r.cn2

NAME

r.cn2 - Generates a curve number map layer.
(GRASS Raster Program)

SYNOPSIS

r.cn2 sg=hysoilgroup lu=landusemap pr=practicemap hc=hyconditionmap cn=cnmap amc=AMCnumber

DESCRIPTION

r.cn2 is a command-line interface for generating an NRCS (SCS) CN map. The command format is:

r.cn2 sg=hysoilgroup lu=landusemap pr=practicemap hc=hyconditionmap cn=cnmap amc=AMCnumber

Parameters:

sg=map
Hydrologic soil group map name
lu=map
Landuse map name
pr=map
Practice or management map name
hc=map
Hydrologic condition map name
cn=map
Output CN map name
amc=number
Equivalent AMC condition number for the CN output
The command-line ordering can be in any form but all key words must be there to run the program.

EXAMPLE

r.cn2 sg=hy.soil.group lu=landuse hc=hy.cond pr=veg.cover cn=cnname amc=2 will create a CN map cnname for equivalent AMC condition II

ATTENTION

r.cn2 uses information from the four map layers by reading the cell layer and its category files. So it is important to update the category files for all four layers and it expects the categories of the map layer exactly as shown below:

For the hydrologic soil group map the categories may be either A, B, C, or D.

For the landuse map layer the categories may be either fallow, row crops, small grain, close-seeded legumes, rotation meadow, pasture, range, meadow, woods, farm¡steads, roads (dirt), hard surface, or water.

For the practice or management map layer the categories may be either straight row, contoured, or contoured and terraced.

For the hydrological condition map the categories may be poor, fair, or good.

If the combination of the four layers categories does not exist in the NRCS (SCS) CN table, an error message is printed and the program quits.

NOTE

The r.cn2 program is sensitive to the current window setting. Thus the program can be used to generate a CN map of any sub-area within the full map layer. Also, r.cn2 is sensitive to any mask in effect.

Changes made in r.cn2 (comparing to r.cn):

  • added landuse "water"
  • corrected import of landuse "fallow" ("good condition")
  • SEE ALSO

    r.cn, r.weighted.cn

    AUTHORS

    Raghavan Srinivasan and Dr. Bernie A. Engel, Agricultural Engineering Department, Purdue University

    Extensions by Markus Neteler, University of Hannover, Germany