Computer tools for development of parameters for an urban watershed using desktop GIS

Scope of study. An interface is developed which links a powerful desktop Geographical Information System (GIS)-ArcView, with a surface water management model-XP-SWMM. This interface, written in Avenue script language, consists of several tools which automate the spatial analysis, preparation of data for XP-SWMM, and display of simulated results from XP-SWMM within GIS environments. An automated extraction of subcatchment characteristics from a digital elevation model (DEM) is performed by Spatial Analyst. The derived data are used as input for the Runoff Block of XP-SWMM and subsequently correlated to the runoff quantity of a watershed. The tools programmed for this interface construct the runoff collection and conveyance system in the GIS environment. The network drawn in XP-SWMM can be imported into the ArcView environment, which can be edited and exported to XP-SWMM for runoff simulation. The simulated results from XP-SWMM are combined with other GIS data for the visualization of subcatchment boundaries, potential hazards due to inundated areas, over capacity pipes and the natural flow path of the runoff.; Findings and conclusions. The interface is able to accurately generate the terrain attributes of the watershed by using spatial analysis techniques performed by GIS. A validation study was conducted and two sets of urban watershed parameters—GIS-derived versus manually-estimated—were tested for 46 subcatchments of the Allen Creek Watershed in the City of Ann Arbor, Michigan. The manually-estimated and GIS-derived sets of parameters were used as the input for the runoff estimation. The comparison conducted on runoff quantities generated by both sets of parameters showed an average difference of 10 percent.