A coastal development hazard is something that affects the natural environment by human activities and products. As coasts 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 Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

is a process that happens naturally on the Canterbury Bight as a part of the coastal

geomorphology Geomorphology () is the scientific study of the origin and evolution of topographic and bathymetric features generated by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand wh ...

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 disaster is the very harmful impact on a society or community brought by natural phenomenon or hazard. Some examples of natural hazards include avalanches, droughts, earthquakes, floods, heat waves, landslides - including submarin ...

is defined as the release of

energy Energy () is the physical quantity, quantitative physical property, property that is transferred to a physical body, body or to a physical system, recognizable in the performance of Work (thermodynamics), work and in the form of heat and l ...

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 thunderstor ...

event or

tsunami A tsunami ( ; from , ) 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 underwater explosions (including detonations, ...

, 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 Wind wave, waves, Ocean current, currents, tides, wind-driven water, waterborne ice, or other impacts ...

sea-level rise The sea level has been rising from the end of the last ice age, which was around 20,000 years ago. Between 1901 and 2018, the average sea level rose by , with an increase of per year since the 1970s. This was faster than the sea level had e ...

. 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 A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

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

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

of people living on the coasts since 1995. The average

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

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

city A city is a human settlement of a substantial size. The term "city" has different meanings around the world and in some places the settlement can be very small. Even where the term is limited to larger settlements, there is no universally agree ...

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

economic An economy is an area of the Production (economics), production, Distribution (economics), distribution and trade, as well as Consumption (economics), consumption of Goods (economics), goods and Service (economics), services. In general, it is ...

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 Hamburg, Manch ...

s. In 1950, there were only 2 megacities (cities with greater than 8 million people) in the coastal zone,

London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...

and

New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...

. 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 ant ...

s over the last 200 years around the

Bay of Bengal The Bay of Bengal is the northeastern part of the Indian Ocean. Geographically it is positioned between the Indian subcontinent and the Mainland Southeast Asia, Indochinese peninsula, located below the Bengal region. Many South Asian and Southe ...

exceeding 1.3 million. However, in

developed countries A developed country, or advanced country, is a sovereign state that has a high quality of life, developed economy, and advanced technological infrastructure relative to other less industrialized nations. Most commonly, the criteria for eval ...

, 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 compact, but very powerful and devastating tropical cyclone that struck the Bahamas, Florida, and Louisiana in August 1992. It was the most destructive hurricane to ever hit Florida in terms of structures dama ...

, which hit

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

and

Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...

in 1992. This rushing to the coast is exhibited in property value. A study by Bourassa et al. (2004) found that in

Auckland Auckland ( ; ) is a large metropolitan city in the North Island of New Zealand. It has an urban population of about It is located in the greater Auckland Region, the area governed by Auckland Council, which includes outlying rural areas and ...

, 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 () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

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 protect ...

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 happiness, enjoyment, amusement, ...

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

natural Nature is an inherent character or constitution, particularly of the ecosphere or the universe as a whole. In this general sense nature refers to the laws, elements and phenomena of the physical world, including life. Although humans are part ...

phenomena A phenomenon ( phenomena), sometimes spelled phaenomenon, is an observable Event (philosophy), event. The term came into its modern Philosophy, philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which ''cannot'' be ...

are likely to pose a significant threat for the loss of

capital assets A capital asset is defined as property of any kind held by an assessee. It need not be connected to the assesse’s business or profession. The term encompasses all kinds of property, movable or immovable, tangible or intangible, fixed or circula ...

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 the change in the heritable characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certa ...

process of fine

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

, 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 (geology), rock, such as sand, gravel, shingle beach, shingle, pebbles, etc., or biological s ...

. Increased wave energy in storms leads to the removal of

foreshore The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of Marine habitat, habitats ...

berm A berm is a level space, shelf, or raised barrier (usually made of Soil compaction, 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 b ...

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, flat ...

sediments. These displaced sediments are then deposited as near

shore A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

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. 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 from erosion and minimising coastal retreat.

Dune destruction

Sand dunes 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 oth ...

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, on the west coast of the

North Island The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...

, 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 in New Zealand was said to have reached up to 8 meters per year. This coastal process could be measured in more ways than one, the aforementioned distance of coastal retreat or the decreased 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 pri ...

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 organism, forms of lifeparticularly the rearing of livestock and production of cropsto produce food for humans. It is generally synonymous ...

