Sand dune stabilization is a

coastal management Coastal management is defence against flooding and erosion, and techniques that stop erosion to claim lands. Protection against rising sea levels in the 21st century is crucial, as sea level rise accelerates due to climate change. Changes in s ...

practice designed to prevent erosion of sand dunes.

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 ...

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 ...

s are common features of shoreline and desert environments. Dunes provide habitat for highly specialized plants and animals, including rare and

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

. They can protect beaches from erosion and recruit sand to eroded beaches. Dunes are threatened by human activity, both intentional and unintentional (see

sand theft Sand theft or unauthorised or illegal sand mining leads to a generally unknown global example of natural and non-renewable resource depletion problem comparable in extent to global water scarcity. Beach theft is illegal removal of large quanti ...

and sand mining). Countries such as the United States, Australia, Canada, New Zealand, the United Kingdom, and Netherlands, operate significant dune protection programs. Stabilizing dunes involves multiple actions. Planting

vegetation Vegetation is an assemblage of plants and the ground cover they provide. It is a general term, without specific reference to particular Taxon, taxa, life forms, structure, Spatial ecology, spatial extent, or any other specific Botany, botanic ...

reduces the impact of wind and water. Wooden sand fences can help retain sand and other material needed for a healthy sand dune ecosystem.

Footpath A footpath (also pedestrian way, walking trail, nature trail) is a type of thoroughfare that is intended for use only by pedestrians and not other forms of traffic such as Motor vehicle, motorized vehicles, bicycles and horseback, horses. They ...

s protect dunes from damage from foot traffic. Helmgras kijkduin februari 2005

The location of the dune limits the types of plant that can thrive there. Beach dunes consist of the ''foredune'', the angled side which faces the ocean, the ''sand plain'' at the top of the dune, which may or may not be present, and the ''backdune'', the angled side that faces away from the ocean.

Foredune flora

Plants that thrive on the foredune must be tolerant to

salt spray Sea spray consists of aerosol particles formed from the ocean, primarily by ejection into Earth's atmosphere through bursting bubbles at the air-sea interface Sea spray contains both organic matter and inorganic salts that form sea salt aerosol ...

, strong winds, and burial by blowing/accumulating sand. Examples of beach and foredune vegetation of temperate zones include ''

Ammophila arenaria ''Ammophila arenaria'' is a species of grass in the family Poaceae. It is known by the common names marram grass and European beachgrass. It is one of two species of the genus '' Ammophila''. It is native to the coastlines of Europe and North Afr ...

'' (an invasive species on the west coast of North America), ''

Honckenya peploides ''Honckenya peploides'', the sea sandwort (UK) or seaside sandplant (Canada), is the only species in the genus ''Honckenya'' of the plant family Caryophyllaceae. Other common names include sea chickweed, sea pimpernal, sea-beach sandwort, and sea ...

'', '' Cakile maritima'', and ''

Spartina ''Spartina'' is a genus of plants in the grass family, frequently found in coastal salt marshes. Species in this genus are commonly known as cordgrass or cord-grass, and are native to the coasts of the Atlantic Ocean in western and southern Eu ...

coarctata''.

Backdune flora

Plants which thrive on the broad dune plain and backdune grow together into dense patches termed "dune mats" that hold the dune together. Examples of temperate zone flora of the plain and backdune include '' Hudsonia tomentosa'', '' Spartina patens'', '' Iva imbricata'', and '' Erigeron glaucus''. Introduced

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), ...

can out compete native plants and disrupt animal life, making them formally "invasive species".

Shrub stage

The above species are

herbaceous plant Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition o ...

s. After they have rooted and developed fully, a second stage, the "

shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...

stage", can begin. During this phase, larger plants with deeper root systems can be planted. Examples are '' Empetrum nigrum'', '' Ilex vomitoria'', and ''

Vaccinium ovatum ''Vaccinium'' is a common and widespread genus of shrubs or dwarf shrubs in the heath family (Ericaceae). The fruits of many species are eaten by humans and some are of commercial importance, including the cranberry, blueberry, bilberry (w ...

