Flooding and Flood Risks
What Is a Flood?
Anywhere it rains, it can flood. A flood is a general and temporary condition where two or more acres of normally dry land or two or more properties are inundated by water or mudflow. Many conditions can result in a flood: hurricanes, broken levees, outdated or clogged drainage systems and rapid accumulation of rainfall.
Just because you haven't experienced a flood in the past, doesn't mean you won't in the future. Flood risk isn't just based on history, it's also based on a number of factors: rainfall, river-flow and tidal-surge data, topography, flood-control measures, and changes due to building and development.
Flood-hazard maps have been created to show different degrees of risk for your community, which help determine the cost of flood insurance. The lower the degree of risk, the lower the flood insurance premium.
A Flood for All Seasons
Flooding can happen any time of year. Below are some of the more frequent causes.
Tropical Storms and Hurricanes
Hurricanes pack a triple punch: high winds, soaking rain, and flying debris. They can cause storm surges to coastal areas, as well as create heavy rainfall which in turn causes flooding hundreds of miles inland. While all coastal areas are at risk, certain cities are particularly vulnerable and could have losses similar to or even greater than those caused by the 2005 hurricane, Katrina, in New Orleans and Mississippi.
When hurricanes weaken into tropical storms, they generate rainfall and flooding that can be especially damaging since the rain collects in one place. In 2001, Tropical Storm Allison produced more than 30 inches of rainfall in Houston in just a few days, flooding over 70,000 houses and destroying 2,744 homes.
During the spring, frozen land prevents melting snow or rainfall from seeping into the ground. Each cubic foot of compacted snow contains gallons of water and once the snow melts, it can result in the overflow of streams, rivers, and lakes. Add spring storms to that and the result is often serious spring flooding.
Several areas of the country are at heightened risk for flooding due to heavy rains. The Northwest is at high risk due to: snow melts, heavy rains, and recent wildfires. And the Northeast is at high risk due to heavy rains produced from NorEasters.
This excessive amount of rainfall can happen throughout the year, putting your property at risk.
West Coast Threats
The West Coast rainy season usually lasts from November to April, bringing heavy flooding and increased flood risks with it; however, flooding can happen at anytime.
A string of large wildfires have dramatically changed the landscape and ground conditions, causing fire-scorched land to become mudflows under heavy rain. Experts say that it might take years for vegetation to return, which will help stabilize these areas.
The West Coast also has thousands of miles of levees, which are meant to help protect homes and their land in case of a flood. However, levees can erode, weaken, or overtop when waters rise, often causing catastrophic results.
Levees and Dams
Levees are designed to protect against a certain level of flooding. However, levees can and do decay over time, making maintenance a serious challenge. Levees can also be overtopped, or even fail during large floods, creating more damage than if the levee wasn't even there.
Because of the escalating flood risks in areas with levees, especially in the mid-west, FEMA strongly recommends flood insurance for all homeowners in these areas.
Flash floods are the #1 weather-related killer in the U.S. since they can roll boulders, tear out trees, and destroy buildings and bridges. A flash flood is a rapid flooding of low-lying areas in less than six hours, which is caused by intense rainfall from a thunderstorm or several thunderstorms. Flash floods can also occur from the collapse of a man-made structure or ice dam.
Construction and development can change the natural drainage and create brand new flood risks. That's because new buildings, parking lots, and roads mean less land to absorb excess precipitation from heavy rains, hurricanes, and tropical storms.
Understanding Flood Areas
Flooding can happen anywhere, but certain areas are especially prone to serious flooding. To help communities understand their risk, flood maps (Flood Insurance Rate Maps, FIRMs) have been created to show the locations of high-risk, moderate-to-low risk, and undetermined-risk areas. Here are the definitions for each:
High-Risk Areas (Special Flood Hazard Area or SFHA)
High-risk areas have at least a 1% annual chance of flooding, which equates to a 26% chance of flooding over the life of a 30-year mortgage. All homeowners in these areas with mortgages from federally regulated or insured lenders are required to buy flood insurance. They are shown on the flood maps as zones labeled with the letters A or V.
Moderate-to-Low-Risk Areas (Non-Special Flood Hazard Area or NSFHA)
In moderate-to-low risk areas, the risk of being flooded is reduced, but not completely removed. These areas are outside the 1% annual flood-risk floodplain areas, so flood insurance isn't required, but it is recommended for all property owners and renters. They are shown on flood maps as zones labeled with the letters B, C or X (or a shaded X).
No flood-hazard analysis has been conducted in these areas, but a flood risk still exists. Flood insurance rates reflect the uncertainty of the flood risk. These areas are labeled with the letter D on the flood maps.
