By Yulia Mariska – (Thesis M.Si Sriwijaya University, 2012), Supervised by Prof. Bart Schultz, PhD, MSc; Prof. Ir. Robiyanto H. Susanto, PhD, M.Agr.Sc; Layzo Hayde, PhD, M.Sc.

Prabumulih City, the study area, is one of the cities in South Sumatera. Although Prabumulih City is a new city formed based on law No 21 year of 2001, but it has rapid growth in population and economics. This is because Prabumulih City is a City of trade and services. Due to the population and economic growth, most of the land use in Prabumulih City is used for some urban infrastructure such as settlements, buildings, and offices. The topographic conditions of Prabumulih City are relatively flat. According to its altitude from sea level, Prabumulih City is categorized as lowland, with the altitude of around 14-78 metres.

In the region Prabumulih, there are (three) permanent streams with three Sub-Basins, namely sub River Basin Kelekar, Water Rambang and Lematang. Most of the area of Prabumulih City is located in Kelekar River Basin such as West, East Prabumulih and Cambai District. Kelekar River flow condition and its tributaries often create flooding and inundation in Prabumulih City. The factors that cause flooding and inundation in Kelekar river are : there are bottle necks in the bank of the river, high sedimentation rates because of the garbage, no retention ponds for the runoff, narrowing the channel, changing land use in the river basin area from not built to built area. In some locations, there are micro-drainage channels disconnected or not connected with the channel in the downstream section while in other parts the drainage channels are only on one side of the road, even in some locations there are also roads that do not have a drainage channel. Thus, the drainage system at Prabumulih City can be said yet planned.

Tree main objectives are developed in this research. First is defining the existing urban drainage and flood protection systems in Prabumulih City. Second is analysing the topographic map by using the GIS. DUFLOW is developed to analyze the rainfall and evaporation data, cross and longitudinal sections, discharge of each urban drain in the study area. For this purpose, chance of occurrence of 2% per year has been applied. Three scenarios have been developed: using existing condition, sediment and garbage, improvement of culvert dimension. The simulation of DUFLOW presents that the capacity of drainage and culvert dimension is insufficient to flow the water from the city. Structural and Non Structural measures can be proposed in order to cope with the flooding problem in Prabumulih City.

Keywords: flooding, urban drainage, DUFLOW, GIS