Discontinuity in Equilibrium Wave‐Current Ripple Size and Shape and Deep Cleaning Associated With Cohesive Sand‐Clay Beds

Abstract

Ripples are primary sedimentary structures that are ubiquitous on the bed of estuaries and coastal seas. These bedforms often preserve information of the flow parameters by which they were formed (e.g., Soulsby & Clarke, 2005;Southard, 1991). Ripple-related bed roughness in turn modifies near-bed hydrodynamics and turbulence, ultimately affecting sediment fluxes, a process which is essential for the modeling of sediment transport (e.g., Soulsby, 1997;Van Rijn, 2007). Many estuarine and coastal environments face extreme weather events, which are predicted to increase in frequency with rising sea levels (e.g., Woodruff et al., 2013). Storm-induced waves combined with currents cause particularly dynamic ripple behavior and thus large and rapidly changing sediment transport rates (e.g., Li & Amos, 1999;Wengrove et al., 2018). The understanding of how hydrodynamics control ripple dimensions is therefore essential for ensuring the improved performance of coastal

Effect of Bed Clay on Surface-Water Wave Reconstruction from Ripples

“…It is important to clarify how a representative clay content, C 0 , for the ripples should be determined. In the modern environment this usually involves measuring C 0 below the active layer (below trough level), as efficient winnowing often removes clay from the body of the ripples during development (Wu et al, 2022). In the geological record, clay content in deposits should be based on primary clay minerals and diagenetic alterations for which it can be established that the original mineral was part of the primary clay fraction.…”

“…Davies (2016) argued that the distinction between cohesive and non-cohesive sedimentary structures is artificial, as they represent end members of a spectrum, and thus predictions based on one classification may result in misinterpretations. This position is re-enforced by recent experiments that have shown how sandy bedforms can be affected by small amounts of biological and physical cohesion (Malarkey et al, 2015;Parsons et al, 2016;Wu et al, 2018;2022). The consequence for wave ripples of physical cohesion associated with kaolin clay in the bed has been detailed by Wu et al (2024).…”

Hummocky sedimentary structures within rippled beds due to combined orbital waves and transverse currents

“…As a typical wave flux (discharge: Q w = 10 800 L per min) passed through the test area, the ratio Q j / Q w was ca 11%. Although wave velocity was affected slightly by the side walls, the wave velocities in most of the section showed little variation (Wu et al ., 2022a). The ratio declined rapidly across and down the flume outside of the test area where wave activity dominated both flow patterns and bed sediment deformation.…”

Use of remote-sensing to quantify the distribution of progradation/erosion along a forced-regressive modern coastline: driving factors and impact on the stratigraphic record

“…Furthermore, the i) nature of the substrate, as well as the spatial distribution of cohesive clays (and other cohesive biogenic substances) along the coastline (e.g. Lichtman, et al, 2018;Wu et al, 2022), ii) the change in gradient through time and space associated with varying rates of relative sea-level change (Rodriguez et al, 2001;Ruggiero et al, 2016), and iii) the type, rates of change, and degree of vegetation near the shoreline (e.g. Thampanya et al, 2006;Konlechner et al, 2019) could certainly enhance or dampen the overall mobility of the coastline (how much the coastline migrates) and the rates at which the coastline moves (how fast the coastline migrates).…”