Running Water

Running water

Water as an agent of erosion; water in streams, tributaries (larger streams) and rivers that flow down hill therefore changing the landscape (erosion)

Running water

• Abrasion – wearing away of rock by grinding action

3 ways rock is carried by water

• Solution – mineral matter dissolved from bedrock is carried in a river (25%)

3 ways rock is carried by water

• Suspension – small rock materials, silt and clay, carried by a river are stirred up & kept from sinking by the turbulence of stream flow (50%)

3 ways rock is carried by water

• Bed Load – sand, gravel, pebbles, and boulders that are moved along the bed of a stream & that are too heavy to be carried in suspension (25%)

• Carrying Power – how much total sediments a stream can carry and the size of the particles being carried by the stream at given time and stream velocity

• Discharge – volume of water flowing past a given point in a stream at a given time

• Stream Velocity – the speed of water at a given point at a given time • Drainage system - Streams flow into larger streams (tributaries), which flow into rivers, which flow into oceans … cumulative denotes a “drainage system”

Lengthening of a valley…

• Gully – a miniature valley formed by erosion from heavy rains

• Headward Erosion – wearing away of land at the head of a gully or a stream valley

More Headward Erosion

More Headward Erosion

• Drainage Basin (watershed) – an area of land who’s runoff supplies water to the stream of a drainage system - area drained by a river system

• Base Level – the level of the body of water into which a stream flows

Divide – the higher land separating two adjacent drainage basins •

Continental Divide

made of Rocky Mountains and Sierra Madre Occidental Mountains – Streams on the East drain into the Atlantic Ocean or Gulf of Mexico – Streams to the West drain into the Pacific

• Stream Piracy – the diversion of the upper part of one stream by the headward growth of another stream

• Water Gap – a pass in a mountain ridge through which a stream flows, created by resistant rock layers

Life of a River

• • • •

A Youthful Stream

• Narrow V-shaped valley Down cutting Swift water Steep gradient Erosion is dominant

• •

Mature Stream

• Lateral Erosion begins Meanders develop Floodplains develop • Gradient lowers

• • • •

Old Age

• Wide meanders and oxbow lakes Wide floodplain Low velocity Low gradient Dynamic equilibrium between erosion and deposition

High velocity (erosion):

• Outside of curve • Middle of surface • Well below the surface • Increase in discharge • Increases with increase in gradient

Flow speed

Flow speed

Low velocity (deposition):

• • Inside of curve Edges of river surface • Decrease in discharge • Decreases with decrease in gradient

Stream features depend on 3 major things

1. The type of rock being eroded.

2. The amount of water & sediment 3. The climate of the area

Features…

Meander – a curve in a mature or old stream

Mississippi River

Features…

• Oxbow Lake – crescent- shaped lake formed when a river meander gets cut off from the river and the ends of the original bend have ‘silted up’ – Erosion on the outside bend of a river – Deposition of the inside bend of a river

Features…

• Floodplain – the broad flat valley floor carved by a meandering stream and often covered with water when a stream floods • Levee – a natural or artificial bank confining a stream or river channel

Flash Flood – a sudden rush of water, usually caused by a single cloudburst over the narrow valley of a young mountain stream

3 Common types of natural dams

A. landslides B. ice jams  C. volcanoes

3 Common types of artificial flood control

A. build up levees B. pump rising water into back swamp reservoirs C. build a series of dams and control the overall flow of the river

• Pothole – deep oval or circular holes cut into a stream bed by abrasion from swirling sand & pebbles. Very large ones are called plunge pools

• Delta – a fan-shaped deposit of sediment formed at the mouth of a stream or river when it flows into a quiet body of water, such as a lake, gulf, or inland sea (ex. Mississippi & Nile river deltas)

Laizhou Bay ( Laizhou Wan ) is the southern arm of the Bohai Sea (also Known as the Bohai Bay , or just Bo Hai ), which is a large relatively shallow extension of the Korea Bay

Nile River Delta

Alluvial Fan – sloping triangular deposits of sediment located where a mountain stream reaches level land (ex. At the foot of the Rocky Mountains and the Sierra Nevada’s)

Angel Falls, Venezuela



Victoria Falls, Zimbabwe

Niagara Falls

Online practice quiz…

• http://www.uh.edu/~jbutler/physical/chap 13mult.html

• Problem: What factors cause the greatest stream erosion?

• Compare: straight, curvy, very curvy and various heights (1, 2, 3 books)

• • Problem: What factors cause the greatest stream erosion?

Compare: straight, curvy, very curvy and various heights (1, 2, 3 books) ======================== Problem (research) Hypothesis Design and perform experiment (procedure) Collect Data Analyze Data Conclusion