A coastal development hazard is something that affects the natural environment by human activities and products. As

coasts The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. The Earth has around of coastline. Coasts are important zones in n ...

become more developed, the vulnerability component of the equation increases as there is more value at risk to the hazard. The likelihood component of the equation also increases in terms of there being more value on the coast so a higher chance of hazardous situation occurring. Fundamentally humans create hazards with their presence. In a coastal example,

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is d ...

is a process that happens naturally on the

Canterbury Bight The Canterbury Bight is a large bight on the eastern side of New Zealand's South Island. The bight runs for approximately from the southern end of Banks Peninsula to the settlement of Timaru and faces southeast, exposing it to high-energy storm w ...

as a part of the coastal

geomorphology Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or ...

of the area and strong long shore currents. This process becomes a hazard when humans interact with that coastal environment by developing it and creating value in that area. A

natural hazard A natural hazard is a natural phenomenon that might have a negative effect on humans and other animals, or the environment. Natural hazard events can be classified into two broad categories: geophysical and biological. An example of the distinc ...

is defined as the release of

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of ...

or materials that threaten humans or what they value. In a coastal context these hazards vary temporally and spatially from a rare, sudden, massive release of energy and materials such as a major

storm A storm is any disturbed state of the natural environment or the atmosphere of an astronomical body. It may be marked by significant disruptions to normal conditions such as strong wind, tornadoes, hail, thunder and lightning (a thunderstorm), ...

event or

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

, to the continual chronic release of energy and materials such long-term

coastal erosion Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of waves, currents, tides, wind-driven water, waterborne ice, or other impacts of storms. The landwar ...

sea-level rise Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cryo ...

. It is this type coastal hazard, specifically around erosion and attributes surrounding erosion that this article will focus on.

Coastal population growth and development on coasts

Globally, the number of people living on the

coast The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. The Earth has around of coastline. Coasts are important zones in n ...

is increasing. It has been stated that there has been over a 35% increase in the

population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction usi ...

of people living on the coasts since 1995. The average

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematicall ...

of people in coastal regions is 3 times higher than the global average density. Historically,

city A city is a human settlement of notable size.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routledge. It can be def ...

development, especially large cities, was based on coasts due to the

economic An economy is an area of the production, distribution and trade, as well as consumption of goods and services. In general, it is defined as a social domain that emphasize the practices, discourses, and material expressions associated with th ...

benefits of the

port A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as H ...

s. In 1950, there were only 2

megacities A megacity is a very large city, typically with a population of more than 10 million people. Precise definitions vary: the United Nations Department of Economic and Social Affairs in its 2018 "World Urbanization Prospects" report counted u ...

(cities with greater than 8 million people) in the

coastal zone The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. The Earth has around of coastline. Coasts are important zones in ...

London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...

and

New York City New York, often called New York City or NYC, is the List of United States cities by population, most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the L ...

. By the mid-nineties, there were 13. Although coastal areas have globally shown population growth and increases in density, very few in-depth quantitative global studies of population have been carried out, especially in terms of distribution across specific environs, like coasts. The spatial distribution and accuracy of global data must be significantly improved before realistic quantitative assessments of the global impacts of coastal hazards can be made, as currently much of the data is collected and analysed in the aftermath of disasters. On the heavily developed East Coast of USA, a strong correlation exists between human development, determined by satellite imagery, and reduced rates of erosion, even when studied at regional scales. A combination of the relative permanence of urban infrastructure and coastal defense efforts made to protect such infrastructure is likely the cause of such a relationship. Even after destructive storm events, evidence suggest that US East and Gulf Coast communities tend to rebuild homes and structures that are larger than before the event. Historical studies have put estimates of the number of deaths due to

cyclone In meteorology, a cyclone () is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an an ...

s over the last 200 years around the

Bay of Bengal The Bay of Bengal is the northeastern part of the Indian Ocean, bounded on the west and northwest by India, on the north by Bangladesh, and on the east by Myanmar and the Andaman and Nicobar Islands of India. Its southern limit is a line bet ...

exceeding 1.3 million. However, in

developed countries A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state that has a high quality of life, developed economy and advanced technological infrastruct ...

, as can be expected, the death toll is significantly lower but the economic losses due to coastal hazards are increasing. The US for example had major losses through

Hurricane Andrew Hurricane Andrew was a very powerful and destructive Category 5 Atlantic hurricane that struck the Bahamas, Florida, and Louisiana in August 1992. It is the most destructive hurricane to ever hit Florida in terms of structures damaged o ...

, which hit

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...

and

Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is bord ...

in 1992. This rushing to the coast is exhibited in

property value Real estate appraisal, property valuation or land valuation is the process of developing an opinion of value for real property (usually market value). Real estate transactions often require appraisals because they occur infrequently and every prop ...

