Base Levels

Shaping Stream Valleys

Base level
Lowest point a stream can erode to
Two general types
Ultimate – sea level
Temporary or local
Changing causes readjustment of the stream – deposition or erosion

Valley sides are shaped by
Weathering
Overland flow
Mass wasting
Characteristics of narrow valleys
V-shaped
Downcutting toward base level
Incised meanders

Characteristics of narrow valleys
Features often include
Rapids
Waterfalls
Characteristics of wide valleys
Stream is near base level
Downward erosion is less dominant
Stream energy is directed from side to side

Characteristics of wide valleys
Floodplain
Features often include
Meanders
Cutoffs
Oxbow lakes