SEDIMENT RATING CURVES DEVELOPED ON STAGE AND SEASONAL MEANS IN DISCHARGE CLASSES FOR THE MELLAH WADI, ALGERIA

The focus of the present study was to estimate suspended sediment load from the Mellah catchment (550 km²) during storms. Suspended sediment rating curves were developed on data from a 23-year period. The regression technique of this paper involves a division of data into discharge-based classes, the mean concentrations and discharges of which are used to develop power regressions through log-transformation. Sediment rating curves were also developed on means of data grouped into seasons and stages. Sediment loads estimated by rating curves uncorrected for bias involved underestimations of down to 9% compared with loads from measured concentrations. Correction for bias reduced underestimations to a range from 0.79 to 3%. Rating curves divided into rising and falling stages had the lowest underestimation and were used to estimate load during periods without concentration measurements. During the 23-year study period, the mean annual suspended sediment yield was 373 TI km².
Sediment transport is dominated by winter storms accounting for 61% of the annual load. A high exponent 'b' of the power regression equations during the winter season confirms the intense geomorphic work by winter season storms caused by high intensity rainfall, low vegetation cover, and heavy machine activity in the fields.