A coastal plain (also coastal plains, coastal lowland, coastal lowlands) is an area of flat, low-lying land adjacent to a sea coast. A

fall line A fall line (or fall zone) is the area where an upland region and a coastal plain meet and is noticeable especially the place rivers cross it, with resulting rapids or waterfalls. The uplands are relatively hard crystalline basement rock, and the ...

commonly marks the border between a coastal plain and an upland area.

Formation

Coastal plains can form in one of two ways; some begin as a

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 islan ...

, a flat piece of land located below sea level, and are created when the ocean level falls, exposing the land. Others develop when river currents carry

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 ...

into the ocean, which is deposited and builds up over time until it forms a coastal plain. They are generally separated from the rest of the interior by proximate landforms, like mountains.

Locations

Some of the largest coastal plains are in

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 ...

and the southeastern

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. The

Gulf Coastal Plain The Gulf Coastal Plain extends around the Gulf of Mexico in the Southern United States and eastern Mexico. This coastal plain reaches from the Florida Panhandle, southwest Georgia (U.S. state), Georgia, the southern two-thirds of Alabama, over m ...

of North America extends northwards 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 ...

along the Lower

Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...

to the

Ohio River The Ohio River () is a river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing in a southwesterly direction from Pittsburgh, Pennsylvania, to its river mouth, mouth on the Mississippi Riv ...

, which is a distance of about . The

Atlantic Coastal Plain The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

runs from the New York Bight to Florida. The Coastal Plains of India lie on either side of the

Deccan Plateau The Deccan is a plateau extending over an area of and occupies the majority of the Indian peninsula. It stretches from the Satpura Range, Satpura and Vindhya Ranges in the north to the northern fringes of Tamil Nadu in the south. It is bound ...

, along the western and eastern coasts of India. They extend for about 6,150 km from the Rann of Kutch in the west to

West Bengal West Bengal (; Bengali language, Bengali: , , abbr. WB) is a States and union territories of India, state in the East India, eastern portion of India. It is situated along the Bay of Bengal, along with a population of over 91 million inhabi ...

in the east. They are broadly divided into the Western Coastal Plains and the

Eastern Coastal Plains The Eastern Coastal Plains is a stretch of landmass lying between the eastern part of the Deccan plateau and the Bay of Bengal in India. The plains stretch from the Mahanadi delta to Kaniyakumari at the southern tip of the Indian peninsula with ...

. The two coastal plains meet at Kanyakumari, the southernmost tip of the Indian mainland. The eastern coastal plain is located between 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 ...

and the

eastern Ghats The Eastern Ghats is a mountain range that stretches along the East Coast of India, eastern coast of the Indian peninsula. Covering an area of , it traverses the states and union territories of India, states of Odisha, Telangana, Andhra Prade ...

and the western coastal plain is located between 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 ...

and the western Ghats. In Australia, there exists the South East Coastal Plain in Victoria that includes the

Gippsland Gippsland () is a rural region in the southeastern part of Victoria, Australia, mostly comprising the coastal plains south of the Victorian Alps (the southernmost section of the Great Dividing Range). It covers an elongated area of east of th ...

Plain, the eastern portion of

Melbourne Melbourne ( , ; Boonwurrung language, Boonwurrung/ or ) is the List of Australian capital cities, capital and List of cities in Australia by population, most populous city of the States and territories of Australia, Australian state of Victori ...

, Otway Plain and

Warrnambool Warrnambool (; Eastern Maar, Maar: ''Peetoop'' or ''Wheringkernitch'' or ''Warrnambool'') is a city on the south-western coast of Victoria (Australia), Victoria, Australia. At the Census in Australia#2021, 2021 census, Warrnambool had a populati ...

Plain subregions. The Gippsland Plain features the depressed coastal and alluvial plains, barrier dunes and

swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...

y flatlands. They mostly consist of grassland and grassy woodlands on yellow and grey textured fertile soils.South East Coastal Plain
Biodiversity of South-Eastern Australia. Retrieved December 11, 2024. Another is the

Swan Coastal Plain The Swan Coastal Plain in Western Australia is the geographic feature which contains the Swan River as it travels west to the Indian Ocean. The coastal plain continues well beyond the boundaries of the Swan River and its tributaries, as a geol ...

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

, which includes the city of

Perth Perth () is the list of Australian capital cities, capital city of Western Australia. It is the list of cities in Australia by population, fourth-most-populous city in Australia, with a population of over 2.3 million within Greater Perth . The ...

.IBRA Version 6.1
data It is one of the distinct physiographic provinces of the larger West Australian Shield division.

References

{{topography-stub Coastal and oceanic landforms Coastal plains

Formation

Locations

See also

References