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Flash Floods

UNDERSTAND FLASH FLOODS

Flash floods are short-term events, occurring within 6 hours of the causative event (heavy rain, dam break, levee failure, rapid, snowmelt and ice jams) and often within 2 hours of the start of high intensity rainfall. A flash flood is characterized by a rapid stream rise with depths of water that can reach well above the banks of the creek.

In Boulder, flash floods are often the result of strong afternoon thunderstorms over the foothills during the summer months which produce short, but heavy rainfall.  Boulder may also experience flash flooding as a result of heavy rainstorms when combined with snowmelt run-off in the springtime.

All campus affiliates are encouraged to become familiar with the different notifications the National Weather Service will issue regarding the potential for flash flooding.

  • A flood advisory means that thunderstorms have produced heavy rainfall that may result in ponding of water on roadways and in low-lying areas, as well as rises in small stream levels, none of which pose an immediate threat to life and property.
     
  • A flash flood watch indicates that conditions are favorable for flash flooding. During a watch, normal campus activity should continue, but you should tune in to local media and monitor the situation. Be aware of your location relative to streams and creeks, Boulder Creek in particular. Be prepared to take immediate action if a warning is issued for your area.
     
  • A flash flood warning means that flooding is imminent or is already occurring. You may only have a few minutes to seek safety, so take immediate action by moving to higher ground on foot as soon as a warning is issued.

Flash floods can occur rain or shine. Understand the warning signs of a potential flash flood including; sudden, heavy rains, a sudden increase in creek level, or the creek water begins to become muddy or debris-filled

PREPARE FOR FLASH FLOODS

The main CU Boulder campus sits atop a hill out of the Boulder floodplain, and therefore out of the danger of flash flood waters. However, portions of East Campus and Family Housing are located within the floodplain. Those who work or reside in these areas should familiarize themselves with what safety actions they should take when a flash flood warning is issued. Whether you should shelter-in-place or evacuate depends on which campus building you are in on East Campus or in the Family Housing area.

Campus affiliates who are registered CU-Alert users will receive an e-mail or text message informing them of a flash flood warning affecting the campus. By registering for CU Alerts, you will receive quick notification when a flash flood warning is issued that affects the campus. During the emergency, updates will be sent out as appropriate, and an all-clear will be provided by University officials once the danger has passed. Sign up to receive alerts at www.colorado.edu/alerts

Outdoor warning sirens are located throughout the city of Boulder, and are used to inform residents that a flash flood is imminent or occurring.  The sirens are tested on the first Monday of every month between April and August.

Flash flood warnings will also announced by local media outlets such as radio, television, and internet news sites.


WHAT TO DO WHEN A FLASH FLOOD WARNING IS ISSUED

 If a flash flood warning is issued for the city of Boulder heed all instructions and stay away from areas where flooding is occurring.  Even if there is no other indication that a flash flood may be occurring, immediately take the following actions to protect yourself from harm when you receive notification of a flash flood warning.

If you are outdoors:

  • If you are outdoors and near a creek or stream when a warning is issued, climb to higher ground on foot immediately. Avoid drains, ditches, ravines, and culverts.
  • Do not attempt to outrun a flood in a vehicle—cars will float in as little as one foot of water. Over half of all flash flood fatalities occur in vehicles.
  • If your vehicle stalls or is surrounded by water, abandon it and move to higher ground on foot.
  • If you are unable to move to higher ground, seek shelter on the upper floors of a sturdy building.
  • Remain alert for instructions and updates as they become available from emergency personnel and University officials.

If you are indoors:

  • In campus buildings, follow your building’s instructions regarding evacuation/shelter-in-place for flash floods.
  • Move to the highest floor possible, or follow the flash flood procedures for the building you are in. Remain in a sheltered location until an all clear has been provided by public safety officials.
  • If you are in a main campus location, affiliates are encouraged not to leave campus until flooding has subsided and you have been told by public safety or University officials that it is safe to leave the area.

Other helpful information:

  • Use caution after a flash flood as risk of electrocution, dangerous debris, and other hazards may exist.
  • Use special caution at night because flood danger is more difficult to recognize.
  • In the event of a flash flood, or any other campus emergency, visit the CU-Boulder homepage for the most accurate, up-to-date information.
  • Check the Boulder County Office of Emergency Management website for up-to-date emergency information regarding the larger Boulder community at www.boulderoem.com.