Ryo Matsumaru

Classification of Tsunami and Evacuation Areas

On March 11, 2011, a large earthquake that occurred offshore the north-east coast of Japan generated a large tsunami which devastated extensive areas of the Tohoku coastline. Despite Japan being considered a country well prepared for these types of disasters, large casualties were recorded, with numerous discussions amongst the Japanese coastal engineering community ensuing. As a result, two different levels of tsunamis have been proposed and now recognized in Japan, depending on the frequency of such extreme events. The idea that hard measures can protect the lives of inhabitants of coastal areas has been abandoned, and these measures are only considered to be effective in protecting properties against the more frequent but lower magnitude events. Soft measures should always be used to protect against the loss of lives, and to this respect, the authors of the paper propose the introduction of a Classification of Evacuation Areas, to show which of these should be prioritized by residents as they seek to evacuate.

Track analysis, simulation, and field survey of the 2013 Typhoon Haiyan storm surge

The authors have examined the characteristics of Typhoon Haiyan (Yolanda), which made landfall on the coast of the Philippines on November 2013, generating a substantial storm surge. In order to better understand the storm surge phenomenon, its nature and severity were analysed by means of a numerical simulation and a field survey. Unlike most other tropical cyclones that weaken before they hit land, Haiyan struck Leyte Island at near peak strength, with maximum sustained wind speeds of 160 knots, the strongest in the recorded history of the Western North Pacific. Haiyan approached very quickly with a forward speed of 41 km/h towards Leyte, which was also the fastest among typhoons with similar intensities. As a result of these extreme gusts and the exceptionally low central pressure of the typhoon (895 hPa), Haiyan caused the largest storm surge in the recorded history of the Philippines. Numerical simulations show that the maximum storm surges occurred in Leyte Island and Samar Island. A storm surge field survey conducted by the authors corroborated this, with maximum inundation height of 7 m recorded in Tacloban, located at the northern end of Leyte Gulf. The simulation results also corroborate the fact that water levels at some locations first lowered and then rapidly began to increase after an hour.

Storm Surge Heights and Damage Caused by the 2013 Typhoon Haiyan Along the Leyte Gulf Coast

Typhoon Haiyan (Yolanda) struck the islands of Leyte and Samar, the central part of the Philippines, on 8 November 2013, bringing large-scale devastation to coastal areas due to the high winds and large storm surge and waves associated with it. In order to obtain the distribution of storm surge heights and damage covering the wide stretch of affected coastline, the authors carried out a series of field surveys in the aftermath of the typhoon (in December 2013, May 2014, and October 2014). In the present paper, the authors detailed the results of these field surveys and summarized the characteristics of the storm surge and main causes of the damage, especially focusing on the Leyte Gulf coast, which is surrounded by the eastern coast of Leyte and the southern coast of Samar. Finally, the wide range of types of storm surge disasters were also discussed by comparing Typhoon Haiyan with other recent major events.

Storm Surge Awareness in the Philippines Prior to Typhoon Haiyan: A Comparative Analysis with Tsunami Awareness in Recent Times

Category 5 Typhoon Haiyan was one of the strongest typhoons to hit the Philippines in modern times, and introduced the term “storm surge” to the vocabulary of many local residents, who had not heard about such phenomena prior to this event. The storm surge manifested itself on the 8th November 2013 as Haiyan made landfall, devastating large areas in the islands of Leyte and Samar. To attempt to gain an understanding of the level of awareness that local residents had about storm surges the authors conducted structured questionnaires (n = 172) and focus group interviews with local residents, and discussed the results obtained with key informants (government officers and disaster risk managers). One of the key problems identified during the interviews was how people were not able to clearly understand the concept of a storm surge, with many respondents emphasizing how it would have been better for authorities to describe it as a “tsunami”. A discussion is also made on the recent evolution in world-wide coastal disaster awareness, comparing it to recent developments in storm surge awareness in the Philippines and other countries in the area, such as Vietnam and Japan. The authors conclude that, in terms of its influence on worldwide disaster awareness, typhoon Haiyan constitutes an event of similar importance to major recent high-impact tsunami events such as the 2004 Indian Ocean and 2011 Tohoku events. As a result, the authors will outline a number of lessons learnt from Haiyan, such as the necessity for creating multi-layer safety strategies and improving how information about storm surges is transmitted to local residents.

Reconstruction from the Indian Ocean Tsunami Disaster: Case Study of Indonesia and Sri Lanka and the Philosophy of “Build Back Better”

The Indian Ocean Tsunami Disaster was one of the most catastrophic events ever recorded and Indonesia and Sri Lanka were the most affected countries. After the tsunami both countries have made great efforts in terms of disaster response, relief, rehabilitation and reconstruction. However, as each country exhibited different damage patterns, and given the social and economic characteristics intrinsic to each of them, different reconstruction paths were chosen in each case. Nevertheless, the process of reconstruction after a large-scale disaster is often considered an opportunity to create a safer society, especially for developing countries. In this chapter the reconstruction process, in terms of urban reconstruction, housing relocation and organizational rearrangement for disaster risk management after the disaster in Indonesia and Sri Lanka will be compared from the point of view of a “Build Back Better” philosophy. As a conclusion: (1) a strong intention to build stronger and more resilient settlements and societies could be observed in the reconstruction process of both countries, even beyond the disaster-affected area and (2) there are trade-offs and dilemmas between the speed in reconstruction, in this case rapid housing reconstruction and the creation of safe areas, and between the rapid revival of livelihoods and the creation of safe areas, especially where primary sector industries are dominant. Such trade-offs have frequently been observed in disaster reconstruction and they can complicate the reconstruction process. To minimize the negative impact of the trade-offs, strong leadership by the government is required to enforce the reconstruction policy, regulations and measures. It is clear that prolonged reconstruction processes will negatively impact the to recovery of economic and social activities. Therefore, in order to minimize such disruption it is important that for areas where future disasters are anticipated pre-disaster recovery planning, basically to plan for reconstruction before a disaster actually hits, should be undertaken as a preparedness measure.

Implicaciones del tsunami de Tohoku del año 2011 para la gestión de desastres naturales en Japón

El 11 de Marzo del 2011 un terremoto de magnitud 9.0 en la escala Richter genero un devastador tsunami que arraso una extensa area de la costa noreste de Japon. El Gran Terremoto y Tsunami del Este ha sido descrito como un evento que solo sucede una vez cada varios miles de anos aproximadamente, y como consecuencia de este es necesario que la filosofia sobre Gestion de Desastres Naturales en Japon sea revisada para tener en cuenta varias lecciones aprendidas a raiz de este desastre. En este articulo los auotres presentan los resultados de investigaciones de terreno en el area de Tohoku. Se detalla el dano en varias localidades y se analizan los mecanismos de dano sobre diversos tipos de estructuras. Los autores tambien presentan una serie de cambios que estan ocurriendo en la filosofia de gestion de riesgos en Japon. Esencialmente, la idea que solo los metodos de infraestructura fisica son siempre capaces de proteger las vidas de la poblacion local ha sido descartada, y aunque se mantiene la idea de que estos metodos pueden resultar utiles para la proteccion de las propiedades, en ultima instancia los metodos de planificacion deberian formar la pieza mas importante del sistema de medidas para la proteccion de las vidas de las personas en estas areas.