Tsunamis, Storm Surges and Floods

With almost 34,000 miles of tidal coastline and hundreds of rivers and streams, flooding is a serious threat in Alaska. Whether caused by distant earthquakes, hurricanes, snowmelt, spring ice jams or excessive rain, floods result in millions of dollars in damage as well as loss of property and life. Flooding may develop slowly or it may be sudden, like a catastrophic flash flood. Although you can’t always predict flooding, you can take steps to prevent or reduce its impact.

Basic emergency preparedness involves risk assessment, preventative measures and mitigation. Is your property in a flood zone? If you live near a river or stream or on land with a low elevation, then chances are you live in a flood zone. Government maps and information will assist you in making this determination. If you do live in a flood zone, consider purchasing flood insurance. Avoid building in a floodplain unless you elevate and reinforce your home, although even that may not be enough if the riverbanks erode up to and under your home, as is happening in parts of Alaska today. Rivers in Alaska are not static, and the changing dynamics of a current can alter a river’s course. Many rivers carry high glacial silt loads, and as this silt gets deposited in different areas, it can create new channels, eroding tons of material out of the riverbanks. Coastal erosion is also increasing as the climate warms and shore ice freezes later, allowing fall storms to batter the unprotected coastline.

Flooding can strike quickly, so it’s important to know how to evacuate and what to take. If flooding threatens your area, listen to the radio or television for weather and evacuation reports and follow the direction of local authorities. If you live in a remote location, you will be on your own and you must be prepared.

You may be able to build flood barriers or drainage devices or take other potential control measures. If your home is more than one level, you may want to have your main level above the ground and store valuable items there, with waterproof items and items of lesser value in the garage at or below ground level. It may also be advisable to raise utilities and furnaces, water heaters and similar equipment off the ground and add sewer line check valves to prevent floodwater from backing up into your house drains. Consider sealing lower-level interior floors with waterproofing materials.

If your property is within a mile of a coastline, additional concerns arise, particularly during a tsunami or other storm-related surges. Tsunamis, ocean waves caused by earthquakes and other disturbances, can be many feet high and cause significant damage. The National Oceanic and Atmospheric Administration (NOAA) is responsible for issuing tsunami warnings and alerts, often based on events thousands of miles away. If you experience an earthquake lasting more than 20 seconds or observe the coastal waters receding to an excessive distance, evacuate to higher ground. Evacuation routes are usually marked, but it is important to be aware of these routes ahead of emergencies. Check to see what procedures your community has in place for evacuation. Many communities already have emergency plans in place — make sure you know what yours is. If your community does not have a plan, you might want to help develop one. Check to see if your community has a Local Emergency Planning Committee (LEPC) and get involved.

Derylee Hecimovich, Extension Faculty, 4-H and Youth Development, and Valerie Barber, Extension Forest Resource Specialist