Evaluation of Three Sampling Technologies for Measuring Sand Suspension in Rivers

Suspended-sand concentration and grain size are essential parameters for understanding sediment transport and river geomorphology. They are often measured using direct physical sampling with specifically designed samplers deployed across river cross-sections. Common sampler designs rely on passive capture, settling or pumping mechanisms. Comparative evaluations of sampler performance remain limited, although they are crucial for quantifying sampler‑related uncertainty, identifying methodological constraints, and validating new sampling technologies. We field-evaluated two samplers based on settling and pumping principles, the Delft bottle and novel, low-cost pump PP36, compared to the US P-6 reference sampler based on passive capture. In field experiments, the maximum sand concentration and median grain sizes were below 2 g/l and 250 μm, respectively. The pump PP36 measured sand concentration and grain size consistent with the US P-6, while the Delft bottle systematically underestimated sand concentrations. This discrepancy was investigated by exploring several error sources, including the correction factor α and the sand mass collected during transit of the open Delft bottle. Moreover, we evaluated the influence of nozzle type and orientation, and potential crushing of sand particles by the pump PP36. Overall, the PP36 pump emerged as a robust alternative to conventional samplers, offering high precision, operational flexibility and the capacity to collect large sample masses suitable for laser-diffraction grain size analysis. This study highlights the importance of sampler selection in sediment monitoring, as accuracy differences can lead to divergent interpretations of suspended-sand dynamics. Rigorous comparison across samplers is therefore critical to ensure reliable assessments and sediment management decisions.