an order of magnitude higher than that of major (paleo)tsunamis (e.g., Nanayama et al., 2003). The tsunami database
has been expanded during the last decades and, in combination with an improved understanding of tsunami depositional mechanisms (Shiki et al., 2008), has helped to
identify paleotsunami deposits in many parts of the world.
Recognizing and identifying paleotsunami deposits and
assigning the magnitude and extent of (pre)historic tsunamis are important parts of paleoseismological studies.
An outstanding example of this is from Japan, where tsunami deposits of a historical event in AD 869 were identified on the Sendai plain by Minoura et al. (2001). The
2011 Tohoku-oki tsunami deposits now cover the AD
869 deposits in the same area. The presence of the older
deposits was used to determine/verify the occurrence of
a previous large earthquake and tsunami event and proved
that this area is susceptible to large-scale tsunami inundation. The world then realized that this part of Japan had
experienced magnitude 9 earthquakes with associated tsunamis in the past. Sedimentary, geochemical (inorganic,
organic, isotopic), and paleontological proxies are usually
used for the identification of tsunamites.
Field surveys aim to map the three-dimensional distribution of a sand sheet and to find evidence for a regional
continuity of the layer. Washover fans, typically taper
and fine landward, have a common height above mean
sea-level and contain marine fossils. These observations
can easily be achieved by shallow drillings and GPS control of the drilling locations for large strips along a coast.
Ground-penetrating radar surveys as a shallow, nondestructive geophysical tool have been proven to produce
reliable images of the facies architecture of fine-grained
tsunami sediments (Koster et al., 2014).
When dating event deposits, the same challenges are
faced as for paleostorm deposits. This is because
reworking is a common process during deposition. Any
dates obtained from the event deposits thus give a maximum age, and the youngest date would ideally give an
indication of the timing.
Conclusions
Coastal hazards have the potential to cause havoc, especially where the coastline is densely populated. As the
hazards involved are the consequence of natural processes, they cannot be avoided. Hence, adaptation strategies have to be implemented. A proper risk assessment
should be based on knowledge of recurrence intervals as
well as the definition of the worst-case scenario. As the
recurrence interval might be rather long and historical
information may not be available, this information can
only be derived from deposits left behind by the impact
of high-energy events. However, at the moment, there is
no clear sedimentological fingerprint to discriminate
storm and tsunami deposits; for more information, the
reader is referred to the benchmark papers of Kortekaas
and Dawson (2007), Morton et al. (2007), Switzer and
Jones (2008), and Chagué-Goff et al. (2011). Mapping
of high-energy deposits along the world’s coastal zones
requires an interdisciplinary (geoarchaeology) multiproxy
and holistic approach. Transdisciplinary studies between
geoscientists and historians are necessary as catalogs of
past extreme wave events should include instrumental,
historical, and geological data. Based on the results of
these investigations, coastal engineers should design
defense structures accordingly.
Bibliography
Adger, W. N., Hughes, T. P., Folke, C., Carpenter, S. R., and
Rockström, J., 2005. Social-ecological resilience to coastal
disasters. Science, 309(5737), 1036–1039.
Atwater, B. F., 1987. Evidence for great Holocene earthquakes
along the outer coast of Washington state. Science, 236(4804),
942–944.
Atwater, B. F., Cisternas, M., Bourgois, J., Dudley, W. C., Hendley,
J. W. II., and Stauffer, P. H., 1999. Surviving a Tsunami – Lessons from Chile, Hawaii and Japan. US Geological Survey Circular 1187. This report and any updates to it are available online
at: http://pubs.usgs.gov/circ/c1187/
Atwater, B. F., Fuentes, Z., Halley, R. B., Ten Brink, U. S., and
Tuttle, M. P., 2014. Effects of 2010 Hurricane Earl amidst geologic evidence for greater overwash at Anegada, British Virgin
Islands. Advances in Geosciences, 38(38), 21–30.
Bahlburg, H., and Spiske, M., 2012. Sedimentology of tsunami
inflow and backflow deposits: key differences revealed in a
modern example. Sedimentology, 59(3), 1063–1086.
Bird, E. C. F., 1985. Coastline Changes. New York: Wiley. 219 pp.
Brázdil, R., Kundzewicz, Z. W., and Benito, G., 2006. Historical
hydrology for studying flood risk in Europe. Hydrological Sciences Journal, 51(5), 739–764.
