Common physical and anthropogenic causes of coastal land loss

Land loss is the term typically used to refer to the conversion of coastal land to open water by natural processes and human activities. The term ''land loss'' includes

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 ...

. It is a much broader term than coastal erosion because land loss also includes land converted to open water around the edges of estuaries and interior bays and lakes and by subsidence of coastal plain wetlands. The most important causes of land loss in coastal plains are

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 ...

, inadequate sediment supply to

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

es and

wetland 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 ...

subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...

, and global

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 ...

. The mixture of processes responsible for most of the land loss will vary according to the specific part of a coastal plain being examined.Morton, R.A., 2003
''An overview of coastal land loss: with emphasis on the Southeastern United States.''
''Open-File report 03-337. US Geological Survey'', Center for Coastal and Watershed Studies, St. Petersburg, Florida. 28 pp.Britsch, L.D. and Kemp III, E.B., 1990. ''Land loss rates: Mississippi River deltaic plain. Technical Report no. WES/TR/GL-90-2''. Geotechnical Lab, Army Waterways Experiment Station, Vicksburg, Mississippi. The definition of land loss does not include the loss of coastal lands to agricultural use, urbanization, or other development.Barras, J.A., P.E. Bourgeois, and L.R. Handley. 1994. ''Land loss in coastal Louisiana 1956-90.'' ''National Biological Survey, National Wetlands Research Center Open File Report 94-01.'' 4 pp.

Wetland loss

Although seemingly related,

loss, is defined differently than land loss. Commonly, wetland loss is defined as the conversion of vegetated wetlands into either uplands or drained areas, unvegetated wetlands (e.g., mudflats), or (submerged habitats (open water). According to this, and similar definitions, wetland loss includes both land loss and land consumption as components of it. In historic times, both wetland and land loss typically are the result of a varying, often controversial mixture of natural and anthropogenic factors.Boesch, D.F., Josselyn, M.N., Mehta, A.J., Morris, J.T., Nuttle, W.K., Simenstad, C.A. and Swift, D.J., 1994. ''Scientific assessment of coastal wetland loss, restoration and management in Louisiana. '' ''Journal of Coastal Research, Special Issue No. 20'', pp.1-103.Chan, A.W. and Zoback, M.D., 2007. ''The role of hydrocarbon production on land subsidence and fault reactivation in the Louisiana coastal zone.'' ''Journal of Coastal Research'', 23(3) pp.771-786. There are other definitions of wetland loss commonly used. For example, some researchers defined wetland loss as "the substantial removal of wetland from its ecologic role under natural conditions."Craig, N.J., Turner, R.E. and Day, J.W., 1979. Land loss in coastal Louisiana (USA). Environmental Management, 3(2), pp.133-144.

Land loss mechanisms

The main causes of land loss are

, inadequate sediment supply,

, and

. Coastal erosion occurs when the rate of sediment deposition is slower than the rate of sediment removal by coastal currents.McManus, John., 2002. "Deltaic responses to changes in river regimes." "Marine Chemistry", 79(3-4) pp. 155-170. The most important cause of decreased rates of sediment deposition is the construction of dams and reservoirs although sediment control and conservation programs can also play a role.Walling, D.E. and Fang, D., 2003. "Recent trends in the suspended sediment loads of the world's rivers." "Global and Planetary Change", 39(1-2), pp. 111-126. Once a dam is constructed, sediment that previously traveled freely in the river is trapped in the reservoir. Decreased sediment loads downstream of the dam prevent sediment from replenishing the delta.Kondolf, G. Mathias, et al., 2014. "Sustainable sediment management in reservoirs and regulated rivers: Experiences from five continents." "Earth's Future", 2(5), pp. 256-280. Subsidence is the compaction of soil resulting in a lower elevation. Subsidence can occur when oil, gas, or groundwater are extracted. These substances hold the land up until they are removed. Compaction due to heavy urban infrastructure also occurs.Schmidt, Charles W., 2015. "Delta Subsidence: An Imminent Threat to Coastal Populations." "Environmental Health Perspectives", 123(8), pp. 204-209. Sea level rise due to

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

is another threat to coastal land.Ericson, Jason P. et al., 2006. "Effective sea-level rise and deltas: Causes of change and human dimension implications." "Global and Planetary Change", 50, pp. 63-82.

Land loss and deltas

Because of a highly variable combination of

, sediment starvation, coastal erosion, wetland deterioration,

, and various human activities, land loss within delta plains is a significant global problem. The large delta plains of the world, including the

Danube The Danube ( ; see also #Names and etymology, other names) is the List of rivers of Europe#Longest rivers, second-longest river in Europe, after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest sou ...

