Remember the story of the young boy who saved several people during the 2004 tsunami in Thailand because he knew that the sudden and extreme withdrawal of water of the sea, exposing the ocean floor and reefs, was a natural warning sign for a tsunami?
Bali is located very close to the collision zone between the Indian-Australian Plate and the Eurasian Plate. Being aware of the Tsunami Early Warning System (TEWS) and knowing what to do in case of such warning could save your life. In this region it is expected that tsunami waves will only need 20 to 60 minutes to reach the coast. Hence warning time is very short and time remains the most critical factor when defining procedures for early warning and evacuation. Let’s think about how to react and have plans ready for evacuation and emergency response.
Harald Spahn is an expert in the field of natural disaster management whose passion is to explore nature, hiking volcanoes and diving. German by nationality but cosmopolitan at heart, he is a geologist who has been working for 17 years in international cooperation as technical advisor for environmental and natural resources management. Since 2001 his experience and expertise have led him to work on the reconstruction planning following Hurricane Mitch in Nicaragua, the disaster risk reduction project regarding El Niño and earthquake hazard in Peru. For the last three years he has been the team leader of a German-Indonesian project for a Tsunami Early Warning System in Indonesia working closely with the public sector, civil society organizations like IDEP, the Indonesian Red Cross and the private sector (tourism sector).
Mr Spahn explains that the southern coast of Bali is threatened by tsunamis from the subduction zone. As these areas are low-lying and highly populated they are at highest risk. Tsunami waves can also hit the north coast as part of the back arc source area. Submarine landslides and volcanic activity are also potential causes of tsunamis. Fortunately, not all earthquakes in the collision zone of the tectonic plates cause tsunamis. Whether on land or under the sea, an earthquake has the potential to trigger a tsunami only if its magnitude is higher then 7.0 and if its depth is less than 70-100 km. In Bali, earthquakes frequently occur and the island has experienced several strong earthquakes (M≥ 6 RS) in the past (1976, 1979, 1984 and 2004). As a general rule ground shaking should be treated as the first warning sign! However, since it is not possible to deduce earthquake magnitude and location from ground shaking alone, a high level of uncertainty is involved and this is why the Tsunami Early Warning System is vital.
The Indonesian Tsunami Early Warning System InaTEWS
The need to establish tsunami early warning in the Indian Ocean was one of the major conclusions of an International Conference organized by ASEAN in Jakarta in January 2005 when experts analyzed the aftermath of the Aceh Tsunami. One year later, Indonesia established its own National Tsunami Early Warning System (InaTEWS). As Indonesia is part of the Pacific Ring of Fire, the system covers tsunami sources from the Pacific as well. The system was officially inaugurated in November 2008 by the Indonesian President. Warning services are now provided by the National Tsunami Warning Center (NTWC), operated by BMKG (Badan Meteorology dan Geofisika) in Jakarta. It provides tsunami warnings within 5 minutes after the occurrence of an earthquake and disseminates warning messages to Interface Institutions, including Public Media and Local Governments.
In Bali, warnings will be announced by sirens: six sirens are located on the shorelines of southern Bali (see map). In case of a tsunami warning the siren will sound for 3 minutes continuously. Every 26th of each month at 10:00 am the sirens are tested. From previous disasters we know that hand phone networks, SMS services and electricity are very likely to fail in the wake of a strong earthquake.
Warnings are also broadcasted as breaking news on national television channels such as Metro TV, ANTV, INDOSIAR and GLOBALTV. They will be announced on Balinese radio stations such as RRI. On the Internet warnings and earthquake information can be obtained on www.bmg.go.id
The BHA (Bali Hotel Association) also gives warning and guidance to hotel guests through the hotel managements and operates its own tsunami early warning dissemination system from Kuta’s Hard Rock Hotel. BHA receives earthquake and tsunami information directly from the National Tsunami Warning Center at BMKG via a computerized information system and uses a customized interpretation and decision making tool to forward Bali specific tsunami warnings. The average processing time from the reception of the BMKG data to the dissemination of BHA tsunami warning SMS is about 5 minutes. The dissemination system can be used for multiple purposes. After the last Jakarta bombings it was utilized to inform and coordinate BHA hotels just minutes after the first explosion.
What should you do if you feel strong ground shaking or hear a tsunami warning?
Stay away from bodies of water. If you are at the beach or near the ocean, move immediately inland or to higher ground. Do not wait for a tsunami warning to be issued. Stay away from rivers and streams that lead to the ocean due to strong tsunami wave action and currents. The best strategy is to have a “personal evacuation plan” ready. Find out whether you are living or staying in a tsunami hazard zone (close to the coast) and where to go. If you are and you hear a tsunami warning, you and your family should evacuate your house. Walk in an orderly, calm manner away from the coast. Support children and elderly people as they are most vulnerable once a tsunami strikes. Follow the advice of local emergency authorities. Finally, remember that a tsunami is more than one wave. Do not return until authorities say it is safe.
If you are caught by surprise: don’t panic. Don’t waste time to pick up belongings.
If your children are attending a school in the hazard zone, it is not recommended to pick them up, as the short warning time won’t allow you to do so. But make sure, long before anything happens, that the school has procedures in place to take care of the children. Then they should follow the advice of teachers and other school officials.
Never go down to the shore to watch a tsunami. When you can see the wave, you are too close to outrun it. Most tsunamis are like flash floods full of debris. Tsunami waves typically do not curl and break, so don’t even think about trying to surf a tsunami.
Where to go?
Since the Aceh tsunami, with inundation areas as far as 4 km inland, many areas which before were believed to be safe cannot be considered secure anymore. Nevertheless reliable historical records of tsunamis in Indonesia show that, except for the Aceh tsunami, maximum inundation never exceeded 500 m inland from the coast. In Bali that means as far from the coast as the Bypass in Sanur (or McDonald) or Legian Street in Kuta. Secondly, experiences show that the more distant you are from the coast the better are your chances to survive. If you are unable to quickly move inland, high, multi-story, reinforced concrete buildings may provide a safe refuge on the third floor and above. Many of the big hotels in Bali are considered potential shelter buildings. Some of them already have assigned higher floors as tsunami assembly areas. Currently tsunami evacuation plans are under development for Kuta, Sanur and Tanjung Benoa. These plans will line out evacuation zones and provide references for evacuation routes and shelter areas. Once these plans are officially recognized by the local authorities, they will be published.
Although tsunami preparedness in Bali is still not yet on everybody’s agenda, there are some motivating initiatives for tsunami preparedness on the way or already implemented in Bali. A tsunami hazard map has already been developed, evacuation planning is ongoing and the Tsunami Early Warning System is making progress. Tsunami preparedness is also on the agenda of an increasing number of hotels in Bali. As residents or visitors you can significantly improve your safety. Get familiar with tsunami facts and natural warning signs. Determine if you live, work, play, or transit a coastal low lying area or tsunami hazard zone and if so, define evacuation procedures for you and your family.
Special thanks to Harald Spahn and Alexander Kesper, Advisor to the Indonesian Ministry of Culture and Tourism (BUDPAR), Security and Safety Executive of Bali Hotels Association (BHA).
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