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Introduction How Rivers Run Stories Value Of A River What We Can Do
Shape of a River - Geomorphology
Consequences (pg 1 of 2)

We often alter the hydrodynamic forces of free-flowing rivers for economic purposes. We channelize streams and drain wetlands to speed the drainage of floodwaters. We also construct dams to store water, restrain floodwaters, support commercial navigation, provide recreation, and generate electricity. We reinforce banks with boulders (riprap*) and concrete to prevent erosion.

Restraining these natural forces often causes unintended and costly consequences. For example, channelization increases the slope through the straightened reach causing headcutting of the streambed upstream of the project and sedimentation downstream. Headcutting is erosion of the streambed which progresses in an upstream direction, causing severe erosion that can continue miles upstream of the channelized reach.

The increased sediment supply deposits downstream causing the streambed to rise. This, coupled with increased peak flows characteristic of channelized streams can create downstream flooding problems.

Channelization or "channel training" through construction of dikes and wingdams** and riprapping shorelines often causes the simplification or destruction of plant and animal habitats that evolved under dynamic conditions. Quality aquatic habitat is replaced with a uniform channel largely devoid of fish, invertebrates, and plants. The costs are also economic. Rather than allowing the river to naturally spill over onto its floodplain, restricting high water with levees speeds the flow of water and exacerbates flooding downstream.

* Riprap refers to large rocks placed on shorelines in an attempt to stabilize the banks and prevent erosion.
** Wingdams are brush and rock structures that are installed along the main channel border to focus the river's energy down the middle of the channel. This is done to scour the bed and make the channel deeper.

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Introduction
Flow
Shape
Description
Variables
Bankfull flows
Classification
Sediment
Patterns
Slope
Habitat
Change
Consequences
Stories
Connections
Quality
Life
Summary
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