r.cn

NAME

r.cn - Generates a curve number map layer (G Language Tool)

(GRASS Raster Program)

SYNOPSIS

r.cn
r.cn sg=hy_soil_group lu=landuse_map pr=practice_map hc=hy_condition_map cn=cn_map amc=AMC_number

DESCRIPTION

r.cn is a command-line interface for generating an SCS CN map. The command format is:


     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.cn sg=hy.soil.group lu=land_use hc=hy.cond pr=veg.cover
     cn=cn_name amc=2

will create a CN map cn_name for equivalent AMC condition II

ATTENTION

r.cn 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, farmsteads, roads (dirt) or hard surface.

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 SCS CN table, an error message is printed and the program quits.

NOTE

The r.cn 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.cn is sensitive to any mask in effect.

AUTHORS