Restoration measures after the 2011 Tohoku-oki tsunami and their impact on tsunami research

Following the 2011 Tohoku-oki tsunami, many studies were carried out to provide insights into processes involved with this event, as well as to assess its impact on the landscape and the environment, evaluate the evidence that was left behind and how it changed with time. Much can be learned from analogues of events that have occurred in the past, the study of which providing information that is required to improve hazard preparedness. This can best be achieved if deposits of the latest tsunami and any previous events have been left undisturbed. On the other hand, restoration measures needed to be implemented shortly after the 2011 tsunami, in order to allow operations of vital infrastructures and agricultural activities to resume. While these measures are required for social and economic reasons, they are unfortunately in conflict with tsunami research, as they have led to the loss of the 2011 and even older deposits in many areas. As such, much of the geological record is missing in a number of places. A few case studies are presented in this chapter, with an emphasis on the area north of Sendai airport in the Miyagi Prefecture. There we show how a study focussing on the temporal changes and preservation potential of the tsunami deposit and associated chemical signatures was affected by restoration measures. Further examples from the Miyagi, Iwate and Fukushima Prefectures are also briefly presented.