A ria (; gl, ría) is a coastal inlet formed by the partial submergence of an unglaciated

river valley A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams ...

. It is a drowned river valley that remains open to the sea.

Definitions

Typically rias have a dendritic, treelike outline although they can be straight and without significant branches. This pattern is inherited from the dendritic drainage pattern of the flooded river valley. The drowning of river valleys along a stretch of coast and formation of rias results in an extremely irregular and indented coastline. Often, there are naturally occurring islands, which are summits of partly submerged, pre-existing hill peaks. (Islands may also be artificial, such as those constructed for the

Chesapeake Bay Bridge-Tunnel Chesapeake often refers to: *Chesapeake people, a Native American tribe also known as the Chesepian * The Chesapeake, a.k.a. Chesapeake Bay *Delmarva Peninsula, also known as the Chesapeake Peninsula Chesapeake may also refer to: Populated plac ...

.) A ria coast is a coastline having several parallel rias separated by prominent ridges, extending a distance inland.Goudie, A. (2004) ''Encyclopedia of Geomorphology.'' Routledge. London, England.Bird, E.C.F. (2008) ''Coastal Geomorphology: An Introduction'', 2nd ed. John Wiley and Sons Ltd. West Sussex, England. The sea level change that caused the submergence of a river valley may be either eustatic (where global sea levels rise), or isostatic (where the local land sinks). The result is often a very large

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

at the mouth of a relatively insignificant river (or else sediments would quickly fill the ria). The

Kingsbridge Estuary The Kingsbridge Estuary (also, erroneously, known as the 'Salcombe Estuary') in the South Hams area of Devon, England runs from Kingsbridge in the north to its mouth at the English Channel near Salcombe and lies between Bolt Head and Sharpitor t ...

Devon Devon ( , historically known as Devonshire , ) is a ceremonial and non-metropolitan county in South West England. The most populous settlement in Devon is the city of Plymouth, followed by Devon's county town, the city of Exeter. Devo ...

, England, is an extreme example of a ria forming an estuary disproportionate to the size of its river; no significant river flows into it at all, only a number of small streams. The word ''

ria A ria (; gl, ría) is a coastal inlet formed by the partial submergence of an unglaciated river valley. It is a drowned river valley that remains open to the sea. Definitions Typically rias have a dendritic, treelike outline although they ca ...

'' comes from Galician ''

ría A ria (; gl, ría) is a coastal inlet formed by the partial submergence of an unglaciated river valley. It is a drowned river valley that remains open to the sea. Definitions Typically rias have a dendritic, treelike outline although they c ...

'', which is related to Spanish and Galician '' río'' and Portuguese '' rio'' (river). Rias are present all along the Galician coast in

Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...

. As originally defined, the term was restricted to drowned river valleys cut parallel to the structure of the country rock that was at right angles to the coastline. However the definition of ria was later expanded to other flooded river valleys regardless of the structure of the country rock. For a time European geomorphologists considered rias to include any broad estuarine river mouth, including

fjord In physical geography, a fjord or fiord () is a long, narrow inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Alaska, Antarctica, British Columbia, Chile, Denmark, Förden and East Jutland Fjorde, Germany, ...

s. These are long narrow inlets with steep sides or cliffs, created in a valley carved by glacial activity. In the 21st century, however, the preferred usage of ''ria'' by geologists and geomorphologists is to refer solely to drowned unglaciated river valleys. It therefore excludes fjords by definition, since fjords are products of glaciation.