, threatened valuable infrastructure including

holiday A holiday is a day or other period of time set aside for festivals or recreation. ''Public holidays'' are set by public authorities and vary by state or region. Religious holidays are set by religious organisations for their members and are often ...

settlements, and reduced coastal

lagoons A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into '' coastal lagoons'' (or ''barrier lagoons'') a ...

and

wetlands A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...

. 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 in the South Island of New Zealand. It drains the Mackenzie Basin and runs south-east to enter the Pacific Ocean between Timaru and Oamaru on the east coast. It starts at the confluence of the Ōhau Ri ...

was the dominant source of sediments for the beaches between

Oamaru Oamaru (; ) 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 Ocean, Pacific coast; State Highway 1 (New Zealand), Sta ...

and

Timaru Timaru (; ) 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 Ocean, Pacific coast of the South Island. The Timaru urban area is home to peo ...

. 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 Canterbury.

Erosion mitigation

Engineered structures

This destruction of sand dunes is often then mitigated with

construction Construction are processes involved in delivering buildings, infrastructure, industrial facilities, and associated activities through to the end of their life. It typically starts with planning, financing, and design that continues until the a ...

of seawalls, revetments and

groynes A groyne (in the U.S. groin) is a rigid aquatic structure built perpendicularly from an ocean shore (in coastal engineering) or a river bank, interrupting water flow and limiting the movement of sediment. It is usually made out of wood, concrete ...

in often futile attempts to prevent storm erosion hazards to unsuitably located assets and infrastructure on coasts. These engineered methods are commonly ineffective and frequently actually magnify the hazard or just move the hazard down coast. In

Porthcawl Porthcawl () is a town and community in the Bridgend County Borough of Wales. It is located on the south coast, west of Cardiff and south-east of Swansea. Historically part of Glamorgan and situated on a low limestone headland on the South ...

South Wales South Wales ( ) is a Regions of Wales, 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 Wales, historic counties of Glamorgan and Monmouthshire ( ...

, 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 (also spelled esthetics) is the branch of philosophy concerned with the nature of beauty and taste (sociology), taste, which in a broad sense incorporates the philosophy of art.Slater, B. H.Aesthetics ''Internet Encyclopedia of Ph ...

due to the lack of a sand beach resulted in

tourists Tourism is travel for pleasure, and the Commerce, commercial activity of providing and supporting such travel. World Tourism Organization, UN Tourism defines tourism more generally, in terms which go "beyond the common perception of tourism as ...

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 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 legumes are ...

and

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

fencing Fencing is a combat sport that features sword fighting. It consists of three primary disciplines: Foil (fencing), foil, épée, and Sabre (fencing), sabre (also spelled ''saber''), each with its own blade and set of rules. Most competitive fe ...

, 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. Some researchers regard the evolution of forethought - the cap ...

by developing away from or well behind the dune structures not on them. On the New Brighton Spit the spread of marram grass ''(Ammophila arenaria)'' has resulted in effective dune stabilisation in areas. However this invasive exotic

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

has mostly replaced indigenous species like pingao ''(Desmoschoenus spiralis)'' meaning that although the stability of the coastal area has gained, the

historic History is the systematic study of the past, focusing primarily on the human past. As an academic discipline, it analyses and interprets evidence to construct narratives about what happened and explain why it happened. Some theorists categ ...

, native

cultural Culture ( ) is a concept that encompasses the social behavior, institutions, and Social norm, norms found in human societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, Attitude (psychology), attitudes ...

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

of the area have suffered.

Beach nourishment

A further soft-engineering method for protecting the

shoreline A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

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 c ...

. 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. For example, erosion

Miami Beach Miami Beach is a coastal resort city in Miami-Dade County, Florida, United States. It is part of the Miami metropolitan area of South Florida. The municipality is located on natural and human-made barrier islands between the Atlantic Ocean an ...

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 product (business), goods and services related to the primary operations of a business. Commercial revenue may also be referred to as sales or as turnover. Some compan ...

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 mandatory financial charge or levy imposed on an individual or legal entity by a governmental organization to support government spending and public expenditures collectively or to regulate and reduce negative externalities. Tax co ...

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

nation A nation is a type of social organization where a collective Identity (social science), identity, a national identity, has emerged from a combination of shared features across a given population, such as language, history, ethnicity, culture, t ...

. 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