r.basin.html

<h2>DESCRIPTION</h2> 

<em>r.basin</em> generates the main morphometric parameters of the 
basin starting from the digital elevation model and the coordinates 
of the basin's closing section (outlet). 

<h3>Important:</h3>

<p>
<em>r.basin</em> works in projected locations, geographic or 
xy-locations are not supported. 
</p>

<p>
The closing section's coordinates must belong to the river network 
generated by <a href="r.stream.extract.html">r.stream.extract</a>. 
It is suggested to run it beforehand.
In G7, r.basin has been improved to take in input coordinates not 
exactly belonging to the river network (but not too far from it). 
It basically snaps to the closest point belonging to the network. 
This feature is experimental and might not produce the expected result. 
To check if the snapped outlet is acceptable, at the end of the 
computation, two outlet vector maps are produced: the one with the 
coordinates inserted by the user and the snapped one. If the user is 
not happy with this latter, should tweak the coordinates to match with 
the river network.
</p>

<h3>Morphometric parameters of basin</h3> 

The main parameters are: 
<ul>
<li>The coordinates of the vertices of the rectangle containing 
the basin.</li> 
<li>The center of gravity of the basin: the 
coordinates of the pixel nearest to the center of gravity of the 
geometric figure resulting from the projection of the basin on the 
horizontal plane.</li> 
<li>The area of the basin: is the area of a single cell multiplied 
by the number of cells belonging to the basin.</li>
<li>The perimeter: is the length of the contour of the figure 
resulting by the projection of the basin on the horizontal plane.</li>
<li>Characteristic values of elevation: the highest and the 
lowest altitude, the difference between them and the mean elevation 
calculated as the sum of the values of the cells divided by the 
number of the cells.</li> 
<li>The mean slope, calculated averaging the slope map.</li> 
<li>The length of the directing vector: the length of the vector 
linking the outlet to the center of gravity of the basin.</li>
<li>The prevalent orientation: in GRASS GIS the 
aspect categories represent the number degrees of east and they 
increase counterclockwise: (90deg is North, 180 is West, 270 is 
South 360 is East). The aspect value 0 is used to indicate undefined 
aspect in flat areas with slope=0. We instead calculate the 
orientation as the number of degree from north, increasing 
counterclockwise.</li> 
<li>The length of main channel: is the length 
of the longest succession of segments that connect a source to the 
outlet of the basin.</li> 
<li>The mean slope of main channel: it is calculated as follows

<br>
<center>
<img src="r.basin1.gif" border="0" alt="mean slope">
</center> 

<br> where N is the topological diameter, i.e. the number of links 
in which the main channel can be divided on the basis of the 
junctions.</li> 
<li>The circularity ratio: is the ratio between the area of the 
basin and the area of the circle having the same perimeter of the 
basin.</li> 
<li>The elongation ratio: is the ratio between the diameter of the 
circle having the same area of the basin and the length of the main 
channel.
</li> 
<li>The compactness coefficient: is the ratio between the perimeter 
of the basin and the diameter of the circle having the same area of 
the basin.</li> 
<li>The shape factor: is the ratio between the area of the basin and 
the square of the length of the main channel.</li> 
<li>The concentration time (Giandotti, 1934):

<br> 
<center>
<img src="r.basin2.gif" border="0" alt="concentration time">
</center> 

<br> Where A is the area, L the length of the main channel and H the 
difference between the highest and the lowest elevation of the basin.
</li>
<li>The mean hillslope length: is the mean of the distances 
calculated along the flow direction of each point non belonging to 
the river network from the point in which flows into the network.
</li>
<li>The magnitudo: is the number of the branches of order 1 
following the Strahler hierarchy.</li>
<li>The max order: is the order of the basin, following the Strahler 
hierarchy.</li>
<li>The number of streams: is the number of the branches of the 
river network.</li>
<li>The total stream length: is the sum of the length of every 
branches.</li>
<li>The first order stream frequency: is the ratio between the 
magnitudo and the area of the basin.</li>
<li>The drainage density: is the ratio between the total length of 
the river network and the area.</li>
<li>The Horton ratios (Horton, 1945; Strahler, 1957).</li>
</ul>