Determining the Risk
To identify a community's flood risk, FEMA conducts a Flood Insurance Study. The study includes statistical data for river flow, storm tides, hydrologic/hydraulic analyses, and rainfall and topographic surveys. FEMA uses this data to create the flood hazard maps that outline your community's different flood risk areas.
Floodplains and areas subject to coastal storm surge are shown as high-risk areas or Special Flood Hazard Areas (SFHAs). Some parts of floodplains may experience frequent flooding while others are only affected by severe storms. However, areas directly outside of these high-risk areas may also find themselves at considerable risk.
Understanding Your Area
Changing weather patterns, erosion, and development can affect floodplain boundaries. FEMA is currently updating and modernizing the nation's Flood Insurance Rate Maps (FIRMS). These digital flood hazard maps provide an official depiction of flood hazards for each community and for properties located within it.
FEMA has published almost 100,000 individual Flood Insurance Rate Maps (FIRMs). See your map and learn how to read it so you can make informed decisions about protecting your property, both financially and structurally.
Flood Preparation and Recovery
Being prepared for a flood can not only help keep your family safe, but it can also help minimize potential flood damage and accelerate recovery efforts.
Along with flood insurance, you can also protect yourself by safeguarding your home and possessions, developing a family emergency plan, and understanding your policy.
Learn how to deal with a flood, both before and after it happens, right now.
Before a Flood: Educate Yourself
After getting flood insurance, there are several things you can do to minimize losses in your home and ensure your family's safety.
1. Safeguard Your Possessions
Create a personal file containing information about all your possessions and keep it in a secure place, such as a safe deposit box or waterproof container. This file should have:
- A copy of your insurance policies with your agent's contact information.
- A room-by-room inventory of your possessions, including receipts, photos, and videos.
- Copies of all other critical documents, including finance records or receipts of major purchases.
2. Prepare Your House
- First make sure your sump pump is working and then install a battery-operated backup, in case of a power failure. Installing a water alarm will also let you know if water is accumulating in your basement.
- Clear debris from gutters and downspouts.
- Anchor any fuel tanks.
- Raise your electrical components (switches, sockets, circuit breakers, and wiring) at least 12 inches above your projected flood elevation.
- Place the furnace, water heater, washer, and dryer on cement blocks at least 12 inches above the projected flood elevation.
- Move furniture, valuables, and important documents to a safe place.
3. Develop a Family Emergency Plan
- Create a safety kit with drinking water, canned food, first aid, blankets, a radio, and a flashlight.
- Post emergency telephone numbers by the phone and teach your children how to dial 911.
- Plan and practice a flood evacuation route with your family. Know safe routes from home, work, and school that are on higher ground.
- Ask an out-of-state relative or friend to be your emergency family contact.
- Have a plan to protect your pets.
During a Flood: Protect Yourself and Your Home
Here's what you can do to stay safe during a flood:
- If flooding occurs, go to higher ground and avoid areas subject to flooding.
- Do not attempt to walk across flowing streams or drive through flooded roadways.
- If water rises in your home before you evacuate, go to the top floor, attic, or roof.
- Listen to a battery-operated radio for the latest storm information.
- Turn off all utilities at the main power switch and close the main gas valve if advised to do so.
- If you've come in contact with floodwaters, wash your hands with soap and disinfected water.
After a Flood: The Road to Recovery
As soon as floodwater levels have dropped, it's time to start the recovery process. Here's what you can do to begin restoring your home.
- If your home has suffered damage, call your insurance agent to file a claim.
- Check for structural damage before re-entering your home to avoid being trapped in a building collapse.
- Take photos of any floodwater in your home and save any damaged personal property.
- Make a list of damaged or lost items and include their purchase date and value with receipts. Some damaged items may require disposal, so keep photographs of these items.
- Keep power off until an electrician has inspected your system for safety.
- Boil water for drinking and food preparation until authorities tell you that your water supply is safe.
- Prevent mold by removing wet contents immediately.
- Wear gloves and boots to clean and disinfect. Wet items should be cleaned with a pine-oil cleanser and bleach, completely dried, and monitored for several days for any fungal growth and odors.
Additional Flood Preparation Information
- Flood Safety Tips and Resources
- New York Extension Disaster Education Network (NY EDEN) - Floods
- Repairing Your Flooded Home
- Flood Safety Tips
- Flood Safety Social Media Toolkit
- Turn Around Don't Drown: Flood Safety
- Safety Tips for Flooding
- Flood Basics and Safety
- Flooding: Iowa State University
- Flood Safety Tips for Austin Residents
- Emergency Planning and Preparedness - Flash Flood
By Jim Olenbush