Locations

Europe

Pogled s Golubova kamena na Rijeku dubrovačku

* Portugal: has no ''rias'' as such: the

Ria de Aveiro The Aveiro lagoon (''Ria de Aveiro'') is a lagoon in Portugal. It is located on the Atlantic coast of Portugal, south of the municipality of Espinho and north of Mira (to the north of the Cape Mondego). Its average area covers approximately . It ...

in Aveiro, and

Ria Formosa The Ria Formosa lagoon, located in the Algarve, in southern Portugal, is a system of barrier islands that connects to the sea through six inlets. Five of these inlets are natural and have mobility characteristics. The sixth is an artificial inle ...

in Eastern

Algarve The Algarve (, , ; from ) is the southernmost NUTS II region of continental Portugal. It has an area of with 467,495 permanent inhabitants and incorporates 16 municipalities ( ''concelhos'' or ''municípios'' in Portuguese). The region has it ...

are actually

lagoon 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'') ...

s. * Atlantic coast of Spain ** Galicia: *** The

Rías Baixas The Rías Baixas (Galician language, Galician for "Lower Rias") are a series of four estuarine inlets located on the southwestern coast of Galicia (Spain), Galicia, Spain. They are the Ría de Muros e Noia, the Ría de Arousa, the Ria de Ponteved ...

, including the Ria of Vigo, Ria of

Pontevedra Pontevedra (, ) is a Spanish city in the north-west of the Iberian Peninsula. It is the capital of both the '' Comarca'' (County) and Province of Pontevedra, and of the Rías Baixas in Galicia. It is also the capital of its own municipality wh ...

, Ría de Arousa, Ria of Muros and

Noia Noia () is a town and municipality in the autonomous community of Galicia in northwestern Spain. It is the capital of the comarca with the same name. It has a population of 14,947 inhabitants (2010),Corcubion, Cee and Ría de Aldán. *** The Rías Altas, including the Ria of Corunna, Ria of Ares and

Betanzos Betanzos () is a municipality in the autonomous community of Galicia in northwestern Spain in the province of A Coruña. It belongs to the comarca of Betanzos. In Roman times Betanzos was called Flauvium Brigantium or ''Brigantium''. During the ...

, Ria of

Cedeira Cedeira is a municipality in the province of A Coruña in the autonomous community of Galicia in northwestern Spain. It is situated in the northern coast of the Rías Altas. Cedeira has a population of 7,412 inhabitants ( INE, 2010). Parroquias * ...

, Ria of O Barqueiro,

Ria of Ferrol The Ria of Ferrol (or bay of Ferrol; Spanish language, Spanish and Galician language, Galician: ''ría de Ferrol'') is a ria in Galicia, Spain, Galicia, Spain, the saline estuary of the Xuvia River. Located in the province of A Coruña, in the nor ...

, Ria of

Ortigueira Ortigueira is a seaport and municipality in the province of A Coruña the autonomous community of Galicia in northwestern Spain. It belongs to the comarca of Ortegal. It is located on the northern slope of the Serra da Faladoira, the river Me ...

, Ria of

Viveiro Viveiro () is a town and municipality in the province of Lugo, in the northwestern Galician autonomous community of Spain. It borders on the Cantabric Sea, to the west of Xove and to the east of O Vicedo. It has a residential population of o ...

, Ria of Foz and Ria of

Ribadeo Ribadeo is a municipality in the Spanish province of Lugo in Galicia. It has a population of 10,023 ( INE, 2011) and an area of . It is the capital of the A Mariña Oriental comarca. Geography The municipality of Ribadeo has approximately the ...

. **

Asturias Asturias (, ; ast, Asturies ), officially the Principality of Asturias ( es, Principado de Asturias; ast, Principáu d'Asturies; Galician-Asturian: ''Principao d'Asturias''), is an autonomous community in northwest Spain. It is coextensiv ...

: Ria of Avilés, Ria of

, Ria of Navia, Ria of Villaviciosa, Ria of Ribadesella, Ria of Llanes, Ria of Tina Mayor. **

Cantabria Cantabria (, also , , Cantabrian: ) is an autonomous community in northern Spain with Santander as its capital city. It is called a ''comunidad histórica'', a historic community, in its current Statute of Autonomy. It is bordered on the east ...

: Ria of Tina Mayor, Ria of Tina Menor, Ría de San Vicente de la Barquera, Ría of la Rabia, Ría of San Martín de la Arena, Ría of Mogro, Ría of Solía, Ría of Carmen, Ría of Boo, Ría of Tijero, Ría of Cubas, Ría de Ajo, Ría of Cabo Quejo, Ría of Treto, Ría of Oriñón. ** Basque Country: Ria of Bilbao, mouth of the rivers Nervión,

Ibaizabal The Ibaizabal (''wide river'' in Basque) is a river that drains southeastern Biscay to the Estuary of Bilbao. It is long from its source at Elorrio to the Nervión, and it passes by the towns of Durango and Amorebieta and joins the Nervión rive ...

