Measurement of spatial and temporal fine sediment dynamics in a small river

Empirical measurements on fine sediment dynamicsand fine sediment infiltration and accumulation have beenconducted worldwide, but it is difficult to compare the resultsbecause the applied methods differ widely. We comparedcommon methods to capture temporal and spatial dynamicsof suspended sediment (SS), fine sediment infiltrationand accumulation and tested them for their suitabilityin a small, canalized river of the Swiss Plateau. Measurementsuitability was assessed by data comparison, relationto hydrological data and in the context of previously publisheddata. SS concentration and load were assessed by opticalbackscatter (OBS) sensors and SS samplers. The formerexhibit a better temporal resolution, but were associated withcalibration problems. Due to the relatively low cost and easymounting of SS samplers, they can provide a higher spatialdistribution in the river's cross section. The latter resulted in abetter correlation between sediment infiltration and SS loadassessed by SS samplers than SS concentrations measuredwith OBS sensors. Sediment infiltration baskets and bedloadtraps capture the temporal and spatial distribution of fine sedimentinfiltration. Data obtained by both methods were positivelycorrelated with water level and SS. In contrast, accumulationbaskets do not assess the temporal behaviour offine sediment, but the net accumulation over a certain timeperiod. Less fine sediment accumulated in upwelling zonesand within areas of higher mean water level due to scouringof fine sediments. Even though SS and sediment infiltrationassessed with the bedload traps increased from up- to downstream,less fine sediment accumulated downstream. This isprobably also attributable to more scouring downstream.