Flash floods are the number one cause of weather-related deaths in the world because of their immense power, speed, and unpredictability. In the United States, the amount of deaths caused by floods largely exceeds those killed by tornadoes, hurricanes, and lightning combined. Furthermore, the amount of deaths and injuries caused by these natural disasters increases as outdoor activities, such as canyoneering, grow more popular. However, while these activities are exciting and fun, it is important to remember that we are at the nature’s mercy. Therefore, we need to be aware of warning signs that a flash flood will occur before we enter canyons where we can become trapped by a flash flood.
Why are Flash Floods Dangerous?
Many people underestimate the strength of flash flood waters. It only takes six inches of water to knock over an adult and two feet of water to float a car. Flood water not only has the capacity to drown its victims, but it can also kill by crushing people with the debris it picks up as well as any obstacles it encounters such as canyon walls or buildings. Furthermore, flood waters can knock over trees, roll boulders, and cause dangerous electrical conditions in developed areas. However, the most frightening aspect is how quickly the water rises and gains strength. It can reach over 30 feet in less than fifteen minutes in some cases, which provides little warning to hikers in its path.
What Aspects Increase the Risk of a Flash Flood?
It is common knowledge that flash floods are often caused by rainfall. The two key elements that contribute to flood development are rainfall intensity and the duration of the storm. Rainstorms can drop a lot of water over a small area. The average rainstorm drops 15 inches of rain in 15 minutes. However, what many people are not aware of is that a flash flood can develop as late as six hours after a rainstorm. Furthermore, many people lose their lives because they didn’t take into account the weather in other areas. Many hikers keep a close watch on the local weather, but flash floods can develop in any area further up the watershed.
While rainfall is the most common cause, flash floods can also be caused by dam failures, snow melts, and ice jams.
Much like paves surfaces, the clay and sandstone surfaces of desert areas reduces the amount of water reabsorbed by the ground. This causes the water to runoff and accumulate in the form of a flood. Some of the more common flash floods occur in these environments. Furthermore, common hikes in desert areas commonly include slot canyons. These canyons pose a huge threat because the walls are extremely narrow and smooth that it prevents people from escaping in the event of a flash flood.
In densely populated areas, chances are that there are higher amounts of paved surfaces such as parking lots, highways, and roads. Much like deserts, these surfaces reduce the amount of water absorbed by the ground, which causes the water to runoff and cause flooding. The chances of a flash flood increase in areas of low-altitude and if there are poor drainage systems.
Flash Flood Tragedy in Utah
Tragedy struck in Zion National Park in 2015 when seven hikers descended into Keyhole Canyon, a popular location for canyoneering. Before they began, officials predicted a 40% chance of rain. During their hike, a massive rainstorm hit, which caused a flash flood to develop almost instantly. In a desperate attempt to avoid the flood, the hikers tried to find a way out of the slot canyon and to higher ground. They were too late. The flood eventually caught them and led them to their tragic deaths. Search and Rescue officials recovered their bodies in various locations further down the watershed a few days later. Furthermore, the flood raged through Zion and into a nearby polygamist area where it killed nine children and three adults. Additionally, a man caught in his car went missing and is thought to have perished in the flood.
How do You Avoid a Flash Flood?
The best way to avoid flash floods is to watch the weather. However, flash floods can occur in areas with blue skies and no rain clouds in sight because of runoff from areas further up the canyon. Therefore, you need to look at the local weather forecast as well as the forecast in areas surrounding the canyon. Park officials highly monitor the weather as well as the risk of flash floods. They issue flash flood watches which indicates that conditions are favorable for flash flood formation. This serves as a warning and does not guarantee that a flash flood will happen. They also issue flash flood warnings that alert everyone that a flash flood is occurring or will occur in the very near future.
What if You are Caught in a Flash Flood?
If you are caught in a flash flood, you need to stay out of the water and seek high ground. However, if you are near the entrance of the canyon or if you are trapped in the canyon with no way to higher ground, such as what occurs often in slot canyons, turn and run to the exit. Furthermore, never try to swim or walk through swift water. It has the capacity to sweep you off your feet and carry you away to serious injury or even death.
Resources: https://www.ajc.com/weather/everything-you-need-know-about-flash-flood/gkAop4v0kxRS6N2NJxKNFJ/, https://www.weather.gov/pbz/floods, https://www.nssl.noaa.gov/education/svrwx101/floods/, http://www.canyoneeringusa.com/utah/introduction/hazards/, https://fox13now.com/2015/09/17/authorities-identify-7-people-killed-in-flash-flood-at-zion-national-park/
Picture Resources: Featured Image: https://www.flickr.com/photos/zsuzsi09/10444290875/, https://www.mediawiki.org/wiki/File:2015_Hildale,_Utah,_flash_flood_car_remains.jpg., https://pixabay.com/en/antelope-canyon-arizona-sandstone-543590/, https://commons.wikimedia.org/wiki/File:Oak_Creek_Flash_Flood.webm