The flash flood is one of the most dangerous weather phenomenons on earth. It is also one of the most confusing to people, which tends to increase the amount of potential danger associated with it. Flash floods can be swift, come with little warning, and destructive to both life and property. There are few places on earth that aren’t subject to a flash flood, which is why flash flood warnings are some of the most prevalent types of weather warnings we have.
In the modern age of smartphones, almost everyone has had the “flash flood warning” icon/messaging pop up on their screen. But unlike tornado warnings and hurricane warnings, hardly anyone does anything to prepare or avoid them. This is why people often get caught off guard and require a flash flood rescue. It is also, sadly, how people end up dying.
Let’s break down the often enigmatic flash flood that often puts the fear of God into people who get caught inside of them.
What Is A Flash Flood?
A flash flood, by its very definitions, is any flood that develops in six hours or less. Flash floods can happen in just about any place on earth, making them extremely unpredictable at times. However, low lying basins are typically the most prone to flash floods occurring. Any area that has poor drainage systems is also a hospitable home to a flash flood.
A flash flood requires water to inundate an area faster than the area can drain or absorb the water. Most people associate flash flooding with torrential rain because this is often when we see the weather alerts pop up on our phones. Most people also think of flash floods as extremely visible pools of water on roadways that are easily avoided by enacting common sense avoidance.
While that’s true, its not the entire truth. Flash floods are stealth and can happen without obvious torrential rain coming down.
What Causes Flash Floods?
As mentioned prior, flash flooding is often the result of torrential downpours. When heavy rains come down in a short period of time, urban draining systems often can’t keep up, which leads to water collecting on roadways. These type of flash floods can seep into homes, trap motorist who chose to brave crossing them and sweep away people who venture into them on foot. Depending on how strained the drainage system is and how heavy the rain is falling, an urban flash flood can develop a current and travel for miles.
But an overworked drainage system battling torrential rains is the obvious type of flash flooding. By way of common sense, most people should be able to avoid being harmed by these scenarios.
Other causes include:
Damns that fail: When a damn fails, it can unleash flash floods of epic proportions. Probably the most notable flash flood as a result of a damn failure what Hurricane Katrina’s 9th ward flooding. Hurrican Katrina had passed, however, the water from lake Ponchatrain had piled up furiously along New Orlean’s weakening damn network. Eventually, the damns failed and water was unleashed throughout the 9th ward neighborhoods.
The same damn failure flash flood scenario played out during Hurricane Maria in Puerto Rico in 2017.
Snowmelt Flash Flood: Many people tend to forget that snow is simply frozen water. When snow falls in the mountains, it can certainly appear beautiful. But what about when that snow melts? This is basic chemistry at play here. Snowmelt is often a life-saving resource for places like California that use it for drinking water. However, snowmelt flash floods are common and dangerous because they often occurr when people simply aren’t considering flooding of any sort.
When snow melts at a fast rate on a mountain or hill, it turns to water and then begins to stream down. The ground is often still too frozen to take on any water, so most of the water has to find a new home, which is somewhere down the hill or mountain. When you get enough snowmelt coming down a hill, any urban areas or roadways can quickly become compromised.
Ice Jam Flash Flood: A portion of a river can freeze in upstate New York, but when the ice begins to break away, large chunks of ice can travel down throughout the state, eventually piling up into a big ice jam. When this happens, the water behind it is forced to crest and find a new path, often times through areas that aren’t expecting water. An ice jam flash flood does typically have some warning, but the element of surprise is in play due to the weather potentially not being bad. In fact, it could be sunny outside and a nice day for people when an ice jam flash flood occurs.
The final type of flash flood, in my opinion, can be the most devastating. Sometimes heavy rain can fall in one area, but not in another. However, that rain, particularly in desert environments, will have nowhere to go. So it can often travel great distances. Hikers in canyons, cave explorers, or even those driving through a desert region, can be swept away by a flash flood during seemingly perfect weather.
Watch this flash flood video example from Arizona. In this case, heavy rains were happening 20 miles away in the Tinajas Altas mountains. This may not look like much, but imagine if you were an unsuspecting hiker down in that canyon?
Even more dramatic, Hollywood style, flash flooding desert nightmare…
Clearly, that last flash flood video was created by a production studio, however, the point is clear. The desert simply doesn’t drain water well so when even a small rainstorm happens, those who are even 30 and 40 miles away need to understand they are at risk.
