Identifying a reliable method for estimating suspended sediment load in a temporary river system

Sampling strategies and methods used for estimating load can lead to large uncertainties in suspended sediment
transport quantification, especially in rivers with high variability in streamflow. The aim of this paper is to
evaluate suspended sediment load, using a number of direct estimation techniques, in order to find a suitable
method for temporary river systems and to assess the uncertainty associated with load estimation, due to the
specific method applied. One year of continuous measurement of flow, and discrete sampling (n=216) of
suspended sediment concentrations, taken from 2010 to 2011 in the Celone River (SE, Italy), were used to
estimate annual load. Averaging, ratio and regression estimator methods were applied to the entire dataset, and
to subsets of data, to calculate the load. The results show a wide range of values, from 220 to 1123 t km-2 yr-1, with
respect to the applied suspended sediment load estimation techniques. Averaging methods resulted biased.
Sediment rating curves underestimated load, while, if the back-transformation bias correction was used, load
was overestimated. The ratio methods generally overestimate load. Increased precision and accuracy was
achieved through applying data stratification, based on flow regime and seasonality. After applying three different
flow regime stratifications, the annual load ranged from 240 to 606 t km-2 yr-1 and, using seasonal
stratification, from 258 to 974 t km-2 yr-1. It seems that ratio estimator methods, and the regression equations
applied to the stratification on a flow regime basis, are more suitable for estimating load in temporary, flashy
streams.