Super typhoon Haiyan struck the Philippines on 8 November 2013, marking one of the strongest typhoons at landfall in recorded history. Extreme storm waves attacked the Pacific coast of Eastern Samar where the violent typhoon first made landfall. Our field survey confirmed that storm overwash heights of 6–14 m above mean sea level were distributed along the southeastern coast and extensive inundation occurred in some coastal villages in spite of natural protection by wide fringing reefs. A wave model based on Boussinesq‐type equations is constructed to simulate wave transformation over shallow fringing reefs and validated against existing laboratory data. Wave propagation and runup on the Eastern Samar coast are then reproduced using offshore boundary conditions based on a wave hindcast. The model results suggest that extreme waves on the shore are characterized as a superposition of the infragravity wave and sea‐swell components. The balance of the two components is strongly affected by the reef width and beach slope through wave breaking, frictional dissipation, reef‐flat resonances, and resonant runup amplification. Therefore, flood characteristics significantly differ from site to site due to a large variation of the two topographic parameters on the hilly coast. Strong coupling of infragravity waves and sea swells produces extreme runup on steep beaches fronted by narrow reefs, whereas the infragravity waves become dominant over wide reefs and they evolve into bores on steep beaches.

No abstract

No abstract

No abstract

Field surveys were performed in the southwest of Bangladesh to learn lessons out of severe disasters due to Cyclone Sidr. Spatial distributions of inundation heights were measured around the most damaged area. Inundation heights along the Baleshwar river and the Burishwar river were relatively high compared to those observed on the coast of Kuakata although these sites are far from the coast. Detailed surveys were thus performed in these three areas and there found several residents who witnessed bore-like waves hitting on the damaged area. Embankments along the river had been eroded before the storm while dikes on the coast significantly functioned to reduce the damages of the coastal area behind.

A post-2011 Tohoku earthquake tsunami survey was conducted at the Nakoso Coast, Fukushima Prefecture, Japan, on Mar 24-25 and Apr 1-2, 2011. Spatial distribution of the tsunami inundation height, together with the seawall height and damages, was investigated. We found a sharp contrast of tsunami damages within the target area; tsunami damage is the most serious in the north region (north of the Samegawa River) where seawalls with different heights played diverse roles for protection of local community. A relatively high seawall in this region kept intact after tsunami attack, and protected the lee side human properties; whereas, 71% of the low seawalls were broken during the tsunami and the disaster developed in the corresponding sheltered area. A sharp contrast at the boundary of these two types of seawalls was observed. Behind the high seawall, the tsunami intensity and velocity were significantly reduced and the inundation depth is only 0.6 m. Nevertheless, tsunami intensity was enhanced in the seawall-broken area with an inland inundation depth being 4.7 m, which ruins away the local houses. In the middle region between the Samegawa River and the Bindagawa River, the high seawall survived from the tsunami attack. We confirmed that the coastal pine tree forest, serving as a buffer zone, played a significant role in reducing the tsunami height approximately by 4 m within a cross-shore distance of 230 m. To the south of the Bindagawa River, the tsunami damage is the mildest due to the protection by the robust high seawall as well as high elevation of land topography.

Super typhoon Haiyan/Yolanda in November 2013 caused coastal flooding and severe damage in coastal zones not only in bays but also along open coastlines. In the Town of Hernani, located on the open Pacific coast of Eastern Samar province in the Philippines, the flooding and resulting washed-away houses were recorded in a widely-viewed video. This paper provides field survey results from Hernani including eyewitness accounts of inundation heights and time series profiles, measured ground levels and estimated sea bottom profiles, and measured dimensions of coastal dikes and of houses shown in the video. Information gathered here suggests that wave groups were the direct cause of coastal flooding in Hernani. Results in this paper will contribute to analysis of large wave disasters and flood prevention in open coastal zones.

A strong low-pressure system passed along the coast of Pacific Ocean side of the northern part of Japan in October 2006. High tide level was recorded, many beaches and dunes were eroded and coastal defense systems were damaged on the Ibaraki coast by the low-pressure system. This high tide level due to the low-pressure system continued for over 24 hours with big wind waves and met astronomical high tide two or three times. The results of the numerical simulation in this paper show that Ekman transport was the main physical force to generate this high tide level. Unusual time and spatial distribution of winds around the low-pressure system affected the force considerably.