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France and other regions around the world frequently undergo devastating flood events. Any failure of a flood protection structure can lead to human casualties and material damage. Unfortunately, such long linear structures are often poorly maintained and have shown repeated signs of weakness. Therefore, river levee management raises a number of substantial issues for the decision-makers responsible for ensuring maximum safety for the surrounding population at a reasonable management cost. The aim of the Digsure project is to provide levee managers with scientific methods and information technology (IT) tools for levee management. The Digsure method is a levee assessment method based on a probabilistic pattern. It produces levee performance indicators and integrates data and the uncertainty on results. Digsure is a geographic information system tool that implements the Digsure method. It estimates and displays levee performance and associated uncertainty intervals throughout levee assessments.

Abstract. Risk Flood protection involves works which reduce the hydraulic hazard in protected areas in terms of frequency, duration, water level, water velocity or flood arrival time. These works are parts of protection systems. In this paper, we discuss and compare three structure-based solutions that contribute to flood protection but seem to oppose one another in the mind of general opinion: levees based protection systems, whose purpose is to prevent water from spreading in protected areas; diversion channels that aim to decrease the flow at their downstream; flood expansion areas, whose purpose is to temporary store water, reduce flood peak and spread flow duration. The article also deals with weirs which can be found in addition to dikes in the three types of solutions on which the paper focuses. For each type of these flood protection solutions, the paper describes their functions and limits, details how these solutions are similar, opposite or complementary, and in the end shows that they are globally complementary and not mutually exclusive. It also demonstrates the interest of a multi-scale analysis and of an integrated design and management of these arrangements, taking into account flood risk, morphological changes and associated environmental objectives.

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Improving protection against fluvial floods requires a better estimation of levee failure. We developed an assessment method of levee failure probabilities for sliding, backward erosion, and overflowing each represented by fragility curves. We tested two approaches to aggregate those fragility curves into a global fragility curve respectively using: an enveloping curve and Monte‐Carlo simulations. We implemented this approach to earthen levee reliability for several flood return periods to the Bow River in Calgary, Canada. We used limit equilibrium method to estimate the safety factor of the levee segment and Monte‐Carlo simulations to estimate sliding probabilities. We used Terzaghi's critical hydraulic gradient to estimate backward erosion failure probabilities. The estimation of overflowing probabilities required expert judgment. We discussed how the choice of the hydraulic gradient area and the consideration of a steady state or transient model impact backward erosion failure probabilities. The results showed for our study case that, even though the transient model is a closer representation of reality, the levee saturation parameter has little impact on hydraulic gradient values, by extension, on sliding and backward erosion failure probabilities. The Monte‐Carlo aggregated fragility curve is more realistic than the envelop curve of the failure mechanisms for an equivalent computation time.