Exploring sustainable sand-winning in the White Volta
Estimating transient storage upstream of run-of-river weirs for sand winning purposes via hec-ras 6, 1-d, flume models
J.M. Arends (TU Delft - Civil Engineering & Geosciences)
Nick C. Van De Giesen – Mentor (TU Delft - Water Resources)
M. Marence – Graduation committee member
Marcel Wauben – Graduation committee member (Witteveen+Bos)
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Abstract
This research aims to explore sediment transport behavior and accumulation caused by run-of-river weirs in order to examine there feasibility for sustainable sediment mining purposes in the White Volta River. Weirs are used to raise water levels up-stream to increase water levels and storage, but their is little information regarding sediment continuity and transport over a weir. Observational research studies suggest that weirs do not have a 100% trapping efficiency, however, due to the reduced flows this study hypothesizes that sediment will settle upstream of the structure.
Based on data from the White Volta River, a 1D Flume model is created using
HEC-RAS which tests several sediment transport functions and bed roughness parameters with constant bed slope, suspended and bed-load gradation in order to estimate sediment settling. The results suggest that during peak discharge events settled sediments are flushed up and over the weir. As peak discharges decrease, settling occurs based on particle diameter causing increased sediment storage up-stream until the next flushing event. The volume of sediment stored ramp is highly variable with respect to bed roughness and the used transport function, suggesting river calibration is required for concrete estimates. Based on the model results, approximately 1 − 2% of the White Volta’s yearly suspended load settles in-front of the structure before the discharge flushing event.