Abstract

In France and especially in the Caribbean islands, the serious damage caused in urban areas by the recent flash floods showed the importance of efficient and adapted reactions of the municipality. Faced by a flash flood crisis, decisions should be taken based on the current information available that is often very limited due to the lack of time to obtain, manage and analyse them.

Therefore, the Conseil General of Martinique decided to develop an operational, integrated and innovative tool, SDAC (Systeme Departemental d'Alerte de Crues), to be able to forecast and manage urban flooding in real time. The modelling system is based on predicted precipitations from rain gages (radar imaging will be integrated soon), a rainfall-runoff model, a hydraulic model developed for urban areas and a risk definition representing the flood importance.

This innovative system has been initially implemented on four watersheds of the island in 1999, including the Lezarde basin which is particularly vulnerable to floods that induce significant damage on the road system as well as on the economic activities of the island (e.g. Airport, commercial centre). In 2005, the system was significantly improved and innovative steps were taken to reach different objectives: (i) to improve the robustness and precision of the flood forecast; (ii) to improve the alert system for small watersheds; (iii) to represent in details the flooding zones in the urban areas using GIS; (iv) to insure warning messages reception that allow prevention actions; and (v) to make the forecasting data and maps available on the internet for public information. The system is currently operational and is very promising since the results show the significant advantages obtained when combining growing computer power with increasing urban hydrological knowledge.

The next step in 2009 is to include the radar data and the sea level data in real time in order to (i) enhance the anticipation of rainfall that can produce flood, and (ii) take into account the sea level hydraulic constraint that could be significant for some basins during a big storm.

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