Monday, June 20, 2005

Tsunamis and Rivers

When the recent earthquake rang out from the ocean offshore of California, my first question to my husband was, "What is the effect on the river is there is a tsunami?" Since we live and I work next to the Columbia River between Washington and Oregon in the heart of the Columbia River Gorge, I thought the question was a legitamate one. My husband, however, found the question ridiculous. "We live too far up the river," he said. "And the water would need to make it past the dam." (He is referring to the Bonneville Dam.) He scoffed at me for asking such a question.

But I didn't think his dismissal was valid, so I went in search of the truth. Click this link to read what I learned, first of all, about tsunamis from the University of Wollongong, School of Earth and Environmental Sciences.

What I found most interesting was this passage: "Tsunami treat rivers exactly like long harbours. When a tsunami gets into a tidal river or estuary where water depths can still be tens of meters deep, the wave can travel easily up the river to the tidal limits or beyond. Along some coasts, tide limits may be tens of kilometers upriver, and residents living along the riverbanks may be totally unaware that a threat from tsunami exists. If the river is deep and can allow the penetration of the wave upstream, the height of a long wave can rapidly amplify where depths shoal or the river narrows. At these locations water can spill over levees and banks, flooding any lowlying topography. NOAA is likewise aware of these facts and in its publication Tsunami! The Great Waves warns, "Stay away from rivers and streams that lead to the ocean as you would stay away from the beach and ocean if there is a tsunami."

For clarification, NOAA is the National Oceanic and Atmospheric Administration. I think they would definitely know the results of tsunamis on rivers. Therefore, I will take it that the Columbia River could be affected by a tsunami.

I presented my findings to my husband. Although I must admit that the wave would probably not make it past the Bonneville Dam, there still could be some repercussions felt. Our home is 200 hundred feet above the river, so I think we would be safe there. However, I work right next to the river. Without knowing what could happen at the dam, I would not want to stay at the office. Call me chicken, but it is better to be safe than sorry...or worse.


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