Exploring morphological equilibrium and flow resistance in gravel-bed rivers: insights from channel-scale experimental analysis

Explorando o equilíbrio morfológico e a resistência ao fluxo em rios de leito de cascalho: insights a partir da análise experimental em escala de canal

Abstract

Our aim is to recreate the distinct patterns observed in gravel-bed river channels for studies involving physical modeling by designing a morphological configuration and investigating bed resistance. We used a 10x0.56x0.4m experimental channel that scaled-down a natural river at a ratio of 1:20, utilizing sand as the bed material. Employing both field data and measuring instruments such as a laser profiler and pitot tube, we conducted a total of 12 tests spanning 27 hours. In the initial 15-hour phase, we closely monitored deformations and sediment transport under various flow rates. Subsequently, we adjusted the flow rates and proceeded with testing. The results indicated that a larger diameter of the movable bed led to increased flow resistance, evident in parameters like n, f, and C. Additionally, we observed the deposition of fines within intergrain voids and noted an increase in k_s with reduced discharge volume, illustrating the influence on flow dynamics and sediment transport. Furthermore, this preliminary study provides valuable insights into the physical processes governing water and sediment transport, which are crucial considerations for future physical simulation studies.

Keywords:
Physical modeling; Movable bed; Sediment transport; Bed roughness; Flow resistance