Process-based simulations of deltaic deposition and its application to geological studies

The dataset contains data for 4 different river deltas, simulated using process-based modelling software Delft3D

Crevasse splay morphodynamics near a non-vegetated, ephemeral river terminus: Insights from process-based modelling

Crevasse splays generate subtle local relief and contribute to fluvial basin sedimentary filling but controls on splay development along dryland rivers remain poorly understood owing to limited field, laboratory, and numerical modelling studies. Based on previously-acquired field data and new remote sensing observations of splay morphology and sedimentology (e.g. slope, width, length, grain size) and flooding characteristics (e.g. discharge, water depth and extent) near the terminus of the non-vegetated, ephemeral Río Colorado on the southeastern margin of Salar de Uyuni, Bolivia, we undertake process-based modelling using Delft3D to isolate the role of hydrological controls on crevasse splay morphodynamics. Holding the potential sediment supply constant, we focus on the role of discharge (outflow from trunk channel to crevasse channel during rising stage), floodplain water levels, and backflow (reflux to the trunk channel during falling stage). Using nine different model runs, each with 10 simulated flood cycles, we show that the processes associated with these hydrological controls result in various outcomes, from short crevasse splay channels that may bifurcate and develop depositional bars to longer splays with one primary channel that mainly transfers sediment across the floodplain. Results reveal that increases in flood discharge lead to more rapid splay sedimentation and stabilization of a single crevasse channel. Increases in floodplain water level lead to shorter but wider splays and facilitate the formation of multiple stable crevasse channels. High floodplain water levels probably restrict splay length owing to deceleration of outflow as floodplain water is encountered, but separate crevasse channels may form downstream as backflow breaches the trunk channel levee during falling stage. These findings support and extend previous observations from the Río Colorado and other dryland rivers worldwide. Future modelling studies that consider a wider range of hydrological, sedimentological, and floodplain topographic conditions will help develop more comprehensive numerical models of splay development. A combination of insights from field, laboratory experimentation, remote sensing and modelling will improve knowledge of the cascades of channel-floodplain dynamics that characterise many dryland endorheic basins.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied Geolog

The impact of clastic syn-sedimentary compaction on fluvial-dominated delta morphodynamics

In natural deltaic settings, mixed hydrodynamic forcings and sediment properties are known to influence the preserved delta deposits. One process that has not received much attention yet is syn-sedimentary compaction of clastic sediment on millennial-scale delta evolution. To study how compaction interacts with delta morphodynamics and preserved sediment, a modelling approach is proposed. A 1D grain-size dependent compaction model was implemented into Delft3D-FLOW, which provides an opportunity to understand the underexplored connection between grain sizes supplied to the deltas and sediment compaction. The compaction model allows deposited sediment to decrease in volume due to the accumulation of newly deposited sediments above or the elapsed time. Differences in morphological trends are presented for scenarios defined by the composition of sediment supply (mud rich and sand rich) and the maximum allowed compaction rate in the model (0–10 mm year−1). The resultant deposits are classified into sub-environments: delta top, delta front and pro delta. The delta top geometry (e.g. area increase, rugosity and aspect ratio), sediment distribution alongshore and across sub-environments, and delta top accommodation (e.g. volume reduction and average water depth) are compared. The modelling results show that compaction of the underlying delta front and pro delta deposits increases the average water depth at the delta top, driving morphological variability observed in the mud-rich and sand-rich deltas. The morphological changes are more prominent in the mud-rich deltas, which experience larger compaction-induced volume reduction for the same scenario. Moreover, higher compaction rates further increase the delta top accommodation, resulting in more deposition and evenly distributed sediment at the delta top. This leads to a less significant area increase and a wider delta top with a smoother coastline. The presented modelling results bridge the knowledge gap on the influence of syn-sedimentary compaction on long-term delta morphodynamics and preserved sediment. These findings can be applied to unravel the controlling processes in ancient delta deposits and predict the evolution of modern systems under changing climates.Applied GeologyCoastal Engineerin

