Awareness about the threats posed by different types of coastal disasters has increased throughout the world, as people are exposed to the nature of these hazards through media reports on events in distant countries. This has resulted in coastal residents being aware about the destructive power of tsunamis, despite no such events having taken place in their country in recent times. Regardless of this increased awareness, it has been hypothesized that there is still need for local governments to enact adequate policies to raise the awareness of local residents, for example, by holding regular evacuation drills. The present research presents a comparative assessment of tsunami awareness in two tourist destinations in Japan and the USA, which was derived through structured questionnaire surveys of beach users in the city of Kamakura and various coastal cities in Florida. The results show how despite relatively high level of awareness tsunamis still pose a considerable risk to each of the communities, for example, due to shortcoming in evacuation knowledge and infrastructure.@en

The accurate modelling of overtopping of coastal defences by tsunami waves is of vital importance for the formulation of disaster management strategies. To improve knowledge of this phenomena the authors conducted experiments on coastal structure overtopping using bores that were generated by a dam-break mechanism. Three types of structures were tested, namely a coastal dyke, a wall, and a wall of infinite height. The results highlight the necessity to consider the energy present in a bore to determine if a structure will be overtopped or not. As a result of these experiments an empirical formula to determine the height of overtopping given the incident bore height and velocity was validated. The study highlights the importance of clearly modelling the velocity and Froude number of a tsunami. Such experiments should be conducted on rough beds, for which a suitable Manning's n seems to be around 0.06 sm-1/3. The study also contrasted the results obtained to those of the ASCE7 method, and concludes that the Manning's n values recommended in ASCE7 are probably too low.@en

Following the 2011 Tohoku Earthquake and Tsunami, Japanese tsunami protection guidelines stipulate that coastal defences should ensure that settlements are shielded from the coastal inundation that would result from Level 1 tsunami events (with return periods in the order of about 100 years). However, the overtopping mechanism and leeward inundation heights of tsunami bores as they hit coastal structures has received little attention in the past. To ascertain this phenomenon, the authors conducted physical experiments using a dam-break mechanism, which could generate bores that overtopped different types of structures. The results indicate that it is necessary to move away from only considering the tsunami inundation height at the beach, and also consider the bore velocity as it approaches the onshore area. The authors also prepared a simple, conservative method of estimating the inundation height after a structure of a given height, provided that the incident bore velocity and height are known.@en

In the aftermath of the 2011 Tohoku Earthquake and Tsunami Japanese tsunami protection philosophy now dictates that coastal defences should prevent the land that they protect from being flooded under a Level 1 event (with a return period in the order of about 100 years). To ascertain the overtopping mechanism and leeward inundation heights of tsunamis as they hit coastal structures, the authors conducted physical experiments using a dam-break mechanism, which could generate bores that overtopped different types of structures. Three different types of structures were considered, namely a wall of “infinite” height, a coastal dyke, and a vertical tsunami wall. The results show that the velocity of the tsunami bore is crucial in determining whether the structure will be overtopped or not, and thus it is imperative to move away from only considering the tsunami inundation height at the beach.@en