Spatio-temporal variations in sediment nutrient levels: the River Adour

The retention capacity of the flood zone of the River Adour (SW France) has been estimated. This zone consists of ca, 1 km(2) Of riparian vegetative strips (rvs) and ca. 16 km(2) of floodplain (Barthes), A novel method of sediment collection has been used in both sectors to determine the quantities of sediment together with concentrations of organic nitrogen and carbon. The study indicates that the vegetative strips accumulate large quantities of sediment with total nitrogen and total carbon concentrations of ca, 4 mg/g dry matter and ca. 30 mg/g dry matter respectively. These concentrations were found to vary as a function of topography and vegetation. The floodplain receives less sediment but the observed concentrations of nitrogen and carbon are more variable and found in the range of 1-9 mg/g dry matter and 10-82 mg/g dry matter respectively. The highest levels of C and N are generally found in wooded areas of the floodplain.