Training rivers with longitudinal walls: long-term morphological responses

Rivers have been trained for centuries by series of transverse groynes. This generally results in damages to their ecosystems as well as in undesirable longterm morphological developments. We analyze here the possibility to train rivers in a new way by subdividing their channel in parallel channels with specific functions with longitudinal training walls. In most cases, the goal is that of obtaining one deep, regular navigation channel and one shallower channel that is able to preserve some ecological functions of the river and to contribute to convey high flow discharges. The effectiveness of longitudinal training walls in achieving this goal and their longterm effects on the river morphology have not been thoroughly investigated yet. In particular, studies that assess the stability of the parallel channels separated by the training wall are still lacking. This work studies the long-term morphological developments of river channels subdivided by one or two longitudinal walls, focusing on low-land rivers. These rivers are normally characterized by the presence of steady alternate bars, or point bars inside their bends. For this reason, the presence of these large deposits is taken into account. This is the first study dealing with the combined effects of bars and longitudinal walls. The methodology comprises both laboratory experiments and numerical simulations...