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

Abstract

Abstract. Empirical measurements on fine sediment dynamics and fine sediment infiltration and accumulation have been conducted worldwide, but it is difficult to compare the results because the applied methods differ widely. We compared common methods to capture temporal and spatial dynamics of suspended sediment (SS), fine sediment infiltration and accumulation and tested them for their suitability in a small, canalized river of the Swiss Plateau. Measurement suitability was assessed by data comparison, relation to hydrological data and in the context of previously published data. SS concentration and load were assessed by optical backscatter (OBS) sensors and SS samplers. The former exhibit a better temporal resolution, but were associated with calibration problems. Due to the relatively low cost and easy mounting of SS samplers, they can provide a higher spatial distribution in the river's cross section. The latter resulted in a better correlation between sediment infiltration and SS load assessed by SS samplers than SS concentrations measured with OBS sensors. Sediment infiltration baskets and bedload traps capture the temporal and spatial distribution of fine sediment infiltration. Data obtained by both methods were positively correlated with water level and SS. In contrast, accumulation baskets do not assess the temporal behaviour of fine sediment, but the net accumulation over a certain time period. Less fine sediment accumulated in upwelling zones and within areas of higher mean water level due to scouring of fine sediments. Even though SS and sediment infiltration assessed with the bedload traps increased from up-to downstream, less fine sediment accumulated downstream. This is probably also attributable to more scouring downstream.

Critical assessment and validation of a time‐integrating fluvial suspended sediment sampler

“…This suggests that although reference and TIMS loads may be highly correlated, within‐site variations act to bias the replicate estimates within the cross section. This variability was also observed by Schindler Wildhaber et al ., (), highlighting the sensitivity of flux estimates to sampler positioning. The criteria for determining the sampler location should therefore, wherever possible, be consistent between sites.…”

“…Most recently, Schindler Wildhaber et al . () suggested that both TIMS and turbidity sensors are suitable for capturing large‐scale spatial and temporal variations in SSCs or suspended sediment (SS) loads. They found the total weekly SS load from TIMS was significantly correlated with mean weakly SSCs, with spearman rank correlations of 0.8 ( n = 212), 0.2 ( n = 204) and 0.7 ( n = 204).…”

Use of spatially distributed time-integrated sediment sampling networks and distributed fine sediment modelling to inform catchment management

“…This is likely a consequence of bed-form heterogeneity, and variations in the source and type of sediment. Sampler location should therefore, wherever possible, be consistent between sites (Schindler Wildhaber et al, 2012).…”

Evaluation of a simple, inexpensive, in situ sampler for measuring time‐weighted average concentrations of suspended sediment in rivers and streams

“…However, the laboratory tests were done with chemically dispersed sediment, which prevents the agglomeration and settling processes that occur in natural systems, thus representing a worst‐case scenario for sediment loss. Previous studies have shown that the Phillips sampler can collect a statistically representative sample for analysis of particle size distribution in natural systems, even when flows are elevated (Perks et al, ; Perks et al, ; Schindler Wildhaber, Michel, Burkhardt‐Holm, Bänninger, & Alewell, ; Smith & Owens, ; D. Walling, ). Therefore, it is likely that the average particle size distribution of the sample collected by the PASS and Phillips samplers are representative of the particle size distribution of suspended sediment in Loders Creek during the two sampled events.…”