Flash Flood Alerts: Understanding Warnings, Emergencies, and Safety Protocols

A flash flood is a sudden, violent flood after a heavy rain, or occasionally after a dam break. A flash flood warning (SAME code: FFW) is a severe weather warning product of the National Weather Service that is issued by national weather forecasting agencies throughout the world to alert the public that a flash flood is imminent or occurring in the warned area. Rainfall intensity and duration, topography, soil conditions, and ground cover contribute to flash flooding. Most flash floods occur when there is a heavy amount of precipitation falling in an area and that water is then channeled through streams or narrow gullies. Flash floods may take minutes or hours to develop, and it is possible to experience a flash flood without witnessing any rain.

Types of Flash Flood Alerts

There are two types of alerts for flash floods which are issued by the National Weather Service. One is a flash flood watch, which means that conditions are favorable for flash flooding, and the other is a flash flood warning, meaning that a flash flood is occurring or one will occur imminently. In addition, there is an enhanced version of flash flood warning, referred to as a flash flood emergency, which indicates a severe flooding situation, often, but not always in densely populated areas, similar to the procedure for declaring a tornado emergency.

Criteria for a Flash Flood Emergency

According to the National Weather Service, examples of situations that warrant the inclusion of flash flood emergency language in flash flood warnings may include:

• Emergency manager(s) of the affected county(ies) or the state emergency management association declare a state of emergency and have confirmed that rapidly rising floodwaters are placing or will place people in life-threatening situations.
• Water has rapidly risen or will rapidly rise to levels where people who are ordinarily in safe locations during previous flash flood events are now placed in life-threatening situations.
• Multiple swift water rescue teams have been or are being deployed in response to flash flooding of an exceptional magnitude.
• Stream gages, where available, indicate floodwaters have risen rapidly to at least major levels, or if gages are not available, floodwaters have risen to levels rarely, if ever, seen.
• Total failure of a major high hazard dam that would have a catastrophic impact on the downstream communities.

The Dangers of Moving Water

Flash floods can unfold in moments and wreak havoc. Surprisingly small amounts moving water can sweep you or your vehicle away. In the desert, flash floods can roar through dry river beds miles away from where the heavy rain is falling, making them incredibly dangerous. These floods are sudden and fierce, with rapidly rising water that can cause severe damage and trigger mudslides.

Preparation and Immediate Actions

Since preparation can be critical and life-saving, residents are usually urged to be aware of any signs of heavy rain and move to higher ground if rapidly rising water is seen or heard. It is NEVER safe to drive or walk into flood waters, as noted in the famous Turn Around Don't Drown® safety message.

Before a Flood Hits

• Create a communication plan: Have a specific person to contact to update your status or a safe location to meet up with loved ones.
• Prepare for an emergency: Have enough water, food and medicine to last at least three days. Supplies like batteries, blankets, flashlights, and a first aid kit will also be helpful.
• Know your risk: Research and understand the fastest way to get to higher ground and how flash floods might affect your area.
• Prepare your home: If your home has a sump pump, make sure it is working and consider having a backup. Make sure all electronic devices are charged.

Actions During a Flood

• Get to higher ground, especially if you live in a flood-prone or low-lying area.
• Obey evacuation orders immediately. Lock your home and disconnect utilities and appliances if you have time.
• Practice electrical safety. Stay out of water that may have electricity in it, especially if you see sparks or hear crackling or buzzing noises.
• Avoid floodwaters. Do not walk or drive through floodwaters.