Background The biological recovery of a river is dependent of the recovery of its structure and its physical dynamics. Returning a river to "good ecological status" inevitably involves its physical restoration, given that its physical characteristics affect its functioning. Three types of modification are key obstacles for good ecological status: Alteration of the flow (discharge and sedimentation); Alteration of form; Biotope access alteration (lateral connections breaks, modification of the continuity upstream/downstream, etc.). Taking into account a river’s hydromorphology is needed to implement the Water Framework Directive (WFD) as well as the Flood Directive (2007/60). So far, stakeholders have improved hydromorphological quality without knowing exactly the consequences of their actions: the impact of a dam removal or water course section remeandering, for example. They usually get very little feedback (post-work is usually short-term) on the benefits of restoration of water quality and ecological status. Modifying or ‘manipulating’ ecosystems requires expert knowledge of watercourse dynamic mechanisms. Hydromorphological quality improvements can be measured by changes in physical or chemical parameters of the environment but also by changes in the composition and structure of plant and animal communities (which depend on the aquatic environment). The identification of mechanisms or natural processes that would ensure the sustainability of improvements is needed, in order to improve the restoration approaches, but also because the natural environment is variable. For instance, the effects of climate change, such as an increase in the flood frequency and intensity, has to be taken into account. Objectives The WALPHY project planned to pilot a structured approach to improving the hydromorphological quality of the River Meuse basin in Wallonia, in order to reach the "good ecological status" required by the Water Framework Directive (WFD). The specific objectives of the project were to: Develop of a methodology for helping to define the restoration works to be undertaken to improve the hydromorphological quality of water bodies "at risk"; Carry out restoration works on a significant scale on some water bodies at risk of not reaching the good status, based on two axes: longitudinal continuity and transverse continuity (area of freedom); Monitor the restored river system and its ecological status evolution at the local level (site of intervention) and the scale of the whole water body; Refine the methodology for the development of technical guidelines (decision-making tools) for river stakeholders, in line with the implementation of the WFD; and Disseminate these tools and recommendations to the authorities, stakeholders and the public.Results The WALPHY project achieved its aim of developing a methodology for assessing the hydromorphological river quality. The selection of the water bodies to be restored was based on the score obtained in the ecological evaluation. An additional three water bodies were selected owing to the significant alterations that had carried out on these sites. A preparatory assessment was carried out by adapting and improving an existing tool known as Qualphy (Qualphy stands for Qualité Physique) for estimating the physical status of rivers. The selection of the water sheds to be managed was thus carried out using the improved Qualphy method The selected water bodies were the Bocq aval (Bocq downstream, MM30R), the Bocq amont (Bocq upstream, MM28R) and a part of the Eau Blanche aval (Eau Blanche downstream, MM05R). The preparatory assessment using the improved Qualphy method showed that the transversal connectivity on the Bocq was not that bad, while the longitudinal connectivity was disrupted by numerous obstacles that are difficult or impossible for fish to cross. The team also found that the longitudinal connectivity on the Eau Blanche was acceptable but that the transversal connectivity (the natural connections between the river and the alluvial plain) was very poor. Indeed the Eau Blanche has been heavily affected by works carried out in the middle of the last century. As a result, the project focused on the restoration of the longitudinal connectivity on the Bocq through the removal/management of obstacles and on the restoration of lateral continuity on the Eau Blanche. In total, the project was able to remove 20 obstacles for fish migration (19 on the Bocq and one on the Eau Blanche). In some cases the obstacles were destroyed (e.g. the demolition of a dam). However, in many cases such action was not possible. Some dam owners did not consent because they have or are planning to construct mini hydroelectric power plants. In other cases, the role of the dam is important in relation to bridges and other constructions. In those cases, other solutions were implemented solely or in combination, including the creation of river bypasses, pre-damns, fish ladders etc. At the site of Vivaqua, where the river Bocq transforms into a concrete canal, it was not possible to establish a bypass river. Instead blocks of stone of various sizes were fixed on the concrete bottom. Furthermore, the transversal continuity/connectivity of around a 22 km-stretch of river was improved. Different kinds of techniques were implemented. In several locations the works were limited to the river bed with small-scale meandering. Also, various structures were put in place to diversify the habitat. In other areas, more ambitious works were implemented such as the restoration of a former meander on the Eau Blanche and on the Leignon. A former side river of the Eau Blanche Plain (the Grand Morbi) was reopened and reconnected with the Eau Blanche. The monitoring showed that the removal/management of obstacles is an effective way to improve fish mobility and population size. Furthermore, the removal of obstacles helps improve the transport of the bottom charge (sediments), resulting in higher quality gravel banks as spawning places. The monitoring showed also that the less ambitious works in the river bed are much less effective than the ambitious remeandering and reconnection of side rivulets. Continued action as outlined in the After LIFE Communication and Conservation Plan is already benefitting from lessons learned during this monitoring stage. Finally, the beneficiaries organised a final scientific conference, which attracted 210 attendees, including around 80 from outside Belgium. The results of the project were further communicated by the erection of information panels at the sites and the production of teaching materials. The project also produced a film detailing the restoration techniques developed and implemented by the project. A well-designed technical guide in French was produced. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).