''. The shrub stage is variable depending on

microclimate A microclimate (or micro-climate) is a local set of atmosphere of Earth, atmospheric conditions that differ from those in the surrounding areas, often slightly but sometimes substantially. The term may refer to areas as small as a few square m ...

, and may be influenced the height of the

water table The water table is the upper surface of the phreatic zone or zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, which may be fresh, saline, or brackish, depending on the loc ...

, wind and

. The shrub stage may eventually give way to forest or

chaparral Chaparral ( ) is a shrubland plant plant community, community found primarily in California, southern Oregon, and northern Baja California. It is shaped by a Mediterranean climate (mild wet winters and hot dry summers) and infrequent, high-intens ...

Coastal management

A single beach may be divided into segments with different owners. Gaining agreement among all owners complicates the process of stabilizing the dunes. Without agreement, some parts of the dune may go unplanted, while others host visually appealing plants that do little to stabilize the dune. Inconsistent vegetation, known as a fragmented or decoupled gradient, can create weak points in the dune that limit its effectiveness against floods and even its continued existence. Publicly owned beaches, found in U.S. states such as California and Hawaii and in other jurisdictions, present the opportunity to systematically manage—or mismanage—beaches and their accompanying dunes.

Coastal sand dune management

Coastal sand dunes fringe thousands of kilometres of coastline around the world. They are made up of continuous, hummocky hills of sand that are held together by specially adapted sand dune vegetation. See Figure 1. These plants have

adaptations In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the p ...

that allow them to survive in sand dune

habitats In ecology, habitat refers to the array of resources, 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 manifestation of its ...

, these include adaptations to a moving substrate which covers and uncovers its roots, adaptation to

desiccation Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. The ...

, to strong winds carrying salt and sand and to wildly changing temperatures. Coastal sand dunes formed during a time of low

sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...

where sand and sediments on the foreshore became exposed and in conjunction with sufficient winds, this sand was transported up the beach face via a process known as saltation.Aargard et.al, 2007 Once sufficient wind (>15 km/h) mobilises sand particles they become trapped in vegetation or drift wood at the back of the beach, sand then continues to accumulate among the vegetation and over time slowly builds up the dunes we see today. Sand dunes serve an important purpose by protecting inland areas from coastal water intrusion. They are able to absorb the impact and protect inland areas from high energy

storms 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) ...

and act as a resilient barrier to the destructive forces of wind and

waves United States Naval Reserve (Women's Reserve), better known as the WAVES (for Women Accepted for Volunteer Emergency Service), was the women's branch of the United States Naval Reserve during World War II. It was established on July 21, 1942, ...

Human impacts

It is generally observed that

coastal 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, flat ...

are highly sensitive to any number of human activities. It is also understood that coastal dunes need to have limited interaction with humans in order for their protection and survival. Around the world coastal dunes are eroding and under pressure due to increased

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 ...

loss because of increased coastal human activities. For example, in the last 30 years, mainly because of tourism, nearly 75% of the Mediterranean's coastal dunes have been damaged or destroyed. Human impacts can expand from minor to highly significant adverse effects. Minor effects include pedestrian trampling, constructing footpaths, and off-road vehicle tracks, to the more significant which includes the construction of roads, car parks, houses, the use of sand dunes for ground water extraction, the conversion of sand dunes to land for

farming Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...

forestry Forestry is the science and craft of creating, managing, planting, using, conserving and repairing forests and woodlands for associated resources for human and Natural environment, environmental benefits. Forestry is practiced in plantations and ...

or waste disposal and sand dune mining. China is a country with a very long

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 ...

line that consists of around 1090 km of sand dunes. From the early 1900s to the early 2000s the area of sand dunes has declined by about 70% from 129,000 ha to 39,000 ha. This decline has been mainly due to erosion caused by the depletion of vegetation cover in order to convert sand dunes to land for forestry, farming and urban areas. Loss in vegetation cover exposes sand to the action of wind and leaves sand dunes vulnerable to increased erosion as it is vegetation that binds sand together. The loss of vegetation causes sand to move inland which is a process known as sand encroachment, this process can having damaging effects on inland properties and leaves properties vulnerable to future coastal hazards for example

storm surge A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the ...

