Chapter 11 Section 1 – The Active River
CUE COLUMN
Rivers: Agents
of Erosion
The Water
Cycle
River Systems
Stream
Erosion
The Stages of
a River
DETAILS/NOTES
Erosion is the process by which soil and sediment is transported
from one place to another. Example: Grand Canyon
The water cycle is the continuous movement of water from the
ocean to the atmosphere to the land and back to the ocean.
Evaporation…Condensation…Precipitation…Percolation…Runoff
A tributary is a stream that flows into a lake or into a larger
stream.
River systems are divided into watersheds.
Watersheds (drainage basins) are areas of land that is drained
by a water system. Largest in U.S. = Mississippi River. It covers
more than 1/3 of the U.S. Watersheds are separated by divides.
Divides are areas of higher ground. Example: The Continental
Divide (Rocky Mtns.)
A channel is the path a stream follows. When streams get
longer and deeper they become rivers.
Streams ability to erode depends on gradient, discharge, and
load.
Gradient = change in elevation over a distance. Higher gradient
= more energy and erosion.
Discharge = amount of water a stream carries. Increase in
discharge = increase energy and erosion.
Load = material carried by stream. 3 kinds: bed load (large
pieces/rocks), suspended load (water is muddy), dissolved load
(salt/calcium dissolved)
Factors that influence development = climate, gradient, and
load.
Youthful Rivers = eroded deeper, NOT wider; flows quickly
(steep gradient); channel is narrow and straight; very few
tributaries; has waterfalls
Mature Rivers = erodes channel wider, NOT deeper; gradient is
not as steep; few waterfalls; many tributaries; more discharge
than youthful
Old Rivers = low gradient; little erosion; high deposition; has
flood plains or valleys and bends; few tributaries
Rejuvenated Rivers = caused by tectonic activity; gradient
changes – river flows quicker; creates step-like forms called
Chapter 11 Section 1 – The Active River
terraces.
SUMMARY: Rivers are developed through the process of
erosion and the water cycle. River systems consist of tributaries
and watersheds, which are separated by divides. Stream
erosion is caused by gradient, discharge, and load. The stages
of a river are youthful, mature, old, and rejuvenated. All 4 types
vary in design.