This table allows the user to enter Manning's n values for various Land Classification types. This option requires the user to have added a Land Classification Map layer into the HEC-RAS project inside of RAS Mapper. If a land Classification Layer has been developed within HEC-RAS Mapper, that layer can then be selected (associated with a specific geometry file). Once a Land Classification layer is selected, the types of land classifications contained within that layer will show up in the table (See Figure below). The user can then enter a Manning's n values to associate with each Land Classification type (name). Currently this option for entering Land Classifications, and associating Manning's n values with them, is only used for defining Manning's n values for 2D Flow Areas. See the Figure below for this example:

Figure 5 78. Manning's n by Land Class Table.

As shown in the Figure above, the editor displays the Manning's n values that may be contained within the Land Cover file (Default Mann n). The user can override these default Manning's n values for this specific geometry file by entering their own defaults into the column labeled Base Mann n (Blank for default). If this column is left blank, the software will use the Manning's n values from the Land Cover Layer. If the user enters values in this column, then these values will be used for those Land Cover layer types.
Additionally, the user has the option to draw polygons on top of the geometry, in which they can redefine the Manning's n values within that polygon. This option could be used for calibrating Manning's n values within that region (Inside of the polygon), or it could be used for defining main channel Manning's n values based on user defined regions (polygons). To use this option, draw polygons onto the geometric editor, using the drawing tool labeled 2D Area Mann n Regions. After drawing the polygon the user is required to give it a unique name. Once the polygons are drawn they will show up in the Manning's n by Land Cover Table. Right now these Manning's n values only work for 2D Flow Areas.