Bryant, E., 2005. Natural Hazards. Cambridge: Cambridge University Press.
Chagué-Goff, C., Schneider, J. L., Goff, J. R., Dominey-Howes, D.,
and Strotz, L., 2011. Expanding the proxy toolkit to help identify
past events – lessons from the 2004 Indian Ocean Tsunami and
the 2009 South Pacific Tsunami. Earth-Science Reviews,
107(1), 107–122.
Cox, R., Zentner, D. B., Kirchner, B. J., and Cook, M. S., 2012.
Boulder ridges on the Aran Islands (Ireland): recent movements
caused by storm waves, not tsunamis. The Journal of Geology,
120(3), 249–272.
Dawson, R. J., Dickson, M. E., Nicholls, R. J., Hall, J. W., Walkden,
M. J., Stansby, P. K., and Watkinson, A. R., 2009. Integrated
analysis of risks of coastal flooding and cliff erosion under scenarios of long term change. Climatic Change, 95(1–2),
249–288.
Del Río, L., and Gracia, F. J., 2009. Erosion risk assessment of
active coastal cliffs in temperate environments. Geomorphology,
112(1), 82–95.
Dewez, T. J., Rohmer, J., Regard, V., and Cnudde, C., 2013. Probabilistic coastal cliff collapse hazard from repeated terrestrial laser
surveys: case study from Mesnil Val (Normandy, northern
France). Journal of Coastal Research, 65, 702–707.
Duperret, A., Genter, A., Mortimore, R. N., Delacourt, B., and De
Pomerai, M. R., 2002. Coastal rock cliff erosion by collapse at
Puys, France: the role of impervious marl seams within chalk
of NW Europe. Journal of Coastal Research, 18, 52–61.
Firth, C. A. L. L. U. M., Stewart, I., McGuire, W. J., Kershaw, S.,
and Vita-Finzi, C., 1996. Coastal Elevation Changes in Eastern
Sicily: Implications for Volcano Instability at Mount Etna. London: Geological Society, Special Publications, Vol. 110, No.
1, pp. 153–167.
GEOHAZARDS: COASTAL DISASTERS
281
has been expanded during the last decades and, in combination with an improved understanding of tsunami depositional mechanisms (Shiki et al., 2008), has helped to
identify paleotsunami deposits in many parts of the world.
Recognizing and identifying paleotsunami deposits and
assigning the magnitude and extent of (pre)historic tsunamis are important parts of paleoseismological studies.
An outstanding example of this is from Japan, where tsunami deposits of a historical event in AD 869 were identified on the Sendai plain by Minoura et al. (2001). The
2011 Tohoku-oki tsunami deposits now cover the AD
869 deposits in the same area. The presence of the older
deposits was used to determine/verify the occurrence of
a previous large earthquake and tsunami event and proved
that this area is susceptible to large-scale tsunami inundation. The world then realized that this part of Japan had
experienced magnitude 9 earthquakes with associated tsunamis in the past. Sedimentary, geochemical (inorganic,
organic, isotopic), and paleontological proxies are usually
used for the identification of tsunamites.
Field surveys aim to map the three-dimensional distribution of a sand sheet and to find evidence for a regional
continuity of the layer. Washover fans, typically taper
and fine landward, have a common height above mean
sea-level and contain marine fossils. These observations
can easily be achieved by shallow drillings and GPS control of the drilling locations for large strips along a coast.
Ground-penetrating radar surveys as a shallow, nondestructive geophysical tool have been proven to produce
reliable images of the facies architecture of fine-grained
tsunami sediments (Koster et al., 2014).
When dating event deposits, the same challenges are
faced as for paleostorm deposits. This is because
reworking is a common process during deposition. Any
dates obtained from the event deposits thus give a maximum age, and the youngest date would ideally give an
indication of the timing.
