Coastal flooding

Source: Wikipedia, the free encyclopedia.
Coastal flooding during Hurricane Lili in 2002 on Louisiana Highway 1 (United States)

Coastal flooding occurs when dry and low-lying land is submerged (flooded) by seawater.[1] The range of a coastal flooding is a result of the elevation of floodwater that penetrates the inland which is controlled by the topography of the coastal land exposed to flooding.[1][2] The seawater can flood the land via several different paths: direct flooding, overtopping of a barrier,[3] or breaching of a barrier. Coastal flooding is largely a natural event. Due to the effects of climate change (e.g. sea level rise and an increase in extreme weather events) and an increase in the population living in coastal areas, the damage caused by coastal flood events has intensified and more people are being affected.[4]

spring tides, especially when compounded by high winds and storm surges. This was the cause of the North Sea flood of 1953 which flooded large swathes of the Netherlands and the East coast of England
.

When humans modify the coastal environment this can make coastal flooding worse.

sea walls, alter the natural processes of the beach. This can lead to erosion on adjacent stretches of the coast which also increases the risk of flooding.[1][7][8]

Types

High tide flooding, also called tidal flooding, is one of the causes for coastal flooding. It has become much more common in the past seven decades.[9]

The seawater can flood the land via several different paths:

Causes

Coastal flooding can result from a variety of different causes including

hurricanes and tropical cyclones, rising sea levels due to climate change and tsunamis.

Storm surge from Hurricane Carol
in 1954

Storms and storm surges

high astronomical tide, extensive flooding can occur.[12]
Storm surges involve three processes:

  1. wind setup
  2. barometric setup
  3. wave setup

Wind blowing in an onshore direction (from the sea towards the land) can cause the water to 'pile-up' against the coast; this is known as wind setup. Low

wave breaking height results in a higher water level in the surf zone, which is wave setup. These three processes interact to create waves that can overtop natural and engineered coastal protection structures thus penetrating seawater further inland than normal.[12][13]

Sea level rise

This section is an excerpt from Sea level rise.[edit]

Between 1901 and 2018, average global

temperate glaciers accounted for 21%, while polar glaciers in Greenland accounted for 15% and those in Antarctica for 8%.[17]: 1576  Sea level rise lags behind changes in the Earth's temperature, and sea level rise will therefore continue to accelerate between now and 2050 in response to warming that has already happened.[18] What happens after that depends on human greenhouse gas emissions. Sea level rise would slow down between 2050 and 2100 if there are very deep cuts in emissions. It could then reach slightly over 30 cm (1 ft) from now by 2100. With high emissions it would accelerate. It could rise by 1.01 m (3+1⁄3 ft) or even 1.6 m (5+1⁄3 ft) by then.[16][19]: 1302  In the long run, sea level rise would amount to 2–3 m (7–10 ft) over the next 2000 years if warming amounts to 1.5 °C (2.7 °F). It would be 19–22 metres (62–72 ft) if warming peaks at 5 °C (9.0 °F).[16]
: 21 

Rising seas affect every coastal and island population on Earth.
mangroves. Crop yields may reduce because of increasing salt levels in irrigation water. Damage to ports disrupts sea trade.[22][23][24] The sea level rise projected by 2050 will expose places currently inhabited by tens of millions of people to annual flooding. Without a sharp reduction in greenhouse gas emissions, this may increase to hundreds of millions in the latter decades of the century.[25]
Areas not directly exposed to rising sea levels could be vulnerable to large-scale migration and economic disruption.

Tidal flooding

Tidal flooding on a sunny day, during the "king tides" in Brickell, Miami in 2016
The last remaining house on Holland Island that collapsed and was torn down in the 2010s as erosion and tides reached the foundation.
This section is an excerpt from Tidal flooding.[edit]

high tide events, such as at full and new moons. The highest tides of the year may be known as the king tide, with the month varying by location. These kinds of floods tend not to be a high risk to property or human safety, but further stress coastal infrastructure in low lying areas.[28]

This kind of flooding is becoming more common in cities and other human-occupied coastal areas as
vulnerability of infrastructure.[29] Geographies faced with these issues can utilize coastal management practices to mitigate the effects in some areas, but increasingly these kinds of floods may develop into coastal flooding that requires managed retreat or other more extensive climate change adaptation
practices are needed for vulnerable areas.

Tsunami Waves

Coastal areas can be significantly flooded as the result of

meteor impact into the ocean.[31] Tsunami waves are so destructive due to the velocity of the approaching waves, the height of the waves when they reach land, and the debris the water entrains as it flows over land can cause further damage.[30][32]

Depending on the magnitude of the tsunami waves and floods, it could cause severe injuries which call for precautionary interventions that prevent overwhelming aftermaths. It was reported that more than 200,000 people were killed in the earthquake and subsequent tsunami that hit the Indian Ocean, on December 26, 2004.[33] Not to mention, several diseases are a result of floods ranging from hypertension to chronic obstructive pulmonary diseases.[33]

Mitigation and adaptation

Further information: Climate change adaptation § Flooding
This section is an excerpt from Flood control.[edit]
A weir was built on the Humber River (Ontario) to prevent a recurrence of a catastrophic flood.

