GIS Based Urban Drainage Analyses and Their Preliminary Applications in Urban Stormwater Management

ABSTRACT Watersheds and surface stream networks are two main fundamental elements in urban drainage system. They are also very valuable in urban water management and making urban development master plan. The urban watersheds are traditionally delineated according to the convergent boundary of a river or creek, or the sewer systems. It is generally a river basin or a large urban area. In practice, however, the flooding frequently occurs in some small areas rather than the whole watershed. In those cases, to delineate small subcatchments and fine flow routes on surface by manual method is thus not very user friendly. Moreover, it is difficult to take the manmade interventions on topography into consideration. Therefore, this paper aims to provide a reliable, but simple and user friendly approach to carry out above analyses and study their applications. A GIS-based hydrological approach to create urban watersheds, to compute their characteristics and delineate stream networks, was studied in this paper. The impacts of buildings on surface were taken into account and the influence of grid cell size was investigated, too. The generated results were then applied in a preliminarily analysis of urban flooding. In addition, their valuable in making emergency action plan and urban water management, particularly in sewer design and improvement was put forward. The study was carried out by a Norwegian case.