mirror of
https://github.com/qgis/QGIS.git
synced 2025-03-12 00:02:25 -04:00
105 lines
6.2 KiB
HTML
105 lines
6.2 KiB
HTML
<html>
|
|
<head><link rel="stylesheet" type="text/css" href="help.css"/></head>
|
|
<body>
|
|
<h1 class='module'>D-Infinity Transport Limited Accumulation</h1>
|
|
<div class='author'>(c) 2010 by David G. Tarboton</div>
|
|
<div class='description'>This function is designed to calculate the transport
|
|
and deposition of a substance (e.g. sediment) that may be limited by both
|
|
supply and the capacity of the flow field to transport it. This function
|
|
accumulates substance flux (e.g. sediment transport) subject to the rule
|
|
that transport out of any grid cell is the minimum between supply and transport
|
|
capacity, <tt>T<sub>cap</sub></tt>. The total supply at a grid cell is
|
|
calculated as the sum of the transport in from upslope grid cells, <tt>T<sub>in</sub></tt>,
|
|
plus the local supply contribution, <tt>E</tt> (e.g. erosion). This function
|
|
also outputs deposition, <tt>D</tt>, calculated as total supply minus actual
|
|
transport.</div>
|
|
<p align="center"><img src="img/tlaeqn.gif"></img></p>
|
|
<div class='description'>Here <tt>E</tt> is the supply. <tt>T<sub>out</sub></tt>
|
|
at each grid cell becomes <tt>T<sub>in</sub></tt> for downslope grid cells
|
|
and is reported as Transport limited accumulation (<tt>tla</tt>). <tt>D</tt>
|
|
is deposition (<tt>tdep</tt>). The function provides the option to evaluate
|
|
concentration of a compound (contaminant) adhered to the transported
|
|
substance. This is evaluated as follows:</div>
|
|
<p align="center"><img src="img/tlaceqn1.gif"></img></p>
|
|
<div class='description'>Where <tt>L<sub>in</sub></tt> is the total incoming
|
|
compound loading and <tt>C<sub>in</sub></tt> and <tt>T<sub>in</sub></tt>
|
|
refer to the Concentration and Transport entering from each upslope grid
|
|
cell.</div>
|
|
<p align="center"><img src="img/tlaceqn2.gif"></img></p>
|
|
<div class='description'>If</div>
|
|
<p align="center"><img src="img/tlaceqn3.gif"></img></p>
|
|
<div class='description'>else</div>
|
|
<p align="center"><img src="img/tlaceqn4.gif"></img></p>
|
|
<div class='description'>where <tt>C<sub>s</sub></tt> is the concentration
|
|
supplied locally and the difference in the second term on the right represents
|
|
the additional supply from the local grid cell. Then,</div>
|
|
<p align="center"><img src="img/tlaceqn5.gif"></img></p>
|
|
<div class='description'><tt>C<sub>out</sub></tt> at each grid cell comprises
|
|
is the concentration grid output from this function.</div>
|
|
<div class='description'>If the outlets shapefile is used the tool only
|
|
evaluates that part of the domain that contributes flow to the locations
|
|
given by the shapefile.</div>
|
|
<div class='description'>Transport limited accumulation is useful for
|
|
modeling erosion and sediment delivery, including the spatial dependence
|
|
of sediment delivery ratio and contaminant that adheres to sediment.</div>
|
|
|
|
<h2>Parameters</h2>
|
|
<dl class='parameters'>
|
|
<dt>Number of Processes <div class='type'>Integer</div></dt>
|
|
<dd>The number of stripes that the domain will be divided into and the
|
|
number of MPI parallel processes that will be spawned to evaluate each
|
|
of the stripes.</dd>
|
|
<dt>D-Infinity Flow Direction Grid <div class='type'>Raster Grid</div></dt>
|
|
<dd>A grid giving flow direction by the D-infinity method. Flow direction
|
|
is measured in radians, counter clockwise from east. This can be created
|
|
by the tool "D-Infinity Flow Directions".</dd>
|
|
<dt>Supply Grid <div class='type'>Raster Grid</div></dt>
|
|
<dd>A grid giving the supply (loading) of material to a transport limited
|
|
accumulation function. In the application to erosion, this grid would give
|
|
the erosion detachment, or sediment supplied at each grid cell.</dd>
|
|
<dt>Transport Capacity Grid <div class='type'>Raster Grid</div></dt>
|
|
<dd>A grid giving the transport capacity at each grid cell for the
|
|
transport limited accumulation function. In the application to erosion
|
|
this grid would give the transport capacity of the carrying flow.</dd>
|
|
<dt>Input Concentration Grid <div class='type'>Raster Grid (optional)</div></dt>
|
|
<dd>A grid giving the concentration of a compound of interest in the
|
|
supply to the transport limited accumulation function. In the application
|
|
to erosion, this grid would give the concentration of say phosphorous
|
|
adhered to the eroded sediment. <strong>NOTE</strong>: if you need
|
|
this optional parameter please use "D-Infinity Transport Limited
|
|
Accumulation - 2" tool.</dd>
|
|
<dt>Outlets Shapefile <div class='type'>Point Shapefile (optional)</div></dt>
|
|
<dd>This optional input is a point shapefile defining outlets of interest.
|
|
If this file is used, the tool will only evaluate the area upslope of
|
|
these outlets.</dd>
|
|
<dt>Check for Edge Contamination <div class='type'>Boolean</div></dt>
|
|
<dd>This option determines whether the tool should check for edge
|
|
contamination. Edge contamination is defined as the possibility that
|
|
a value may be underestimated due to grid cells outside of the domain
|
|
not being considered when determining the result. Default <strong>True</strong>.</dd>
|
|
</dl>
|
|
|
|
<h2>Outputs</h2>
|
|
<dl class='parameters'>
|
|
<dt>Transport Limited Accumulation Grid <div class='type'>Raster Grid</div></dt>
|
|
<dd>This grid is the weighted accumulation of supply accumulated respecting
|
|
the limitations in transport capacity and reports the transport rate
|
|
calculated by accumulating the substance flux subject to the rule that
|
|
the transport out of any grid cell is the minimum of the total supply
|
|
(local supply plus transport in) to that grid cell and the transport
|
|
capacity.</dd>
|
|
<dt>Deposition Grid <div class='type'>Raster Grid</div></dt>
|
|
<dd>A grid giving the deposition resulting from the transport limited
|
|
accumulation. This is the residual from the transport in to each grid
|
|
cell minus the transport capacity out of the grid cell. The deposition
|
|
grid is calculated as the transport in + the local supply - the tranport
|
|
out.</dd>
|
|
<dt>Output Concentration Grid <div class='type'>Raster Grid (optional)</div></dt>
|
|
<dd>If an input concentation in supply grid is given, then this grid
|
|
is also output and gives the concentration of a compound (contaminant)
|
|
adhered or bound to the transported substance (e.g. sediment) is calculated.
|
|
<strong>NOTE</strong>: to produce this output please use "D-Infinity
|
|
Transport Limited Accumulation - 2" tool.</dd>
|
|
</dl>
|
|
</body></html>
|