Suspended sediment load estimation using sediment rating curves in two intermittent rivers

The determination of suspended sediment (SS) load is essential for understanding soil erosion magnitude. This study quantifies SS loads in two mountainous river basins in Apulia (S-E, Italy): the Carapelle (506 km2) and the Celone (72 km2). Continuous and discrete sampling strategies were used to monitor streamflow (Q) and SS concentrations (SSC) across diverse hydrological conditions. Sediment rating curves were developed to rectify lacks in daily observed SSC time series. For the Carapelle River, continuous SSC and Q monitoring was conducted from 2007 to 2011 using an optical probe and an ultrasonic stage recorder. In the Celone River, a comprehensive dataset of continuous Q measurements and discrete SSC measurements was collected from 2010 to 2011. Sediment rating curves were tailored for three subsets of data representing high, normal, and low flow conditions, while addressing missing SSC data. Annual specific sediment load ranged from 2.4 to 6.06 t ha-1 yr-1 for the Celone River and 0.9 to 7.45 t ha-1 yr-1 for the Carapelle River. Over 80% of the SS load was transported during highflow conditions, while less than 1% occurred during low-flow conditions. The findings highlight the importance of the hydrological regime in regulating sediment transport in hilly Mediterranean rivers and show that the length and characteristics of the sample period can significantly impact the accurate estimation of sediment load.