Real Time Flood Warning Decision Support Systems Utilizing Client-Side XML/XSLT/SVG

Real-time flood warning Decision Support Systems (DSS) have been developed in the past several years to aid emergency managers to respond quickly to rainfall and flooding events. In the past four years, the Urban Drainage and Flood District (UDFCD) in Denver Colorado have developed several web based DSS interfaces using XML/XSLT/SVG technology. These displays allow real-time analysis of radar images, thunderstorms, rainfall, river stage, inundation areas, and future rainfall potential. This paper will discuss the specific techniques developed for these displays.

The UDFCD has been operating a real-time flood warning system since the early 1980's using radio technology to send rainfall and stage information to a computer base station. The commercial software operating the base station has evolved over the years to include detailed displays of hydrographs, maps, and summary tables of the flood-warning system. Nevertheless, the user had to be directly connected to the base station either directly at the machine or via a dial-in connection. In 1994 the first web based displays were created by delivering pre-formatted tables or GIF images via an early web server program. Since that time the demand for web-based information from the UDFCD flood-warning system has increased dramatically along with the types of displays and information available. The price for this demand has been an ever increasing load on both the processor and bandwidth of the UDFCD base station.

Starting in 2003, the UDFCD requested we investigate potential new technology available to display real-time decision aids in a web display while reducing the load on the base station. Several promising applications were developed using client-side XML/XSLT to create a full graphical interface using SVG technology. The displays allowed the integration of GIS information for spatial reference along with the real-time rainfall and stage information. Programs were developed on the base station to deliver any flood-warning system data in XML format via the existing web server software. XSLT stylesheets were then created to transform the XML data from the base station into SVG using exclusive client-side processing. This greatly reduced the bandwidth and processing load on the base station. In addition, additional data sources were converted to XML allowing an integrated DSS for emergency managers. The additional data sources included radar images, aerial photographs, projected thunderstorm movement, hydro-meteorological data, and post-storm rainfall observer readings. GIS data is also integrated in the display for additional reference for the user. The use of SVG allowed not only the common graphical display of this information, but the ability to animate the information in a synchronized fashion. The XML data stream also allowed us to develop prediction models using spreadsheets with an automatic update for current data.

The development of these applications will be described in detail in our session. It includes SVG displays of :

Additional development will continue including the conversion of the flood-warning system metadata to XML format allowing automatic updates to systems status via XML/XSLT/SVG. In addition, the interfaces will connect directly to the metadata to allow instant updates of the displays based on new information of the system.