An Active River

Beth Roland

Eighth Grade Science

Jacobs Fork Middle

The Birth of a River

Beth Roland

Eight Grade Science

Jacobs Fork Middle School

It starts with a single drop!

• Individual drops of water are drawn together by the process of cohesion. The chemical composition of water (2 atoms of Hydrogen, bonded to one atom of Oxygen) creates a polar molecule with a positive side and a negative side. This polar opposites allow one water molecule to be attracted to another.

A drop to a stream.....

• A stream of water joins other streams to eventually form a tributary. From a tributary to a river and with other rivers, a larger body of water is created!

Drop

Stream

Tributary

River

Lake, Gulf, Ocean

Here, there and Everywhere

• River systems are divided into watersheds or drainage basins. The area of land interrelated by close rivers comprise the basin.

A Day in the Life..

• A river serves many purposes to wildlife, humans, and Flora (plant life), – Habitat– Necessity of Life– Food Web– Recreation– Energy (Hydrologic

Plants)– Transportation

Characteristics of a River• Channel~ A channel is the path that a stream

follows. A channel begins narrow and steep and over time as rock and soil is transported becomes longer and wider.

• Gradient~ the measure of the change in elevation (height) over a certain distance. The higher the gradient, the greater the energy of the moving water.

• Discharge~ The amount of water that a stream or river carries in a given amount of time. This is influenced by addition of water into a waterway (melting snow, large amounts of rain).

Characteristics Continued..

Erosion~ is the process of transportation of soil and sediment from one location to another.-Wind, water (ice, snow, and rain) all agents of erosion.

Load~ The materials carried by a river- size of the load is effected by the stream’s speed and will also then effect the erosion process.

Stages of a River

• In the early 1900’s William Morris Davis developed a model for the stages of river development

• Youthful River~ erodes the channel wider, is steeper in gradient, has very few tributaries

Mature River

• Mature River~ erodes it channel wider rather than deeper, gradient is less than a youthful river, fewer falls and rapids, fed by many tributaries.

• A greater discharge is found in a mature river.

Old Age

• Old River~ has a low gradient and little erosive energy. Instead of widening or deepening its banks, an older river deposits rock and soil along the channel.

• Old rivers have flat flood plains and many bends.

• Tributaries join together to feed into a mature river.

Rejuvenated Rivers

• Rejuvenated River~ found wehre the land is raised by tectonic activity. As land rises, the gradient becomes steeper, river flows more quickly, cuts more deeply into the valley floor.

• Terraces are often formed.