I Didn't Know That!: Keeping Rivers Wild

You’re hanging out by a river on a hot summer day. The cool water feels great on your feet, but the water is a little too shallow to provide any real relief from the heat. If only you could divert the river channel into a more convenient spot to build a rock dam. Then you would have a nice soaking pool to cool off in! While this miniature engineering project might sound like a brilliant and harmless idea, it may cause more harm than good.

Gauley River National Recreation Area.

NPS Photo

Why are Rivers Important?

Rivers provide more than just a fun place to play. They serve as an active provider of clean water. The sand and rocks (substrate) at the bottom of a river help to filter and purify the water. The flow of the water itself also keeps sediments and pollutants from building up in one spot.

Rivers also prevent floods! (What?!) Rainwater and snowmelt need a place to go. While it may seem counterintuitive, rivers provide a perfect system for that water to go, minimizing the impact to surrounding areas. While the river itself may flood, the places around it will be less affected by the extra water.

Rivers naturally twist and turn, with different sections of faster or slower moving water. The variety in water flow combined with different kinds of substrates on the river bottom creates diverse habitats for all kinds of living things.

Did You Know?

Rivers are some of the most biodiverse ecosystems. Compared to other ecosystems, they are also home to some of the highest concentration of threatened and endangered species. 

A salamander rests on a rock in a stream in Great Smoky Mountains National Park.

NPS / Mike Bell

Impacts to River Organisms

Many organisms that live in rivers rely on specific combinations of water flow and substrates, like sand and rock, to survive. Fish, like trout and salmon, lay their eggs among the rocks at the bottom of streams. The rocks help to improve oxygen flow to the eggs. Other animals, like salamanders and aquatic invertebrates, often rely on river rocks for shelter – both from predators and from the current.

If we stack rocks in rivers, we may be removing important sources of shelter for these species. We might also accidentally squish small, often camouflaged, animals underneath the weight of the extra rocks. Best practice for leaving no trace near a river is to leave the rocks in their natural places.

Water Flow Impacts

By building rock dams or by digging new channels in a river, we can affect the flow and quality of the water, even well upstream. A dam will raise water levels, cause abnormally high amounts of sediment to build up, and slow the flow rate. Digging new channels will lower the water level of the river and increase the flow rate upstream, which also leads to higher levels of erosion. If the character of the river is changed, we reduce the diversity of habitats for different species, and remove some of the attributes that make naturally flowing rivers thriving ecosystems.

Did You Know?

Less than one percent of rivers in the United States are free-flowing, with no human-made obstructions. The U.S. protects certain free-flowing rivers for the enjoyment of present and future generations as Wild and Scenic Rivers. 

Bluestone National Scenic River

NPS Photo

What You Can Do

Rivers are important habitats and active providers of clean water. We need your help to keep rivers wild. Here are some ideas on how to help protect rivers:

• When visiting rivers, enjoy their natural beauty and practice Leave No Trace!
• Leave the river rocks in the river.
• Avoid altering the flow of water in a river —don’t build dams or dig new channels, especially near a river outlet.
• Join a river clean up.
• Practice fishing responsibly.
• Find a river near you!

Pass It On!

Did you learn something new? Pass it on! Protecting our ecosystems is a job for us all, but there’s no way for everyone to be an expert in everything. That’s why sharing knowledge is so important!

Download or screenshot this card to share with a friend or help you remember how to help keep rivers wild. Thank you for helping protect park waters so that they can continue to be enjoyed for generations to come.

Check out other I Didn’t Know That! topics.

Text description of infographic

I Didn't Know That! Keeping Rivers Wild

Rivers are more than just a fun place to play—they're valuable resources! They actively provide clean water and are diverse habitats.

By building rock dams of digging new channels, we can affect the flow and quality of the water, even well upstream.

Help Keep Rivers Wild:

• Enjoy the natural beauty of rivers & Leave No Trace.
• Don't build dams or dig new channels.
• Leave river rocks in the river.
• Join a river clean up.

go.nps.gov/idkt