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Uniform sediment flux or sediment balance

Method indicator
Bottom-Up Hybrid Top-Down

Summary of key issues:

Issue Description
Description In this type of model, sediment is moved within the estuary until a steady state is achieved when equal amounts on the flood and ebb tide.
Temporal applicability Typically applied over the long-term (10-100 years).
Spatial applicability Most often applied over the whole estuary as discrete areas of particular interest (e.g. tidal lagoon, channel, saltmarsh etc).
Links with other tools Most recently applied to the ASMITA (Aggregated Scale Morphological Interaction between Tidal inlet and Adjacent coast) developed under ERP Phase 2.
Data sources An understanding of the sediment dynamics including:
  1. Density
  2. Size
  3. Diffusion coefficients
  4. Fall velocity
  5. Hydrodynamic information (Flow speeds, water levels)
Necessary software tools / skills A top-down sediment flux/balance model and access to hydrodynamic information. The modelling requires a good understanding of the sediment transport regime within the estuary, long term evolution based on the equilibrium morphological state.
Typical analyses Changes in estuary hypsometry (area and shape).
Limitations An understanding of equilibrium regime theory based on the balance of sediment flux for a particular estuary or environment is extremely complicated and requires specialist knowledge. Calibration and interpretation of model results is limited to historic evidence based on previous bathymetry.
Example applications Humber Estuary

One of the earliest models to use the balance of net transport was a zero-dimensional model of a tidal lagoon by di Silvio (1989). The lagoon was schematised into just three components, tidal flat, littoral and tidal channel and the model was based on the idea that although locally and at any instant sediment transport is not in equilibrium, averaged over the system as a whole and a long enough period a relationship exists between the hydrodynamic quantities and the sediment concentrations.

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Analysis and modelling

Last Modified on: 19 June 2011
Printed from the Estuary Guide on 17/01/2017 06:46:05