River terrace
Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 11, Ch 6 "Landforms and their Evolution"
Meaning
A river terrace is a flat step on the side of a valley. It marks a level where the river's floodplain once lay. It forms when the river starts cutting down into its own floodplain, often because the land has been uplifted or the base level has fallen. The base level is the lowest level a river can cut down to, and the sea is the final one. A fall in base level or fresh uplift is called rejuvenation. The old floor is left high and dry as a step. Repeated downcutting can leave several terraces at different heights. Terraces at the same height on both sides of the river are called paired terraces. Terraces are evidence that a river has been rejuvenated.
Example
In the Alaknanda valley around Srinagar (Garhwal, Uttarakhand), fields and settlements sit on flat terraces above the present river.
Don't confuse with
- Floodplain: a floodplain is still flooded by the river now. A terrace stands above it and is no longer reached by ordinary floods.
- Terrace farming: these are steps cut into hill slopes by people. A river terrace is made naturally by the river.