Earth Science: Streams


Streams are the channelized flow of surface water, and the single most effective geologic agent responsible for the landforms we see.

Stream downcutting is followed by mass wasting from the sides of the canyon so that a stream valley is formed.

Rivers and tributaries each drain a portion of land known as a drainage basin, shown below for the Mississippi river.

Water flows downhill from stream head in the highlands to stream mouth at a lake or (usually) the ocean. The drop in elevation with distance is called the stream gradient. The stream gradient is steep near the stream head, and shallow toward the mouth.

Floods occur when a stream is overloaded with more water than it can carry within its banks. The excess water spills into the stream's floodplain. In the natural (no humans) state, floods are common, and sometimes occur yearly.

Downtown Davenport, July 1993.

Landsat images of the Mississippi River at St. Louis, Missouri, in normal and flood stages.

Artifical controls on flooding:

Sequence of stream erosion.

Evolution of a floodplain.

Meanders in the Sweetwater River, Wyoming.

Formation of oxbow lakes.

Landsat view of braided stream Brahmaputra r., India.

Entrenched meanders in the San Juan r., Utah.

Flood plain terraces, Snake r., Wyoming.

Delta sediment.

Landsat view of the Mississippi delta.

Last modified: Wed Mar 1 13:38:44 CST 2000