River Systems

Stream Erosion

Target #22- I can label the parts of a river

system on a diagram

draw diagram on board

Target #23- I can define all the parts of a river system

• A river system is made up of a main stream and tributaries–Tributary: a stream that flows into a lake or into a larger stream

Target #23 cont.

• The land from which water runs off into these streams is called a watershed–Watershed: the area of land that is drained by a river system• The ridges or elevated regions that separate watersheds are called divides

Target #23 cont.

• Channel: the relatively narrow depression that a stream follows as it flows downhill

Target #23 cont.

• Banks: the edges of a stream channel that are above water level• Bed: the part of the

stream channel that is below the water level• Mouth: where the

stream enters a larger body of water

Target #24- I can describe how stream load, stream discharge, and velocity affect

the erosion of a stream

• A stream transports soil, loose rock fragments, and dissolved minerals as it flows downhill–Stream Load:

the materials other than the water that are carried by a stream

Target #24 cont.

• Stream discharge: the volume of water moved by a stream in a given time period–The faster a stream flows, the higher its discharge and the greater the load the stream can carry

Target #24 cont.

• A stream’s velocity also affects how the stream cuts down and widens its channel– Swift streams

erode their channels more quickly than slow-moving streams do

Target #25- I can define the term “meander”

• As a river evolves, it may develop curves and bends–A river that is flat,

or nearly flat, has lots of beds & curves•Meander: one of the bends, twists, or curves in a low-gradient stream or river

Target #26- I can draw the process of oxbow lake formation

Target #27- I can explain the process of oxbow lake formation

• 1- When a river rounds a bend, the velocity of the water on the outside of the curve increases–The fast moving

water on the outside of a river bend erodes the outer bank of that bend

Target #27 cont.

• 2- As this process continues, the curve enlarges on one side, while further sediment deposition takes place on the opposite bank

Target #27 cont.

• 3- Meanders can become so curved that they almost form a loop separated by only a narrow neck of land

• 4- When the river cuts across the neck, the meander can become isolated from the river and an oxbow lake forms