Have you ever walked past storm drains after a big rain and it is overflowing onto the streets? This can sometimes cause a small but manageable flood. Did you know a flood is one of the most common natural disasters you can experience? There are so many ways a flood can occur. They often happen so fast people cannot even prepare for them.
So how do a few inches of water turn into flash floods? A few inches or a few feet of water can cause extensive damage to homes, businesses, and the surrounding area. Let’s learn a little more about floods.
How Do Floods Happen?
Floods can happen during any time of the year, but they happen a lot after winter when the snow melts quickly and during the spring after heavy rainfall.
Flooding is an overflow of water onto dry land. A common cause of flooding is heavy rains. However, floods also occur when ocean waves come to shore in coastal areas and levees or a dam breaks. Flood water can be only a few inches or could cover a house to the roof. When there are ice jams, a beaver dam, or storm drains can not handle the amount of water, there is also a chance of floods.
When there is excessive rainfall, rivers, lakes, ponds, and even sea levels rise. River floodplains and coastal areas have a higher flood risk than other areas.
Mountainous Regions can have large floods as well. When a lot of water has nowhere to go, it will quickly flow downhill and can create flash floods destroying houses and anything in its path.
Types of Floods
You might think a flood is a flood. But there are actually 5 different types of floods.
Water accumulates because of waves, tides, storm surges, or heavy rainfall. Coastal areas will have this type of flooding because they are close to the ocean. The risk of coastal floods is growing due to climate change. Rising sea levels are causing floods more often because the sea water is going into low-level wetlands and drylands, eroding shorelines.
There are three types of coastal flooding:
- Minor: Low likelihood of property damage and not directly life-threatening
- Moderate: Elevated likelihood of property damage and possibly life-threatening
- Major: Significant likelihood of property damage and seriously life-threatening
River flooding occurs when water levels rise over the river banks. Any size river or stream can flood. Some causes of river floods are extreme rainfall from tropical storm systems, long-lasting thunderstorms, a combination of rain and snow melt, or ice jams. Experts can typically predict river floods ahead of time.
Flash flooding begins within 6 hours of the heaviest rain and is often caused by severe thunderstorms, hurricanes, or tropical storms. They can also result from a dam failure or a levee breaking.
Some factors contribute to how severe a flash flood can be:
- The intensity of the rainfall
- Location of the rainfall
- Soil type and condition
Urban areas are more likely to see flash flooding than suburban areas because there is often little to no soil to soak up the water, and this is often referred to as urban flooding. The greatest danger with flash flooding is that it happens so quickly and people often don’t have time to prepare.
Groundwater floods usually occur when drainage systems can not handle the water. Groundwater floods happen when there is a large rainfall, and the water overflows into the streets, houses and properties. Groundwater flooding occurs gradually or over time, and the water level is often shallow, so people can grab belongings if needed. Groundwater flooding can happen over weeks or months until the soil can absorb the water. This can cause flood damage to homes, such as structural damage, and the risk of mold.
Sewage flooding happens when an unexpected heavy rain or thunderstorm overwhelms the sewage and treatment plants. They can then break down and release sewage into the water. This flooding causes sewage to come up through drains, pipes, toilets, sinks, and showers. These types of floods are the most dangerous because they cause the contamination of water or germs get into the water. Contaminated water can cause many sicknesses, like infections, vomiting, diarrhea, and more.
Types Of Flood Warnings
Three types of flood warnings are used in the United States and they are all very different. The national weather service is the one who often issues these warnings and you will see and hear them on your local news and weather reports.
Aerial Flood Warning
An aerial flood warning is when there is aerial flooding, or a larger area is at risk of flooding. It happens more gradually from rainfall that lasts a few hours, and the water rises over time and can potentially flood low areas and some roads. This type of flood happens over time unless there are flash floods.
River Flood Warning
This warning is issued when a river has the potential to overfly onto the river banks and beyond. It can happen if there have been multiple days of rain or larger storms. It can also be caused when small streams and rivers flow into a bigger ones after long periods of rain. These warnings can last for a longer period of time because rivers take a long time to flood and go back to normal.
Flash Flood Warning
Before a flash flood warning is made, there usually is a flash flood watch. This warning is given when there is a chance a flash flood could happen, but it does not mean flooding will occur. A flash flood warning means bad weather is coming and flooding will probably occur. This warning happens when a lot of rain falls in a short amount of time, and this situation can become dangerous very quickly. Flash flooding can happen anywhere, and the amount of water, the force of the water, and high speeds could be deadly.
Flood water is not clean water, and it may not be safe to cook, clean, or drink after an emergency. During and after floods, water can come in contact with many things that can contaminate it. Contamination can be from things such as bacteria, sewage, industrial waste, chemicals, heating oil, and more!
A couple of famous floods have taken lives and gone into history books.
Hurricane Katrina was one of the most famous hurricanes because it caused tremendous flooding in the southern part of the United States, especially in New Orleans, Louisiana.
The flooding of New Orleans happened due to the storm surge, which caused the levees to break. Then, the Mississippi River flooded the city. Eventually, 80% of the city was underwater. About 250 billion gallons of water flooded the streets, homes, and businesses, even going into other towns and cities around New Orleans. The flooding killed over 1,800 people and caused $100 billion in damages.
The Yellow River flood of 1938 is another famous flood. This flood happened in China and was a man-made flood in the central part of the country. During the beginning of the second Sino-Japanese war, the Nationalist Government tried to flood the Yellow River to stop the fast approaching Japanese.
The Yellow River also flooded in 1887. The river overflowed and covered over 55,000 square miles. It is said to have killed over nine hundred thousand people and two million people were left homeless. This would make the flood the deadliest flood of all time.
Fast Flood Facts
- 66% of flood-related deaths are due to drivers attempting to drive through flood water that is too deep.
- Get to higher ground during a flood.
- Wetlands save the United States almost $30 billion in flood damages.
- River water overflows its banks at least once every two years.