Rivers, Streams, and Flash Floods
This page presents some basic information on the rivers, streams, and flash floods in canyon country.
All narrow canyons are potentially hazardous. Flash floods, cold water, and strong currents present real dangers that can be life-threatening. Your safety depends on your own good judgment, adequate preparation, and constant attention. By entering a narrow canyon, you are assuming a risk. It is your responsibility to know the current and predicted conditions. Your safety is your responsibility.
- Rivers, streams, and waterfalls can be treacherous at all times, but especially when water levels are high and turbulent. Approach them cautiously and be alert for undermined banks and slippery rocks. Fast currents and cold water are a deadly combination. The best time to cross a stream is in the morning, when the flow is lowest. During the day, snow melt can dramatically swell a stream.
- Swimming in many western rivers is not recommended due to currents and hidden hazards.
- If you must swim, wear a life jacket.
- Never dive into a river. Underwater hazards are hidden by the muddy water.
- During thunderstorms stay away from washes, low-lying areas, and be aware of flash floods.
- Cross unbridged streams with caution, especially during spring runoff. Slippery stream bottoms and swift currents can knock you down and sweep you away.
- Do not drink wilderness water without first filtering and then sterilizing it. Learn about giardiasis.
- Do not swim above waterfalls or in swift water.
- Most rivers, streams, and lakes within the parks and monuments allow only hand-propelled boats and rafts. Check for local restrictions.
- A microscopic amoeba (Naegleria fowleria) common to some hot springs can cause infection and sometimes death; do not dive or put your head into hot springs or streams.
Especially during the summer months and monsoon season, thunderstorms can move into canyon country very quickly and drop large amounts of rain. This rain concentrates with little warning in narrow canyons and washes and causes flash flooding. When the water is forced into these narrow areas, a wall of water forms that pushes along with great force anything in its path, including sand, dirt, rocks, boulders, shrubs, and trees. Water, along with the erosional agents it carries, has formed many tall, very narrow, and beautiful "slot" canyons that attract visitors from around the world. Slot canyons are a work in progress. Flash floods that created what you see today will alter these same canyons in the future.
When hiking, be observant. If you see rain, even 30 to 40 miles away, or if it is during or after a rain thunderstorm, avoid washes and canyon bottoms. If you believe that a flash flood may be approaching, immediately climb out of the canyon bottom and to high ground. Flash floods have been reported to sound like freight trains.
Flash floods can occur at any time of the year, but are typically most common in late Summer and early fall, corresponding to the brief, heavy thunderstorm activity normal for that time of the year. Flooding can occur under a clear sky as rainfall may drain from vast areas many miles upstream, funneling into washes, building volume, power, and speed. Flood water rushing down a canyon may sound like an approaching jet. It can appear as a headwall a few feet deep, becoming several feet deep within minutes, and reaching depths of up to 15 feet or more in a short time as it races toward the river. Without warning, flash floods can inundate deep, narrow canyons.
In 1997, flash floods in Antelope Canyon and in the Grand Canyon's Phantom Creek area killed a total of 13 people. Respect the forces of Nature. Flash floods can be strong enough to carry away vehicles. Flood waters typically recede in a few hours. Enjoy the thrill of experiencing this natural process from a safe distance.
- Flash floods can happen at any time of the year. Check ranger stations for weather updates.
- Observe weather conditions and use common sense.
- Avoid hiking in narrow canyons when rain is possible. Do not enter a wash if a storm is threatening.
- If a wash begins to flow, climb to high ground. If in a vehicle, drive to points of high ground on the road.
- Don't try to drive through a flood.
- If it is raining hard but the wash is not flowing, begin to hike out, or to drive out on the road.
- Do not camp or park your vehicle in wash bottoms or stream beds.
- Remain on high ground until the water recedes.
Working to protect and restore the nation’s rivers and streams.
Earth's Waters: Rivers and Streams
The USGS water and science school.
International Rivers Network
At the heart of the global struggle to protect rivers and the rights of communities that depend on them.
National Wild and Scenic Rivers System
From the National Park Service site.
National Oceanic and Atmospheric Administration's site.
To increase educational awareness, improve communication across disciplines, and provide the timely delivery of knowledge and data on stream processes, watersheds, and design concepts.
What is a Stream?
From the Gulf of Maine Research Institute site.
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