In-Stream Laser Diffraction for Measuring Suspended Sediment Concentration and Particle Size Distribution in Rivers: Insights from Field Campaigns

This study evaluates the laser in situ scattering and transmissometry (LISST) instrument LISST-SL2, a diffraction for suspended sediment sampling rivers, with concurrent physical measurements of concentration (SSC) particle size distribution (PSD) as well velocity by an acoustic Doppler current profiler (ADCP). We collected 136 LISST-SL2 samples along 61 SSC measurement, which 24 included PSD measurement during 2018–2020 from 11 sites Washington state Virginia. An effective density is required to convert measured volumetric into reported mass SSC, default assumes value 2.65 g/mL. From our data set, we computed densities (mass SSC/volumetric SSC) that ranged 0.5 5.4 g/mL, best-fit 2.05 Additionally, was not able measure finest sizes suspension, affects resulting PSD. Therefore, propose some adjustments supporting sample account these issues. When doing so, were reduce root-mean square relative error (RMSRE) 18% 117% 26% 78% velocities generally higher than ADCP 21% RMSRE. Our results guidance will allow more accurate has potential studying spatial temporal variation characteristics rivers.