Streams, Lakes & Wetlands

UNIT 6STANDARDS: NCES 2.3.2, 2.4.1, 2.4.2LESSON 2

Lesson Objectives

In this lesson, you will learn about:– Some physical features of stream development– The process of rejuvenation in stream

development– The formation of freshwater lakes, and wetlands– Recognize the effects of human activity on lake

development.

Stream Development

As a stream develops

Moving Water Carves a Path

What are headwaters

It changes shape, width, and the landscape.

Needs a steady supply of water

Temperate regions experience regular rain

The region where water accumulates to supply the stream

Stream Development continued

Stream Channel

What are stream banks

Moving water carves a path through the sediment and rock.

The stream channel widens and deepens as more water accumulates.

The ground bordering the stream on each side.

Waterfalls and rapids are common

Formation of Stream Valleys

As water moves it erodes the surrounding rock as it cuts a channel.

Note the V-shaped valley in Yellowstone, Wyoming

The Lower Falls drop 308 feet to the Yellowstone River below and continue to carve out the canyon.

Meandering Streams

What causes a meandering stream?

As the water carries material downstream, the heavier particles are deposited.

Other materials deposit or are trapped on the forming sandbars.

The buildup over time causes new banks to form on one side and the bank on the opposite side to be eroded.

The continual bending back and forth of the river is known as a meander.

Meandering Stream or River

Deposition of Sediment by Water

What causes the deposition on sediment?

As the stream velocity slows, it loses a the ability to carry sediment.

If the slope of the river decreases abruptly, the river gets shallower.

If the stream load meets other materials that trap the sediment.

Examples of Deltas, New Land

Mississippi River Delta Nile River Delta

Deltas

What causes a delta to form?

What is the mouth of a river?

What happens to the suspended materials?

When the stream or river enters a larger body of water, the velocity of the stream slows.

The point were the river enters the lake is known as the mouth.

All of the transported materials are then dropped near the mouth of the river.

Section Review

1. Compare and contrast the river headwaters and the river mouth.

2. What factor of a stream or river determines the amount of erosion that takes place?

3. Describe how sediment moves from the surface water and run-off to deposition in deltas.

4. Describe the typical valley formed by a river, and WHY it has these characteristics.

Lakes and Freshwater Wetlands

What is a lake?

Erosion forms Lakes

A lake is a depression in the surface of the earth that collects and holds water.

Oxbow lakes form when the meander of a stream cuts off a meander.

Glaciers are responsible for carving many of the depressions in the rock that later became lakes…the Great Lakes.

In areas with limestone, the erosion of the limestone will expose bedrock and allow for a lake to form.

Eutrophication (eu·tro·phi·ca·tion)

What is eutrophication

The process by which a lake becomes rich in nutrients.

Eutrophication is a natural process but can be sped up by outside sources.

Fertilizer run-off can cause algae blooms…green scum

Algae depletes the oxygen and fish kills occur.

Freshwater Wetlands

What is a wetland? Land area that is covered with water for majority of the year.

Examples: bogs, marsh, swamps

In NC, peat bogs are home to the Venus Flytrap and pitcher plant. (both carnivorous)

Wetlands act to filter water. Conservation is needed. Great Dismal Swamp Video

Great Dismal Swamp, NC

Section Review

1. Describe the process of eutrophication. 2. What human activities affect eutrophication? 3. What conditions are necessary for the

formation of a natural lake? Critical Thinking… 4. Describe a situation where the protection of

wetlands may conflict with human plans for land use.