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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