, and Cadagua. **

Andalusia Andalusia (, ; es, Andalucía ) is the southernmost autonomous community in Peninsular Spain. It is the most populous and the second-largest autonomous community in the country. It is officially recognised as a "historical nationality". The t ...

: Ria of Carreras, Ria of

Huelva Huelva (, ) is a city in southwestern Spain, the capital of the province of Huelva in the autonomous community of Andalusia. It is between two short rias though has an outlying spur including nature reserve on the Gulf of Cádiz coast. The ria ...

at the mouth of the rivers

Odiel The Odiel ( es, Río Odiel) is a river in the Atlantic basin in southern Spain, more precisely in the province of Huelva, Andalusia. It originates at Marimateos in the Sierra de Aracena at an elevation of above sea level. At the Punta del S ...

and Tinto. * Brittany: The rias in northern Brittany are called ''Abers'': '' Aber Wrac'h'' (), ''Aber Benoît'' (), ''Aber Ildut'' () etc. The Roadstead of Brest also includes several rias. * Ireland:

Bantry Bay Bantry Bay ( ga, Cuan Baoi / Inbhear na mBárc / Bádh Bheanntraighe) is a bay located in County Cork, Ireland. The bay runs approximately from northeast to southwest into the Atlantic Ocean. It is approximately 3-to-4 km (1.8-to-2.5 mil ...

, on the southwest coast of Ireland, is an example of an Irish ria. * Wales:

Milford Haven Waterway Milford Haven Waterway (''Welsh: Dyfrffordd Aberdaugleddau'') is a natural harbour in Pembrokeshire, Wales. It is a ria or drowned valley which was flooded at the end of the last ice age. The Daugleddau estuary winds west to the sea. As one ...

in Pembrokeshire is a ria. * England: The south coast of England is a

submergent coastline Submergent coastlines or drowned coastlines are stretches along the coast that have been inundated by the sea by a relative rise in sea levels from either isostacy or eustacy. Submergent coastline are the opposite of emergent coastlines, whic ...

which contains many rias, including Southampton Water,

Poole Harbour Poole Harbour is a large natural harbour in Dorset, southern England, with the town of Poole on its shores. The harbour is a drowned valley (ria) formed at the end of the last ice age and is the estuary of several rivers, the largest being t ...

, the estuary of the River Medina on the Isle of Wight, the estuaries of the Exe, Teign and Dart, then

Plymouth Sound Plymouth Sound, or locally just The Sound, is a deep inlet or sound in the English Channel near Plymouth in England. Description Its southwest and southeast corners are Penlee Point in Cornwall and Wembury Point in Devon, a distance of abou ...

, and the estuaries of the River Fowey,

River Fal The River Fal ( kw, Dowr Fala) flows through Cornwall, England, rising at Pentevale on Goss Moor (between St. Columb and Roche) and reaching the English Channel at Falmouth. On or near the banks of the Fal are the castles of Pendennis and ...

and Helford River in

Cornwall Cornwall (; kw, Kernow ) is a historic county and ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people. Cornwall is bordered to the north and west by the Atlantic ...

. On the north coast is the

River Camel The River Camel ( kw, Dowr Kammel, meaning ''crooked river'') is a river in Cornwall, England. It rises on the edge of Bodmin Moor and with its tributaries its catchment area covers much of North Cornwall. The river flows into the eastern Ce ...

and the

River Taw The River Taw () rises at Taw Head, a spring on the central northern flanks of Dartmoor, crosses North Devon and at the town of Barnstaple, formerly a significant port, empties into Bideford Bay in the Bristol Channel, having formed a large ...

