Model help:CEM

CEM

Model Introduction

The CEM model, the Coastline Evolution Model, simulates the evolution of a shoreline due to gradients in breaking-wave-driven alongshore sediment transport. The original CEM has been componentized to consist of the longshort tranport module (CEM) and a wave input module (WAVES).

Extended model introduction

The CEM model assumes that the coast consists of a high percentage of mobile sediment and its other assumptions are more applicable at shoreline lengths of km’s and larger. The model was initially designed to investigate an instability in the shape of the coast caused by waves approaching with ‘high’ angles (with the angle between deepwater crests and the coast > 45 degrees).
Although a number of wave (and geometry) parameters can be entered, the most vital input control for CEM is the wave climate. The current version of the CEM is driven by simplified directional wave climate controlled by two main input parameters: the asymmetry of the incoming waves angle and the proportion of high-angle waves. This model is not designed to accurately simulate a specific geographic location in detail but rather to more generally represent how a shoreline with highly mobile sediment may respond to varying wave angles. The value in this model is in the breadth it offers in representing how different wave climates can result in different potentially interesting shoreline configurations. Ashton and Murray (2006b) present a more thorough description of the model parameters and theoretical underpinning.

Model input parameters

CEM does not need input files from the user, its input is entirely specified in the CMT graphical user interface. One can set the ‘site prefix’ and the ‘case prefix’ to identify model experiments. These prefixes are used throughout the CMT and allow users to organize their simulations according to geographic setting (site prefix) and simulation scenario (case prefix). The fields do need to be filled in, in this project these two fields determine the name of the output files.

Run Parameters

Run duration	= number of simulation time steps	[-]
Shoreface Slope	= Longitudinal Slope of the Shoreface	[-]
Shoreface Depth	= Critical threshold depth defining the shoreface	[m]
Shelf Slope	= Longitudinal Slope of the Shelf	[-]

The parameters, “Shoreface Slope”, “Shoreface Depth” and “Shelf Slope” set the initial geometry of the shoreface domain and the shelf domain. Simulations will use the shoreface depth as an effective erosion depth, but deposition can take place to deeper depths if the shoreface is accreting on a deeper shelf.

Model output parameters

Use the 'ON' toggle to specify whether you want outfiles to be written or not.

DEPTH	= evolving land and ocean bottom grid	[meters]
PERCENT-FILLED	= records the fill of the individual cells for the entire grid	[%]

Coupling parameters

Uses ports

This will be something that the CSDMS facility will add

Provides ports

This will be something that the CSDMS facility will add

Main equations

A list of the key equations. HTML format is supported; latex format will be supported in the future

Numerical scheme

Output variable

Notes

Any notes, comments, you want to share with the user

Examples

An example run with input parameters as well as a figure / movie of the output

Follow the next steps to include images / movies of simulations:

• Upload file: http://csdms.colorado.edu/wiki/Special:Upload
• Create link to the file on your page: [[Image:<file name>]].

See also: Help:Images or Help:Movies

Developer(s)

Andrew Ashton

References

Ashton A., Murray B.A. Arnault O. Formation of Coastline Features by Large-Scale Instabilities Induced by High-Angle Waves. Nature Magazine. Volume 414. 15 November 2001
Ashton A.D., Murray A.B. High-Angle Wave Instability and Emergent Shoreline Shapes: 1. Wave Climate Analysis and Comparisons to Nature. Journal of Geophysical Research. Volume 111. 15 December 2006.
Ashton A.D., Murray A.B. High-Angle Wave Instability and Emergent Shoreline Shapes: 2. Wave Climate Analysis and Comparisons to Nature. Journal of Geophysical Research. Volume 111. 15 December 2006.

External links

Movies generated with the stand-alone CEM model are documented in the CSDMS movie gallery. http://csdms.colorado.edu/wiki/Coastal_animations