Do the research, know the risks of the area you might be hiking or camping in.
Flash Flood Warning
If you are in an area that comes under a flash flood warning, that means that a flash flood is happening and you need to take precautions. Any areas known to poorly drain are likely areas to avoid. Always follow flash flood warning instructions from officials and avoid areas that are either listed by officials as under the flash flood warning or areas prone to flash flooding. If you aren’t sure, it is best to stay home so long as your home isn’t in the direct path of a flash flood.
How To Survive a Flash Flood
Flash flood survival is often based on both knowledge and common sense. Most people who end up in a flash flood survival scenario made mistakes along the way that got them into the predicament. Heeding flash flood warnings from officials is the very start of flash flood survival.
First things first, it doesn’t matter how great of a swimmer you are, flash floods can and will injure and kill you. Its that simple. Flash flood videos do no justice to the power of water in motion. Trying to cross a flash flood in a car, or by foot, is putting yourself in a high-risk situation that likely won’t end well for you. You can’t just swim through a flash flood.
Not all flash floods look like rapids, many flash floods look like still pools of water. However, the dark side is the powerful currents that are just under what appears to be calm water. Looks are deceiving.
Here are some tips to survive a flash flood:
Flash flood warnings and watches are your friends: Make sure your smartphone is activated to alert you of all weather issues, this includes when you travel. A flash flood watch means to be aware that flash flooding is a potential hazard in your area, possibly in spots prone to flooding. A flash flood warning means its already happening. If you are traveling, on vacation, or in an area that you aren’t familiar with, don’t be shy in asking locals about areas that may be prone to flooding.
If you are in a flash flood warning, or you notice heavy rains collecting in an area you are at, head for higher ground with immediacy.
When it rains, pay attention: Water has to go somewhere. If it’s raining, particularly hard, understand that flash flooding is a potential option anywhere in the area.
Take Precautions when exploring canyons and desert areas: If you intend to go hiking or travel to a canyon area that has unreliable drainage, research the area and learn more about flash flood potential. As mentioned before, it doesn’t need to be raining near you for a flash flood to sweep through the area you are hiking in. Be particularly careful before venturing into any cave systems which are often very attractive drainage systems for water. Remember, most canyons and caves are the result of flash flood waters!
Don’t cross pools of water: Not on foot, not in your car. Even when water appears still, it likely has a current underneath of it that can sweep you away. Even 2 feet deep waters can trap you or sweep you away. Motorists often get trapped in flash floods because they underestimated a flash flood. We see this on roadways and even in parking lots. And once you are trapped, things get very complicated. Typically, your engine will become disengaged once the water reaches the engine. Its tough for rescuers to get to you and help you.
You Are Stuck On Food in a Flash Flood: If you are stuck on foot in a flash flood, try getting out by walking out in the most shallow appearing areas. If possible, get a stick and use it to check how deep the water is. Flash flood waters are often murky and can trick you in depth. Even if you don’t fall into super deep waters, not knowing the depth of the water could result in an ankle or knee injury and worsen your predicament. If your phone works, dial 911 and call for help.
If you are with children, pick them up. Make sure you don’t touch any downed power lines or anything that looks like it might use electricity.
If you are inside your home, head to the highest point and do not use any electrical devices.
You are stuck in your car during a Flash Flood: According to FEMA, a car can get stuck in six inches of water. Deeper than that and your vehicle can be swept away as it becomes more and more buoyant. You should never attempt to cross water piling up, find another way instead.
If you are stuck, however, you need to do a few things immediately. Release your seatbelt and any other passenger’s seatbelts. Roll down the windows or even break them using a windshield breaker tool (everyone should have one of these in their car). If you don’t understand why these steps are so important, read my how to escape a sinking car guide. If you don’t open your windows and allow the flood waters into the vehicle, you will be unable to open your car doors.
Your best bet, once your car doors are open, is to leave on foot. Cars get swept away rather easily as flood waters build up.
Flash floods are dangerous and often underestimated weather phenomenon. Most of the time, a little common sense will go a long ways. Your life is always more important than a car or a late appointment. When you travel, always research the area and be aware of the dangers involved, particularly in areas you intend to hike or camp. Don’t cross what appears to be standing water. If you are ever under a flash flood warning, get to higher ground.
Author: Jim Satney
PrepForThat’s Editor and lead writer for political, survival, and weather categories.
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