Edouard Patault, Jérôme Ledun, Valentin Landemaine, Arnaud Soulignac, Jean-Baptiste Richet, Matthieu Fournier, Jean-François Ouvry, Olivier Cerdan, Benoit Laignel

While soil erosion and runoff physical aspects are widely addressed in the literature, few studies have focused on the economical dimension. However, it is essential to consider this dimension to conduct appropriate land use management policies. Erosion and runoff are known to result into on-site and off-site impacts. A fully exhaustive analysis of erosion and runoff economic costs may be difficult and ambitious due to the availability of the data and a lack of actual knowledge. In this study, we chose to analyze the main off-site economic costs induced by these processes in two specific areas located in the northwestern European loess belt (Normandy, France). We quantified avoidance and social damages over the last 25 years through a global and retrospective analysis of financial databases provided by regional or local authorities (water agencies, departmental councils, reinsurance, drinking water companies, transport infrastructures managers) and existing literature review. Our analysis suggested that over that period, the total damages cost ranged from 611 to 721 M€. Off-site avoidance damage costs accounted for almost 2/3 of the total expenditure. In the Seine-Maritime area, the mean cost was evaluated to 21.6 € yr-1 cap-1 and to 9.1 € yr-1 cap-1 in the Eure area. Even if we tried to be as exhaustive as possible some off-site economic costs remained unknown. It appeared that more research is necessary for the scientific community to get a full picture of off-site economic costs induced by erosion and runoff.