<h3>Plots</h3> 
<ul>
<li>The distance-area function, also known as Width Function: in x 
axis is the length and in y axis is the area.</li>
<li>The hypsographic curve provides the distribution of the areas at 
different altitudes. Each point on the hypsographic curve has on the 
y-axis the altitude and on the x-axis the percentage of basin 
surface placed above that altitude.</li>
<li>The hypsometric curve has the same shape but is dimensionless.</li>
</ul> 

<h2>EXAMPLE</h2>

North Carolina sample dataset example:

<div class="code"><pre>
g.region raster=elevation -p
r.basin map=elevation prefix=my_basin coord=637304.924954,218617.100523 \
 dir=/tmp/bla threshold=1000

# visualize some results
d.mon wx0
d.rast my_basin_elevation_hack

d.rast my_basin_elevation_dist2out

d.his i=aspect h=my_basin_elevation_dist2out
</pre></div>

<h3>Dependencies</h3> 
<ul>
<li>Matplotlib</li>
<li>r.hypso</li>
<li>r.stream.basins</li>
<li>r.stream.distance</li>
<li>r.stream.extract</li>
<li>r.stream.order</li>
<li>r.stream.snap</li>
<li>r.stream.stats</li>
<li>r.width.funct</li>
</ul>

<h2>SEE ALSO</h2>  

<em>
<a href="http://grass.osgeo.org/grass70/manuals/addons/r.hypso.html">r.hypso</a> (Addon),
<a href="http://grass.osgeo.org/grass70/manuals/addons/r.stream.basins.html">r.stream.basins</a> (Addon),
<a href="http://grass.osgeo.org/grass70/manuals/addons/r.stream.channel.html">r.stream.channel</a> (Addon),
<a href="http://grass.osgeo.org/grass70/manuals/addons/r.stream.distance.html">r.stream.distance</a> (Addon),
<a href="r.stream.extract.html">r.stream.extract</a>,
<a href="http://grass.osgeo.org/grass70/manuals/addons/r.stream.order.html">r.stream.order</a> (Addon),
<a href="http://grass.osgeo.org/grass70/manuals/addons/r.stream.segment.html">r.stream.segment</a> (Addon),
<a href="http://grass.osgeo.org/grass70/manuals/addons/r.stream.slope.html">r.stream.slope</a> (Addon),
<a href="http://grass.osgeo.org/grass70/manuals/addons/r.stream.snap.html">r.stream.snap</a> (Addon),
<a href="http://grass.osgeo.org/grass70/manuals/addons/r.stream.stats.html">r.stream.stats</a> (Addon),
<a href="r.watershed.html">r.watershed</a>,
<a href="http://grass.osgeo.org/grass70/manuals/addons/r.width.funct.html">r.width.funct</a> (Addon)
</em>   

<h2>CITE AS</h2> 

Di Leo Margherita, Di Stefano Massimo (2013) An Open-Source Approach for Catchment's 
Physiographic Characterization, Abstract H52E-06 presented at 2013 Fall Meeting, AGU, 
San Francisco, CA, USA 9-13 Dec. 
<a href="http://abstractsearch.agu.org/meetings/2013/FM/sections/H/sessions/H52E/abstracts/H52E-06.html">

<h2>REFERENCES</h2> 
<ul>
<li><em>Rodriguez-Iturbe I., Rinaldo A. (2001) Fractal River Basins, 
Chance and Self-Organization. Cambridge Press </em></li>
<li><em>In Italian: Di Leo M., Di Stefano M., Claps P., Sole A. 
(2010) Caratterizzazione morfometrica del bacino idrografico in 
GRASS GIS (Morphometric characterization of the catchment in GRASS 
GIS environment), <a href="http://geomatica.como.polimi.it/workbooks/"> 
Geomatics Workbooks</a>, n. 9</em></li>
</ul>

<h2>AUTHORS</h2> 

Margherita Di Leo (dileomargherita AT gmail DOT com), Massimo Di Stefano  

<p> 
<i>Last changed: $Date: 2016-04-12 14:04:04 +0200 (Di, 12 Apr 2016) $</i>