A Froude-scaled model of a bedrock-alluvial channel reach: 1. Hydraulics

Hodge, R.A.; Hoey, T.B.

Abstract

The controls on hydraulics in bedrock-alluvial rivers are relatively poorly understood, despite the importance of the flow in determining rates and patterns of sediment transport and consequent erosion. To measure hydraulics within a bedrock-alluvial channel, we developed a 1:10 Froude-scaled laboratory model of an 18 × 9 m bedrock-alluvial river reach using terrestrial laser scanning and 3-D printing. In the reported experiments, water depth and velocity were recorded at 18 locations within the channel at each of five different discharges. Additional data from runs with sediment cover in the flume were used to evaluate the hydraulic impact of sediment cover; the deposition and erosion of sediment patches in these runs are analyzed in the companion paper. In our data (1) spatial variation in both flow velocity and Froude number increases with discharge; (2) bulk flow resistance and Froude number become independent of discharge at higher discharges; (3) local flow velocity and Reynolds stress are correlated to the range of local bed topography at some, but not most, discharges; (4) at lower discharges, local topography induces vertical flow structures and slower velocities, but these effects decrease at higher discharges; and (5) there is a relationship between the linear combination of bed and sediment roughness and local flow velocity. These results demonstrate the control that bedrock topography exerts over both local and reach-scale flow conditions, but spatially distributed hydraulic data from bedrock-alluvial channels with different topographies are needed to generalize these findings.

Citation

Hodge, R., & Hoey, T. (2016). A Froude-scaled model of a bedrock-alluvial channel reach: 1. Hydraulics. Journal of Geophysical Research: Earth Surface, 121(9), 1578-1596. https://doi.org/10.1002/2015jf003706

• Journal Article Type: Article
• Acceptance Date: Jul 23, 2016
• Online Publication Date: Sep 16, 2016
• Publication Date: Sep 16, 2016
• Deposit Date: Aug 4, 2016
• Publicly Available Date: Mar 16, 2017
• Journal: Journal of Geophysical Research: Earth Surface
• Print ISSN: 2169-9011
• Electronic ISSN: 2169-9011
• Publisher: American Geophysical Union
• Peer Reviewed: Peer Reviewed
• Volume: 121
• Issue: 9
• Pages: 1578-1596
• DOI: https://doi.org/10.1002/2015jf003706
• Public URL: https://durham-repository.worktribe.com/output/1376908