Floods and Flash Floods: #COwx

Today’s Severe Weather Awareness Week Topic is on Flood & Flash Flood Safety

In Colorado, there are two distinct types of flooding.

The first type occurs when the snow begins to melt in the high country and rivers begin to rise. Flooding along rivers and streams can occur with a very rapid snow melt, or from thunderstorm rains combining with the runoff from melting snow.

The second type of flooding, flash flooding, refers to a dangerous sudden rise in water along a creek, wash, river, or over a normally dry land area. Flash floods result from heavy rainfall, sudden breaks in river ice jams, and dam or levee failures. Flash floods can occur within a few minutes or hours, and can move at surprisingly high speeds, striking with little warning. Flash floods are quite destructive because of the force of the moving water, and the debris that accumulates in flood waters, such as trees and boulders, which can destroy roadways, bridges and buildings.

In recent years we have seen serious flooding when heavy rain falls on recently burned areas. Residents in and near burned areas should plan ahead on response actions for flooding.

Hazardous Weather Outlooks

The National Weather Service will discuss flood and flash flood potential in daily Hazardous Weather Outlooks and in the “Weather Story” on National Weather Service websites.

On days with a high threat for flooding you may hear:
  • a flash flood or flood watch, which means that flash flooding or flooding is possible within the watch area.
  • a flood warning, which means that flooding is imminent or has been reported along a river. 
  • a flash flood warning, which means that flash flooding has been reported or is imminent. When a flash flood warning is issued for your area, act quickly. If advised to evacuate, do so immediately. Go to higher ground or climb to safety before access is cut off by flood waters.

An Urban Flood Advisory will be issued for impact flooding that is not in itself life threatening. In an urban area if you were commuting during rush hour during a Flood Advisory you could expect some intersections to be underwater and a much longer commute. A Small Stream Flood Advisory might be issued when flows are at bank-full with minor lowland flooding along the stream.

Flood SafetyInformation

Nearly half of all flash flood fatalities are vehicle related. Do not enter a flooded roadway. Instead, “Turn Around, Don’t Drown”. In rapidly rising waters, backing up away from water may be safer. One to two feet of water will carry away most vehicles. Additionally, roads inundated by water may be damaged or washed out with no way for you to see that the road is impassable.

Colorado’s Severe Weather Awareness Week continues through Saturday.

...on Sunday............Introduction
...on Monday……...Watches and Warnings
...on Tuesday……..Tornadoes and Tornado Safety
...on Wednesday...Flood and Flash Flood Safety
...on Thursday…....Downburst Wind and Hail
...on Friday………...Lightning and Lightning Safety
...on Saturday…......Severe Weather Awareness Week in Review

This blog provided by the Colorado Forecast Offices of  the National Weather Service.