Emergent vegetation development, wave extinction and soil erosion are strongly interrelated processes in exposed riparian zones. The above-ground parts of the vegetation reduce wave energy, while the below-ground parts strengthen the soil. On the other hand, vegetation development may be restricted as a result of wave stress. Interactions between waves, soil erosion, and emergent vegetation were studied during three consecutive years. Two helophyte species, Phrugmites australis (Cav.) Trin. ex Steudel and S&pus lucustris L., were planted in separate bank sections on two types of sediment, sand and silty sand, in a wave tank. Regular waves were transmitted through 4 m wide bank sections with and without helophytes growing on a horizontal part. Bank profiles, wave transmission patterns and vegetation parameters were measured after exposure to waves with a height of 10 cm (Year 1) and 23 cm (Years 2 and 3). Both 10 cm and 23 cm waves affected bank profiles. Erosion of the banks occurred due to downslope transport of sediment. Soil erosion patterns closely reflected the patterns of standing waves over the horizontal part of the bank. Emergent vegetation influenced the erosive impact of waves by both sediment reinforcement and wave attenuation. A smaller amount of net erosion was measured in the wave-exposed sections covered by vegetation than in the unplanted sections. The stands of Scirpus lucustris were damaged due to uprooting of rhizome parts by 23 cm waves, followed by increased erosion of the soil. No damage occurred to the Phragntites australis stands. The greatest ' Cortespondiig author.

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Assessing actual and potential biodiversity of river-floodplain ecosystems on the basis of policy and legislation concerning endangered and protected species is necessary for consistency between different policy goals. It is thus a prerequisite to sustainable and integrated river management. This paper presents BIO-SAFE, a transnational model that quantifies the relevance of species and ecotopes, characteristic of the main channels and floodplains of the rivers Rhine and Meuse, on the basis of international treaties and directives and national Red Data Lists. BIO-SAFE was developed into a tool for biodiversity assessment with regard to design and evaluation of physical planning projects, Environmental Impact Assessments and comparative landscape-ecological studies. It was conceived to be applicable in Germany, France, Belgium and the Netherlands.Taxonomic groups involved are higher plants, birds, herpetofauna, mammals, fish, butterflies, and dragonflies and damselflies. The linkage of habitat requirements of species to ecotopes allows the user to derive information at the level of several ecotope types and scales. The model requires input data on presence of species and/or surface area of ecotopes. BIO-SAFE has been applied to flood risk reduction projects along the rivers Rhine and Meuse. Results show that BIO-SAFE yields quantitative information regarding the degree to which actual situations, reconstruction designs and developments of species and ecotope composition meet national and international agreements on biodiversity conservation.Attuning biodiversity conservation and flood risk reduction measures is a major issue in applied ecology and spatial planning. Assessments with BIO-SAFE can help find an optimal balance. Because of its policy-based character, BIO-SAFE yields information that is complementary to ecological biodiversity indices, single-species habitat models and ecological network analysis. The development of BIO-SAFE was based on species characteristic of rivers and floodplains, but the method can easily be applied to other ecosystems as well.

Policy makers are confronted with the question of how to combine sustainable flood protection and floodplain rehabilitation in the best possible way. Both topics deal with spatial planning aspects in a range of scales. This question was the starting point for the development of an evaluation method within the IRMA/SPONGE project Intermeuse, illustrated on the basis of assumed flood protection strategies in the Meuse river basin (the 'sponge' strategy, the 'retention' strategy, and the 'floodplain lowering' or 'winter bed' strategy). The integration of flood protection and floodplain rehabilitation can be performed on two scale levels that are interrelated: on the regional level the focus is on (large parts of) an entire stream basin; on the local level specific site conditions are taken as starting point. Ecological aspects under study are spatial cohesion of habitats as identified by species population persistence modelling (regional, longitudinal level) and required habitat quality for carabid beetles and for meadow vegetation gradients as assessed by correspondence analysis (local, transversal level). The carabid beetles are taken as indicative for the ecological integrity of the river bed, the meadow vegetation for that of the floodplain.A unifying concept in the evaluation of ecological integrity is the ecological minimum: the critical boundary or minimum level of habitat conditions for a potentially good ecological functioning. It is the least acceptable state for a river ecosystem that is still functional to some extent, compared to a natural river ecosystem. The results of this study show clearly that there is a good chance to combine floodplain rehabilitation aims with flood protection activities, both on a local and on an international scale. Although ecological effect assessment and ecological optimizing (referring to a natural reference state) remain basic, additionally the assessment of the ecological minimum helps to define design strategies for integrated flood protection, especially in situations where there is an opportunity for river rehabilitation.

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