. A study by Bourassa et al. (2004) found that in

Auckland Auckland (pronounced ) ( mi, Tāmaki Makaurau) is a large metropolitan city in the North Island of New Zealand. The most populous urban area in the country and the fifth largest city in Oceania, Auckland has an urban population of about I ...

, New Zealand, wide sea views contributed on average an additional 59% to the value of a waterfront property. This effect diminished rapidly the further the property was from the coast. In another study, it was found that moving 150 m away from the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...

lowered property values by 36%.

Insurance Insurance is a means of protection from financial loss in which, in exchange for a fee, a party agrees to compensate another party in the event of a certain loss, damage, or injury. It is a form of risk management, primarily used to hedge ...

premiums in coastal hazard areas are an inconsequential determinant of property values, given the significant amenity values provided by the coast in terms of views and local

recreation Recreation is an activity of leisure, leisure being discretionary time. The "need to do something for recreation" is an essential element of human biology and psychology. Recreational activities are often done for enjoyment, amusement, or plea ...

. Sea-level rise, coastal erosion, and the exacerbating interaction between these two

natural Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans ar ...

phenomena A phenomenon ( : phenomena) is an observable event. The term came into its modern philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which ''cannot'' be directly observed. Kant was heavily influenced by Gottfried ...

are likely to pose a significant threat for the loss of capital assets in coastal areas in the future. It is hard to say if the vulnerability to coastal hazards by those residing there is perceived, yet dominated by the amenity value of coasts, or simply ignored.

Coastal erosion hazards

Coastal erosion is one of the most significant hazards associated with the coast. Not in terms of a rare massive release of energy or material resulting in loss of life, as is associated with tsunami and cyclones, but in terms of a continual chronic release that forms a threat to infrastructure, capital assets and property.

Beach erosion process

Storm induced large erosion events are a part of the natural

evolutionary Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variati ...

process of fine

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...

, gently sloping

beaches A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shells ...

. Increased

wave energy Wave power is the capture of energy of wind waves to do useful work – for example, electricity generation, water desalination, or pumping water. A machine that exploits wave power is a wave energy converter (WEC). Waves are generated by win ...

in storms leads to the removal of

foreshore The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various specie ...

berm A berm is a level space, shelf, or raised barrier (usually made of compacted soil) separating areas in a vertical way, especially partway up a long slope. It can serve as a terrace road, track, path, a fortification line, a border/ separation ...

and

dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...

sediments. These displaced sediments are then deposited as near

shore A shore or a shoreline is the fringe of land at the edge of a large body of water, such as an ocean, sea, or lake. In physical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water past a ...

sand bars and act to dampen the wave energy lessoning the amount of sediment that is being eroded from the coast. When wave energies decrease post storm events, the sediments from these newly deposited near shore bars are returned to the upper beach, rebuilding the berm. This self-correcting cycle is an active balance between wave energies and fine sediment

deposition Deposition may refer to: * Deposition (law), taking testimony outside of court * Deposition (politics), the removal of a person of authority from political power * Deposition (university), a widespread initiation ritual for new students practiced f ...

. This store of sediment being available for erosion in storms and re-depositing when the event has subsided is an important natural buffer mechanism against protecting the

mainland Mainland is defined as "relating to or forming the main part of a country or continent, not including the islands around it egardless of status under territorial jurisdiction by an entity" The term is often politically, economically and/or dem ...

from erosion and minimising coastal retreat.

Dune destruction

Sand dunes A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, fl ...

are very dynamic fragile structures that act as stores of sediment used to carry out the coastal processes mentioned above. This removal of the upper beach sediments is important from a hazard perspective as this is the area of the coast that is often utilised for

property development Real estate development, or property development, is a business process, encompassing activities that range from the renovation and re- lease of existing buildings to the purchase of raw land and the sale of developed land or parcels to others. ...

due to the high prices sea front properties with a view can achieve. In

Pegasus Bay Pegasus Bay, earlier known as Cook's Mistake, is a bay on the east coast of the South Island of New Zealand, to the north of Banks Peninsula. Toponymy Pegasus Bay takes its name from the brig ''Pegasus'', a sealing ship that was sailing from H ...

, New Zealand, storm events in 1978 and 2001 caused significant erosion of the New Brighton and Waimairi sand beaches. In the 1978 storm event houses on the seaward side of the New Brighton Spit suffered from undercutting as the dune sediment in which they were built on was eroded by high wave energy. This same storm event caused similar erosion damage to houses built on the upper dunes in

Raumati Beach Raumati Beach is a beach community on the Kapiti Coast of New Zealand's North Island; located 60km north-west of Wellington, and about 10 km north of Raumati South. It is immediately to the south-west of the larger town of Paraparaumu. The Ma ...

