How to Prepare for and Be Aware of Floods

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As with all types of weather, it’s important to know the differences between categories of Weather Alerts. Floods have three basic classifications of potential alerts: Watches, Warnings, and Advisories.

Types of Flood Watches, Warnings, and Advisories

  • Flood Watch: Conditions are right for possible flooding (stay alert for announcements).
  • Flash Flood Watch: Conditions are right for a possible flash flood (stay alert for announcements).
  • Flood Warning: Flooding has started or is about to start in the immediate warning area. You may be advised to evacuate soon.
  • Flash Flood Warning: A flash flood is occurring in the warning area. Seek higher ground immediately!
  • Urban and Small Stream Advisory: Conditions are likely to produce flooding of small streams, streets, and
    low-lying areas such as underpasses, underground parking, and storm drains. It’s best to avoid these areas.

Floods constitute some of the most frequent and disruptive weather hazards in the US. Normal floods tend to develop slowly, with obvious signs of the impending condition (usually giving ample warning of the danger). Flash floods tend to develop very rapidly, sometimes in a matter of minutes, with little to no warning signs, creating significantly increased danger.

While your specific region may not often experience flooding, never assume it can’t happen in your area. Floods with significant damage have been recorded in many parts of the US that rarely see flood waters.

Basic Factors that Create Flood Conditions

Rainfall: Heavy rain storms (especially close together) can saturate the ground and prevent water from being absorbed. This causes the fresh rain to “run off” and collect in areas it usually doesn’t (or at least at higher rates than normal).

Rivers: Most rivers have high and low cycles that are normal. If you've ever lived near one, this will be familiar. When you get combinations of high river levels and add excessive rain, it’s not uncommon to see rivers overflow their banks.

Tidal Areas: If you live near a coastal area, you will be aware of the ebb and flow of the lunar tides. During storms, the combination of lower barometric pressure and effects of winds can drive waves and tides higher than usual.

Urban Flooding: Urban areas, inherently and significantly built up, require artificial drainage solutions, since there are usually very few natural drainage options remaining. These drain systems can easily (and often) become inundated with excessive runoff and debris.

Catastrophic Events: Dams, levees, and sea walls are all man-made structures designed to hold water back, to facilitate the development of an area. In the event that one of these structures has a failure, the resulting release of water is usually a catastrophic event.

Facts to Consider about Floods

  • Floods are the number one weather-related event resulting in loss of life.
  • Flooding occurs in every state in the US.
  • Anywhere it rains, it can flood (floods can also happen in places where it's not raining).
  • If you hear a flood-related alert, you should be prepared to evacuate at a moment’s notice.
  • You should be aware of potential flood hazards, both where you live and work (especially if it’s in a low-lying area).
  • The worst flash flood in the US occurred in Johnstown, PA, on May 31, 1889, due to the  catastrophic failure of the South Fork Dam, which sat astride the Little Conemaugh River, 14 miles upstream.

Having a flood evacuation plan is highly recommended. Have a means of contacting family members (and a backup). Be prepared with an emergency evacuation kit, and know in advance how to use the items in the kit. In the case of flooding, you need to get to higher ground as quickly and safely as you can to escape the danger area. Make sure you also have one or two alternative routes planned, in case the main evacuation route is impassable.

Safety Tips

  • Learn about the potential flood hazards in your area ahead of time.
  • If you hear a “Watch” issued, pay close attention to on-going reports. You may have limited notice of a warning.
  • Never walk through moving water that is more than ankle deep. Six inches of moving water can sweep the average person off their feet.
  • Avoid driving in a flooded street. Even very shallow flood water can result in loss of control, and/or stalling, in most passenger vehicles.
  • Never drive through moving flood water. Most cars can be swept away in less than a foot of water, and most SUVs and pick-up trucks in less than two feet.
  • If your evacuation route is flooded, turn around and go an alternate way.
  • Never drive over a road washed by flood water. The road bed could be washed out, causing a collapse if you drive on it.
  • Don’t drive around barricades―they are there for a reason.

Dangers in the Wake of a Flood

You need to exercise caution around your home and when traveling after a flood. Roadways are often undermined by flood waters, and that can create very dangerous conditions (roads can collapse into sinkholes without warning). Don’t attempt to return to your home until officials advise it safe to do so. If you attempt to enter an area before that, you not only risk danger to yourself, but you could interfere with rescue operations and restoration efforts.

"Floods constitute some of the most frequent and disruptive weather hazards in the US."

Downed power lines pose a danger after a flood. If there are any lines down in your area, never walk through standing water. Similarly, if your area is serviced by natural gas, be wary of potential leaks (leave the immediate area and call authorities).

Before entering your home following a flood, inspect the outside for signs of damage (cracked foundation, openings, and structural concerns). Watch out for wild animals that may have entered during the flood, especially dangerous reptiles native to your area (snakes are common). Avoid walking in standing water at anytime—it has a high probability of being contaminated with chemicals or raw sewage.

After any major weather event, even if your neighborhood is spared any serious damage, you still may be without power for some time. It’s always a good idea to have some standard supplies on hand (water, food, extra batteries). Once again, planning ahead can make a huge difference.

As I mentioned in the other installments in this series, on thunderstorms and tornadoes, one key item that applies to all types of dangerous weather is good Base Weather Radio. These are very affordable and invaluable for the advanced warning they can provide in an emergency. Every home should have something similar to the Midland WR-120.

Other Key Items to Have in Your Kit

I hope you found this information to be beneficial. Remember: the key is to plan ahead.

Check out the other installments in this series:

How to Prepare for and Be Aware of Tornadoes

How to Prepare for and Be Aware of Thunderstorms