There is a large threat to Knappa from an earthquake that will happen on the Juan de Fuca/ Pacific Plate fault. Some short time after the earthquake, a tsunami will come up the Columbia River and ruin the fishing industries of Knappa, as well as the lives of many. A tsunami is a large wave that is formed when a large earthquake happens. When a plate of the Earth snaps up to its original position, creating the earthquake, it will displace tons and tons of water. This water will cause a large wave, called a tsunami to form at the epicenter, the place where the earthquake originates. When the wave comes nearer to the shore, the front slows down, and the back of the wave catches up with the front. This creates a wave that can be over 100 feet high! Luckily, when the tsunami reaches 30 miles down the Columbia, it will be much smaller, from about 10 feet. The danger is that this tsunami can go all the way up the Columbia River, and hit Knappa completely unexpectedly. If you live in a float house, immediately after the earthquake, use any means to get to the dike and up the road to high ground.
Tsunamis can endanger human lives as well, so you need to be very careful. There are NO tsunami warning systems in the area, so you have to use your own wits to survive. You can learn more in the safety section. Liquefaction is when the soil and water come together, and this can cause dangerous conditions.