the observed data. In order to investigate runoff-response change due to urbanization, flood events in 2002 are simulated using 1972 land cover. The simulation results showed that urbanization during 1972 to 2002 has increased flood discharge significantly. Keywords: urbanization, distributed model, flood simulation.
urbanization, distributed model, flood simulation