Pipe network shown using ArcScene in ArcGIS 3D Analyst, allowing the modeler to quickly identify errors in the network data.

Situated between Roskilde Fjord and the Sound, 10 miles northwest of central Copenhagen, Denmark, lies Ballerup, on the boundary between the city and the country. After World War II, Ballerup developed around two small villages with historical roots in the Stone Age, but modern Ballerup has left the stone tools behind and become the "Silicon Valley of Denmark" with a vibrant information technology (IT) industry. The current population is 47,000, and the area covers approximately 6,000 acres.

The Ballerup City Authority is responsible for a sewer network consisting of 120 miles of pipeline, a storm drainage network with more than 100 miles of pipeline, and a water distribution network with 200 miles of pipeline.

Two important tools used in the planning and management of the water and collection systems are GIS and simulation models. Until recently, these tools were more or less isolated "islands" with data transfer taking place through cumbersome file transfers.

Simulation Models

Simulated surface flooding in Ballerup during a severe storm.

Like most modern sewer and water authorities, Ballerup uses simulation models extensively for analysis of operational problems, such as flooding and sewer overflows. The models are also crucial tools for the city planners, who need to identify future bottlenecks and find the most cost-effective solutions to ensure adequate capacity of the infrastructure when new areas are urbanized.

Simulation models need information about the physical properties of the pipe network, such as pipe sizes, materials, hydraulic structures, pumps, and valves. Such information is typically managed in an asset management system, which is frequently another isolated island in the IT systems of the city or utility. In Ballerup, this information is maintained in a separate system as one island in the IT system.

GIS to Connect the Islands

Following an intensive study of available vendors, Ballerup selected DHI Water & Environment of H�rsholm, Denmark, to partner in its efforts to bridge these various islands of information. DHI is a business partner of Esri distributor Informi GIS A/S.

The open architecture of ArcGIS Desktop (ArcInfo, ArcEditor, ArcView) made it an ideal connectivity tool for the many applications that are used to manage data related to urban water infrastructure. In Ballerup, the use of a geodatabase as the data repository for its modeling made it easy to exchange data and combine information that originates from separate applications.

Collection system pipe network displayed in MIKE URBAN.

DHI's new water/wastewater modeling tool MIKE URBAN made full use of this openness and was used to combine the modeling of Ballerup's water distribution and collection systems. This application integrates specialized DHI modeling components with ArcGIS components into an urban water and wastewater modeling environment for Ballerup. The user interface makes extensive use of ArcGIS technology and is immediately intuitive to Ballerup's ArcGIS users.

The GIS components are fully integrated with a wide range of numerical simulation engines for water and collection system networks. The engines include the most modern versions of classical public domain engines (SWMM5 and EPANET), as well as engines from the MOUSE family developed by DHI.

Connecting the IT Islands

Ballerup's MIKE URBAN application uses the geodatabase as the repository for all network-related data. The data model is open and documented, and the data can be accessed and even managed through other GIS applications. This makes it easy for Ballerup to maintain and update its data within its own GIS, then update the model whenever new data is available. At the same time, the application can use whatever other relevant data that users may be storing in their GIS system, such as land-use data, aerial photographs, and digital elevation data, as background information for the modeling.

The geodatabase is effectively opening bridges between the IT islands.

Quality assurance is always a major part of the model-building process, and utilizing the facilities available in the ArcGIS 3D Analyst extension made visualizing the network a time- and money-saving technique. Ballerup also used its new ability to combine traditional GIS visualization techniques with powerful, dynamic, and results-oriented visualization based on DHI's MIKE Objects components. The results provided animations of flows and water levels that were essential for the interpretation, comparison, and presentation of the model simulations.

Simulating Climate Change

In addition to the traditional uses of modeling for operational and planning purposes, Ballerup is also using models to prepare for the potential consequences of climate change. In Denmark, it is expected that rainfall will become more intense in the coming decades, and this may lead to increased flooding in urban areas. The city's new application includes long-term simulation tools, which are well suited for the analysis of the effects of changes in rainfall patterns in terms of statistical quantification of a range of possible scenarios.

2D Flood Simulations

In addition, Ballerup linked with DHI's 2D overland flow model, which is capable of simulating the detailed flow pattern above the ground. This provided the storm water authorities with a realistic impression of likely flooding scenarios. The overland flow model receives overflows from the underground network, routes the water dynamically, and allows it to reenter the drainage network when and where the capacity is available. The results from the 2D simulations were then visualized dynamically within the GIS environment.

For more information, contact Sven J. Nielsen, Ballerup Kommune (tel.: 45-44-772-339, e-mail: sjn@balk.dk, Web: www.ballerup.dk), or Henrik S. Andersen, DHI (tel.: 45-45-16-90-94, e-mail: hsa@dhi.dk, Web: www.dhisoftware.com).