Model help:AgDegNormalFault

AgDegNormalFault

This is used to calculate aggradation and degradation of a river reach using the normal flow approximation; with an extension for calculation of the response to a sudden fault along the reach.

Model introduction

This program computes 1D bed variation in rivers due to differential sediment transport in which it is possible to allow the bed to undergo a sudden vertical fault of a specified amount, at a specified place and time. Faulting is realized by moving all notes downstream of the specified point downward by the amount of the faulting.

The sediment is assumed to be uniform with size D. All sediment transport is assumed to occur in a specified fraction of time during which the river is in flood, specified by an intermittency. A Manning-Strickler formulation is used for bed resistance. A generic relation of the general form of that due to Meyer-Peter and Muller is used for sediment transport. The flow is computed using the normal flow approximation.

Model parameters

Input Files and Directories

Run Parameters

About

Parameter	Description	Unit
Input directory	path to input files
Site prefix	Site prefix for Input/Output files
Case prefix	Case prefix for Input/Output files

Parameter	Description	Unit
Flood discharge		m3 / s
Intermittency		-
Channel Width		m
Grain size		mm
Bed Porosity		-
Roughness height		mm
Ambient Bed Slope
Imposed Annual Sediment Transfer Rate from Upstream		tons / annum
Length of reach		m
Time step		year
Number of Time Steps per Printout
Number of printout
intervals
Upwinding coefficient (1 = full upwind, 0.5 = central difference)
Coefficient in Manning-Strickler Resistance Relation
Coefficient in Sediment Transport Relation
Exponent in Sediment Transport Relation
Critical Shield stress
Fraction of bed shear stress that is skin friction
Submerged specific gravity of sediment
Height of faulting		m
Fraction of reach length such that all points downstream undergo downward faulting		-
Time from beginning of calculation at which faulting occurs		yrs

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

• Manning-Strickler formulation

[math]\displaystyle{ C_{f}=\alpha _{r}\left ( \frac{H}{K_{c}} \right )^{\frac{1}{6}} }[/math]

(1)

• Total bed material load per unit width

[math]\displaystyle{ \frac{q_{t}}{{\sqrt{RgD}D}}=\alpha_{t}\left ( \frac{\varphi_{s}\tau _{b}}{\rho RgD} -\tau_{c}^* \right )^{n_{t}} }[/math]

(2)

Nomenclature

Symbol	Description	Unit
X	Streamwise coordinate	m
ΔX	Spatial step length	m
t	Temporal coordinate	seconds
Cf	Non-dimensional friction coefficient	-
Qw	Flood discharge	m3/s
If	Flood intermittency	-
Bc	Channel width	m
D	Characteristic grain size	mm
λp	Bed porosity	-
kc	Composite roughness height	mm
SI	Ambient bed slope	-
Gtf	Imposed annual sediment transport rate	tons/annum
L	Length of reach	m
Δt	Time step	year
Ntoprint	number of time steps to printout	-
Nprint	number of printouts	-
M	Number of spatial intervals	-
au	Upwinding coefficient (1 = full upwind, 0.5 = central difference)	-
αr	Coefficient in Manning-Strickler	-
αs	Coefficient in sediment transport relation	-
ηt	Exponent in sediment transport relation	-
τ*c	Reference Shields number in sediment transport relation	-
φs	Fraction of bed shear stress due to skin friction	-
R	Submerged specific gravity	-
Cz	Non-dimensional Chézy friction coefficient	-
Gtf	imposed annual sediment transport rate	-
rf	the fraction of reach length such that all points downstream of x = rfL undergo downward faulting	-
tf	the time from beginning of calculation at which faulting occurs	-
∆η	height of faulting	m

Output

Symbol	Description	Unit
η	Bed surface elevation	m
S	Bed slope	-
H	Water depth	m
τb	Total (skin friction + form drag) Shields number	-
qt	total bed material load	m2/s

Notes

If the channel slope is negative and the water depth is not a number, “nan”, check the time step and the spatial step length. In particular, the time step may be too large or equivalently the spatial step length may be too small. Change these values and run the model again

The water depth is calculated using a Chézy formulation, when only the Chézy coefficient is specified in the input text file. The Manning-Strickler formulation is implemented, when only the roughness height, k_c, and the coefficient α_r are given in the input file. When all the three parameters are present, the program will ask the user which formulation they would like to use.

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>]].

See also: Help:Images or Help:Movies

Developer(s)

Name of the module developer(s)

References

Key papers

Links

Any link, eg. to the model questionnaire, etc.