Slope angle is measured from the horizontal in degrees, and the dominant slope within the map unit area is recorded as one of the following seven slope groups (Table 6 - section 2.3 of LUC Handbook).
In the field the dominant slopes can be measured by hand-held Abney level or clinometer, or estimated by eye. Slope can also be calculated from a Digital Elevation Model (DEM) where one of suitable accuracy and precision is available.
Slope groupings are:
|
Slope |
Slope angle (degrees) | Description | Typical examples |
| A | 0-3° | Flat to gently undulating | Flats, terraces |
| B | 4-7° | Terraces, fans | |
| C | 8-15° | Rolling | Fans, downlands |
| D | 16-20° | Strongly rolling | Downlands, hill country |
| E | 21-25° | Moderately steep |
|
| F | 26-35° |
Steep |
Hill country, steeplands |
| G | >35° | Very steep | Steeplands, cliffs |
A map polygon with a single slope classification is recorded as a single letter code (e.g. A for flat to gently undulating land), but compound slope classifications can be used where more than one major slope group occurs in a map unit. For example, D+E slopes means that slopes are mainly strongly rolling but the map unit contains a significant area of land with moderately steep slopes. Slopes which are borderline between two slope groupings can be recorded in the form D/E (i.e. most slopes are 20–21 degrees). The superscript ' is used to denote dissected slopes, and + or - to denote where slopes are nearer the upper or lower end of the slope group.
