Warning Signs of a Flash Flood

Flash floods are a kind of water damage that people can experience that is completely on a different scale than typical plumbing or roofing leaks we often talk about here.

Not only are flash floods devastating in terms of how much property loss they can inflict, but they can also cause serious injuries. 

Categorized as the most severe “category 3 water damage” or “black water”, floodwaters carry with them a number of different objects, big and sharp, along with a plethora of contaminants, bacteria, and all types of human and industrial waste.

Being prepared for a flash flood in advance helps a ton, as you can protect more of your items and have a clear evacuation plan in place.

How Do Flash Floods Happen?

Flash floods are rapid and intense floods that occur within a short period, typically within six hours, of heavy rainfall. When precipitation exceeds the normal absorption capacity of the soil or drainage systems in place, excess water accumulates rapidly, leading to a flood.

It doesn’t have to be just rainfall. Flash floods can occur when rivers or streams experience a sudden surge in water, like the convergence of multiple tributaries, which overloads their river banks and forces the water to escape. Snowmelt can also lead to floods.

Urban areas are flood-prone because their development alters natural drainage patterns. Increased impervious surfaces, like roads and buildings, redirect water flow, concentrating runoff into a flood.

This can be made worse by the area’s topography. Places with steep slopes, canyons, or narrow valleys exacerbate the speed and force with which water travels downhill.

Hazards Brought on by Flash Floods

Across the entire country, urban flooding occurs once every 2-3 days. These disasters have cost the US taxpayer over $850 billion since the year of 2000.

Flash floods can quickly overwhelm low-lying areas and streets. The waters can overwhelm sanitary sewers and bring debris that can clog the lines and lead to sewer water backing up.

These waters carry with them all sorts of objects that can damage the surrounding property and injure people.

When inside a home, floodwaters can soak and destroy most of your porous materials, like wood, drywall, insulation, upholstery, and concrete, break glass and permanently damage your electronics.

According to CDC, floodwaters carry three main hazards to flooded buildings that can harm people, besides the risk of injury or drowning, which is the most severe.

The first one is mold. Thriving in damp and flooded areas, mold can grow in as little as 24 hours. Mold eats up organic materials and releases mycotoxins, which can cause respiratory problems.

Then there is the risk of electrocution since the floodwater has likely reached your electrical system. Even after extensive drying, most electrical items are still unsafe for use.

And lastly, hazardous waste present in the water, including urine, feces, dirt, soil, chemicals, dead animals, industrial waste, and other.

What Are The Warning Signs of a Flash Flood?

Let’s go over some of the things that raise a red flag:

  • Heavy Rainfall: Especially in a short amount of time. Look at the weather forecasts and pay attention to rainfall rates.
  • Early Snowmelt: Rapid snowmelt on the still-frozen ground. If officials indicate such a possibility, it could be a sign of a flash flood.
  • Rising Water Levels: One of the most evident warning signs is a sudden increase in the water level of rivers, streams, or even small channels.
  • Changes in the Water Itself: A noticeable change in the color of the stream, often becoming muddy or murky, indicates the presence of sediments and debris and is likely due to increased water flow. If you can see the debris, such as logs, branches, or even rocks, in water bodies, it shows the change in the force and speed of the flowing water, which is a warning sign.
  • Water Pools: These indicate that the soil is oversaturated.
  • Dam or Levee Failures: If you hear the news of these events, be on the lookout.
  • Slow-moving Storms: Watch for slow storms hanging over the same area
  • Hurricanes: These are some of the most devastating types of storms, and they often cause flooding.

How to Prepare for a Flood

Now that you know flash flood warning signs, here are some things you can do to be prepared:

  • Stay Informed: This is crucial for flood preparedness. Follow weather forecasts, listen to local news, and use emergency alert systems (National Weather Service has the Flood Warning and Flood Watch systems). 
  • Know Your Risk: Use flood maps, available on FEMA’s website, to identify flood-prone areas in your community.
  • Secure Important Documents: Place documents like insurance policies, medical records, and identification in a waterproof container.
  • Flood Insurance: We strongly recommend obtaining flood insurance. Standard homeowners’ insurance typically does not cover flood damage. Flood insurance can be purchased through the NFIP.
  • Elevate Utilities: Get electrical components and utilities above potential flood levels to minimize damage and ensure a safer recovery process.
  • Emergency Supplies Kit: Have an emergency supplies kit containing essentials such as non-perishable food, water, medications, flashlight, batteries, and a first aid kit.
  • Evacuation Plan: Know the designated evacuation routes, have transportation arrangements, and follow local authorities’ instructions.
  • Communication Plan: Establish contact points for family members, have a battery-powered or hand-crank radio for updates, and consider using text messages during emergencies.
  • Protect Your Home: Install sump pumps, check and maintain gutters and downspouts, and consider using sandbags to divert water away from your property.
  • Post-Flood Actions: Avoid returning home until authorities declare it safe, document the damage for insurance claims, and seek professional assistance for cleanup and repairs.


Flooding is a difficult topic, but hopefully this post was helpful to you. Make sure to check more government resources to stay up-to-date if you’re concerned about flooding.

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