Flash floods are often initiated by heavy rain or debris blocking a waterway and cause a rapid rise of water over low-lying areas. Flooding can occur miles from the site of the initial rainfall.

Although April showers have come and gone this year, the risk of flooded roadways has not evaporated. There is no “season” for flash floods, and a flooded roadway can occur with as little as 3 to 4 inches of water in a particular location, according to Jarred Thomas, Williamson County Emergency Management coordinator. Williamson County is experiencing an elevated flood risk because of recent rainfall, Thomas said, and­—unlike in dry times— it will not take as much water to flood an area.

Known flood risks and low water crossings

The city of Austin Flood Early Warning System team monitors weather and road conditions and maintains a listing of roadways susceptible to flooding. This map depicts low water crossings but is not comprehensive.

Risks of a flooded roadway

6 inches of water
Six inches of fast-moving floodwater can knock over an adult.
Water may be moving more rapidly than it appears.
Tires can lose traction.

12 inches of water
One foot of rushing floodwater can sweep away a small car.
Tires can act as flotation devices, lifting vehicles.
Water may rise even higher in the time it takes to cross a flooded road section.

24 inches of water
Most vehicles, including trucks and SUVs, are at risk of being carried away.
Water may hide potholes or gouged roadbeds and may be deeper than it appears.
It is often more difficult to judge water depth at night.

Flash flood safety tips

• Do not drive during heavy rainfall.
• Check www.atxfloods.com to see if any roads have already been flooded.
• Be alert for water covering the road.
• Do not attempt to cross flooded roadways.
• Avoid known low water crossings.
• Stay away from creeks and drainage infrastructure during rainfall.
• During stormy weather, do not park along streams.