Glossary of Terms in Soil Science
- underground runoff (or seepage)
- Water flowing toward stream channels after infiltration into the ground.
- undifferentiated soil map unit
- Soil mapping unit in which two or more soil units occur but not in a regular geographic association. For example the steep phases of two or more soils might be shown as a unit on a map because slope is the prime characteristic.
See also association / soil and complex / soil.
- unsaturated flow
- The movement of water in a soil that is not filled to capacity with water.
- upper plastic limit
- See liquid limit.
- urban land
- Areas so altered or obstructed by urban works or structures that identification of soils is not feasible. A miscellaneous land type.