, on the west coast of the

North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-larges ...

, New Zealand. Bulldozing and bulk removal of sand from protective coastal dunes is therefore an extremely hazardous activity, and one that has been widely carried out in New Zealand in order to form a surface on which to build on to obtain sea views.

Canterbury bight

In Kirk (2001) coastal erosion on the Canterbury bight, South Canterbury was said to have reached up to 8 m per year. This coastal process could be measured in more ways than one, the aforementioned distance of coastal retreat or the decreased

dollar Dollar is the name of more than 20 currencies. They include the Australian dollar, Brunei dollar, Canadian dollar, Hong Kong dollar, Jamaican dollar, Liberian dollar, Namibian dollar, New Taiwan dollar, New Zealand dollar, Singapore dollar, ...

value of developed assets, land and

infrastructure Infrastructure is the set of facilities and systems that serve a country, city, or other area, and encompasses the services and facilities necessary for its economy, households and firms to function. Infrastructure is composed of public and priv ...

that are at risk. To date, erosion on the Canterbury Bight has led to the loss of

agricultural land Agricultural land is typically land ''devoted to'' agriculture, the systematic and controlled use of other forms of lifeparticularly the rearing of livestock and production of cropsto produce food for humans. It is generally synonymous with ...

, threatened valuable infrastructure including

holiday A holiday is a day set aside by custom or by law on which normal activities, especially business or work including school, are suspended or reduced. Generally, holidays are intended to allow individuals to celebrate or commemorate an event or t ...

settlements, and reduced coastal lagoons and

wetlands A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The p ...

. Historically, erosion on the Canterbury Bight was a natural process, but has now been exacerbated by human intervention. The

Waitaki River The Waitaki River is a large braided river that drains the Mackenzie Basin and runs some south-east to enter the Pacific Ocean between Timaru and Oamaru on the east coast of the South Island of New Zealand. It starts at the confluence of the � ...

was the dominant source of sediments for the beaches between

Oamaru Oamaru (; mi, Te Oha-a-Maru) is the largest town in North Otago, in the South Island of New Zealand, it is the main town in the Waitaki District. It is south of Timaru and north of Dunedin on the Pacific coast; State Highway 1 and the ra ...

and

Timaru Timaru (; mi, Te Tihi-o-Maru) is a port city in the southern Canterbury Region of New Zealand, located southwest of Christchurch and about northeast of Dunedin on the eastern Pacific coast of the South Island. The Timaru urban area is home to ...

. Since the damming of the Waitaki River in 1935 erosion of the coastal cliffs has become the primary source of sediment in the north flowing current moving up the coast of

South South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþa ...

Canterbury Canterbury (, ) is a cathedral city and UNESCO World Heritage Site, situated in the heart of the City of Canterbury local government district of Kent, England. It lies on the River Stour. The Archbishop of Canterbury is the primate of t ...

Erosion mitigation

Engineered structures

This destruction of

sand dunes A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, fl ...

is often then mitigated with

construction Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and ...

seawalls A seawall (or sea wall) is a form of coastal defense constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a seawall is to protect areas of human habitation, conservatio ...

revetments A revetment in stream restoration, river engineering or coastal engineering is a facing of impact-resistant material (such as stone, concrete, sandbags, or wooden piles) applied to a bank or wall in order to absorb the energy of incoming water a ...

and groynes in often futile attempts to prevent storm erosion hazards to unsuitably located assets and infrastructure on coasts. These

engineered Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad range of more speciali ...

methods are commonly ineffective and frequently actually

magnify Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a calculated number also called "magnification". When this number is less than one, it refers to a reduction in si ...

the hazard or just move the hazard down coast. In

Porthcawl Porthcawl (, ) is a town and community on the south coast of Wales in the county borough of Bridgend, west of the capital city, Cardiff and southeast of Swansea. Historically part of Glamorgan and situated on a low limestone headland on the S ...

South Wales South Wales ( cy, De Cymru) is a loosely defined region of Wales bordered by England to the east and mid Wales to the north. Generally considered to include the historic counties of Glamorgan and Monmouthshire, south Wales extends westwards ...

, a seawall constructed to stop erosion in 1887 was replaced in 1906, 1934 and finally in 1984 when the beach was paved as each prior structure was undermined by further erosion. The loss of

aesthetics Aesthetics, or esthetics, is a branch of philosophy that deals with the nature of beauty and taste, as well as the philosophy of art (its own area of philosophy that comes out of aesthetics). It examines aesthetic values, often expressed t ...

due to the lack of a sand beach resulted in tourists utilising alternative beaches. Therefore, incurring an even greater economic loss on top of the cost of the engineering.

