ABSTRACT
Urban flooding due to high-intensity rainfall along coastal Semarang City is a major problem every winter. Such urban flooding cannot be avoided, but it can be controlled. Thus, it is necessary to extract real information regarding the flood events as well as to understand the landscape of Semarang using an integrated approach of remote sensing and a geographic information system (GIS) together with field measurements to propose reliable mitigation measures. In this work, the digital elevation model (DEM) of Semarang was used to automatically extract all the morphometric and hydrological parameters. In addition, different satellite images (optical and radar) were used to map the land surface features and to estimate the subsidence rate that affects the city and changes the land slope. Moreover, geological, structural, and groundwater maps were integrated in a GIS database. Consequently, several measures were proposed to mitigate the flooding. These measures are: construct prevention dams at the up streams, striate the meandering rivers, dredge the water channels to increase discharge, increase the river levee height, inject the excess water into a productive groundwater aquifer after performing quantitative hydrological modeling, construct a separate drain network (totally different than the sewer system), and, finally, install artificial water infiltration and attenuation systems in the flat areas. The locations and design of all these mitigation measures were mapped in a GIS format.
