Model help:Avulsion

Avulsion

This model illustrates the realistic looking deltas generated by a stochastic process.

Model introduction

The model assumes that an avulsion happens every time step, the basin is flat-bottomed, and the grid scale is such that one cell is always filled by the river’s sediment with every time step. The model randomly generates angles from the distribution X, moves the mouth of the distributary by these angles around the coastline, and fills empty cells with sediment. A uniform distribution builds a symmetric and radial delta while the normal distribution creates a more lobe-like delta. These river-dominated delta morphologies would change with the inclusion of waves, tides, and other processes.

Model parameters

Parameter	Description	Unit
Site prefix	Site prefix for Input/Output files	-
Case prefix	Case prefix for Input/Output files	-

Parameter	Description	Unit
Run duration	simulation run time	year
Standard deviation of avulsion angles		degree
Minimum angle		degree
Maximum angle		degree
Number of rivers		-
Bed load exponent	exponent used in dividing sediment among branches	-
Discharge exponent	exponent used in dividing water among branches	-

Parameter	Description	Unit
Number of grid rows	number of rows in the computational grid	-
Number of grid columns	number of columns in the computational grid	-
Spacing of grid rows	spacing of rows in the computational grid	m
Spacing of grid columns	spacing of columns in the computational grid	m
Row of hinge point		-
Column of hinge point		-

Parameter	Description	Unit
Output directory	path to output files	-
Interval between output files		-
mean_bed_load_from_river file	output file prefix for variable	-
mean_water_discharge_from_river file	output file prefix for variable	-

Parameter	Description	Unit
Output directory	path to output files	-
Interval between output files		-
Elevation file	output file prefix for variable	-
SedimentFlux file	output file prefix for variable	-

Parameter	Description	Unit
Model name	name of the model	-
Author name	Name of the model author	-

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

Angular position of the distributary channel after n+1 avulsions

[math]\displaystyle{ \Theta _{n+1} = \Theta _{n} + X_{n} }[/math]

(1)

Nomenclature

Symbol	Description	Unit
X	distribution used in the equation	-
X_n	nth realization of X (changes of angle for X distributary after the nth time step)	-
Θ_n	current angle of X distributary before the nth time step	-
Θ_n+1	current angle of X distributary after the nth time step	-

Notes

In this model, the angular position of the distributary on the delta is the sum of angular jumps (X_n) that are generated from the distribution X. Regardless of the underlying physics, some probability distribution must represent this change in angle. The precise distribution will not be known, but observations of large deltas suggest that the probability of avulsing somewhere nearby is high, while the probability of larger avulsions is low (Milliman et al., 1987).

Examples

An example run with input parameters, BLD files, 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>]].

Developer(s)

Eric Hutton

References

Milliman, J.D., Qin, Y.S., Ren-Meie, E., Saito, Y., 1987. Man’s influence on the erosion and transport of sediment by Asian rivers; the Yellow River (Huange) example. Journal of Geology 95 (6), 751–762.
Hutton E. W. H., Syvitski, J. P. M., 2008. Sedflux 2.0: An advanced process-response model that generates three-dimensional stratigraphy. Computers&Geosciences, 34: 1319~1337, Doi: (http://dx.doi.org/10.1016/j.cageo.2008.02.013 10.1016/j.cageo.2008.02.013).

Links

[Model:Avulsion