Abstract
In 1995, a law stated a common regulatory natural risk zoning for French municipalities through a land-use planning procedure called Risk Prevention Plan (PPR). In mountain valleys and especially within torrential watersheds, considering protective structures in those plans is an actual concern. Those protections do have an effect on phenomena and modify hazard and risk levels. This paper gives an overview on how torrential protective works are taken into account in present risk prevention plans. To carry out this study, 53 recent risk prevention plans over 11 French mountain departments were selected and analyzed through a common analysis grid. Torrential protection works are taken into account in more than one third of analyzed plans. Protections mostly considered are dikes, bank protections, check-dams and sediment traps. Modalities of integration of these structures vary from one plan to another, influencing both hazard and regulatory zoning. Results also show a wide range of practices between departments and even inside them. Conclusions brought out enhance knowledge about actual practices which were not sufficiently known so far. Findings and new additional recommendations will be included in a future PPR methodological guide exclusively suited for torrential context, which is currently still missing.
Highlights
Lawful hazard and risk mapping are one of the most used non-structural measures to reduce exposition and vulnerability of people and infrastructures in many western European countries [1]
In order to support PPR establishment, several methodological guides were published by the Ministry of Ecology, Sustainable Development and Energy (MEDDE)
Specific guidelines are being implemented for torrential floods, leading to serious damage in mountain areas through brief and intense events such as debris flows
Summary
Lawful hazard and risk mapping are one of the most used non-structural measures to reduce exposition and vulnerability of people and infrastructures in many western European countries [1]. France has a long historical experience in the matter starting from the Submersible Surfaces Plan (PSS) created in 1935, to the Risk Prevention Plans (PPR) enforceable against third parties since a law promulgated in 1995 These plans aim at defining areas which meet specific land-use rules (and especially constructability rules) over French municipalities according to a natural hazard zoning. It aims to bring a detailed state of actual ways of integration of structural protections¶ effects in land-use planning, focusing only on torrential structures. It deals with the level of traceability of this integration left into PPR, highlighting main missing points and proposing several enhancement axes. It concludes on the operational use of those elements and gives some perspectives related to ongoing scientific developments
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