Variabilité spatio-temporelle des flux de matières en suspension d'un fleuve côtier méditerranéen : la Têt (France)

Abstract

The purpose of this study is to investigate the fluxes of total suspended solids (TSS) in the Têt River system (1 380 km²). On the basis of a great number of measurements, we estimate the mean annual sediment flux at the mouth to be about 53 546 t·yr⁻¹ (nearly 40 t·km⁻²·yr⁻¹) for the period 1980–1999 (average annual water discharge 10.4 m³·s⁻¹). Almost all suspended sediment loads are transported during brief flash floods that mainly occur during autumnal heavy downpours. The scarceness of these events leads to a very large inter-annual variability of the river sediment fluxes (from 1 to more than 100). Despite the damming of the river in the central part of its drainage basin, the observed sediment fluxes are more important downstream the dam than upstream. This can be explained by low sediment retention behind the dam, by greater erosion rates in the downstream part of the basin, filled with crumbly Plio-Quaternary formations, and by heavy storms located in the fore land.