. As well as human activities, natural processes operate within coastal dune environments, these processes include events such as

floods A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

, sea level change, and sediment supply changes. Coastal dune systems are mainly controlled by a principal natural process called the sediment supply and transport system. This system consists of an offshore zone (sediment bank), transit zone (beach and active foredune) and a resting zone (stable sand dunes). The sediment in this system is supplied by long shore drift predominantly from

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

s and from the erosion of cliffs, headlands, other dune systems and when sediment supply is low sand dunes are subject to erosion. Humans affect sediment supply in a number of ways including the damming of rivers,

dredging Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing d ...

in coastal water and the construction of

harbours A harbor (American English), or harbour (Commonwealth English; see spelling differences), is a sheltered body of water where ships, boats, and barges can be moored. The term ''harbor'' is often used interchangeably with ''port'', which is ...

, all of which depletes sediment supply. They also disrupt the long shore transport of sediment through the construction of piers,

marinas A marina (from Spanish language, Spanish , Portuguese language, Portuguese and Italian language, Italian : "related to the sea") is a Dock (maritime), dock or basin with moorings and supplies for yachts and small boats. A marina differs from a ...

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 ...

breakwaters A breakwater is a permanent structure constructed at a coastal area to protect against tides, currents, waves, and storm surges. Breakwaters have been built since antiquity to protect anchorages, helping isolate vessels from marine hazards ...

and other hard structures. Excavating, building roads, houses and walkways on coastal dunes or beaches also causes sand dune erosion by disrupting natural sediment processes. Effective management of coastal dune systems must consider natural processes as a normal part of the natural environment as well as controlling human activities and seeking to alter natural processes should be kept at a minimum in order for restoration to be successful.

Integrated management

Sand dunes are an important part of the coast as they are land's first defence against the forces of the

ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...

. Because of this,

management Management (or managing) is the administration of organizations, whether businesses, nonprofit organizations, or a Government agency, government bodies through business administration, Nonprofit studies, nonprofit management, or the political s ...

of sand dunes will focus on the natural authenticity and values of the dunes themselves including

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

fauna Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...

, and the

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

as a whole. The concept of integrated management can be incorporated into management of coastal sand dunes. This concept is made up of three main aspects: * Restore and conserve natural processes * Create conditions for future natural processes * Develop types of land use that agree with the above These concepts seek to incorporate natural processes and human activities within coastal dunes systems. Sand dune management issues are related to the nature of sediment, which has no cohesiveness so the influence of wind and sediment supply is an important factor in determining erosion and deposition of dry sand grains . Sand dune management consists of restoring natural dune systems and processes with the implementation of “soft” technique which includes the cessation of any activity that adversely effects the sediment supply of the dunes, planting vegetation, fencing off sensitive areas, creating dune walkways, and providing information to the public regarding the importance of maintaining stable sand dunes. The concept of “soft” techniques is in contrast to the widely used “hard” techniques which consist of protecting the coast through the construction of concrete sea walls, revetments,

gabions A gabion (from Italian language, Italian ''gabbione'' meaning "big cage"; from Italian ''gabbia'' and Latin ''cavea'' meaning "cage") is a Cage (enclosure), cage, cylinder (geometry), cylinder or box filled with rocks, concrete, or sometimes s ...

and offshore break waters. The problem with using these “hard” engineering methods is that they only provide temporary protection against ocean hazards and each "hard" method produces an “end effect” that causes erosion problems to adjacent coastal areas. This is why the implementation of “soft” techniques in dune restoration should be used more widely in coastal protection as they provide natural, long term protection with no adverse effect to adjacent coastal areas. The use of soft techniques can be seen in many coastal protection projects around the world including many in New Zealand.

