Cuspate forelands, also known as cuspate barriers or nesses in

Britain Britain most often refers to: * The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands * Great Britain, the largest island in the United King ...

, are geographical features found on coastlines and lakeshores that are created primarily by

longshore drift Longshore drift from longshore current is a geological process that consists of the transportation of sediments (clay, silt, pebbles, sand, shingle) along a coast parallel to the shoreline, which is dependent on the angle incoming wave direction ...

.Craig-Smith, S. J., Cuspate Forelands. In: M. L. Schwartz, ed. 2005. ''Encyclopedia of Coastal Science.'' The Netherlands: Springer, pp. 354–355. Formed by accretion and

progradation In sedimentary geology and geomorphology, the term progradation refers to the growth of a river delta farther out into the sea over time. This occurs when the volume of incoming sediment is greater than the volume of the delta that is lost through ...

of sand and shingle, they extend outwards from the shoreline in a triangular shape. Some cuspate forelands may be stabilised by vegetation, while others may migrate down the shoreline. Because some cuspate forelands provide an important habitat for flora and fauna, effective management is required to reduce the impacts from both human activities and physical factors such as

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

and

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 Cr ...

Formation

The debate involving how cuspate forelands form is ongoing.McNinch, J. E., and Luettich, R. A., 2000. Physical processes around a cuspate foreland: implications to the evolution and long-term maintenance of a cape-associated shoal. ''Continental Shelf Research. '' 20, pp. 2367–2389. However, the most widely accepted process of formation involves

long shore drift Longshore drift from longshore current is a geological process that consists of the transportation of sediments (clay, silt, pebbles, sand, shingle) along a coast parallel to the shoreline, which is dependent on the angle incoming wave directio ...

. Where longshore drift occurs in opposite directions, two spits merge into a triangular protrusion along a coastline or lakeshore. Their formation is also dependent on dominant and prevailing winds working in opposite directions. Formation can also occur when waves are diffracted around a barrier. Cuspate forelands can form both along coastlines and along lakeshores. Those formed along coastlines can be in the lee of an offshore island, along a coastline that has no islands in the vicinity, or at a stream mouth where disposition occurs.Bird, E., 2008 ''Coastal geomorphology: an introduction.'' 2nd ed. England: John Wiley & Sons Ltd.

Formation in narrow straits or on open coastlines

A cuspate foreland can form in a strait or along a coastline that has no islands or

shoal In oceanography, geomorphology, and geoscience, a shoal is a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material and rises from the bed of a body of water to near the surface. It ...

s in the area. In this case, longshore drift as well as prevailing wind and waves bring sediment together from opposite directions. If there is a large angle between the waves and the shoreline, the sediment converges, accumulates, and forms

beach ridge A beach ridge is a wave-swept or wave-deposited ridge running parallel to a shoreline. It is commonly composed of sand as well as sediment worked from underlying beach material. The movement of sediment by wave action is called ''littoral tran ...

s.Ashton, A., et al., 2001. ''Formation of coastline features by large-scale instabilities induced by high-angle waves.'' Nature, 414(6861), pp. 296–300. Over time, a cuspate foreland forms as a result of continued accretion and progradation. An example of this type of cuspate foreland is the one found at Dungeness along the southern coast of Britain.Davis, R. A., and FitzGerald, D., 2004. ''Beaches and Coasts.'' Blackwell Publishing: Australia. This cuspate foreland has formed as a result of the merging of SW waves from the English Channel, and waves from the east from the Strait of Dover. Another example is the cuspate foreland found between Awatere River and White Bluffs in Marlborough, New Zealand.Pickrill, R. A., 1977. Coastal processes, beach morphology, and sediments along the north-east coast of the South Island, New Zealand. ''New Zealand Journal of Geology and Geophysics.'' 20(1). pp. 1–15. This foreland has ridges on the eastern and northern sides which face the prominent waves. In other circumstances, spits are formed when long shore drift moves beach material down the

beach 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 s ...

until the

coastline 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 ...

makes an abrupt change in direction, leading to the beach material 'spilling over' the corner to create a protrusion. This normally occurs across a

river mouth A river mouth is where a river flows into a larger body of water, such as another river, a lake/reservoir, a bay/gulf, a sea, or an ocean. At the river mouth, sediments are often deposited due to the slowing of the current reducing the carrying ...

