Replication dataset for "Fine sediment in mixed sand-silt environments impacts bedform geometry by altering sediment mobility"
This is the data underlying the publication "Fine sediment in mixed sand-silt environments impact bedform geometry by altering sediment mobility".
It consists of the laser scanner data (elevation scans of the bedforms), the ubertone data (velocity profiles), and the corresponding scripts to read out the data from the source files.
Abstract: Geometric characteristics of subaqueous bedforms, such as height, length and leeside angle, are crucial for determining hydraulic form roughness and interpreting sedimentary records. Traditionally, bedform existence and geometry are predicted with phase diagrams and empirical equations, primarily based on uniform, cohesionless sediments. However, mixtures of sand, silt and clay are common in deltaic, estuarine, and lowland river environments, where bedforms are ubiquitous. The exact influence of these mixed sediments on bedform dimensions remains unknown. Here, we investigate the impact of fine sand and silt in sand-silt mixtures on bedform geometry, based on laboratory experiments conducted in a 15 m long tilting, recirculating flume. We systematically varied the content of sand and silt for different discharges, and we utilised a UB-Lab 2C (a type of acoustic Doppler velocimeter) to measure flow velocity profiles. The final bed geometry was captured using a line laser scanner. Our findings reveal that the response of bedforms to mixtures is not straightforward and depends on several factors, including bimodality-driven bed mobility and cohesiveness. When fine, non-cohesive material (fine sand or coarse silt) is mixed with the base material, the hiding-exposure effect comes into play, resulting in enhanced mobility of the coarser material and leading to an increase in dune length. However, the addition of weakly-cohesive fine silt reduces the mobility, suppressing dune height and length. Finally, at the transition from the dune regime to upper stage plane bed, the bed becomes unstable and bedform heights vary over time. The composition of the bed material does not significantly impact the hydraulic roughness, but mainly affects roughness via the geometry of the bedforms, especially the leeside angle.
- 2023-12-21 first online
- 2024-01-17 published, posted
- Netherlands Organization for Scientific Research (NWO), within Vici project “Deltas out of shape: regime changes of sediment dynamics in tide-influenced deltas” (Grant NWO-TTW 17062)
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