Floods are the most common natural disaster in the United States, and one of the biggest threats for Williamson County. Failing to evacuate flooded areas or entering flood waters is dangerous and can lead to injury or death.
Flooding is a temporary overflow of water onto land that is normally dry. Floods may:
- Result from rain, snow, coastal storms, storm surges and overflows of dams and other water systems.
- Develop slowly or quickly. Flash floods can come with no warning. Flash flooding is responsible for more fatalities than any other thunderstorm-associated hazard.
- Cause outages, disrupt transportation, damage buildings and create landslides.
There are several things you can do to prepare in advance for a flood:
- Determine if your property is above or below predicted flood levels. It’s important to know if your home is in a floodplain. Visit FEMA’s Flood Map Service Center for information.
- If flash flooding is common in your area, monitor heavy rain. Learn and practice evacuation routes, shelter plans, and flash flood response. Find out which roads in your area flood the most.
- Keep your emergency kit handy in case of evacuation. You will also need these items in case you are stranded in your home by floodwaters. If you live in an area with a high chance of flooding, add flood-specific items to your kit such as rain gear, evacuation gear, medicine, sleeping bags, and waterproof protection for paperwork. See our page on emergency kits for a list of items to keep ready.
- Learn the safest evacuation routes from your home. Roads often flood before homes, so plan accordingly and think ahead about where you would go in case of evacuation.
- Protect your property. Move valued items to higher levels. Declutter drains and gutters. Install check valves and seal basement walls. Consider a sump pump with a battery. Gather sandbags, plywood, plastic sheeting, and lumber for emergency waterproofing. Raise and reinforce your home if necessary.
- Get flood insurance. Homeowner’s policies do not cover flooding. You can get flood coverage under the National Flood Insurance Program (NFIP).
- Keep important documents in a waterproof container. Create password-protected digital copies.
- Keep your automobile fueled. Do not hoard gas. Panic buying immediately before or during a crisis leads to fuel shortages. Do not fill and store multiple portable gas cans, or use containers not designed to hold gas.
- Charge all essential electronics if inclement weather is expected. Even if you don’t need to evacuate, you may still lose power.
A flood can develop slowly over several days or within minutes, as a flash flood. You should know the difference between a flash flood watch and a warning.
- Flash Flood Watch: Current or developing hydrologic conditions that are favorable for flash flooding in and close to the watch area, but the occurrence is neither certain nor imminent.
- Flash Flood Warning: Flash flooding is in progress, imminent or highly likely.
When Flooding is Anticipated or Imminent
In the event of a flash flood watch or warning, you should:
- Find safe shelter right away!
- Keep your vehicle’s gas tank filled. If electric power is cut off, gas stations may not be able to operate pumps for several days. Do not hoard gas by filling up and storing multiple portable gas cans which can lead to supply issues.
- Have your emergency kit handy.
- Store drinking water in various containers. Water service may be interrupted.
- Move to a safe area before access is cut off by floodwater.
- Depending on the type of flooding:
- If told to evacuate, do so immediately. Check evacuation routes from your home and your workplace. Never drive around barricades. Local responders use them to safely direct traffic out of flooded areas or to warn of unsafe conditions.
- Move to higher ground or a higher floor. If trapped in a building, go up to a safe level. Do not climb into a closed attic. Go on the roof only if necessary and signal for help.
- Stay where you are. If your home is not in danger of flooding but the roads are, then stay home.
- If you are driving during a flood:
- DO NOT attempt to drive, walk, or swim over a flooded road. The depth of the water is not always obvious, or the road could be washed away, and you could be trapped. If you can't see it, you can't be sure it's there. Just six inches of fast-moving water can knock you down, and one foot of moving water can sweep your vehicle away. Turn around, don’t drown!
- Stay off of bridges over fast-moving water. Fast-moving water can wash bridges away without warning.
- If your vehicle is trapped in rapidly moving water, consider staying inside.
- Car electrical systems may not work when affected by rising water. Electric windows should be rolled down in case you need to make an emergency exit.
- Car doors cannot typically be opened due to the pressure of the water against the door.
- Electrical systems may short out causing electric car door locks to engage.
- If water is rising inside the vehicle, seek refuge on the roof.
- Stay away from drainage ditches, culverts and the like and do not allow children to play near them. People can get trapped by fast-moving currents in culverts, drainage ditches and drain pipes, resulting in serious injuries or drowning.
