Coastal Engineering Journal

The extremely intense Typhoon Haiyan (local name Yolanda), struck the Philippines in November 2013, catastrophically impacting the region. It is important to understand the storm surge characteristics and occurrence probability of such super typhoons for reconstruction of the devastated area. This study mainly examines two topics. First, the characteristics of Typhoon Haiyan and its related storm surge were analyzed with a series of numerical experiments using an empirical typhoon model and storm surge model. The maximum surge height and inundation area were estimated and validated against measurements of tides and wind speeds obtained from local agencies NAMRIA and PAGASA, as well as against post-event surveys of maximum inundation heights. Based on the analysis of best hindcast results, the maximum storm surge level was about 5m at Tacloban on Leyte Island. Second, the return period of a Haiyan-like typhoon and associated storm surge was estimated with NOAA’s long-term observed IBTrACS typhoon dataset and a stochastic tropical cyclone model. Statistical analysis of typhoons around Tacloban was performed, and the estimated return period of storm surge levels seen during Typhoon Haiyan is 240–360 years.

This paper investigates the characteristics of coastal damages caused by Super Typhoon Haiyan with special focuses on dynamic behavior of storm surge and waves around San Pedro Bay. Numerical experiments were carried out to investigate the sensitivity of storm surge characteristics to various conditions, such as typhoon tracks, forward speed, and bottom frictions. Computed characteristics of storm surge and waves were compared to the observed inundation characteristics. Primary findings of the study are: (i) bay seiche elevated the peak surge height at the inner part of the bay; (ii) forward speed of Haiyan was close to the worst condition that enhances the bay seiche; (iii) neither storm waves nor storm surge could explain the observed inundation characteristics around the bay mouth, where the witnessed time of initial inundation was about 1h before the one at the inner part of the bay and the water level rapidly descended just after the peak while it remained for an hour at the inner part of the bay; and (iv) strong anti-clockwise circulating current was developed around the peak surge time and this current might have significant impact on wave dissipation and blocking around the San Pedro Bay mouth.

This paper investigates characteristics of coastal damage caused by Super Typhoon Haiyan with special focuses on locally varying wave deformations along the coast of Eastern Samar fronted by shallow fringing reef. The paper first summarized the field survey results and indicated that the erosion depth of the beach had negative correlation with the width of fringing reef along the straight coastline while a drastic variation of the damage levels was observed around Matarinao Bay mouth. A phase-resolved nonlinear dispersive wave model and a linear mild slope equation model were respectively applied for computations of wave deformations on the long-straight coastline with fringing reef and on the coast around Matarinao Bay. Computed rapid decay of waves on the reef reasonably explained observed negative correlations between erosion depth and the reef width. Around Matarinao Bay, on the other hand, wave refraction and diffraction played a significant role to explain wave concentration on the reef just outside of the bay mouth and also significant wave attenuation inside the bay mouth. Observed wave deformation characteristics were not sensitive to incident wave angles and periods and were reasonably consistent with the observed alongshore variation of maximum water levels and corresponding damages along the coast.

Boulders numbering in the high hundreds/low thousands, and with masses up to $\sim$30 tonnes, were transported onshore by Super Typhoon Haiyan in Calicoan Island, Philippines to maximum ground elevations that could exceed 9m and terminal positions up to $\sim$180m inland. One-dimensional Boussinesq hindcasts of coastal boulder motion showed intermittent transport initiated at the fronts of infragravity swash bores. Transport distances were found to be highly sensitive to wave-height, enough so that observations of terminal positions may be a viable method of estimating rough paleostorm magnitudes. The large accelerations at bore fronts generated significant inertial forces, particularly for larger boulders, but drag forces had greater root-mean-square magnitudes in all simulations. Widely used relations to infer fluid velocities from boulder properties were tested using modeled boulders — inferred velocities at modeled terminal boulder positions were compared to maximum computed Boussinesq fluid velocities at these locations and found to be significantly lower. This underprediction of inferred velocities was greatest for smaller boulders that were strongly mobile. Inferred drag loads compared to modeled values were somewhat more accurate for large boulders when a Froude number of unity was assumed to estimate flow depths. Although these boulders were unequivocally transported by storm waves, their large sizes and distances traveled venture into what has been considered the tsunami range. Thus, care must be taken to interpret the provenance of coastal boulder fields with unknown origin for lower to mid-latitude regions.

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.

A survey of 114 households residing in Manicani Island on their capital assets and coping strategies as determinants of their resiliency on Typhoon Haiyan was undertaken. KII and FG validated the survey results. Relationship between capital assets and coping strategies was determined using chi-square test and their degree of association was determined using phi coefficient and Cramer’s V. Results showed that (a) the households’ house condition before the typhoon and knowledge of the typhoon were moderately associated (0.22 to 0.23) with securing houses at 0.05 significance level; (b) the educational attainment of household head was moderately associated (0.34) with safekeeping of household assets/personal belongings at 0.01 significance level; (c) the condition of the house after the typhoon, length of time before house reconstruction and person in-charge in reconstruction have moderate to relatively strong association (0.28 to 0.44) with the housing recovery of the households at 0.01 significance level; and (d) livestock ownership after the typhoon and person in charge in house reconstruction were weakly to moderately related (0.17 to 0.26) with the household’s income recovery at 0.10 and 0.05 significance level, respectively. This implies that capital assets are important in coping with disasters. The local government can use these results for planning and improving its disaster risk reduction and management program especially on extreme events similar to Typhoon Yolanda.

Super Typhoon Haiyan struck the Philippines on 8 November 2013 and caused catastrophic damage due to its remarkably high wind speeds, storm surges, and waves. In this paper, the characteristics of the human losses and building damage in the coastal region of Leyte, the Philippines, were investigated based on data of observed inundation height/depth, the number of deaths and missing people, and damaged buildings in each barangay. Also, the relationship between human loss and the evacuation environment in each barangay was investigated, based on several questionnaire surveys of barangay captains. As a result, the scale of the human damage caused by Haiyan was found to be similar to that caused by other historical tsunamis, yet it was much larger than that caused by historical storm surge disasters in Japan. Moreover, it was found that there were differences in fatality percentages among neighboring barangays, attributable to several factors. Our questionnaire survey analysis revealed the need for disaster mitigation/prevention education and the importance of leadership by barangay captains in the evacuation of local people. The need for such education should be emphasized widely because some barangay captains still do not understand the meaning of “storm surge” even one year after the Typhoon Haiyan event.

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 world-wide 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.

Following typhoon Haiyan in November 2013, the government of the Philippines organized massive housing reconstruction programs that are currently facing complex implementation issues. The present study investigated the mechanisms of three types of housing reconstruction programs (i.e. owner-driven on-site reconstruction, community-driven off-site relocation and contractor-driven off-site relocation) and discussed sustainability challenges by assessing the gaps between community needs and program performance, measured through the level of beneficiary satisfaction. The study conducted semi-structured questionnaire surveys with beneficiary households and key informant interviews with government officials and nongovernment organization representatives in March 2015. Results showed that on-site reconstruction was delayed due to insufficient and poorly implemented assistance schemes relating to reconstruction (e.g. materials, skills training), while off-site relocation was delayed by prolonged land acquisition and subcontracting issues. Disruption of critical infrastructure, such as water utility services, and lack of livelihood opportunities significantly affected the satisfaction levels of respondents with the recovery progress. The study also found that the no-dwelling-zone policy was not strictly enforced as houses were still being rebuilt in high-risk areas near the coast. Finally permanently relocated residents continue to struggle, especially with regard to their source of livelihood, as relocation sites are inaccessible and located away from employment opportunities.