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The Integrated, Section Surface Difference Over Time, version 2 (ISSDOTv2) method provides a means of quantifying bedload in large sandbed rivers. Like all measurements, it is important to understand the uncertainty associated with the method before making management decisions based on its results. A methodology is presented for quantifying and combining the uncertainty for each component of the ISSDOTv2 method including particle density, bed porosity, acoustically measured bed topography, the timing of measurements, sand wave identification, and regression analysis used for geometric correction of bedload measurements. The approach provides an indication of the relative magnitude of each source of uncertainty in addition to the uncertainty in the final resultant transport rate. Laboratory flume measurements were used to evaluate the uncertainty limits and verify the approach. The greatest contributor to uncertainty was found to be the bathymetric uncertainty, and, at the highest transport rates, cumulative relative uncertainty was found to be approximately 10%. Cumulative relative uncertainties grew rapidly with decreasing flow rates, driven primarily by the higher relative contribution of the effect of bathymetric uncertainty on the smaller bedforms that are typically present at lower transport rates. The approach documented here will be transferrable to real-world systems to determine the uncertainty in measured bedload sediment transport rates using the ISSDOTv2 method. [ABSTRACT FROM AUTHOR]

Turbulence measurements over rough beds are used for a variety of purposes, including studies of habitat diversity for aquatic organisms, stream restoration efforts, and assessment of drag induced by vegetation. Turbulent kinetic energy (TKE) has been used to estimate bed shear stress by use of a proportionality constant of 0.19-0.21. The TKE method of bed shear stress estimation is less sensitive to flow misalignment relative to Reynolds stress or mean velocity measurements, but it has not been tested across a broad range of hydraulic conditions. In the work reported here, TKE was compared to bed shear stresses for gravel (D50 = 35 mm) and cobble (D50 = 156 mm) beds with varying discharges and levels of sand fill (D50 = 0.3 mm). The ratio of bed shear stress (τ0) with TKE was not strongly affected by mean velocity for either the gravel or cobble beds, but it was affected by bed roughness. The mean of the median values of τ0=TKE across three mean velocities was 0.24 for gravel with no sand in the bed and was reduced to 0.21 for sand fills of 62-216%. Sand fills of 0-39% for the cobble bed resulted in τ 0=TKE = 0.48; increasing the sand fill to 46-65% produced τ0=TKE = 0.40. These results show that the roughness of the bed can affect the ratio of bed shear stress to TKE, which means that caution is required if TKE is to be used as a surrogate measurement for bed shear stress. [ABSTRACT FROM AUTHOR]

The article describes the practical implications of quantifying ancient sedimentation rates in U.S. lakes. The sediments stored in lakes are considered significant because it can be used to determine the erosion history of watersheds. Examples of opportunities associated with improved understanding and management of watershed processes include quantifying changes in erosion and deposition rates caused by anthropogenic and natural shifts in land use or by climate change. To assess the impact caused by changes in land use, it is significant to identify historical watershed trends.