Restoration and protection

One of the first things a coastal manager must look for when establishing sand dune

is to ascertain the main cause of sediment loss and from there, make decisions on how to minimise the cause and how to restore sand dunes appropriately. In New Zealand the main cause of dune erosion has been the loss of sand vegetation and this means that sand dune management consists primarily of stabilizing dune systems through the “soft” technique of replanting and protecting native dune vegetation. It is advised that dunes should not be restored with the planting of exotic species and managers should aim to only use species indigenous to an area, originally New Zealand used exotic, fast growing dune vegetation called marram grass to stabilize eroding sand dunes. It was later discovered that this exotic species created very high, steep sand dunes that were increasingly susceptible to New Zealand's high storm energy climate. It also became apparent that the native New Zealand dune vegetation was out-competed by this introduced species which caused issues biologically. At present, there is a large push to eradicate marram grass as it is now classed as a pest species in New Zealand, and coastal managers encourage the

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 ...

of the two indigenous species, pingao ('' Desmoschoenus spiralis'') and '' Spinifex sericeus'' as these two species create low angle, strong, stable dunes. The management of dune restoration projects includes planting vegetation successfully. Merely scattering and leaving

seeds In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be sown, which may include seed and husk or tuber. Seeds are the ...

over sandy areas is perceived as a potential waste as strong winds can blow seeds away. Planting of nurseries should be conducted in the hollows of any present sand hills or in depressions of sandy areas. Seeds should be planted in moist conditions and should be lightly covered by a layer of sand and large mature grass individuals should be planted in deep holes with the tops of the plants cut short so as to reduce wind resistance. Planting of sand dune vegetation alone does not entirely restore or protect sand dunes from human impacts.

Seedlings A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle (embryonic root), the hypocotyl (embry ...

need to be protected from human trampling, which is done mainly by fencing off newly planted areas. Fencing also acts as another way of trapping and accumulating sand among the dunes and can also act as protection against strong winds. Figure two shows an area of newly planted vegetation at Spencer Park Beach, New Zealand. It shows that fencing protects plants from trampling and figure three shows how small fencing using

chicken wire The chicken (''Gallus gallus domesticus'') is a domesticated subspecies of the red junglefowl (''Gallus gallus''), originally native to Southeast Asia. It was first domesticated around 8,000 years ago and is now one of the most common and ...

can encourage plants to grow. In addition to erecting fences to protect sand dune vegetation, the establishment of walkways will protect developed sand dunes from degrading again over time. These walkways provide access to beaches for the public that does not require pedestrians to cross the dunes themselves thus preventing damage. Figure four shows a typical walkway at New Brighton Beach, New Zealand. The walkway itself is built to go over the sand dunes as opposed to straight through them, in order to maintain the continuity and strength of the dunes.

The public

Because sand dunes and beaches are extremely popular for

outdoor recreation Outdoor recreation or outdoor activity refers to recreation done outside, most commonly in natural settings. The activities that encompass outdoor recreation vary depending on the physical environment they are being carried out in. These activitie ...

, the success of restoration and dune management depends a great deal on the information available and understanding of the public. This is important because not all aspects of sand dune management are obvious or important to the public if they do not understand why management is necessary e.g. stabilization. There are many ways in which information can be provided to the public including the erection of panels at entrances to dune walkways, leaflets, brochures, maps and council workers who can talk to the public about the importance of protecting sand dunes. Figure five shows a photo of a panel put up at Spencer Park by the Christchurch City Council indicating that people should not walk on the area, as it is an area for sand dune restoration. It needs to be re-iterated that sand dune restoration and protection is in the public's best interest as the loss of sediment on any coast line leads to the erosion of beaches, which in turn leads to a loss of recreational value of many coastlines. The public needs to be aware of the role that sand dunes play in coastal protection, because without public support, coastal sand dune management is virtually impossible.

Notes

References

* Aagaard T, Orford J and Murray AS (2007) "Environmental controls on coastal dune formation: Skallingen Spit, Denmark", ''Geomorphology'', 86: 29–47.

External links

Sand Dune Stabilization And Reclamation In Southeastern ColoradoMonitoring sand dune stabilization along the coastal dunes of Ashdod-Nizanim, Israel, 1945–1999Vetiver System for Sand Dune Stabilization A Vietnamese Experience
* {{Deserts Dunes Ergs Coastal engineering