Flooding 101
Key points
- Flooding occurs when water overwhelms normally dry land, potentially causing major risks and damage.
- This can be caused by heavy rainfall, overflowing rivers, dam/levee failures, storm surges, snowmelt, ice jams, or lack of vegetation.
- Floods can lead to loss of life, property destruction, infrastructure damage, economic loss, and long-term psychological effects.
- Be prepared with emergency supplies, avoid floodwaters (even shallow ones), follow evacuation orders, and understand what to do when alerts are issued (e.g., watches, advisories, and warnings).
Flooding is one of nature’s most powerful and unpredictable forces. This article will address what flooding is, the damage it can cause, and how homeowners can prepare and respond when it happens.
What is a flood?
A flood is when water overwhelms an area of land that is normally dry. A flood may occur suddenly, or happen gradually – regardless, any flood has the potential to cause injuries, disruptions in utility services and transportation or property damage. In fact, just one inch of flood water in a home can cause $25,000, or more, in damage, according to Federal Emergency Management Agency (FEMA).
Types of floods
Though the definition of a flood is relatively simple to understand, the mechanisms behind flooding can vary substantially, leading to different types of flooding. Each can carry a different type of behavior, cause, and present its own unique challenges and hazards. Below are six common types of floods.
| Flood Type | What It Is | Common Causes |
|---|---|---|
| River (Fluvial) | When rivers overflow their banks | Prolonged rain, snowmelt, ice jams |
| Flash (Pluvial) | Rapid flooding after heavy rain | Intense rainfall, poor drainage |
| Coastal | Flooding along coastlines | High tides, wind, rainfall |
| Storm Surge | Abnormal rise in sea level | Hurricanes, severe storms |
| Inland | Flooding away from coasts | Rain, dam/levee failure |
| Sewage | Wastewater backup | Pipe blockages, heavy rain |
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get a quoteFlood causes and risk factors
Regardless of the type of flood, they can be caused by some of the same factors, according to Earth Networks.
| Factor | How it contributes to flooding |
|---|---|
| Heavy rainfall | Overwhelms drainage systems |
| Tropical systems | Brings rain and storm surges |
| Snowmelt | Releases large volumes of water |
| Ice/debris jams | Blocks river flow |
| Dam/levee failure | Sudden release of water |
| Steep terrain | Accelerates runoff |
| Lack of vegetation | Increases erosion and runoff |
| Atmospheric rivers | Delivers extreme precipitation |
| Tsunamis | Push massive water inland |
Where does flooding happen?
A flood can happen anywhere, says the National Severe Storms Laboratory (NSSL). But there are some areas that may be more vulnerable to floods than others. Flood-prone areas include:
- Dense urban areas: Impermeable surfaces increase runoff
- River-adjacent areas: Overflow and dam failure risk
- Canyons and burn areas: Dry soil and lack of vegetation increase runoff
Flood watches, advisories and warnings
Flood watches and advisories are less severe than flood warnings. Under a flood watch, flooding may happen, but it also may not. Under a flood advisory, flooding may occur and is not severe – more of an inconvenience, explains Weather.gov. In both of these cases you should stay aware of your surroundings and ready to act should danger arise.
In the case of a flood warning, you need to get yourself to safety as soon as possible.
| Alert Type | What it means | What to do |
|---|---|---|
| Flood Watch | Conditions are favorable | Stay alert and prepared |
| Flood Advisory | Minor flooding occurring | Be aware and cautious |
| Flood Warning | Flooding imminent or happening | Move to safety immediately |
Flooding effects
Loss of lives
Flooding is one of the deadliest forms of severe weather in the U.S. according to Weather.gov. Deep, fast flowing or rapidly rising flood waters can be particularly dangerous.
Property damage
Flooding can cause considerable damage to property depending on the severity of the flood. It can cause structural damage such as loose or buckling floors or foundation cracks. Flooding can also damage appliances including ventilation, heating, refrigerators, and beyond. There may even be damage after the initial flooding caused by mold and mildew.
Economic impacts
Flooding can have catastrophic effects on the economy of impacted regions. Floods can destroy valuable real estate, damage industrial facilities built with access to waterways in mind, and damage key infrastructure according to the Institute for Water Resources (IWR).
Psychological effects
Flooding can have profound impacts on communities ranging from a loss of life, health, and property. But beyond that, flooding can have negative implications for mental health including increased levels of depression, and post-traumatic stress disorder (PTSD), according to ScienceDirect.
Preparing for a flood
What do I do before a flood?
If you learn that a flood is possible or imminent, there are some important steps you can take to help protect your family and home:
Gather emergency supplies
A basic emergency kit should include several key items, such as a three-day supply of water (one gallon per person per day), nonperishable food, a battery-operated or hand-cranked radio, first aid supplies, a flashlight and batteries, according to Ready.gov.
Prepare your home
Before floodwaters reach your area, the Insurance Institute for Business and Home Safety (IBHS) suggests taking the following steps to help protect your home:
- Clear gutters and downspouts of debris, so water can run freely.
- Elevate furniture and electronics; set appliances on concrete blocks.
- Inspect your sump pump and back-up batteries to make sure they're operational.
You might also want to consider sandbagging, if there’s enough time before water reaches your area, says FloodSmart.gov.
Take safety precautions
If your area floods, consider the National Weather Service's advice on keeping everyone in your home safe:
- Avoid electrical hazards. Don’t enter the basement, or any room where floodwaters cover electrical cords or outlets
- Obey local evacuation orders
- Stay out of floodwaters – do not walk or drive through them
What do I do during a flood?
During a flood, it is vital to be aware of your surroundings and monitor local alerts for updates on the situation. Move to high ground and obey any evacuation orders. Do not go in any room if water covers the outlets. Avoid flood waters. Flood water can be contaminated with chemicals, hazardous objects, etc. Small amounts of moving water can also be hazardous.
What do I do after a flood?
After a flood, you should avoid any standing water still as it can be contaminated and can obscure hazards. If it is likely your house will flood, get to safety if you are able, explains Weather.gov. Obey road closures, cautionary signs, and wait for an all clear before returning home.
How much does repairing flood damage cost?
Water damage restoration costs vary widely depending on the type of water, extent of damage, and location in the home. According to Fixr, here are some national averages:
| Repair Type | Typical Cost |
|---|---|
| Minor cleanup | From $350 |
| Typical repairs | $1,200 – $5,000 |
| Severe damage | $50,000+ |
| Basement repairs | $2,000 – $85,000 |
| Kitchen/living areas | $1,500 – $8,000 |
| Bathrooms/laundry | $500 – $5,500 |
| Waterproofing | $3,000 – $7,000 |
| Leak detection | $500 – $1,500 |
Emergency services, mold remediation, and contaminated (“black”) water cleanups significantly raise overall costs. Immediate action reduces expense and environmental impact, while preventive measures like waterproofing (costing $3,000 to $7,000) or leak-detection systems (costing $500 to $1,500) help avoid future loss.