A simple method for annual sediment transport estimation at ungauged cross-sections and its application to assess sustainable sand mining from river margins in Uruguay

Abstract

Estimation of sediment transport rate in rivers is a complex task that requires a large amount of information, resulting in the need for a considerable budget to address related problems. In this work, a methodology is proposed for mean annual sediment transport estimations at ungauged reaches, based on a simplified calculation of the channel-forming discharge. It consists of (1) determination of the channel-forming discharge from a simulated monthly flow series and a sediment rating curve; (2) calculation of the sediment transport rate corresponding to the channel-forming discharge through the sediment rating curve, and (3) determination of the mean annual transport under the assumption that the channel-forming discharge flows constantly for a year. The method was tested in the Santa Lucía basin, Uruguay. It was validated for the case study by applying it to a gauged cross-section and then used in other ungauged reaches of the basin to assess the sustainability of sediment mining from river margins. Results show that the proposed method tends to overestimate the annual transport. Nevertheless, it is a useful practical tool to set a limit to the annual sediment volume extracted by sand mining at river margins, and to estimate the order of magnitude of annual sediment transport in data-scarce rivers.