Sediment transport and topographic evolution of a coupled river and river plume system: An experimental and numerical study

Abstract

Sediment transfer from rivers to the ocean is the fundamental driver of continental sedimentation with implications for carbon burial, land use dynamics, and unraveling global climate change and Earth history from sedimentary strata. Coastal rivers are dynamically coupled to their offshore plumes at the river mouth creating regions of nonuniform flow that can dictate patterns of erosion and deposition both onshore and offshore. However, there are limited experimental and modeling studies on sediment transport and morphodynamics of coupled river and river plume systems and their response to multiple flood events. To address this knowledge gap, we developed a quasi-2-D, morphodynamic numerical model and conducted exploratory flume experiments in a 7.5 m long flume where a 10 cm wide river channel was connected to a 76 cm wide "ocean basin." Both the numerical model and the flume results demonstrate that (1) during low-discharge flows, backwater hydrodynamics cause spatial-flow deceleration and deposition in the river channel and the offshore plume area, and (2) during high flows the water surface is drawn down to sea level, resulting in spatial-flow acceleration and bed scour. During high-discharge flows, we also found that the offshore river plume self-channelized owing to both levee formation and bed scour. Our study suggests that coastal rivers may be in a perpetual state of morphodynamic adjustment and highlights the need to link rivers and river plumes under a suite of flow discharges to accurately predict fluvio-deltaic morphodynamics and connectivity between fluvial sediment sources and marine sinks.

Laboratory Investigation on Effects of Flood Intermittency on Fan Delta Dynamics

“…Additionally, the deltas in these experiments are also highly simplified compared to their natural counterparts, lacking vegetation and cohesive sediments, which would decrease their degree of erodibility (Edmonds & Slingerland, ; Hoyal & Sheets, ; Shaw et al, ; Tal & Paola, ; Thorne, ). Furthermore, our experimental deltas were not influenced by backwater hydraulics, which have been shown to produce erosion during high‐flow conditions (Chatanantavet et al, ; Chatanantavet & Lamb, ; Lamb et al, ; Nittrouer et al, , ). Using the experimental design here, we aim to understand the fluviodeltaic processes of sediment reworking during base flow periods, which has been missing from the previous physical and computational modeling studies.…”

“…This effect is time‐cumulative and can become magnified as the not fully adjusted delta is the new initial condition for subsequent floods and base flows, which accounts of the overall lower topset gradient as the intermittency decreases. Chatanantavet and Lamb () found similar results on backwater dominated deltas, where rivers that supplied sediment and water discharge to the deltas were in a constant transient state; however, due to backwater hydraulics their systems alternated between aggradation during low flows and riverbed scour during high flows. To further investigate this idea of delta adjustment, we analyze the spatial distribution of deposition during the final flood period using the laser topographic scans collected.…”

New insights into the mechanics of fluvial bedrock erosion through flume experiments and theory

“…Steeper slopes, in turn, often cause Fr to be larger than in natural rivers. One solution to these issues has been to use low density sediment, such as walnut shells or plastic beads, in laboratory experiments to produce transport on lower bed slopes (e.g., Chatanantavet and Lamb, 2014). This is an effective strategy for alluvial river experiments, but low-density sediment and sub-sand-sized particles pose an issue for bedrockerosion experiments because particle-bed impacts must have sufficient kinetic energy to produce measurable erosion rates.…”

Kıyı Sedimentlerinde Tane Boyunu Etkileyen Faktörler: Antalya Körfezi’nde Konyaaltı ve Lara Plajlarının (Antalya) Karşılaştırılması

“…Bu tarz bir yaklaşım yanlış değildir fakat burada buna ek olarak daha çok taşınan sedimanın özelliği ve taşınma mesafesi önemlidir. Ayrıca akarsuların taşıyacakları malzeme eğimle doğru orantılı değildir (Chatanantavet ve Lamb, 2014). Boğaçay ve Aksu çayını karşılaştırdığımızda Boğaçay daha kısa mesafede kıyıya ulaşmaktadır ve taşınan malzemenin aşınmak için yeterli zaman/ mesafesi yoktur.…”