. In

Essex Essex () is a county in the East of England. One of the home counties, it borders Suffolk and Cambridgeshire to the north, the North Sea to the east, Hertfordshire to the west, Kent across the estuary of the River Thames to the south, and Grea ...

are the River Blackwater and

River Crouch The River Crouch is a small river that flows entirely through the English county of Essex. The distance of the Navigation between Holliwell Point which is north of Foulness Island and Battlesbridge is 17.5 Miles, i.e. 15.21 Nautical Miles. ...

. * Croatia: Lim, Rijeka Dubrovačka * Montenegro: The

Bay of Kotor The Bay of Kotor ( Montenegrin and Serbian: , Italian: ), also known as the Boka, is a winding bay of the Adriatic Sea in southwestern Montenegro and the region of Montenegro concentrated around the bay. It is also the southernmost part of the hi ...

* Italy: The Fiordo di Furore on the

Amalfi Coast The Amalfi Coast ( it, Costiera amalfitana) is a stretch of coastline in southern Italy overlooking the Tyrrhenian Sea and the Gulf of Salerno. It is located south of the Sorrentine Peninsula and north of the Cilentan Coast. Celebrated worldw ...

Campania (man), it, Campana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = , demographics1_footnotes = , demographics1_title1 = , demographics1_info1 = , demog ...

is a ria, despite its name. * Malta:

Grand Harbour The Grand Harbour ( mt, il-Port il-Kbir; it, Porto Grande), also known as the Port of Valletta, is a natural harbour on the island of Malta. It has been substantially modified over the years with extensive docks ( Malta Dockyard), wharves, a ...

and

Marsamxett Harbour Marsamxett Harbour (), historically also referred to as Marsamuscetto, is a natural harbour on the island of Malta. It is located to the north of the larger Grand Harbour. The harbour is generally more dedicated to leisure use than the Grand H ...

Africa

Kenya ) , national_anthem = " Ee Mungu Nguvu Yetu"() , image_map = , map_caption = , image_map2 = , capital = Nairobi , coordinates = , largest_city = Nairobi ...

: Kilindini Harbour, which is a deep channel between Mombasa island and South Coast mainland, is a ria.

Asia

Sanriku Coast The is a coastal region on the Pacific Ocean, extending from southern Aomori Prefecture, through Iwate Prefecture and northern Miyagi Prefecture in northeastern Honshū, which is Japan's main island. The name comes from the historical region of ...

: North Japan, east coast of Honshū Island (main island). Sendai city, Miyagi Prefecture and Iwate Prefecture are included. * Ago Coast in

Shima Shima may refer to: Places , Japan * Shima Province (志摩), one of the old provinces of Japan * Shima, Fukuoka (志摩), a former town in Fukuoka Prefecture * Shima, Mie (志摩), a city in Mie Prefecture ** Shima, Mie (town), a former town ...

(Mie Prefecture) is a Ria coast, well known for its pearls. * Coasts on western, southern sides of the Korean Peninsula: Rias formed by sea level rising after

Ice Age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

. * The Chinese east coast, from the Guangdong province (

Hong Kong Hong Kong ( (US) or (UK); , ), officially the Hong Kong Special Administrative Region of the People's Republic of China (abbr. Hong Kong SAR or HKSAR), is a city and special administrative region of China on the eastern Pearl River Delta i ...

coastlines included) to

Shanghai Shanghai (; , , Standard Mandarin pronunciation: ) is one of the four direct-administered municipalities of the People's Republic of China (PRC). The city is located on the southern estuary of the Yangtze River, with the Huangpu River flowin ...

. * The

Musandam Peninsula The Musandam Peninsula ( ar, جَزِيْرَة مُسَنْدَم \ رَأْس مُسَنْدَم, Jazīrat Musandam / Raʾs Musandam), locally known as Ruus Al Jibal ( ar, رُؤُوْس ٱلْجِبَال, ''Ruʾūs al-Jibāl'' Heads of the Mou ...

Oman Oman ( ; ar, عُمَان ' ), officially the Sultanate of Oman ( ar, سلْطنةُ عُمان ), is an Arabian country located in southwestern Asia. It is situated on the southeastern coast of the Arabian Peninsula, and spans the mouth of ...

