Should I return home after the first tsunami wave?

No, you should not return to your home or to low-lying coastal areas immediately after the first wave passes. A tsunami is not a single, isolated wave, but a series of successive waves resulting from a large and sudden displacement of ocean water [3]. A common and dangerous mistake is believing that the danger has passed once the first wave goes by; the first wave to reach the shore is not necessarily the largest or most destructive [3]. The series of waves, which flood the land, recede, and return to flood it again, may continue for several hours, with the time interval between each wave ranging from five minutes to two hours [3]. Consequently, the actual danger may persist for hours or even days, and you must remain outside the danger zone until local officials officially notify you that it is completely safe to return [4].

Nature of Tsunami Waves and Why the Danger Persists

A tsunami is one of the most destructive natural forces, and its waves propagate in all directions from the center of the underwater disturbance, which is often the result of powerful earthquakes, landslides, or volcanic eruptions [1]. In deep water, these waves can travel at speeds exceeding 500 miles per hour, roughly equivalent to the speed of a jet aircraft [3]. As they approach shallow water near land, their speed slows to about 20 or 30 miles per hour, but their height and current intensity increase dramatically and suddenly [3]. In extreme cases, they can strike land with waves reaching 100 feet or more in height, causing catastrophic flooding [1]. Given that the first wave may not be the last or the largest, assuming the disaster is over after the first wave recedes is a grave, life-threatening error [4].

Risks of Returning Early to Affected Areas

Returning to your home or the coastal area before an official all-clear announcement poses serious risks to your life. Drowning is the most common cause of death associated with tsunami disasters [1]. The powerful flow of water and the debris it carries can destroy buildings and vehicles and cause fatal injuries [3]. It takes only six inches of fast-moving water to knock an adult to the ground, and two feet of fast-moving water to sweep away most vehicles [3]. Furthermore, water returning to the sea can be just as dangerous, dragging people and debris along with it as it recedes [3]. After violent waves recede, the disaster leaves behind stagnant floodwater that can expose you to infectious diseases, chemical hazards, and physical injury [2].

Safety Procedures During and After the First Wave

When an event occurs and you receive an official warning or observe natural signs (such as the sea suddenly retreating and exposing the ocean floor), you must immediately move to high or inland ground [4]. Do not wait for instructions if you feel a strong earthquake while on the beach [4]. After reaching safety, it is recommended to adhere to the following medical and preventive instructions:

• Stay out of the tsunami danger zone or evacuation area until local officials tell you it is safe to return home [4].
• Do not drive in flooded areas; vehicles do not provide protection and can be swept away or stall in moving water [2].
• Avoid floodwater completely, as even shallow, fast-moving water can be lethal, and stagnant water poses a severe risk to young children [2].
• In the event of damage caused by the earthquake that triggered the tsunami, stay away from downed power lines and buildings and bridges from which heavy objects might fall during aftershocks [4].

It is essential to remain calm and limit non-emergency phone calls to keep lines open for emergency communications [4]. For more details on preparing for emergencies, you can visit the article Tsunami: Understanding the Phenomenon, Warning Signs, and How to Survive (Arabic).

Subsequent Health and Psychological Considerations

Once you are allowed to return and the recovery phase begins, you must protect your physical and mental health. Wear appropriate protective gear and follow safe cleaning guidelines to avoid diseases transmitted through water contaminated with sewage or chemicals [2]. It is very normal to feel stressed and anxious after surviving a natural disaster of this magnitude [1]. Getting help to cope with these emotions and connecting with family and community members is a necessary step to help you recover from the trauma properly [2].

Medical references

• Tsunamis
• Tsunamis and Your Safety
• About Tsunamis
• During a Tsunami