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
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)
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, kc, and the coefficient αr 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.