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Urban floods can be caused by intense rainfall accumulations in short time periods that eventually exceed the capacity of the sewer networks. Despite the efforts made in the last years in all cities to increase the sewer’s capacity many cities are still exposed to these heavy rainfall events. In this work, we present a simplified flood Early Warning System, called FloodAlert, based on the use of radar observations to issue local flood warnings. Although precipitation accumulation estimates based on radar observations may suffer from different sources of error, they may also be the quickest way to obtain a reliable estimate of the accumulated precipitation, and of the precipitation that may occur in the forthcoming few hours by means of radar-based nowcasting. This short-term forecasting is crucial for urban floods where the response times are usually very short. Radar data are quality-controlled before its use and with cross-correlation techniques the motion field of the precipitation is obtained. This motion field is used to calculate the precipitation nowcasting and to define an observation region surrounding the point of interest, where it is important to be aware. This region changes dynamically with the precipitation according to its direction and speed. Accumulation values are calculated on this observation region for the next hours and warnings issued according to user-defined thresholds. A web-based platform has been developed to display the information and manage the configuration of the product (points of interest, warning thresholds and dissemination information -SMS mobiles, emails, etc.-). The platform dynamically displays geo-referenced information, including the points of interest, present and forecasted precipitation fields and hazard warnings. The warning issues by the platform can be spread not only through the viewer but also by email and SMS. The proposed solution is currently running operationally under several national radar domains.


Session S1-01, Special Sympoisum: Real-time Monitoring of Urban Water Systems



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