The first thing that comes to mind when I hear the word “flood” is water in places where it shouldn’t be. While that explanation is pretty accurate, there’s a lot more to floods than just that. For example, did you know there are five types of floods? It’s true, and they are something you should be aware of so you can know your risks. Some of these types of floods may be more applicable to some regions than others, but there is at least one type that can affect you. So here they are, the five types of floods, courtesy of our the good folks at the National Severe Storms Laboratory.
Just like it sounds, a river flood occurs when a river overflows its banks. This happens for a few different reasons. One, lots of rain. Whether it’s tropical systems (tropical storms, hurricanes, etc.) reaching land and dumping all its contents relatively quickly, or prolonged rain from thunderstorms in the same area, this kind of precipitation can cause rivers to flood. Melting snow can cause rivers to rise quickly, too. Remember all the snow that came for a visit last winter? Well, when it melted, rivers rose well above their banks. The Ohio River rose nearly six feet over its flood stage! So if you live in an area near a river, be prepared for a river flood.
If you live near the coast, be ready for a coastal flood. According to the National Severe Storms Laboratory (NSSL), these are “caused by higher than average high tide and worsened by heavy rainfall and onshore winds.” Lower elevation also plays a factor in coastal water flooding up on land.
[caption id="attachment_19024" align="alignright" width="300"] Courtesy of NOAA[/caption]
Another type of flood found on the coast, storm surges are caused by severe storms. Strong winds, large waves, and low atmospheric pressure all help the tide rise abnormally high. Combined with high tide, storm surges can raise water level by 30 feet or more. As you might imagine, having a surge of ocean water come crashing over land can cause some wide-spread flooding. Storm surges are one of the biggest threats to life and property during hurricanes. According to the NSSL, “at least 1500 persons lost their lives during Katrina and many of those deaths occurred directly, or indirectly, as a result of storm surge.”
There are a few different scenarios in which inland flooding can occur, although the end result is pretty similar. Steady rain over several days or intense precipitation in a short period of time can both cause the soil to become so saturated with moisture that it can’t hold anymore. When that happens…you’ve got yourself inland flooding. Rivers overflowing is another cause of inland flooding. But no matter what the cause, virtually any area is susceptible to this kind of flood. You might not think it, but even homes built on hills can be effected by inland flooding (trust me, I know from experience).
Heavy rainfall in a very short amount of time, the NSSL describes flash floods as usually taking place after less than six hours of rain, and “are usually characterized by raging torrents…that rip through river beds, urban streets, or mountain canyons sweeping everything before them.” Even without heavy rainfall, flash floods can come rushing in unannounced. These surprise visits can occur due to a dam failure, or after water is suddenly released, such as the breaking up of an ice jam. Check out the following video to see an example of a flash flood. Notice how fast the water moves, and the objects it carries with it.
No matter where you live, flooding is a threat you shouldn’t ignore. While some areas are more prone to flooding than others, that doesn’t mean you’re off the hook. Make sure you know the flood risks in your area and what to do to prepare.
For more information about floods (and other disasters), click the image below!