Restorative dune planting

The alternative to hard engineering measures is sand dune conservation. This involves protecting the sand dunes and allowing the natural buffering processes to occur. Dune protection and conservation can be facilitated in a number of ways, actively with

planting Sowing is the process of planting seeds. An area or object that has had seeds planted in it will be described as a sowed or sown area. Plants which are usually sown Among the major field crops, oats, wheat, and rye are sown, grasses and leg ...

and

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class ...

fencing Fencing is a group of three related combat sports. The three disciplines in modern fencing are the foil, the épée, and the sabre (also ''saber''); winning points are made through the weapon's contact with an opponent. A fourth discipline, ...

, or with better

planning Planning is the process of thinking regarding the activities required to achieve a desired goal. Planning is based on foresight, the fundamental capacity for mental time travel. The evolution of forethought, the capacity to think ahead, is c ...

by developing away from or well behind the dune structures not on them. On the New Brighton Spit the spread of

marram grass ''Ammophila'' (synonymous with ''Psamma'' P. Beauv.) is a genus of flowering plants consisting of two or three very similar species of grasses. The common names for these grasses include marram grass, bent grass, and beachgrass. These grasses ar ...

''(Ammophila arenaria)'' has resulted in effective dune stabilisation in areas. However this invasive

exotic Exotic may refer to: Mathematics and physics * Exotic R4, a differentiable 4-manifold, homeomorphic but not diffeomorphic to the Euclidean space R4 *Exotic sphere, a differentiable ''n''-manifold, homeomorphic but not diffeomorphic to the ordinar ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

has mostly replaced indigenous species like

pingao ''Ficinia spiralis'' (pīngao, pīkao, or golden sand sedge) is a coastal sedge endemic to New Zealand (including the Chatham Islands). Originally widespread, it has suffered severely from competition with introduced marram grass and animal gra ...

''(Desmoschoenus spiralis)'' meaning that although the stability of the coastal area has gained, the

historic History (derived ) is the systematic study and the documentation of the human activity. The time period of event before the invention of writing systems is considered prehistory. "History" is an umbrella term comprising past events as well ...

native Native may refer to: People * Jus soli, citizenship by right of birth * Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory ** Native Americans (disambiguation) In arts and entert ...

cultural Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups.T ...

values In ethics and social sciences, value denotes the degree of importance of something or action, with the aim of determining which actions are best to do or what way is best to live (normative ethics in ethics), or to describe the significance of di ...

of the area have suffered.

Beach nourishment

A further soft-engineering method for protecting the

shoreline A shore or a shoreline is the fringe of land at the edge of a large body of water, such as an ocean, sea, or lake. In physical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water past a ...

beach nourishment Beach nourishment (also referred to as beach renourishment, beach replenishment, or sand replenishment) describes a process by which sediment, usually sand, lost through longshore drift or erosion is replaced from other sources. A wider beach ...

. The presence of beach nourishment has been correlated with increases in number of homes and home size along the coast of Florida, US, which ultimately leads to an increase in exposure to coastal hazards. Due to the cost of

, this is a solution that has been used primarily for the benefit of the tourism

industry Industry may refer to: Economics * Industry (economics), a generally categorized branch of economic activity * Industry (manufacturing), a specific branch of economic activity, typically in factories with machinery * The wider industrial sector ...

. For example, erosion

Miami Beach Miami Beach is a coastal resort city in Miami-Dade County, Florida. It was incorporated on March 26, 1915. The municipality is located on natural and man-made barrier islands between the Atlantic Ocean and Biscayne Bay, the latter of which ...

had almost no stored sediment left by the mid 1970s, consequently, visitor numbers declined and development of the area decreased. A beach nourishment program was set up resulting in an influx of development and infrastructure in the late 1970s. Miami Beach was rejuvenated to such an extent that annual

revenue In accounting, revenue is the total amount of income generated by the sale of goods and services related to the primary operations of the business. Commercial revenue may also be referred to as sales or as turnover. Some companies receive rev ...

from foreign tourists alone is $2.4 billion, compared to the $52 million cost of the 20-year nourishment project.

Tax A tax is a compulsory financial charge or some other type of levy imposed on a taxpayer (an individual or legal entity) by a governmental organization in order to fund government spending and various public expenditures (regional, local, or n ...

revenue from tourists who visit Miami Beach alone more than covers the cost of beach nourishment projects across the

nation A nation is a community of people formed on the basis of a combination of shared features such as language, history, ethnicity, culture and/or society. A nation is thus the collective identity of a group of people understood as defined by th ...

. Using the capitalised annual cost of the project, for every $1 that has been invested annually on the nourishment, Miami Beach has received almost $500 annually in foreign exchange.

References

{{coastal management Coastal engineering Hazards ru:Закрепление песков