Flood control (or flood mitigation, protection or alleviation) methods are used to reduce or prevent the detrimental effects of flood waters.[34][35] Flooding can be caused by a mix of both natural processes, such as extreme weather upstream, and human changes to waterbodies and runoff. Flood control methods can be either of the structural type and of the non-structural type. Structural methods hold back floodwaters physically, while non-structural methods do not. Building hard infrastructure to prevent flooding, such as flood walls, is effective at managing flooding. However, best practice within landscape engineering is more and more to rely on soft infrastructure and natural systems, such as marshes and flood plains, for handling the increase in water.

To prevent or manage coastal flooding, coastal management practices have to handle natural processes like tides but also sea level rise due to climate change. Flood control is an important part of climate change adaptation and climate resilience.[36]

Flood control is part of
flood gates
, rather than trying to prevent floods altogether. It also involves the management of people, through measures such as evacuation and flood proofing properties. The prevention and mitigation of flooding can be studied on three levels: on individual properties, small communities, and whole towns or cities.

Non-structural mechanism

If human systems are affected by flooding, an adaption to how that system operates on the coast through behavioral and institutional changes is required, these changes are the so-called non-structural mechanisms of coastal flooding response.[37]

Building regulations, coastal hazard zoning, urban development planning, spreading the risk through insurance, and enhancing public awareness are some ways of achieving this.[5][37][38] Adapting to the risk of flood occurrence can be the best option if the cost of building defense structures outweighs any benefits or if the natural processes in that stretch of coastline add to its natural character and attractiveness.[8]

A more extreme and often difficult to accept the response to coastal flooding is abandoning the area (also known as managed retreat) prone to flooding.[10] This however raises issues for where the people and infrastructure affected would go and what sort of compensation should/could be paid.

Engineered defenses

Groynes are engineered structures that aim to prevent erosion
of the beach front

There are a variety of ways in which humans are trying to prevent the flooding of coastal environments, typically through so-called hard engineering structures such as

breakwaters, and artificial headlands promote the deposition of sediment on the beach thus helping to buffer against storm waves and surges as the wave energy is spent on moving the sediments in the beach than on moving water inland.[39]

Natural defenses

storm surges and flooding. Their high biomass
both above and below the water can help dissipate wave energy.

The coast does provide natural protective structures to guard against coastal flooding. These include physical features like

wetlands are often considered to provide significant protection against storm waves, tsunamis, and shoreline erosion through their ability to attenuate wave energy.[6][32]
To protect the coastal zone from flooding, the natural defenses should, therefore, be protected and maintained.

Longer term aspects and research

Reducing global sea-level rise is said to be one way to prevent significant flooding of coastal areas at present times and in the future. This could be minimised by further reducing

climate change policies like the Kyoto Protocol are seeking to mitigate the future effects of climate change
, including sea-level rise. In addition, more immediate measures of engineered and natural defenses are put in place to prevent coastal flooding.

There is a need for future research into:[citation needed]

  • Management strategies for dealing with the forced abandonment of coastal settlements
  • Quantifying the effectiveness of natural buffering systems, such as mangroves, against coastal flooding
  • Better engineering design and practices or alternative mitigation strategies to engineering

Impacts

Social and economic impacts

The

Gross Domestic Product (GDP).[7]

People's lives, homes, businesses, and city infrastructure like roads, railways, and industrial plants are all at risk of coastal flooding with massive potential social and economic costs.

beaches are eroded resulting in a loss of tourism in areas dependent on the attractiveness of those beaches.[38]

Environmental impacts

Coastal flooding can result in a wide variety of environmental impacts on different spatial and temporal scales. Flooding can destroy coastal habitats such as coastal

extinctions.[30] In addition to this, these coastal features are the coasts natural buffering system against storm waves; consistent coastal flooding and sea-level rise can cause this natural protection to be reduced allowing waves to penetrate greater distances inland exacerbating erosion and furthering coastal flooding.[5] "By 2050, “moderate” (typically damaging) flooding is expected to occur, on average, more than 10 times as often as it does today, and can be intensified by local factors."[44]

Prolonged

aquifers can also be affected by saltwater intrusion.[10][5][40] This can destroy these water bodies as habitats for freshwater organisms and sources of drinking water for towns and cities.[5][40]

Examples

The Thames Barrier provides flood control for London, U.K.
Significant flooding in New Orleans as a result of Hurricane Katrina and the failure of the city's flood protection systems

Examples of countries with existing coastal flooding problems include:

Hurricane Katrina in New Orleans

Land-use change and modification to natural systems in the Mississippi River have rendered the natural defenses for the city less effective. Wetland loss has been calculated to be around 1,900 square miles (4,920 square kilometres) since 1930. This is a significant amount as four miles of wetland are estimated to reduce the height of a storm surge by one foot (30 centimeters).[6]

A village near the coast of Sumatra lies in ruin on 2 January 2005 after the devastating tsunami that struck on Boxing Day 2004

Indonesia and Japan earthquake-related tsunamis

Further information: List of tsunamis

coral reefs, mangroves, beaches, and seagrass beds.[32] The more recent earthquake and tsunami in Japan in March 2011 (2011 Tōhoku earthquake and tsunami
) also clearly illustrates the destructive power of tsunamis and the turmoil of coastal flooding.

