Information systems and diked areas: examples at the national, regional and local levels

There are several thousand kilometers of dammed waterways in France for flood protection. Compared to other natural hazards, flooding is characterized by being largely dependent on the behavior of dikes in situation of crisis. To the natural flood hazard, resulting in the overflowing of a river, is added a technological hazard of the breaching of dikes built to control flooding: this further complicates flood study and prevention. In parallel, protected (up to a point) by these dike systems, social issues have dramatically increased in the last few decades, due to a more or less controlled urban development. A number of initiatives have been taken to ensure dike security since the middle of the 1990s. In 1996, the full-sized Loire Plan Multidisciplinary Team (EPPLGN) launched a historical study of the causes of levee breaching along the Loire river during the 19th floods [HAL 96]. Also in 1996, this team commissioned Cemagref, associated with the engineering consultancy firm ISL, a comprehensive methodological work to develop an operational process to diagnose and monitor dikes [CEM 97]. In 1997, at the request of the ministry of land and environment management, a temporary special committee of the General Council for Roads and Bridges and of the General Council for Rural Engineering, Water and Forests was set up to draft a summary of several missions that had been implemented after the French floods of 1993 and 1995. This request was part of the interministerial circular dated 17 August 1994, which instructed inventory of all the flood protection works and to conduct a technical audit of these works. In compliance with this circular, the commission eventually supported a national survey to draw a list of all dikes, of their respective managers and of everything they protect. The ministry entrusted Cemagref with the creation of a questionnaire and the monitoring of a computer application development on a database management system (DIGUE software) to carry out this inventory and exploit the results [CEM 99, ROY 98]. The survey was started in mid-1999 at departmental level, and the first answers were received in 2000. To complement this inventory, the ministry also urged Cemagref to develop a guide for the monitoring, maintenance and diagnosis of flood protection dikes [MER 01]. As early as 1998, Cemagref wished to answer the need for software and database tools to diagnose dikes, and thus started to analyze and design a geographic information system to support stakeholders involved with flood risk in diked areas to coordinate their actions for an integrated management of these areas [CEM 00]. The context of the document being set, we would like now to detail the information systems dedicated to diked areas by making a fourfold presentation: in order to provide a reference framework for this document, we will use the results of a study conducted by Cemagref in 1998 with the aim of identifying the stakeholders involved with diked area management, their tasks as well as their level of intervention; then, we will study the importance of the spatial dimension relating to the general issue of diked area management; we will describe the three information systems that were developed during the studies mentioned above; finally, we will conclude with a synthesis of these various experiences so as to suggest approaches to develop multi-stakeholder and multiscale GIS that could contribute to a more integrated management of diked areas.