Statistical characterization of hazards and risk in coastal areas

Abstract

We examine the foundation for hazard/risk assessment and its application to coastal problems. Historically, emphasis was on specifying expected values of wind waves and storm surges; however, as shown by the recent tsunamis in Southeast Asia in 2004 and in Japan in 2011, there are critical parts of the world where tsunamis represent the dominant threat to coastal communities. Recently, there has been an increased awareness of the combined effects of heavy rainfall and/or river discharge with surge levels and strong winds. This forcing combination played an important role in the flooding in southern Louisiana during Hurricane Isaac in 2012, where water levels exceeded the 500-year return interval levels. Such forcing combinations complicate both the modeling systems required for their simulation and the treatment of the multivariate probabilities that define the relative importance of their impacts. We begin with a set of consistent hazards and risk definitions, along with comparative definitions from other fields. This should help readers who have focused primarily on traditional coastal hazards and risks understand the broader context of risk assessment and also allow readers with a broader perspective gain insight into the specific nature of coastal hazards and risk. Following this, we introduce the basic concepts used in estimating coastal hazards and risks. We then examine the historical perspective for the evolution of coastal risk assessment, beginning with early deterministic methods and culminating in a recent transition to probabilistic methods. The steady increase in the ability of probabilistic methods to deal with persistent problems such as the lack of data and uncertainty is documented as a part of this transition.