Skip to main content

You are here

Coastal Hazards

Coastal Hazards

Floods and Tsunamis

Floods

Floods are a common hazard in Oregon. The damaging effects of a flood can be local or regional in scale and often result in the loss of land, property, and in some cases life (DLCD, 2000). Some floods develop over time, while others can occur within minutes. In Oregon, flooding is often associated with other hazards such as landslides.

Federal, State, and local laws are in place to protect these assets. However, you should be aware that flooding can occur no matter where you live. Those living in low-lying areas, near water or downstream from a dam are more likely to experience flooding events. Man-made barriers such as levees are also sources of concern. Breaches in these structures can lead to flash flooding.

Oregon's largest recorded flood occurred in December 1964 on many rivers in western and north-central Oregon (although the 1894 flood was larger on the Columbia River). The February 1996 flood in western Oregon was potentially as big as the 1964 flood, but more flood control dams were in place in 1996.

Information on flooding hazards in Oregon is available through the Oregon Department of Land Conservation and Development (DLCD) website. National flood information is available through the FEMA website.

Tsunamis

Animation of hypothetical Tsunami along the Pacific Northwest Coast modeled by USGS

Animation of hypothetical Tsunami along the
Pacific Northwest Coast (modeled by USGS)

Tsunamis are "a series of long-period waves (on the order of tens of minutes) that are usually generated by an impulsive disturbance that displaces massive amounts of water, such as an earthquake occurring on or near the sea floor. Large tsunami have been known to rise to over 100 feet! The amount of water and energy contained in tsunami can have devastating effects on coastal areas." (NOAA National Weather Service Glossary)

"Tsunamis rank as one of the most dangerous natural disasters that could affect the Oregon coast. Although not frequent in occurrence, the damage caused by these catastrophic events is immediate and life threatening. The most destructive type of tsunami would be generated locally by a Cascadia subduction zone earthquake of magnitude of 8.0 to 9.0, or greater. Devastating tsunamis waves would be expected to arrive along the Pacific Northwest coast including Oregon within 5 to 30 minutes after such an event, providing very little evacuation time."
(Oregon Coastal Atlas)

Sources

Department of Land Conservation and Planning (DLCD) (2000). "Planning for Natural Hazards." Natural Hazard Technical Resource Guide, Chapter 4. [Accessed June 18, 2009]

NOAA National Weather Service. National Weather Service Weather Glossary. [Accessed June 20, 2009]

Oregon Coastal Atlas. Tsunami Hazards. [Accessed June 30, 2009]