Controls, budgets and variability of riverine sediment fluxes to the Gulf of Lions (NW Mediterranean Sea)

• Published in: Journal of hydrology (Amsterdam) 2016-09, Vol.540, p.1002-1015
• Main Authors: Sadaoui, Mahrez, Ludwig, Wolfgang, Bourrin, François, Raimbault, Patrick
• Format: Article
• Language: English
• Subjects: Basins; Budgets; Coastal rivers; Continental interfaces, environment; Discharge; Earth Sciences; Fluxes; Freshwater; Gulf of Lions; Gulfs; Oceanography; Rating curves; Rhone River; Rivers; Sciences of the Universe; Sediment fluxes; Sediments; Tributaries
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2016.07.012

[Display omitted] •A simplified rating curve approach is proposed for riverine sediment fluxes.•River sediment fluxes to the Gulf of Lions could be estimated entirely.•Variability of sediment yields in this region is mainly controlled by lithology.•Small coastal rivers have minor importance on the long term but not on the short term.•Sediment transit in the Rhone basin is in equilibrium spatially but not temporally. The present study investigates the spatio-temporal variability of riverine sediment fluxes to the Gulf of Lions, one of the most extensive shelf regions in the Mediterranean Sea. Small coastal rivers compete here with the Rhone River, nowadays the largest Mediterranean river in terms of water discharge. Our scientific objectives were to investigate the major controls of riverine sediment yields (SY) in this area and to quantify the role of the small coastal rivers, largely ignored in previous studies, in the total sediment budgets. Another objective concerned the source identification of the Rhone sediments with regard to the major tributary contributions, and to test whether the sediment fluxes are in equilibrium in the basin. For the calculation of representative long-term fluxes, we used a Simplified Rating Curve Approach (SiRCA) which could be validated by high resolution monitoring and existing literature data. An overall of 13 drainage basins could be distinguished, covering about 86% of the study area (6 coastal rivers, the Rhone River, and 6 of its tributaries). Representative SY range from 19 to 151tkm−2yr−1 in the investigated drainage basins. Despite their smaller basin areas and more torrential discharge regimes, SY of the coastal rivers were generally lower compared to SY of the Rhone River and its tributaries. Confrontation with the lithological, morphological and hydroclimatic basin characteristics indicate that lithology exerts the dominant control on SY in the study region. In particular, the existence of erodible sedimentary rocks in the headwater regions yields high SY. Peak values of 135 and 151tkm−2yr−1 were observed for the Isere and Durance tributaries of the Rhone River, where badlands exist. The coastal rivers contribute on average only to slightly more than 5% of the long-term sediment inputs to the Gulf of Lions. During individual years however, their contribution can strongly increase (up to 27% in 2011). Their contribution is generally important during late spring and autumn, when flash-floods are frequent (up to 90