*convergence*
@@ -192,19 +193,19 @@
#### A^{T} least-cost search algorithm

*r.watershed* uses an A^{T} least-cost search algorithm
-(see REFERENCES section) designed to minimize the
-impact of DEM data errors. This algorithm works slower than
-*r.terraflow* but provides more accurate results in
-areas of low slope as well as DEMs constructed with techniques that
-mistake canopy tops as the ground elevation. Kinner et al. (2005), for
-example, used SRTM and IFSAR DEMs to compare *r.watershed*
-against *r.terraflow* results in Panama. *r.terraflow* was
-unable to replicate stream locations in the larger valleys while
-*r.watershed* performed much better. Thus, if forest canopy exists
-in valleys, SRTM, IFSAR, and similar data products will cause major
-errors in *r.terraflow* stream output. Under similar conditions,
-*r.watershed* will generate better **stream** and **half_basin**
-results. If watershed divides contain flat to low slope, *r.watershed*
+(see REFERENCES section) designed to minimize
+the impact of DEM data errors. Compared to *r.terraflow*, this
+algorithm provides more accurate results in areas of low slope as well
+as DEMs constructed with techniques that mistake canopy tops as the
+ground elevation. Kinner et al. (2005), for example, used SRTM and IFSAR
+DEMs to compare *r.watershed* against *r.terraflow*
+results in Panama. *r.terraflow* was unable to replicate stream
+locations in the larger valleys while *r.watershed* performed
+much better. Thus, if forest canopy exists in valleys, SRTM, IFSAR, and
+similar data products will cause major errors in *r.terraflow*
+stream output. Under similar conditions, *r.watershed* will
+generate better **stream** and **half_basin** results. If
+watershed divides contain flat to low slope, *r.watershed*
will generate better basin results than *r.terraflow*.
(*r.terraflow* uses the same type of algorithm as ESRI's ArcGIS
watershed software which fails under these conditions.) Also, if watershed
@@ -216,11 +217,12 @@
*r.drain* on every cell on the map.
#### Multiple flow direction (MFD)

-*r.watershed* has experimental support for multiple flow
-direction (MFD). Water flow is distributed to all neighbouring cells with
-lower elevation, using slope towards neighbouring cells as a weighing
-factor for proportional distribution. The A^{T} least-cost path
-is always included and assigned the maxmimum observed weighing factor.
+

*r.watershed* offers two methods to calculate surface flow:
+single flow direction (SFD, D8) and multiple flow direction (MFD). With
+MFD, water flow is distributed to all neighbouring cells with lower
+elevation, using slope towards neighbouring cells as a weighing factor
+for proportional distribution. The A^{T} least-cost path is
+always included and assigned the maxmimum observed weighing factor.
As a result, depressions and obstacles are overflown with a gracefull
flow convergence before the overflow. The convergence factor causes flow
accumulation to converge more strongly with higher values. The supported