Conclusions
Coastal hazards have the potential to cause havoc, especially where the coastline is densely populated. As the
hazards involved are the consequence of natural processes, they cannot be avoided. Hence, adaptation strategies have to be implemented. A proper risk assessment
should be based on knowledge of recurrence intervals as
well as the definition of the worst-case scenario. As the
recurrence interval might be rather long and historical
information may not be available, this information can
only be derived from deposits left behind by the impact
of high-energy events. However, at the moment, there is
no clear sedimentological fingerprint to discriminate
storm and tsunami deposits; for more information, the
reader is referred to the benchmark papers of Kortekaas
and Dawson (2007), Morton et al. (2007), Switzer and
Jones (2008), and Chagué-Goff et al. (2011). Mapping
of high-energy deposits along the world’s coastal zones
requires an interdisciplinary (geoarchaeology) multiproxy
and holistic approach. Transdisciplinary studies between
geoscientists and historians are necessary as catalogs of
past extreme wave events should include instrumental,
historical, and geological data. Based on the results of
these investigations, coastal engineers should design
defense structures accordingly.
Bibliography
Adger, W. N., Hughes, T. P., Folke, C., Carpenter, S. R., and
Rockström, J., 2005. Social-ecological resilience to coastal
disasters. Science, 309(5737), 1036–1039.
Atwater, B. F., 1987. Evidence for great Holocene earthquakes
along the outer coast of Washington state. Science, 236(4804),
942–944.
Atwater, B. F., Cisternas, M., Bourgois, J., Dudley, W. C., Hendley,
J. W. II., and Stauffer, P. H., 1999. Surviving a Tsunami – Lessons from Chile, Hawaii and Japan. US Geological Survey Circular 1187. This report and any updates to it are available online
at: http://pubs.usgs.gov/circ/c1187/
Atwater, B. F., Fuentes, Z., Halley, R. B., Ten Brink, U. S., and
Tuttle, M. P., 2014. Effects of 2010 Hurricane Earl amidst geologic evidence for greater overwash at Anegada, British Virgin
Islands. Advances in Geosciences, 38(38), 21–30.
Bahlburg, H., and Spiske, M., 2012. Sedimentology of tsunami
inflow and backflow deposits: key differences revealed in a
modern example. Sedimentology, 59(3), 1063–1086.
Bird, E. C. F., 1985. Coastline Changes. New York: Wiley. 219 pp.
Brázdil, R., Kundzewicz, Z. W., and Benito, G., 2006. Historical
hydrology for studying flood risk in Europe. Hydrological Sciences Journal, 51(5), 739–764.
Bryant, E., 2005. Natural Hazards. Cambridge: Cambridge University Press.
Chagué-Goff, C., Schneider, J. L., Goff, J. R., Dominey-Howes, D.,
and Strotz, L., 2011. Expanding the proxy toolkit to help identify
past events – lessons from the 2004 Indian Ocean Tsunami and
the 2009 South Pacific Tsunami. Earth-Science Reviews,
107(1), 107–122.
Cox, R., Zentner, D. B., Kirchner, B. J., and Cook, M. S., 2012.
Boulder ridges on the Aran Islands (Ireland): recent movements
caused by storm waves, not tsunamis. The Journal of Geology,
120(3), 249–272.
Dawson, R. J., Dickson, M. E., Nicholls, R. J., Hall, J. W., Walkden,
M. J., Stansby, P. K., and Watkinson, A. R., 2009. Integrated
analysis of risks of coastal flooding and cliff erosion under scenarios of long term change. Climatic Change, 95(1–2),
249–288.
Del Río, L., and Gracia, F. J., 2009. Erosion risk assessment of
active coastal cliffs in temperate environments. Geomorphology,
112(1), 82–95.
Dewez, T. J., Rohmer, J., Regard, V., and Cnudde, C., 2013. Probabilistic coastal cliff collapse hazard from repeated terrestrial laser
surveys: case study from Mesnil Val (Normandy, northern
France). Journal of Coastal Research, 65, 702–707.
Duperret, A., Genter, A., Mortimore, R. N., Delacourt, B., and De
Pomerai, M. R., 2002. Coastal rock cliff erosion by collapse at
Puys, France: the role of impervious marl seams within chalk
of NW Europe. Journal of Coastal Research, 18, 52–61.
Firth, C. A. L. L. U. M., Stewart, I., McGuire, W. J., Kershaw, S.,
and Vita-Finzi, C., 1996. Coastal Elevation Changes in Eastern
Sicily: Implications for Volcano Instability at Mount Etna. London: Geological Society, Special Publications, Vol. 110, No.
1, pp. 153–167.
GEOHAZARDS: COASTAL DISASTERS
281