Storm Prep Saturday: Flooding

Flooding can be one of the deadliest of all weather phenomenon because it is so vastly underrated. In the United States, more people are killed by floods than tornadoes, hurricanes, or lightning.1 Flooding occurs when an area that is normally dry gets inundated with water due to an excess of water, usually from rains, melting ice, or when a dam or levee breaks. A flood can cause an average of $7.96 billion and 82 fatalities per year.2

flooded houses

Dangers

Floods can happen anywhere, anytime. They occur in all states and territories of the United States, and in almost all countries throughout the world that receive rain. There are some factors that increase the chances for a flood in your area:

  • Densely populated areas are at risk for floods because there is less ground to absorb the water. The building of parking lots, pavement, roadways, and buildings mean the water has to runoff somewhere, which can cause flooding as well in the areas that the water drains to. Storm drains often help move water away from a city, but those can get overwhelmed as well and overflow.
  • Areas near rivers are a flood risk because too much water can cause the level in the river to rise, sometimes rapidly, causing it to breach the bank and overflow into nearby areas.
  • Dams and levees can break or be breached or broken, causing massive flooding in an area that rises very quickly.
  • Mountains and hills, with their natural shape, can cause massive amounts of water to run down the sides, causing a flash flood in an area if too much rain or melting ice sits at the top too long. A creek only 6 inches deep in mountainous areas can swell to a 10-foot deep raging river in less than an hour if a thunderstorm lingers over an area for an extended period of time.1
  • Dry conditions, ironically, can cause flooding. When the ground is so hard and solid, it makes it hard for any rainfall to penetrate into the ground, so it isn’t absorbed.
  • Snow and ice melting will create a flood when it melts too quickly for an area that is not ready for that much water at once.
us flood risk map

Src: http://femafloodbarriers.com/dominican-republic/santo-domingo.php

Formation

Src: https://beprepared.com/flood-preparedness

There are multiple types of of flooding, beyond just floods and flash floods. The types are determined by the way that the flood forms.

Related:  Storm Prep Saturday: Hail

River floods are common with excessive amounts of rain. This usually happens when a river is already at a high level, and then the area gets a large rainstorm, or even a tropical systems such as a hurricane, or even a multi-cell thunderstorm with torrential amounts of rain. When the river gets too full, it will start to flood over the top of the riverbank and flood the area. Most places also drain into a nearby river, so if it’s already full, there is nowhere for other waters to drain either.

As I’m writing this, the state of Missouri is suffering from inland flooding. They’ve had so much rain in the state lately, that the water has had nowhere to go. The area is just completely saturated, and the ground can’t absorb any more water, though it continues to rain.

Storm surge, caused from a severe storm that moves inland from off the coast, is a very dangerous type of flood because it can happen quickly. Storm surge is the combination of winds, waves, and low atmospheric pressure causing the waters to rise onto the land. The low pressure means makes the waters lift slightly, and the wind pushes the waves onshore. If this happens to occur during high tide, it can be devastating.

Similar to the storm surge, coastal flooding occurs in coastal areas usually when it’s already high tide and then the area gets too much rainfall, adding to the amount of water that is pushing onshore. This also tends to happen in areas that are developed at low elevations.

A flash flood is the most dangerous type of flood because it happens so quickly. Any of these types of floods can cause a flash flood, but storm surge and river flooding are the usual culprits. A flash flood occurs when there is an excessive amount of rainfall in an area and it can’t drain quick enough, causing the waters to rise extremely fast. A flash flood happens generally in less than 6 hours and usually have very fast-moving waters.

Related:  Hurricane Guide: What to Expect During the Storm and After

Burn scar floods occur when an area has had a recent wildfire because the vegetation that would normally absorb any rain or water has been burned away.

Be Weather Alert

There are many different watches and warnings associated with floods, so make sure you know what your area is susceptible to, and what types you need to be aware of.

Flash Flood or Flood Watch: Be prepared. A flood or flash flood is possible.

Flash Flood or Flood Warning: Get to higher ground. A flash flood or flood has been reported or is imminent, move now before it’s too late.

Urban and Small Stream Advisory: Be watchful. Some flooding of small streams, streets, and low areas is occurring.

Flash Flood or Flood Statement: Be informed. Contains information following a flood event.

Floods are detected in a few ways. Meteorologists watch the radar to see what locations are predicted to have the most rainfall, and issue flood watches/warnings if necessary depending on how prone the area is to flooding and how intense the rain is supposed to be. Rain gauges are also checked to know how high the water level is and how much rain has fallen in a specific area. More and more rain gauges are on automatic detection systems which gives real-time information without having to have someone there to read in person.

During a Flood and After

DO NOT DRIVE IN A FLOODED AREA! If you can’t see the road, don’t drive on it. More deaths occur in a vehicle during a flood than anywhere else because people think they can drive through the waters. It only takes 12″ of water to sweep a vehicle off the road. If you can’t see the road, you can’t see any potential dangers there. Flood waters can wash away portions of a road, it can open sinkholes, there may be down trees or other debris in your way. Once your car stalls, you are in danger of drowning if the water rises fast. Turn Around, Don’t Drown.

It’s also not safe for you to be in flood waters if you can avoid it. Most people will be swept off their feet in only 6″ of moving water. Flood waters can also be contaminated with so many hazardous materials, such as sewage and chemicals. Gas can leak into the waters. Power lines may be down and still active in the water.

Related:  Hurricane Guide: Glossary

If you are in any low-lying area, get to higher ground as soon as possible. Don’t wait until you see the flood waters starting to rise, it’s usually too late by then. A flash flood can happen in minutes!

flooded car

Personal Experience

The first time I remember worrying about flooding was when Hurricane Charley threatened. As it got closer to the Florida coast, and closer to the city I lived in at the time, we started to get very worried about the storm surge. My parents live in a neighborhood with canals on 3 sides that go straight into the Caloosahatchee River, and it was a possibility for the storm to turn up the river. If that happened, they were predicting up to a 15 foot storm surge, and my parents house sits on about 4 feet elevation. When we heard this, we evacuated. Thankfully for us, the storm wobbled at the last minute, and hit the next big city north of us. Some of our streets were a little flooded and it came up to the sidewalks, but none of the homes in our neighborhood were damaged by flood.

Since we’ve been in Houston (about 2.5 years), we have seen 3 record-breaking floods in the area. Again, we are lucky that the area of Houston that we live in doesn’t have too many problems, and we haven’t had any damage to our home or neighborhood. Other areas of Houston have not been so lucky. After one of the floods last year, Justin and I drove to pick his grandma up, and had to change our route because of flooded roads, and I was both horrified and awestruck at the flood damage we saw, just miles up the road from our house. The way we would usually get to her place was completely under water, and another foot or so of water and it would have been over the interstate.

san jacinto river flood

This is the predicted flooding of the San Jacinto River, just north of us.
Src: Meteorologist Travis Herzog and ABC13


Sources:

  1. http://www.nssl.noaa.gov/education/svrwx101/floods/
  2. http://www.nws.noaa.gov/hic/

flooding flooding

Stephanie Lynch

I’m a stay-at-home mom, I am a children/family photographer, I am a Legacy Maker with Legacy Republic, I am a mom, I am a wife. I wear many different hats and do many different things, but I wouldn’t have it any other way!

RELATED POSTS

Leave a Reply