Emergency alert system
Warnings, Watches and Advisories are issued by the National Weather Service (NOAA) and can alert communities to hazardous weather. You can get forecast, advisories and warnings from the National Weather Service on local radio and television stations or the National Weather Service Web site at www.wrh.noaa.gov/Portland. NOAA Weather Radio broadcasts forecasts and warnings 24 hours a day.
Clark Regional Emergency Services Agency issues warnings in our area. Familiarize yourself with their warning methods at www.cresa911.org/demwarning.htm.
River levels for our area may be monitored on the National Weather Service Web site at www.ahps2.wrh.noaa.gov/ahps2/index.php?wfo=pqr.
Flood warning terms
The following are a few important definitions for understanding flood warnings, watches and advisories.
Warnings are issued if hazardous weather is occurring, imminent, or has a very high probability of occurrence. Flood warnings are issued when a river is expected to reach or exceed flood stage. Warnings are issued for weather conditions that threaten life and property. Warnings may be extended in time or area coverage or canceled.
Watches are issued if conditions are favorable for the development of hazardous weather. Flood watches are issued 12 to 72 hours before an event where conditions may lead to flooding and hazardous weather. In other words, the risk for dangerous weather has increased significantly, but its location and timing are still uncertain. Due to this uncertainty, watches cover general areas. A watch may be upgraded to a warning, downgraded to an advisory or canceled.
Advisories are issued for less serious weather conditions that cause inconvenience, but life and property are usually not at risk if caution is exercised.
More useful definitions
Danger Zones: Floods and flash floods occur within many areas. Communities particularly at risk are those located in low-lying areas, near water, or downstream from a dam. Flood conditions result in heavy rains falling over a region for some duration of time sometimes combined with snowmelt.
Flash floods: result of intense storms dropping large amounts of rain within a brief period. Flash floods occur with little or no warning and can reach full peak in only a few minutes.
Mitigation: any activities that prevent or reduce the chance of emergencies or lessen the damage caused by unavoidable emergencies.
Bankfull: the point at which the river has reached the top of its bank. For some rivers this may not be well defined.
Crest: the point at which the river is at its greatest flow or height.
Flood Stage: the level at which the flood begins to create damage to property.
Flow: the volume of water flowing in the river measures in cubic feet per second.
