WMS:Mapping Tables

The mapping table is different depending on whether composite curve numbers or runoff coefficients are being computed. A mapping table must be imported using the Import button prior to computing the composite curve numbers. The radio group above the mapping window specifies whether the land use or soil type mapping table is displayed. For a land use or soil type coverage the mapping table may be set up interactively by selecting each polygon and assigning the appropriate parameters. Such files can then be exported and later imported. For grid attributes, you can define a land use or soil type table by defining a land use or soil type coverage and then using the Attributes command from the Feature Objects menu (in the Map module) to define individual polygon attributes that constitute the table. See Land Use Coverages and Soil Type Coverages for information on assigning parameters to land use and soil type polygon coverages. See File Formats for the different mapping parameters.

Composite CN Table

Because land use tables with corresponding CNs vary from text to text and agency to agency, WMS supports a user-definable method for relating land use to CNs. This is done through a simple table file that is imported prior to computing the composite CN. The file scsland.tbl is an example of such a file and was created from a table given in the Handbook of Hydrology. This file can be edited to supply user defined values or a new table with the same format can be created. See Land Use Files to view the format of the table.

Runoff Coefficient Table

The runoff coefficient table must be defined to relate soil type IDs to runoff coefficient values. A very simplified file named soiltype.tbl is provided with the distribution of WMS. This file can be edited to supply user directed values or a new table with the same format can be created. See Soil Type Runoff Coefficient Files to view the format of the table.

Related Topics

• Compute GIS Attributes
• Land Use
• Soil Type