PHYSICAL LABORATORY MODELING OF THE SEDIMENT TRANSPORT AND PLANFORM MORPHOLOGICAL ADJUSTMENTS IN SKEWED MEANDERING RIVERS

Meandering river systems play important roles in shaping geological landscapes around the world. Their sediment transport processes, hydraulic conditions, and long-term morphological evolution are driven by complex interactions between their hydrological and geological characteristics. Understanding these interactions can help inform future predictions of river evolution or assist in reconstructing past effects of rivers on the landscape. Both of these applications can provide beneficial insights for the sustainable management of river systems to protect people, property, and ecological functions.

To scale down and simplify river systems, physical modeling in the laboratory has been commonly used to investigate individual variables or to simulate river evolution over time. In many studies, the planform geometry is simplified with a symmetric meandering shape. However, past research has shown that a more complex asymmetric geometry, such as skewed meandering bends, can lead to different in-stream hydraulic conditions and morphological development processes. In a skewed meander bend, the apex is shifted in either the up-valley or down-valley direction in comparison to a symmetric meander bend. Efforts thus far to physically model skewed river planforms have primarily used confined banks to investigate hydraulic and bed morphological conditions, with limited research examining these behaviours in fully unconfined bed and bank conditions.

For this study, a physical laboratory model of a skewed meandering river with fully unconfined bed and bank conditions was used to investigate the sediment transport and planform morphological adjustments. Two different skewness orientations were tested in a sand-filled laboratory flume under the same hydraulic conditions. Sediment transport rates were measured at the laboratory channel outlet while planform morphological adjustments over time were captured with photogrammetric techniques. Results related rates of sediment transport with rates of planform morphological adjustments and best-fit equations were proposed to represent the adjusted planform geometries. The findings can assist in understanding the impacts that skewed river systems had on past landscapes and in predicting how they will continue to evolve in the future.