What to do during a flood, and how dangerous is a tsunami?
What is a flood?
- During a flood, large amounts of water reach places where it normally wouldn't. Flooding can occur with either freshwater or saltwater.
- Freshwater floods can occur when rivers, canals, or lakes overflow their banks, for example, due to heavy rainfall or a rapid increase in the amount of meltwater.
- When a dam breaks a flood wave can occur, it's like a wall of water running down the mountain or river with a devastating power.
- Seawater floods occur primarily during storms and hurricanes, where winds push seawater further and further inland, inundating coastal areas. Backwater impoundment can also cause river deltas to flood.
- Large waves during high tide combined with a severe storm is called a storm surge. The combination of spring tide or even king tide with a storm can create the worst storm surges.
- Climate change and the resulting sea level rise increase the risk of flooding from oceans and seas. Slow land subsidence, often due to mismanagement of groundwater, also increases the number of localized floods.
What is a rogue wave or monster wave?
- A rogue wave is an exceptionally high wave of water. This natural phenomenon occurs when several factors come together by chance and form several small waves into one large wave.
- True rogue waves are seldom and mostly occur at open ocean, but also near the coast a sudden extra large wave can occur, sometimes called tidal wave or sneaker wave.
What is a tsunami?
- A tsunami is a special and relatively rare cause of flooding.
- A tsunami is created when an earthquake, landslide, or volcanic eruption occurs beneath the sea.
- A tsunami wave doesn't behave like a normal wave that overturns or rolls onto the coast. A tsunami that comes ashore is more like a very sudden spring tide and is much more destructive than the waves that wind can cause.
- The tsunami wave that hit Southeast Asia in 2004 was 30 meters high in some places.
What should you do to avoid being hit by a flood or tsunami?
- Check beforehand whether your destination has an official website with reliable information about natural disasters such as floods and tsunamis.
- Check the following questions:
- Are floods or tsunamis common in the country or region?
- During which months are floods most likely?
- What are the areas most frequently and severely affected?
How can you prepare for a flood?
- Know your surroundings: where is the water, where does it come from, and where does it flow towards?
- If there is a risk of flooding, pitch your tent or camper on a higher part of the campsite.
- Stay informed about the (local) weather forecast (radio/TV/internet).
- If you live in a flood-prone area, move electrical appliances to safe, elevated areas in a timely manner.
What should you do during a flood?
- Seek higher ground. Don't look for spectacular images: that impressively churning river can suddenly erode banks and bridges under the pressure of the water.
- When the water approaches your home: turn off the main switch to prevent damage from short circuits and fire.
- Once your basement or parking garage starts flooding, don't try to move your belongings. Especially below street level, such a space can suddenly fill up very quickly.
- Avoid travel, especially on roads leading to or along the river or sea.
What should you do after a tsunami warning?
- Seek higher ground. In areas with tsunami experience, there are often signs with escape routes.
- Before a tsunami hits the coast, you can often see the seawater suddenly receding; this is the final warning and a sign to run. Between the receding water and the tsunami wave, you have anywhere from a few seconds to a few minutes before the wave arrives.
- A tsunami can continue for hours, and the first wave isn't the highest. Don't turn back too quickly and keep escaping until you're high enough for disaster scenarios.
- If you hear a growl or roar from the sea after an earthquake, or see the water receding, don't wait for an official alarm; start your ascent.
