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The human pressure upon an alluvial river in the Mediterranean region has changed its riverine and deltaic landscapes. The river has been channelized in the last 70 years while the delta has been retreating for more than a century (a set of data unknown, so far). The paper concentrates on the fluvial component, trying to connect it to the delta evolution. Is the channelization responsible for the delta retreat? We develop a method to compute the actual bed load transport with real information of the past river morphology. The paper compares the computation with very limited measurements, among which are bulk volumes of trapped material at a modern, deep river mouth. The decrease in sediment availability in the last 30 km of the channelized river is deemed responsible for the decrease in the sediment yield to the delta. Moreover, power development and flood frequency should be responsible for a baseline delta retreat during the 20th century. The sediment trapping efficiency of dams is less important than the flow regulation by dams, in the annual sediment yield. Therefore, it is more effective to dismantle channelization than to pass sediment at dams, to provide sand to the beaches. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to determine the influence of length, width, and protrusion of noncontinuous riprap protections on shear failure conditions. The incipient motion of particles as a failure criterion and the reference transport method as the threshold of motion were used. In each test, riprap transport rates were measured at different time intervals using a sediment trap placed immediately downstream from the test reach so that time dependence could be well described. Results reveal that incipient motion conditions of transverse (cross-sectional) protections are strongly influenced by both the protrusion and length of bed protection, which indicates that stability significantly increases as protection length increases and decreases as protrusion increases. In the case of longitudinal protections, almost the same failure conditions were found as in the case of continuous protection. Furthermore, these conditions are unrelated to the width of the protection. A coefficient to correct design formulas obtained by other authors is proposed to take into account the effect of the geometry of transverse protections on their stability. [ABSTRACT FROM AUTHOR]