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Introduction

In this tool (coastline development) you can compute alongshore sediment transports and shoreline dynamics.
The tool requires a shoreline, cross-shore profile, a wave climate and sediment characteristics (you can inspect the generic data availability in the top panel of the tool). Breakwaters will also be used in case they are provided. Breakwaters fully block alongshore transports at the nearest coastline grid cell.

Alongshore transports are based on either the Kamphuis or CERC alongshore sediment transport formula.

Shoreline dynamics are computed through alongshore transport gradients based on shoreline orientation relative to the wave direction. The computation is performed on a staggered 1-dimensional coastline grid. Transport gradients give rise to shoreline position changes, which in turn results in changing alongshore transports in time.

How to use the tool

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Please be aware that the speed of this tool scales:

• Kwadraticly (!) with dx (based on distance of coast and/or number of points N)
• Linearly with with the maximum sediment transport in the S-phi curves (non-linearly with Hs and Tp)
• Linearly with the number of wave conditions
• Linearly with the active height
• Linearly with the duration of the computation

E.g.: when increasing both the number of gridpoints and the run-period by a factor 2, the computation will take 8x longer (!)

User input fields

A number of input fields are present which can be used to adjust the calculation according to the specific, local stituation. Default value are provided for each input parameters. The following input parameters can be defined:

Sediment parameter summary

This section provides an overview of the sediment characteristics (Median grain size D50, Porosity and Density) used for the sediment transport calculation. They can be changed in the Sediment inputfields in Generic Data.

Transport formula

Select the transport formula that is used for the sediment transport calculation. You can choose between Kamphuis or CERC.

Physical parameters

• Breaker index - Defines the wave height at which waves start to break. The maximum wave height is defined by the breaker index times the local waterdepth. Value should be between 0.0001 and 1.
• Depth of closure - Maximum waterdepth at which waves still induce sediment transport. Beach volume changes are calculated up to this waterdepth. Value should be between 0.0001 and 30 m.
• Active height - Maximum height (on the dry beach) which can still be considered active by sediment transport gradients. Beach volume changes are calculated up to this active height. Value should be between 0.0001 and 40 m
• Water density - Value should be between 1000 kg/m³ (e.g. fresh water) and 1025 kg/m³ (e.g. salty water).

Computation parameters

• N points - The number of points on the staggered grid. A staggered grid with an equal grid spacing according to the number of points is defined along the coastline. Value should be between 1 and 999.
• Total time - The total number of years for the simulation. Value should be between 1 and 1000 years.
• Time interval - The number of years after which a calculated shoreline position will be plotted on the map. Value should be between 1 and 20 years.

Boundary parameters

• Left and right boundary - Define the boundary condition applied on the left and right boundaries of the staggered grid. You can choose between: 
  dS = 0 - the sediment transport on the boundary cell equals the sediment transport on the left/right most grid cell.
  S = 0 - no sediment transport on the boundary cell.

Tool limitations

The following processes are not included in the tool: wave shadow zoning, alongshore varying wave climates, by-passing of breakwaters, non-linear beach profiles etc.
Results in terms of alongshore transports and coastline dynamics should therefore be interpreted with a considerable range of uncertainty.

Example cases

The following files (.dsproject) can be downloaded and loaded into CoDeS to serve as examples. They are not based on actual projects, but are intended as illustration.