. In the case of a cuspate foreland, the

prevailing wind In meteorology, prevailing wind in a region of the Earth's surface is a surface wind that blows predominantly from a particular direction. The dominant winds are the trends in direction of wind with the highest speed over a particular point o ...

and a powerful secondary wind in the opposite direction move shingle down the coastline from both directions to a place where the coastline changes, causing a foreland to develop. The majority of cuspate forelands are formed over a coastline that juts out into the sea at enough of an angle to allow the drifting beach material to 'spill over' as a result of long shore drift in both directions.

Formation in the lee of an island

A cuspate foreland can form in the lee of an island. In this case, oncoming waves are diffracted around the island, protecting the coastline from the oncoming wave fronts.

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 ...

s brought along the shoreline via longshore drift are then able to settle and accumulate in the lee of the island where there is less wave energy. This type of foreland has formed on the west shore of the North Island of New Zealand, in the lee of

Kapiti Island Kapiti Island () is an island about off the west coast of the lower North Island of New Zealand. It is long, running southwest/northeast, and roughly wide, being more or less rectangular in shape, and has an area of . Its name has been used s ...

.Wright, L. W., 1988. The sand country of the ‘Golden Coast’, Wellington, New Zealand. ''New Zealand Geographer.'' 44(1). pp. 28–31. Waves refract around Kapiti Island, forming an area of low wave energy where sediment from the Waikanae River is able to settle. There is uncertainty whether the cuspate foreland has formed as a result of sediments coming from the north via longshore drift, or whether it has formed as a result of a complex cycle of sediments moving out to the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

and then back again.

Formation along lakeshores

As well as forming along coastlines, cuspate forelands can also form along lake shores, although less is known about this type of cuspate foreland. This type of cuspate foreland includes

Point Pelee Point Pelee National Park (; french: Parc national de la Pointe-Pelée) is a national park in Essex County in southwestern Ontario, Canada where it extends into Lake Erie. The word is French for 'bald'. Point Pelee consists of a peninsula of la ...

along the shoreline of Lake Erie, and those found along the shoreline of Lake Victoria in Australia. There are two theories with regard to the formation of Point Pelee. Firstly, it is thought that Point Pelee has formed from depositional processes.Trenhaile, A. S., 2000. Point Pelee: a large cuspate foreland on Lake Erie. ''Canadian Geographer, '' 44(2), pp. 191–195. Alternatively, it is suggested that Point Pelee is a relic of a past feature that has eroded over time. This gap in knowledge provides the opportunity for further research. It is likely that Point Pelee is migrating westwards since accretion is occurring on the western side, and erosion is occurring on the eastern side. Lake Victoria in Australia also has a number of cuspate forelands. Point Scott is a cuspate foreland along this lakeshore that has formed from the gradual accumulation of sand and gravel.Department of Primary Industrie
Point Scott – Raymond Island
''Department of Primary Industries, 2008. Accessed 31 March 2011.

Features

Cuspate forelands can be separated into three distinct areas: the central nose or apex, and two marginal wings. The apex usually has ridges that run parallel to the converging shorelines. Cuspate forelands can extend up to 5 km from the shoreline, and an underwater shoal may extend much further, up to 15 km from the exposed apex. Located between the mainland and the foreland are often lagoons or marshy areas. In some areas, such as along the North Carolina coastline, a series of cuspate forelands may form at least 100 km apart. In areas that have a large amount of shingle, such as the cuspate foreland at Dungeness, it is also common for a fresh

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...

to be present.

Movement

Once formed, cuspate forelands can remain where they are and continue to develop as sediment accumulates, or alternatively they may migrate down the coast as one side of the foreland erodes and the other side accretes. Cuspate Forelands that move are typical of those that are formed on open coastlines. The direction of migration is often indicated by a series of successive beach ridges on the advancing side of the foreland where there is less wave energy. The movement of cuspate forelands is commonly explained by longshore drift acting as the main process. However, there have been observed cases where two cuspate forelands on the same shoreline have migrated in opposite directions, showing that longshore drift does not always provide a sufficient explanation for their migration. If there is an offshore sandbank present, the position of the cuspate foreland is usually related to its position. If there is a change in the position of the sandbank, the position of the cuspate foreland typically follows. Not only does the sandbank act like an island since it causes waves to refract around it, but it also provides a source of sediment. As sand erodes from the sandbank, it is pushed towards the coastline, contributing to the formation of the cuspate foreland as the sandbank migrates along the coast. This often occurs in the opposite direction to longshore drift. In the case of a cuspate foreland that has formed close to an island, it is possible for it to extend right up to the island, forming a

tombolo A tombolo is a sandy or shingle isthmus. A tombolo, from the Italian ', meaning 'pillow' or 'cushion', and sometimes translated incorrectly as ''ayre'' (an ayre is a shingle beach of any kind), is a deposition landform by which an island becom ...

