Hyperpycnal Delta Progradation in a Lake of Constant Depth: Mathematical Modeling and Laboratory Measurements of Morphology, Suspended Sediment Concentration, and Velocity Field

Sediment deposition has significantly impacted the storage capacity of reservoirs in Taiwan. Delta progradation may be influenced by factors such as creep landslide, current-driven bedload, or suspended load. To better understand hyperpycnal mechanisms in reservoirs, small-scale experimental simulations were conducted in the laboratory. In order to observe and model more on-site phenomena, a series of experiments were performed, involving the fabrication of a 2-D channel using acrylic material. A specific type of sand was used to ensure that it neither settles too quickly nor remains continuously suspended in the water. Fortunately, the initial goal of generating a traveling wave in the laboratory using a moving source was successfully achieved. Velocity flow field and concentration distribution analyses were conducted using a high-speed camera with dense laser and the Spectrophotometric Method, respectively. Experimental results were compared with computational simulations based on the Shallow Water Theory. The conventional theory of two-layer flow proved insufficient to adequately describe the experimental results. To address this, an additional layer theory called the sub-layer was introduced into our numerical modeling. Ultimately, by incorporating shallow flow equations with settling and mixing, three long interfaces were simulated and compared favorably with the experimental results.