Ganges The Ganges ( ; in India: Ganga, ; in Bangladesh: Padma, ). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international which goes through India, Bangladesh, Nepal and China." is a trans-boundary rive ...

Brahmaputra The Brahmaputra is a trans-boundary river which flows through Southwestern China, Northeastern India, and Bangladesh. It is known as Brahmaputra or Luit in Assamese, Yarlung Tsangpo in Tibetan, the Siang/Dihang River in Arunachali, and ...

Indus The Indus ( ) is a transboundary river of Asia and a trans- Himalayan river of South and Central Asia. The river rises in mountain springs northeast of Mount Kailash in the Western Tibet region of China, flows northwest through the dis ...

, Mahanadi, Mangoky, McKenzie,

Mississippi Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...

Niger Niger, officially the Republic of the Niger, is a landlocked country in West Africa. It is a unitary state Geography of Niger#Political geography, bordered by Libya to the Libya–Niger border, north-east, Chad to the Chad–Niger border, east ...

Nile The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...

, Shatt el Arab,

Volga The Volga (, ) is the longest river in Europe and the longest endorheic basin river in the world. Situated in Russia, it flows through Central Russia to Southern Russia and into the Caspian Sea. The Volga has a length of , and a catchment ...

Yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...

Yukon Yukon () is a Provinces and territories of Canada, territory of Canada, bordering British Columbia to the south, the Northwest Territories to the east, the Beaufort Sea to the north, and the U.S. state of Alaska to the west. It is Canada’s we ...

, and

Zambezi The Zambezi (also spelled Zambeze and Zambesi) is the fourth-longest river in Africa, the longest east-flowing river in Africa and the largest flowing into the Indian Ocean from Africa. Its drainage basin covers , slightly less than half of t ...

deltas, have all suffered significant land loss as the result of either coastal erosion, internal conversion of wetlands to open water, or a combination of both. For the 15 deltas studied by Coleman and others,Coleman, J.M., Huh, O.K. and Braud Jr, D., 2008. ''Wetland loss in world deltas.'' ''Journal of Coastal Research, '' 24(sp1), pp. 1-14. these deltas experienced a total irreversible land loss of of wetlands between the early 1980s and 2002. During this period, the total average land loss for all these deltas was about per year. In the case of the Mississippi River Delta, they found that in 12 years, some of wetlands had been converted to new open water at a rate of per year. The factors contributing to land loss in the deltas below do not include the direct conversion of delta wetlands into agricultural or urban land, although this is happening concurrently in many of them. * The

Danube Delta The Danube Delta (, ; , ) is the second largest river delta in Europe, after the Volga Delta, and is the best preserved on the continent. Occurring where the Danube, Danube River empties into the Black Sea, most of the Danube Delta lies in Romania ...

is located in

Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...

and

Ukraine Ukraine is a country in Eastern Europe. It is the List of European countries by area, second-largest country in Europe after Russia, which Russia–Ukraine border, borders it to the east and northeast. Ukraine also borders Belarus to the nor ...

where the

River enters into the

Black Sea The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bound ...

. The loss of this delta is primarily due to sediment starvation caused by dams along the river. After the construction of the two largest of these dams, the Iron Gates dams, sediment in the river decreased by 60% - 70%.Panin, Nicolae and Jipa, Dan C., 2002. "Danube River Sediment Input and its Interaction with the North-western Black Sea." "Estuarine Coastal and Shelf Science", 54(3), pp. 551-562. * The

Ganges Delta The Ganges Delta (also known the Ganges-Brahmaputra Delta, the Sundarbans Delta or the Bengal Delta) is a river delta predominantly covering the Bengal region of the Indian subcontinent, consisting of Bangladesh and the Indian state of West Be ...

forms where the combined waters of the

and

rivers enter 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 ...

. The delta is damaged by sediment starvation due to the construction of many upstream dams. The location is also susceptible to sea level rise, with most of the delta below 5 m in elevation.Rahman, M.M. et al., 2020. "Ganges-Brahmaputra-Meghna Delta, Bangladesh and India: A Transnational Mega-Delta." "Deltas in the Anthropocene", pp. 23-51. * The

Indus River Delta The Indus River Delta forms where the Indus River flows into the Arabian Sea, mostly in the southern Sindh province of Pakistan with a small portion in the Kutch Region of India. The delta covers an area of about , and is approximately across ...

forms as the

Indus River The Indus ( ) is a transboundary river of Asia and a trans-Himalayas, Himalayan river of South Asia, South and Central Asia. The river rises in mountain springs northeast of Mount Kailash in the Western Tibet region of China, flows northw ...

enters the

Arabian Sea The Arabian Sea () is a region of sea in the northern Indian Ocean, bounded on the west by the Arabian Peninsula, Gulf of Aden and Guardafui Channel, on the northwest by Gulf of Oman and Iran, on the north by Pakistan, on the east by India, and ...

