Temporal variability of suspended sediment transport and rating curves in a Mediterranean river basin: The Celone (SE Italy)

In the Mediterranean region suspended sediment transport is the predominant process in sediment export in most river basins. The aim of this paper is to analyze suspended sediment variability over a period of 12 months in the Celone river, a temporary river located in the Puglia region (SE-Italy), and to evaluate sediment rating curves for estimating suspended sediment concentrations for subsequent load calculations. Similarly to most temporary rivers, the Celone river shows relevant differences among mean daily flows and the extreme instantaneous flows during floods. To take into account these peculiarities, the rating curves were developed as a function of hydrological conditions: high, normal and low flows. Continuous measures of streamflow and frequent samplings of suspended solid concentrations (SSCs) during flood events, normal flow and low flow were used. The plot of the SSC against discharge takes the form of a hysteresis loop. Clockwise, anticlockwise and mixed-shaped loops were observed. Suspended sediment yield was found to be in the range of 250-384 t kin(-2) y(-1). The results show that about 94% of the total suspended materials were transported during the high flow regime, while less than 0.1% were under low flow conditions. Moreover, it was observed that 90% of the total annual suspended loads were moved between November to May. Flash floods that occur in summer exhibit the highest values of SSC. The proposed method, which was based on sediment rating curves, has proved to be valuable to generate SSC data for high and normal flows although it tends to underestimate the highest values. It can represent a useful tool for water resource managers who need a quick and inexpensive method, specific for temporary rivers, to evaluate suspended sediment yield. (C) 2015 Elsevier B.V. All rights reserved.