ObjectivesDescribe how surface water can move weathered materials.

Explain how a stream carries its load.

Describe how a floodplain develops.

Surface Water MovementSection 9.1

Running water is an agent of erosion, carrying sediments in streams and rivers and depositing them downstream.

1. Runoff

Section 9.1

Section 9.1

1. Soil compositionPore spaces:

The particle size that makes up a soil helps determine the pore space of the soil.

Large grain size Fine grain size Mixed grain size

Porosity Activity

What determines the amount of runoff?

If precipitation exceeds infiltration, the water will become runoff.

Section 9.1

2. Rate of precipitation

What determines the amount of runoff?

Vegetation slows runoff

3. Vegetation

Section 9.1

What determines the amount of runoff?

Surface Water MovementSection 9.1

1. Water from precipitation falling on slopes flows to areas of lower elevation.

2. The steeper the slope, the faster the water flows.

4. Slope

Runoff Activity

Stream Systems

Some surface water flows in thin sheets and eventually collects in small channels, which are the physical areas where streams flow.

Surface Water MovementSection 9.1

Surface Water MovementSection 9.1

Stream Systems

Rivers that flow into other streams are called tributaries.

Tributaries

Surface Water MovementSection 9.1

Stream Systems

All of the land area whose water drains into a stream system is called the system’s watershed.

A divide is a high land area that separates one watershed from another.

Watersheds and divides

Surface Water MovementSection 9.1

The watershed of the Mississippi River

Surface Water MovementSection 9.1

Stream Load

The material that a stream carries is known as stream load. Stream load is carried in three ways.

Surface Water MovementSection 9.1

1. Suspension

all particles are held up by the turbulence of a stream’s moving water.

Sketch

Surface Water MovementSection 9.1

sand, pebbles, and cobbles that can be rolled or pushed along the bed of the stream.

2. Bed load

Sketch

Surface Water MovementSection 9.1

When water runs through or over rocks with soluble minerals, it dissolves small amounts of the minerals and carries them away in the solution.

3. Solution

Stream Load Activity

Sketch

Surface Water MovementSection 9.1

Stream Carrying Capacity

•The ability of a stream to transport material, referred to as its carrying capacity,

•Depends on both the velocity and the amount of water moving in the stream.

Surface Water MovementSection 9.1

Floods

A flood occurs when water spills over the sides of a stream’s banks onto the adjacent land.

Surface Water MovementSection 9.1

Flood plainsThe area that extends out from a stream’s bank and is covered by excess water during times of flooding is known as the stream’s floodplain

ObjectivesDescribe some of the physical features of stream development.

Describe the relationship between meanders and stream flow.

Explain the process of rejuvenation in the stream development.

Stream DevelopmentSection 9.2

Streams erode paths through sediment and rock, forming V-shaped stream valleys.

Supply of Water The region where water first accumulates to supply a stream is called the headwaters.

Stream DevelopmentSection 9.2

Stream channels

Moving water carves a narrow pathway into the sediment or rock called the stream channel.

Stream DevelopmentSection 9.2

Stream channels

Stream DevelopmentSection 9.2

Formation of Stream Valleys

Meanders A bend or curve in a stream channel caused by moving water is called a meander.

Stream DevelopmentSection 9.2

Meanders - Movie Clip

Outside of meander

• Water moving along the outside of a meander curve experiences the speed with the meander and erodes the side of the streambed.

Inside of meander

• Along the inside of a meander, the water moves more slowly and deposition is dominant.

Sketch

Deposition of Sediment

When streams lose velocity, they lose some of the energy needed to transport sediment, and deposition of sediment occurs.

Stream DevelopmentSection 9.2

1. Alluvial fans• fan-shaped, sloping

depositional features that form when water flows down steep slopes onto flat plains.

• composed mostly of sand and gravel.

Stream DevelopmentSection 9.2

2. Deltas

•triangular deposit that forms where a stream enters a large body of water

•consist of layers of silt and clay particles.

Stream DevelopmentSection 9.2

Nile delta

Complete the diagram on page 43

Complete the front side of the worksheet using your notes and textbook “Features of a Meandering Stream”