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

and

Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...

. The construction of barrages and reservoirs for irrigation has drastically reduced the flow of the Indus and its ability to carry sediment.Memon, Altaf A., 2005. "Devastation of the Indus River Delta." "World Water and Environmental Resources Congress 2005". * The Mahanadi River Delta forms where the Mahanadi, Brahmani, and Baitarini rivers enter into the

on the east coast of

. Similar to the Ganges River Delta, significant amounts of the Mahanadi Delta are below 5 m in elevation and are threatened by sea level rise. Dams for irrigation and flood control, including the Hirakud Dam, contribute to sediment starvation.Hazra, Sugata et al., 2020. "The Mahanadi Delta: A Rapidly Developing Delta in India." "Deltas in the Anthropocene", pp. 53-77. 65% of the coastline faces erosion.Mukhopadhyay, Anirban et al., 2018. "Threats to coastal communities of Mahanadi delta due to imminent consequences of erosion – Present and near future." "Science of the Total Environment", 6337-638, pp. 717-729. * The Mangoky River Delta is formed by the Mangoky River draining into the

Mozambique Channel The Mozambique Channel (, , ) is an arm of the Indian Ocean located between the Southeast African countries of Madagascar and Mozambique. The channel is about long and across at its narrowest point, and reaches a depth of about off the coa ...

off the west coast of

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

Mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...

forests face deforestation by coastal fishermen and inland farmers, increasing coastal erosion.Rakotomavo, Andriamparany and Fromard, François., 2010. "Dynamics of mangrove forests in the Mangoky River delta, Madagascar, under the influence of natural and human factors." "Forest Ecology and Management", 259(6), pp. 1161-1169. * The Mackenzie River Delta is formed by the

Mackenzie River The Mackenzie River (French: ; Slavey language, Slavey: ' èh tʃʰò literally ''big river''; Inuvialuktun: ' uːkpɑk literally ''great river'') is a river in the Canadian Canadian boreal forest, boreal forest and tundra. It forms, ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

flowing north into the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five oceanic divisions. It spans an area of approximately and is the coldest of the world's oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, ...

. Rising sea levels combined with the melting of

permafrost Permafrost () is soil or underwater sediment which continuously remains below for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below ...

near the permafrost table results in land subsidence.Liu, Lin, Zhang, Tingjun and Wahr, John., 2010. "InSAR measurements of surface deformation over permafrost on the North Slope of Alaska." "Journal of Geophysical Research: Earth Surface", 115(F3). * For the Mississippi River Delta see Mississippi River Delta page. * The

Niger Delta The Niger Delta is the delta of the Niger River sitting directly on the Gulf of Guinea on the Atlantic Ocean in Nigeria. It is located within nine coastal southern Nigerian states, which include: all six states from the South South geopolitic ...

is formed by the

Niger River The Niger River ( ; ) is the main river of West Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in south-eastern Guinea near the Sierra Leone border. It runs in a crescent shape through Mali, Nige ...

entering into the

Gulf of Guinea The Gulf of Guinea (French language, French: ''Golfe de Guinée''; Spanish language, Spanish: ''Golfo de Guinea''; Portuguese language, Portuguese: ''Golfo da Guiné'') is the northeasternmost part of the tropical Atlantic Ocean from Cape Lopez i ...

on the west coast of

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

. Dams, erosion, and subsidence due to wetland conversion are the major contributing factors to loss of the delta.Uluocha, N.O. and Okeke, I.C., 2004. "Implications of wetlands degradation for water resources management: Lessons from Nigeria." "GeoJournal", 61, pp. 151-154. * The Nile River Delta is formed by the

River flowing north through

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

and entering into the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

. The primary reason for Nile Delta loss is sediment entrapment behind the

Aswan Aswan (, also ; ) is a city in Southern Egypt, and is the capital of the Aswan Governorate. Aswan is a busy market and tourist centre located just north of the Aswan Dam on the east bank of the Nile at the first cataract. The modern city ha ...

dams. Secondary reasons include subsidence, sea level rise, and strong coastal currents.Stanley, Daniel Jean., 1996. "Nile delta: extreme case of sediment entrapment on a delta plain and consequent coastal land loss." "Marine Geology", 129(3-4), pp.189-195. * The Shatt al-Arab River Delta is formed when the Shatt al-Arab River flows into the

Persian Gulf The Persian Gulf, sometimes called the Arabian Gulf, is a Mediterranean seas, mediterranean sea in West Asia. The body of water is an extension of the Arabian Sea and the larger Indian Ocean located between Iran and the Arabian Peninsula.Un ...

