Evolution of an Integrated 1D/2D Modeling Package for Urban Drainage
Recent flooding events in North America have revealed deficiencies in existing stormwater infrastructure and management practices. The development of effective and efficient designs requires a comprehensive understanding of flooding in urban areas and complex open channel and overland flow systems. Traditional one dimensional (1D) models are used to simulate flow in river channels and gravity collection networks but are inadequate for simulating phenomenon such as significant street flooding and overbank flow in flood plains that occurs during extreme events. 1D/2D and 2D models have begun to be used but their complexity, cost and significant data requirements have limited their application.
The availability of high quality digital terrain models (DTMs), the increased power of desktop computers as well as the need for more realistic simulation of flooding have all contributed to the adoption of 2D models for flood plain mapping and the analysis of overland flows. Xpswmm is a comprehensive 1D hydraulics and hydrology modeling package for stormwater and wastewater systems. xpswmm2D was created by coupling the 1D capabilities of the xpswmm software package with the 2D hydrodynamic model TUFLOW. An additional feature was created to dynamically link 1D nodes and links to 2D cells in a single model.
New technologies were required to create the integrated package for both the model building and the presentation of results. For example, the incorporation of a DTM into the hydrodynamic model allows the generation of the 2D grid elevations, automatic creation of cross sections and the results to be displayed in perspective views. New modeling objects were developed to represent head and flow boundaries, 1D/2D interfaces, breaklines, catchments and 2D domains.
A variety of case studies are presented that demonstrate the new combined 1D/2D hydraulic routing including a comparison of 1D, 1D/2D and 2D results. This chapter concludes that combined 1D/2D modeling in xpswmm2D offers modelers increased capabilities to investigate the performance of urban drainage systems and of urban waterways and floodplains during extreme events.
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