By Eldowan Arief – (Thesis M.Si Sriwijaya University, 2011), Supervised by Prof. Bart Schultz, PhD, MSc; Prof. Ir. Robiyanto H. Susanto, PhD, M.Agr.Sc; L. Hayde, Ph.D., M.Sc.

Lubuklinggau City, second largest city of South Sumatra, is experiencing rapid development due to its geographical advantage and strategic role as development centre in the western part of the region. The development not only gives economic growth of the city, but also creates some problems to environment such as conversion of agricultural lands and open space into settlement and public buildings, causing new problems on the drainage system mainly in increasing surface runoff by impermeable urban surfaces. Some inundations in the streets of a few centimeters to decimeters are ofien found in several locations. Today, public expectations and concerns regarding stormwater runoff and its impact on urban development have also been increasing and are forcing the municipality to address the matter by appropriate stormwater drainage planning and design. With respect to this, a master drainage plan is needed to ensure that the optimal drainage system is developed to meet present and future requirements. The drainage area included would either be determined by existing drainage boundaries or boundaries imposed by a watershed drainage plan. Hydrologic and hydraulic modeling can be used as decision support system tool. The first step is to define the existing local drainage system. Analysis of spatial and geographical condition has been performed to define the natural drainage system which will invariably become the major drainage system. A Geographic Information System (GIs) has been used resulting in whole municipal drainage network. The second step has been to assess the need for discharge controls to meet downstream hydrologic constraints identified. In a specific site, catchment basis, the process of runoff in the urban drains has been simulated by using the one dimensional unsteady hydraulic model DUFLOW. Then the model results have been combined with the Geographic Information System (GIs) data of the area and analyzed with appropriate a~alysisto ols from many sources. The simulations performed indicate that the problem of existing stormwater drainage and discharge system in Lubuklinggau City occurs in the local level, not in the river basin level. Inundation created in the local system is mainly due to the obstruction in the urban drains. In fact, with good operation and maintenance, the capacity of drainage is relatively sufficient to convey the storm water runoff. However, model simulation of the drainage was conducted in small catchment area. Therefore, it needs to be extended to larger catchment or watershed to get more comprehensive and clear perspective. In that case, GIs and DUFLOW can be used as effective tools to indicate the possibility of drainage development. It mus be supported by the availability of detailed data such drainage network and dimension, 0.5 – 1 meter contour data, land use data.

Keywords: stormwater runoff; GIs, model, DUFLOW, urban drainage