The 'Storm Network' as a participative network for monitoring the impacts of coastal storms along the littoral zone of the Gulf of Lions, France
Résumé
The French coast of the Gulf of Lion is a low-lying coastal plain. Along this microtidal coastline, where the mean wave climate is moderate, humans have strongly developed infrastructure and urbanized the coastal zone, disregarding the potential impact of extreme events. This results in an increase of coastal vulnerability to extreme storms. Major storm events (1982, 1997 and 2003) have illustrated this phenomenon and caused damage to harbor facilities, coastal tourism infrastructures, and urban infrastructures. To improve the management and prevention of such threats on the coastal zone, the 2007-2013 coastal studies program of the State-Region Contract Project in Languedoc-Roussillon promotes the creation of a monitoring network of coastal storms and the resulting impacts. This "Storm Network", concerning the entire littoral zone of the Languedoc-Roussillon region, is based on a volunteering partnership between several local collectivities, government and research institutions. The aim of the network is to obtain good quality and homogeneous data along the entire coastline to enhance the regional knowledge on coastal extreme events and their impacts and to validate morphological models. According to the analysis of all historical events, an assessment of three thresholds of morphological impacts was done, basing on the offshore significant wave height indicator. A monitoring program was defined with three corresponding levels of intervention such as: level 1 (3m 5m) additional quantitative surveys and numerical modeling. In order to anticipate the event, an operational model for wave forecasting is used (WaveWatch3 Mediterranean model, by Ifremer). When reaching the defined levels, an automatic email is sent to the operators of the network to organize the survey. The Storm Network was implemented in 2011, and was activated during the winter 2011/2012. A storm group in October/November was particularly monitored by geolocalized pictures and observations (weather data, drift lines,...). The regional network permitted to localize precisely the storm impacts, and analyses their spatial variability. All the participant operators have a full access to the entire database, and contribute to feed it. A notable fact of this initiative lies in the voluntary participation and pooling approach adopted by the partners with no special funding (only the development of common network management tools). This data base will be helpful to provide pertinent indicators to better anticipate and develop mitigation strategies for tomorrow and the next decades.