Statistical Ch
567
Part C | 26.1
26. Statistical Characterization of Hazards
and Risk in Coastal Areas
Donald T. Resio, Mark A. Tumeo, Jennifer L. Irish
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 determinis26.1 Overview of Risk and Uncertainty ......... 567
26.1.1 Definitions of Basic Terms .......... 568
26.2 Quantifying Coastal Hazards/Risks ........ 570
26.3 Historical Perspective........................... 574
26.3.1 The Development
of Deterministic Methods ........... 575
26.3.2 The Development
of Probabilistic Methods ............ 577
26.3.3 The Development
of the Historical Storm Method
for Estimating Coastal Extremes .. 581
26.3.4 The Development
of Alternative Methods............... 583
26.3.5 Probabilistic Analyses
of Extratropical Storms ............... 586
26.3.6 Future Directions
and Final Comments.................. 586
26.4 Summary ............................................ 587
26.5 Nomenclature...................................... 587
26.A Appendix: Glossary of Probability
and Risk Terms .................................... 587
References................................................... 593
tic 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.
26.1 Overview of Risk and Uncertainty
Technically, risk is defined as the mathematical probability that a specific outcome will occur multiplied by
the magnitude of the impact of that occurrence. However, there are many other definitions in use, and while
a technical working definition such as the one presented
is useful, it is more important that there is a contextual
understanding of the concept.
While risk is now used in some manner across almost every discipline, the entire cultural framework
upon which the concept is based is only a few hundred
years old (and relatively young as a basis compared
to other engineering and mathematical concepts). Most
ancient cultures took the stance that the future was either fated (deterministic) or subject to the whims of
567
Part C | 26.1
26. Statistical Characterization of Hazards
and Risk in Coastal Areas
Donald T. Resio, Mark A. Tumeo, Jennifer L. Irish
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 determinis26.1 Overview of Risk and Uncertainty ......... 567
26.1.1 Definitions of Basic Terms .......... 568
26.2 Quantifying Coastal Hazards/Risks ........ 570
26.3 Historical Perspective........................... 574
26.3.1 The Development
of Deterministic Methods ........... 575
26.3.2 The Development
of Probabilistic Methods ............ 577
26.3.3 The Development
of the Historical Storm Method
for Estimating Coastal Extremes .. 581
26.3.4 The Development
of Alternative Methods............... 583
26.3.5 Probabilistic Analyses
of Extratropical Storms ............... 586
26.3.6 Future Directions
and Final Comments.................. 586
26.4 Summary ............................................ 587
26.5 Nomenclature...................................... 587
26.A Appendix: Glossary of Probability
and Risk Terms .................................... 587
References................................................... 593
tic 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.
26.1 Overview of Risk and Uncertainty
Technically, risk is defined as the mathematical probability that a specific outcome will occur multiplied by
the magnitude of the impact of that occurrence. However, there are many other definitions in use, and while
a technical working definition such as the one presented
is useful, it is more important that there is a contextual
understanding of the concept.
While risk is now used in some manner across almost every discipline, the entire cultural framework
upon which the concept is based is only a few hundred
years old (and relatively young as a basis compared
to other engineering and mathematical concepts). Most
ancient cultures took the stance that the future was either fated (deterministic) or subject to the whims of