. Depending on the physical conditions such as storms, the feature can alternate between a cuspate foreland and a tombolo. Gabo Island in South Australia is an example of where this occurs.

Succession

After the formation of the cuspate foreland into its distinctive triangular shape, it will start to be colonised by pioneer species that are hardy and tough enough to survive in the environment. These pioneer species secure the cuspate foreland and allow a greater amount of sediment to further secure it. Colonization and

succession Succession is the act or process of following in order or sequence. Governance and politics *Order of succession, in politics, the ascension to power by one ruler, official, or monarch after the death, resignation, or removal from office of ...

of vegetation is dependent on a number of factors. Firstly, if the shingle is too coarse, the amount of fine sediment that can remain between the spaces is reduced, and the likelihood that seeds will germinate and grow upwards is low.Randall, R. E., 2004. Management of coastal vegetated shingle in the United Kingdom. ''Journal of Coastal Conservation'', 10, pp. 159–168. Seeds will also fail to germinate and grow if there is insufficient retention of fresh water. Stable cuspate forelands that are composed of shingle often have vegetation above the high tide line. As vegetation is established, mites and collembolans break down plant matter such as roots, resulting in the accumulation of organic matter. Plants also cause the soil to develop and water retention to increase, therefore providing a habitat where more plants can grow. Vegetation above the high tide line is common on cuspate forelands that are stable and composed of shingle.

Biological habitat

Cuspate forelands provide a habitat for various

flora Flora is all the plant life present in a particular region or time, generally the naturally occurring ( indigenous) native plants. Sometimes bacteria and fungi are also referred to as flora, as in the terms '' gut flora'' or '' skin flora''. ...

and

fauna Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is '' flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as '' biota''. ...

. If a foreland is relatively stable and experiences low wave impact, it may be possible for vegetation to grow. In the United Kingdom, 11 taxa of

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordat ...

are found on shingle habitats. Shingle beaches also provide a habitat for birds to breed, nest, and rest en route while migrating.

Impacts and management

There are different management issues with regard to cuspate forelands depending on their formation. If a cuspate foreland has formed from deposition, it may be vulnerable if human interference alters the transport of sediments from the shoreline. However, if the cuspate foreland is a relic of a past feature that has eroded, human interference with longshore sediment movement will not have a significant impact on the cuspate foreland. For a cuspate foreland to be maintained, the input of sediment must be greater than output of sediment. Activities such as coastal development or engineering must be regulated for sediment to continue moving towards the foreland where it can be deposited. Development along cuspate forelands is risky due to erosion and the vulnerability to storms and sea level rise. As sea levels rise, cuspate forelands are likely to be at risk as they could move inland. At Point Pelee, approximately 1,900 hectares of former agricultural land on the cuspate foreland is now under water as a result of wind erosion and compaction of organic soils on the foreland. This foreland is particularly vulnerable to erosion when high lake levels are combined with spring and autumn cyclonic activity. Erosion can also occur as spring storms cause ice to scour the lake bottom at the edge of the foreland. Because there is uncertainty about its formation, there is uncertainty with regard to management, although Parks Canada realises the importance of including Point Pelee National Park in management plans.Parks Canada
Point Pelee National Park of Canada
''Parks Canada'', 2010. Accessed 8 April 2011. When there is an

aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials ( gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characte ...

present under a cuspate foreland, regulation of water removal is required. At Dungeness, water restrictions have been put in place to maintain the aquifer level. The management of coastlines needs to take into account the natural processes that occur on cuspate forelands since many provide a

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

for birds. Alternative ways of managing coastal erosion is needed, such as the use of ‘soft’ defences instead of high impact defences such as sea walls. Some cuspate forelands naturally do not contain any vegetation due to a high level of disturbance from physical factors such as wave action. However, with the frequency of storms arising from climate change, the effect on forelands and their associated vegetation needs to be effectively managed.