Abstract. 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. 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 50 years while the delta is being retreating for more than a century. The paper concentrates on the fluvial component, trying to connect it to the delta evolution. It develops a method to compute the actual bed load transport with real data. The paper compares the computation with measurements and bulk volumes of trapped material at a deep river mouth. Sediment availability in the last 30 km of the river channel is deemed responsible for the decrease in the sediment yield to the delta. Moreover, reforestation is deemed responsible for a baseline delta retreat. 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 a step back from channelisation than to pass sediment at dams, to provide sand to the beaches.
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