Storm surge and evacuation in urban areas during the peak of a storm Hiroshi Takagi a, ⁎, Siyang Li a , Mario de Leon b , Miguel Esteban c , Takahito Mikami d , Ryo Matsumaru e , Tomoya Shibayama d , Ryota Nakamura d a Tokyo Institute of Technology, Graduate School of Science and Engineering, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan b De La Salle University, Civil Engineering Department, 2401 Taft Avenue, Manila 1004, Philippines c The University of Tokyo, Graduate School of Frontier Sciences, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan d Waseda University, Department of Civil and Environmental Engineering, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan e Toyo University, Faculty of Regional Development Studies, 5-28-20 Hakusan, Bunkyo-ku, Tokyo 112-8606, Japan abstract article info Article history: Received 4 April 2015 Received in revised form 22 October 2015 Accepted 2 November 2015 Available online xxxx The present paper examines the impact of floodwater caused by the storm surge brought about by Typhoon Haiyan in 2013, focusing on downtown Tacloban in Leyte Island, the Philippines. A reliable numerical model for predicting such flooding was developed by calibrating the results of field investigations, including footage from a video clip taken during the storm surge. The simulation reveals that flow velocities along the streets in downtown Tacloban reached up to 7 m/s due to flow contraction along the high-density blocks of houses, and how water levels reached their peak in just 10 min. According to the depth–velocity product criteria, often used for evaluating the vulnerability of people and buildings to floodwaters, only 8% of the length of streets in downtown Tacloban were within the safe limits that allow pedestrian evacuation. Based on these findings, the present research concludes that pedestrian evacuation in the middle of a storm surge generated by a strong ty- phoon is a high-risk behavior. Thus, clearly and objectively, evacuation during this time should not be encouraged, even when seawater intrudes the houses of local residents. In this respect, it would appear imperative that prior to the arrival of the typhoon all residents should evacuate areas at risk of being flooded. Though the flood height was significant in the downtown area, the damage to these houses was limited. If it was not possible for some reason to evacuate prior to the arrival of the typhoon, those in solid houses should first consider vertical evacu- ation and the possibility that they could survive in their place, rather than courageously evacuating in an unpre- dictable water flow. © 2015 Elsevier B.V. All rights reserved. Keywords: Typhoon Haiyan (Yolanda) Tacloban Storm surge Pedestrian evacuation Numerical simulation Depth–velocity product 1. Introduction Typhoon Haiyan (Yolanda, according to its local name) struck the Philippines on November 8, 2013, causing enormous damage to Leyte, Samar and many other islands. 6245 individuals were reported dead, 28,626 were injured and 1039 are still missing (NDRRMC, as of 6 March 2014). Such a large death toll was caused not only by the large size of the storm surge, but also due to issues related to the level of knowledge and awareness by local residents on what is a “storm surge” (Esteban et al., 2014, 2015). Indeed, despite the fact that two his- torical storm surges had previously devastated Tacloban, one in 1897 killing up to 1500 and another in 1912 killing 15,000 (Lagmay et al., 2015), local awareness about such events was non-existent (Esteban et al., 2014). The total economic loss associated with infrastructure and agriculture was estimated to be around 34,366 million pesos (776 million USD), possibly the most expensive natural disaster in the history of the country (TIME, 2013). Haiyan was one of the strongest typhoons known to have ever made landfall, not only in the Philippines but the entire world (Lin et al., 2014; Schiermeier, 2013). The forward speed of the typhoon, reaching around 41 km/h at landfall, was also unusual among other events of comparable intensity during the past 6 decades in the Western North Pacific(Takagi et al., 2015a). Haiyan can be characterized as both the fastest moving and strongest typhoon measured in the Philippines. The return period for a Haiyan-class typhoon to make landfall was estimated to be 200 years (Takagi and Esteban, 2015). As a result of its strong intensity, the typhoon caused a massive storm surge in many islands in the Philippines. The storm surge inundated most of the coastline of Leyte Gulf, causing particularly large damage to Tacloban City, the biggest city in Leyte Island. A maximum inundation height of up to 6–7 m was observed in this city, where the largest number of casualties took place (Mas et al., 2014; Shibayama et al., 2014; Takagi et al., 2015a; Coastal Engineering 108 (2016) 1–9 ⁎ Corresponding author at: 2-12-1-S6-212 Ookayama, Meguro-ku, Tokyo 152-8550, Japan. E-mail addresses: takagi@ide.titech.ac.jp (H. Takagi), lsyiverson0510@gmail.com (S. Li), mario.deleon@dlsu.edu.ph (M. de Leon), esteban.fagan@gmail.com (M. Esteban), takahito8765@gmail.com (T. Mikami), matsumaru@toyo.jp (R. Matsumaru), shibayama@waseda.jp (T. Shibayama), ryota_nakamura617@yahoo.co.jp (R. Nakamura). http://dx.doi.org/10.1016/j.coastaleng.2015.11.002 0378-3839/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Coastal Engineering journal homepage: www.elsevier.com/locate/coastaleng