. The river itself is formed by the joining of the

Tigris The Tigris ( ; see #Etymology, below) is the eastern of the two great rivers that define Mesopotamia, the other being the Euphrates. The river flows south from the mountains of the Armenian Highlands through the Syrian Desert, Syrian and Arabia ...

and

Euphrates The Euphrates ( ; see #Etymology, below) is the longest and one of the most historically important rivers of West Asia. Tigris–Euphrates river system, Together with the Tigris, it is one of the two defining rivers of Mesopotamia (). Originati ...

rivers. A decrease in freshwater entering the river due to irrigation and, thus, a decrease in sediment load has increased coastal erosion of the delta. Hydraulic structures and sea level rise also play a role in the loss of the delta.Al-Aesawi, Qassim, Al-Nasrawi, Ali K. M. and Jones, Brian G., 2020. "Short-term Geoinformatics Evaluation in the Shatt Al-Arab Delta (Northwestern Arabian/Persian Gulf)." "Journal of Coastal Research", 36(3), pp. 498-505. * The Volga Delta is formed when the

River enters into the

Caspian Sea The Caspian Sea is the world's largest inland body of water, described as the List of lakes by area, world's largest lake and usually referred to as a full-fledged sea. An endorheic basin, it lies between Europe and Asia: east of the Caucasus, ...

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

. It has gained land with the drop in the level of the Caspian Sea. As the water level has risen again in the last twenty years, the delta has still not experienced any loss. As the terms are defined above, the delta has experienced wetland loss but not land loss.Li, C. et al., 2009. "Development of the Volga Delta in Response to Caspian Sea-Level Fluctuation during Last 100 Years." "Journal of Coastal Research", 20, pp. 401-414. * The Yellow River Delta is formed as the

Yellow River The Yellow River, also known as Huanghe, is the second-longest river in China and the List of rivers by length, sixth-longest river system on Earth, with an estimated length of and a Drainage basin, watershed of . Beginning in the Bayan H ...

flows into the

Yellow Sea The Yellow Sea, also known as the North Sea, is a marginal sea of the Western Pacific Ocean located between mainland China and the Korean Peninsula, and can be considered the northwestern part of the East China Sea. Names It is one of four ...

. The Yellow River flows through the

Loess Plateau The Loess Plateau is a plateau in north-central China formed of loess, a clastic rock, clastic silt-like sediment formed by the accumulation of Dust#Atmospheric, wind-blown dust. It is located southeast of the Gobi Desert and is surrounded by t ...

and carries large amounts of sediment. Until 1998, the Yellow River Delta was expanding, but it has been decreasing ever since.Gao, Peng et al., 2018. "Land degradation changes in the Yellow River Delta and its response to the streamflow‐sediment fluxes since 1976." "Land Degradation & Development", 29(9), pp. 3212-3220. Many dams have been constructed on the Yellow River and are starving the coastline of sediment.Wang, Houjie and Bi, Naishuang., 2015. The sediment-starved Yellow River Delta as remotely controlled by human activities in the river basin." "American Geophysical Union, Fall Meeting 2015". * The Yukon River Delta is formed when the

and Kuskokwim rivers enter into the

Bering Sea The Bering Sea ( , ; rus, Бе́рингово мо́ре, r=Béringovo móre, p=ˈbʲerʲɪnɡəvə ˈmorʲe) is a marginal sea of the Northern Pacific Ocean. It forms, along with the Bering Strait, the divide between the two largest landmasse ...

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

. The delta is threatened by sea level rise; an increase of 0.5 m would increase erosion due to higher tides. Inactive floodplains where tides and sedimentation rates are not in equilibrium are most at risk.Jorgenson, Torre and Ely, Craig., 2001. "Topography and Flooding of Coastal Ecosystems on the Yukon-Kuskokwim Delta, Alaska: Implications for Sea-Level Rise." "Journal of Coastal Research", 17(1), pp. 124-136. * The Zambezi River Delta is formed when the

River enters the

off of the east coast of

. The construction of the

Kariba Dam Kariba may refer to: * Kariba, Zimbabwe * Lake Kariba * Kariba Dam * Kariba Gorge * Kariba (District) * Kariba weed, plant * For the ship, see MV Tricolor {{dab ...

, the Cahora Bassa Dam, and dykes have altered natural flooding and sediment deposition. The delta coast is in a state of erosion due to sediment starvation and a slowly rising sea level.Beilfuss, Richard, Dutton, Paul and Moore, Dorn., 2000. "Land Cover and Land Use Change in the Zambezi Delta." "Biodiversity of Zambezi Basin Wetlands", vol 3, ch 2, pp. 31-105.

References

{{Geologic Principles, state=collapsed Geomorphology Coastal erosion Sedimentology

Wetland loss

Land loss mechanisms

Land loss and deltas

See also

References