See also

References

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  2. ^ Doornkamp 1998.
  3. ^
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  4. ^ "Report: Flooded Future: Global vulnerability to sea level rise worse than previously understood". www.climatecentral.org. Archived from the original on 2020-03-30. Retrieved 2020-11-09.
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  6. ^ a b c d Griffis 2007
  7. ^ a b c d Dawson et al. 2009
  8. ^ a b c d Pope 1997
  9. ^ Sweet, William V.; Dusek, Greg; Obeysekera, Jayantha; Marra, John J. (February 2018). "Patterns and Projections of High Tide Flooding Along the U.S. Coastline Using a Common Impact Threshold" (PDF). tidesandcurrents.NOAA.gov. National Oceanic and Atmospheric Administration (NOAA). p. 4. Archived (PDF) from the original on 15 October 2022. Fig. 2b
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  11. ^ Kurian et al. 2009
  12. ^ a b Benavente et al. 2006
  13. ^ IPCC, 2019: Summary for Policymakers. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D. C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N. M. Weyer (eds.)]. Cambridge University Press, Cambridge, UK and New York, New York, US. https://doi.org/10.1017/9781009157964.001.
  14. ^ "WMO annual report highlights continuous advance of climate change". World Meteorological Organization. 21 April 2023. Press Release Number: 21042023
  15. ^ a b c IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, New York, US, pp. 3−32, doi:10.1017/9781009157896.001.
  16. doi:10.5194/essd-10-1551-2018
    . This corresponds to a mean sea-level rise of about 7.5 cm over the whole altimetry period. More importantly, the GMSL curve shows a net acceleration, estimated to be at 0.08mm/yr2.
  17. ISBN 978-0-309-15176-4
    . Box SYN-1: Sustained warming could lead to severe impacts
  18. ^ Fox-Kemper, B.; Hewitt, Helene T.; Xiao, C.; Aðalgeirsdóttir, G.; Drijfhout, S. S.; Edwards, T. L.; Golledge, N. R.; Hemer, M.; Kopp, R. E.; Krinner, G.; Mix, A. (2021). Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S. L.; Péan, C.; Berger, S.; Caud, N.; Chen, Y.; Goldfarb, L. (eds.). "Chapter 9: Ocean, Cryosphere and Sea Level Change" (PDF). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK and New York, NY, US.
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  20. ISBN 978-0-521-88009-1. Archived from the original
    on 20 June 2017. Retrieved 25 January 2017.
  21. ISBN 0521-80767-0
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  22. ^ "Sea level to increase risk of deadly tsunamis". United Press International. 2018.
  23. ^ Holder, Josh; Kommenda, Niko; Watts, Jonathan (3 November 2017). "The three-degree world: cities that will be drowned by global warming". The Guardian. Retrieved 2018-12-28.
  24. PMID 31664024
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  25. ^ Erik Bojnansky (March 9, 2017). "Sea levels are rising, so developers and governments need to band together: panel". The Real Deal. Retrieved March 10, 2017.
  26. ^ "What is nuisance flooding?". National Oceanic and Atmospheric Administration. Retrieved December 13, 2016.
  27. ^ "What is nuisance flooding? Defining and monitoring an emerging challenge | PreventionWeb.net". www.preventionweb.net. Retrieved 2021-01-07.
  28. PMID 28894195
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  30. ^ Goff et al. 2010
  31. ^ a b c d Alongi 2008
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    PMID 16781270
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  33. PMID 36850632
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  34. MSN Encarta, 2008 (see below: Further reading
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  35. ^ "Strengthening climate resilience through better flood management". ReliefWeb. 30 July 2021. Retrieved 2021-11-04.
  36. ^ a b Dawson et al. 2011
  37. ^ a b c d Snoussi, Ouchani & Niazi 2008
  38. ^ a b Short & Masselink 1999
  39. ^ a b c d e Hunt & Watkiss 2011
  40. ^ Suarez et al. 2005
  41. ^ Tomita et al. 2006
  42. ^ Nadal et al. 2010
  43. ^ "2022 Sea Level Rise Technical Report". oceanservice.noaa.gov. Retrieved 2022-02-16.
  44. ^ Horner 1986
  45. ^ a b Ebersole et al. 2010

Sources

  • Alongi, D. M. (2008). "Mangrove Forests: Resiliance, Protection from Tsunamis, and Responses to Global Climate Change".
    doi:10.1016/j.ecss.2007.08.024
    .

External links
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