- Secure important documents.
- Follow instructions. Listen to alerts and warnings, they are in place to keep you safe.
Using alert systems is crucial to being informed before and during flooding events, just as with any other disaster. Our alert systems page has resources for a number of alert options.
Although EMA doesn’t endorse any particular products, apps such as Riverapp and Rivercast provide alerts when specified rivers reach user defined water levels. These can be especially helpful for those who are typically affected by flooding from the Harpeth river.
Immediately After a Flood
- Stay informed. Check for updates on affected areas on our emergency updates page and check on the status and safety of your drinking water.
- Avoid floodwaters. Standing water can hide chemicals that can make you sick, power lines that can cause electrocution, storm drains where covers have been dislodged, and sharp debris.
- Avoid disaster areas. Your presence may hamper emergency operations.
- Pay attention to road closure and caution signs.
- Pay attention to authorities for information and instructions. Return home only when authorities say it is safe.
- Contact family and loved ones to let them know you’re okay.
- Report losses and take photos of damage to your property for flood insurance claims or for Public Assistance should the disaster merit a Presidential Declaration. Collect as much documentation as possible, and save all recovery-related receipts. Fill out our damage assessment survey.
- Clean up quickly. Don’t wait on aid from others to begin recovery. Air out your house; mold shows up within 24-48 hours of flooding. Drinking or exposure to contaminated water can infect wounds and make you sick. Wear protective gear while cleaning. It is recommended that people with asthma or other lung conditions should not enter buildings with indoor water leaks or mold growth that can be seen or smelled.
- Check for snakes and insects. Critters may have moved into your home during the flood.
- Don’t bring your kids and pets home immediately. If possible, begin the recovery process without young children seeing the disaster damage, it may cause extra stress and trauma. Animal injuries often occur immediately after a disaster due to debris, and from being on edge due to extra stress.
- Keep away from power lines as these may still be or suddenly become energized.
- Use flashlights as extra light sources, no open flames.
Local Flood Risks
History of flood events in Williamson County
Floods in Williamson County are usually caused by excessive rainfall, and some areas in the county are more flood-prone than others. One of the easiest ways to identify areas that are flood-prone from rainfall is by reviewing the county flood maps.
Flooding may also be caused by other means such as failure to keep debris clear of culverts, creeks, streams, drainage ditches, drainage grates and other areas where water is designed to flow. Most of the streams and creeks in Williamson County are the responsibility of the property owner.
Williamson County has had many flood events in the past. National Oceanic and Atmosphere Administration (NOAA) has a user defined searchable online database of flood events occurring in the county, available here.
Small localized flood events are likely to occur several times a year in Williamson County. When 2-4 inches of rain are called for in Williamson County, the National Weather Service (NWS) is normally prompted to issue a flood watch. This is because localized flooding is often experienced throughout the county when rainfall is within this amount.
As seen with the May 2010 Tennessee Flood Event (DR-1909), it is possible for 20 inches or more of rainfall to amass within two days.
According to a NOAA Flood Risk Map, the majority of Tennessee was located in an “above average” risk of flooding zone during spring 2010. This proposed vulnerability is coupled with the fact that on average Tennessee usually receives over 50-60 inches of rainfall a year.
The Harpeth River
Flooding remains one of the biggest threats for Williamson County, due to the local Harpeth River and its branching creeks. According to the NWS Advanced Hydrologic Prediction Service, the Harpeth River near the city of Franklin reaches Flood Stage at 30 ft. The gauge for this measurement is located off Murfreesboro Road, near Pinkerton Park. In this area, even when Flood Stage is not reached, there are local impacts.
The Harpeth River also has impacts below the City of Franklin. The gauge location for this area is located off Hillsboro Rd and Judge Fulton Greer Park, and the flood stage here is 27 ft.
What is a 100-year flood?
Contrary to what it sounds like, a 100-year flood is not a flood that happens once every 100 years. To avoid confusion, the National Flood Insurance Program (NFIP) uses the term “base flood.” A 100-year base flood is as having a 1% chance of being reached or exceeded in any single year.
For example, during 30-year mortgage, a house sitting low enough may have a 26% chance of being hit by a 100-year flood, but a 96% that it will be hit by a 10-year flood. Compare those odds to the 1-2% chance that the house will catch fire during the same 30-year mortgage.