The estimation of estuary dimensions using a simplified form model and the exogenous controls

Townend, Ian

doi:10.1002/esp.3256

Cited by 39 publications

(57 citation statements)

References 38 publications

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“…Although numerical models, because of the recent increase in computational power, now can consider more processes, longer time frames, and larger spatial scales, many studies seek to simplify the problem in order to understand the inherent estuarine processes (Ganju and Schoellhamer 2009;Guo et al 2014;Townend 2012). Simplifications such as estuarine numbers, non-dimensional numbers, and 1D models allow for a quick assessment of a study area without requiring high computational power.…”

Section: Responsible Editor: Carlos Augusto França Schettinimentioning

confidence: 99%

Suspended sediment dynamics in a tidal channel network under peak river flow

Achete¹,

Wegen²,

Roelvink

et al. 2016

Ocean Dynamics

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Peak river flows transport fine sediment, nutrients, and contaminants that may deposit in the estuary. This study explores the importance of peak river flows on sediment dynamics with special emphasis on channel network configurations. The Sacramento-San Joaquin Delta, which is connected to San Francisco Bay (California, USA), motivates this study and is used as a validation case. Besides data analysis of observations, we applied a calibrated process-based model (D-Flow FM) to explore and analyze high-resolution (∼100 m, ∼1 h) dynamics. Peak river flows supply the vast majority of sediment into the system. Data analysis of six peak flows (between 2012 and 2014) shows that on average, 40 % of the input sediment in the system is trapped and that trapping efficiency depends on timing and magnitude of river flows. The model has 90 % accuracy reproducing these trapping efficiencies. Modeled deposition patterns develop as the result of peak river flows after which, during low river flow conditions, tidal currents are not able to significantly redistribute deposited sediment. Deposition is quite local and mainly takes place at a deep junction. Tidal movement is important for sediment resuspension, but river induced, tide residual currents are responsible for redistributing the sediment towards the river banks and to the bay. We applied the same forcing for four different channel configurations ranging from a full delta network to a schematization of the main river. A higher degree of network schematization leads to higher peak-sediment export downstream to the bay. However, the area of sedimentation is similar for all the configurations because it is mostly driven by geometry and bathymetry.

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Section: Responsible Editor: Carlos Augusto França Schettinimentioning

confidence: 99%

Suspended sediment dynamics in a tidal channel network under peak river flow

Achete¹,

Wegen²,

Roelvink

et al. 2016

Ocean Dynamics

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“…Corresponding modelling study results are often assumed to be valid for a divergent range of basin types, thereby disregarding the fact that these studies are invariably carried out in a very specific geomorphic setting. Zhou et al, 2017;Townend, 2012). Townend, 2005;Rees, 2006) and the Netherlands (e.g.…”

Section: Introductionmentioning

confidence: 99%

The links between entrance geometry, hypsometry and hydrodynamics in shallow tidally dominated basins

Ruiter

Mullarney

Bryan

2019

Earth Surf Processes Landf

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Geomorphological characteristics of tidal basins control hydrodynamics and sediment transport potential within such basins, for example, by adjusting the balance in tidal asymmetry. In this study we examine the effects of entrance geometry on tidal velocity asymmetry, slack water asymmetry, bed shear stress patterns and hypsometric profile shapes by comparison of six shallow meso‐tidal basins of Tauranga Harbour, New Zealand. Numerical model results show how tidal distortion increases with distance from a basin entrance. A simple ratio between basin width and entrance width defines levels of basin dilation. Sub‐basins with a constricted geometry and deep entrance channels are associated with small bed shear stress values and high rates of flood‐directed tidal velocity asymmetry in the sheltered basin centres, indicating a large potential for sediment deposition of larger particles. Moreover, slack water asymmetry within these basins is weakly ebb‐directed, indicating a small potential for transport of fine sediments out of the basins. The constricted depositional basins are characterized by convex hypsometric profiles with elevated intertidal regions. Unconstricted geometries are associated with larger bed shear stress values and more ebb‐directed tidal velocity asymmetry within basin centres, suggesting limited potential for overall sediment deposition. The slack tide duration asymmetry is weakly flood‐dominant indicating that limited input of fine sediment into the basins is possible. The comparatively high‐energy conditions within these exposed basins are associated with a less convex hypsometric intertidal profile. The ability to estimate tidal asymmetries is advantageous when developing management strategies related to ecosystem functioning, navigability or coastal protection in specific geomorphic settings. © 2019 John Wiley & Sons, Ltd.

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“…The present‐day morphology and degree of filling therefore also reflect sediment unbalance. In addition many tidal systems are confined by antecedent topographic and geological conditions such as valley shape and the presence of resistant lithologies [ Townend , ]. This raises the question to what extent present equilibrium depends on antecedent basin properties and history.…”

Section: Introductionmentioning

confidence: 99%

Turning the tide: Growth and dynamics of a tidal basin and inlet in experiments

Kleinhans

Scheltinga

Vegt

et al. 2015

J. Geophys. Res. Earth Surf.

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Dynamic equilibrium of short tidal systems with ebb deltas, inlets, and basins is poorly understood. Observations suggest the possibility of equilibrium with sediment import balancing export, while individual channels and shoals at the local scale remain dynamic. Our objectives are to ascertain (1) whether tidal systems under entirely steady forcing can attain this state and (2) under what conditions cyclic channel‐shoal migration occurs. We present experiments of tidal systems developing from an initial breach in the coast. We periodically tilted the entire flume to obtain reversing tidal currents and sediment transports. The surface area of the back‐barrier basin with an inlet channel with erodible boundaries continued to enlarge while sediment mobility decreased. Experiments with fixed inlet boundaries remained smaller and much more dynamic and had cyclically migrating ebb and flood channels. The same cyclicity with a period of about 80 tides is observed in shifting dominance of the two channels of the inlet and in the shifting channels in the basin. Experiments with stepwise sea level rises resulted in more rapid channel and bar shifting, increased channel dimensions and basin size. We conclude that cyclic migration of channels is coupled between inlet and basin but the ebb delta did not show such cyclicity. Furthermore, tidal basins with erodible boundaries slowly enlarge by margin erosion toward a system where sediment mobility is at the threshold for motion, as in braided gravel‐bed rivers. Consequently, in nature dimensions of tidal systems are partly determined by naturally formed cohesive and vegetated margins and geological context.

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The estimation of estuary dimensions using a simplified form model and the exogenous controls

Cited by 39 publications

References 38 publications

Suspended sediment dynamics in a tidal channel network under peak river flow

Suspended sediment dynamics in a tidal channel network under peak river flow

The links between entrance geometry, hypsometry and hydrodynamics in shallow tidally dominated basins

Turning the tide: Growth and dynamics of a tidal basin and inlet in experiments

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