README
1Main algorithm sources are rewritten from GRIDATB.FOR.
2GRIDATB.FOR is available from http://www.es.lancs.ac.uk/hfdg/topmodel.html.
3
4Thanks to Keith Beven.
5
6
7
8[r.topidx]
9creates topographic index, ln(a/tan(beta)), map from elevation map.
10
11 where
12 a: the area of the hillslope per unit contour length that drains
13 through any point
14
15 tan(beta): the local surface topographic slope
16 (delta vertical) / (delta horizontal)
17
18
19Elevation map need not to be rectangular if study basin was already determined.
20Non-interesting region may have NULL values. Study basin map can be taken
21from r.water.outlet then the following r.mapcalc statements will create
22study basin extracted elevation map.
23
24 r.mapcalc "belev = if(isnull(basin), basin, elev)"
25
26