Predominance of wind-wave transport and resuspension of fine river sediments in a great lake: A Delft3D modelling study of lake Turkana, East African Rift

International audienceDepositional models for clastic sedimentation in large lakes, notably in rift lakes, emphasize on downslope river and gravity-driven processes. Wind-driven waterbodies (WWB), a recently-defined category of lakes, display features created by wave related processes and wind-induced water circulation such as beach ridges or spits along the coasts, as well as sediment drifts, sedimentary shelf progradation and erosional surfaces in deeper, offshore domains. A coupled hydrodynamic, wave and sediment transport three-dimensional Delft3D model was established for Lake Turkana, East Africa, one of the world's greatest lakes in order to test the WWB validity for fine sediments. Using available data, the model is forced for 1.5 years with river liquid and solid discharge, as well as wind data, in order to simulate cohesive sediment transport and resuspension. The model simulates stratification due to salinity, wave generation and dissipation, and sediment advection and resuspension by waves and currents, with multiple cohesive sediment fractions. Model results were compared with remote sensed imagery and with available in-situ sediment deposition rates, reproducing the general surface suspended sediment patterns, and agreeing with the mass deposition rates data from the literature.By creating scenarios in which certain processes were switched off, the contribution of waves resuspension, wind-induced currents, salinity-induced stratification, and river jet, in resuspending and transporting sediment along the lake could be investigated. With just the wind and/or the river influence, most of the sediment deposition occurs in the first 10 km from the river mouth and at depths from 0 to 10 m. When waves are switched on, significant quantities of sediments can be resuspended by waves, and most of the sediments are deposited in the first 30 km from the river mouth, at depths from 10 to 30 m. This study provides insights on sediment transport in the Lake Turkana, and similarly in great lakes in general, supporting waves as the main agent transporting fine sediments away from river mouths into deeper areas, as opposed to river-plume derived transport

The role of wind-wave related processes in redistributing river-derived terrigenous sediments in Lake Turkana: A modelling study

A complete annual cycle of the dynamics of fine-grained sediment supplied by the Omo and smaller rivers is simulated for Lake Turkana, one of the world’s large lakes, with the hydrodynamic, wave and sediment transport model Delft3D. The model is forced with river liquid and solid discharge and wind data in order to simulate cohesive sediment transport and resuspension. It simulates stratification due to salinity, wave generation and dissipation, and sediment advection and resuspension by waves and currents, with multiple cohesive sediment fractions. A comparison of the simulation results with remotely-sensed imagery and with available in-situ sediment deposition rates validates the model. By devising simulation scenarios in which certain processes were switched on or off, we investigated the contribution of waves, wind-induced surface and bottom currents, salinity-induced stratification and river jet, in resuspending and transporting fine sediments in the lake basin. With only the wind or river influence, most of the sediment deposition occurs in the first 10 km off the Omo River mouth and at a depth  30 m. This study sheds new light on sediment transport in Lake Turkana and in great lakes in general, favouring the view that wind-waves can be the main agent that transports sediment away from river mouths and to deeper areas, as opposed to river-plume or gravity-driven transport

Input files of validated simulations of 3D turbidity currents Delft3D4

Input files of validated Delft3D4 models of three-dimensional turbidity currents at laboratory and field scales that simulate laboratory-scale turbidity currents in previously published works

The Lake Turkana Delft3D input files and dataset

Delft3D model input data, analyses (mat files) and supplementary material linked to the Lake Turkana paper by Zainescu et al 2022 Journal or Great Lakes. https://doi.org/10.1016/j.jglr.2022.12.013 </p

The Lake Turkana Delft3D input files and dataset

Delft3D model input data, analyses (mat files) and supplementary material linked to the Lake Turkana paper by Zainescu et al 2022 Journal or Great Lakes. https://doi.org/10.1016/j.jglr.2022.12.013 </p