, comprising the southern shore of the Strait of Hormuz.

Oceania

* Papua New Guinea: Rias formed by eroded volcanic lava flow are found all around the town of

Tufi Tufi is a town located on the south eastern peninsula of Cape Nelson, Oro Province, Papua New Guinea. Tufi is located on one of many rias, or drowned river valleys, locally referred to as 'fjords', on Cape Nelson surrounded by many uncharted ree ...

at Cape Nelson, in Papua New Guinea's

Oro Province Oro Province, formerly (and officially still) Northern Province, is a coastal province of Papua New Guinea. The provincial capital is Popondetta. The province covers 22,800 km2, and has 176,206 inhabitants (2011 census). The province shares l ...

. * Australia: The east coast of Australia features several rias around Sydney, including Georges River,

Port Hacking Port Hacking Estuary ( Aboriginal Tharawal language: ''Deeban''), an open youthful tide dominated, drowned valley estuary, is located in southern Sydney, New South Wales, Australia approximately south of Sydney central business district. Po ...

, and Port Jackson, which includes Sydney Harbour. There are many examples in

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

, including the Swan River around Perth and several rivers in the west Kimberley region. * New Zealand: Rias of various scales abound on the eastern shores of the upper North Island. On the west coast, in contrast, they are fewer but larger.

Kaipara Harbour Kaipara Harbour is a large enclosed harbour estuary complex on the north western side of the North Island of New Zealand. The northern part of the harbour is administered by the Kaipara District and the southern part is administered by the Auckla ...

is the country's largest, and the

Hokianga Harbour The Hokianga is an area surrounding the Hokianga Harbour, also known as the Hokianga River, a long estuarine drowned valley on the west coast in the north of the North Island of New Zealand. The original name, still used by local Māori, is ' ...

, further north, is of historical significance to the native

Māori people The Māori (, ) are the indigenous Polynesian people of mainland New Zealand (). Māori originated with settlers from East Polynesia, who arrived in New Zealand in several waves of canoe voyages between roughly 1320 and 1350. Over several c ...

. The

Marlborough Sounds The Marlborough Sounds are an extensive network of sea-drowned valleys at the northern end of the South Island of New Zealand. The Marlborough Sounds were created by a combination of land subsidence and rising sea levels. According to Māori ...

at the northern tip of the South Island form a large network of rias. *

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...

Pearl Harbor Pearl Harbor is an American lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. It was often visited by the Naval fleet of the United States, before it was acquired from the Hawaiian Kingdom by the U.S. with the signing of the R ...

Oahu Oahu () ( Hawaiian: ''Oʻahu'' ()), also known as "The Gathering Place", is the third-largest of the Hawaiian Islands. It is home to roughly one million people—over two-thirds of the population of the U.S. state of Hawaii. The island of O� ...

is a ria, with the branches of West Loch, Middle Loch, East Loch, and Southeast Loch formed by the submerged drainages of Waikele, Waiau, Waimalu, and Hālawa streams respectively.

North America

* United States: Narragansett Bay, New York Harbor,

Delaware Bay Delaware Bay is the estuary outlet of the Delaware River on the northeast seaboard of the United States. It is approximately in area, the bay's freshwater mixes for many miles with the saltwater of the Atlantic Ocean. The bay is bordered inland ...

, Indian River Bay, the

Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the Eastern Shore of Maryland / ...

, and

Charleston Harbor The Charleston Harbor is an inlet (8 sq mi/20.7 km²) of the Atlantic Ocean at Charleston, South Carolina. The inlet is formed by the junction of Ashley and Cooper rivers at . Morris and Sullivan's Islands shelter the entrance. Charleston ...

are rias on the East Coast. Willapa Bay and Grays Harbor in Washington and San Francisco Bay in

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

on the West Coast are also rias. * Canada: Charlottetown Harbour,

Prince Edward Island Prince Edward Island (PEI; ) is one of the thirteen provinces and territories of Canada. It is the smallest province in terms of land area and population, but the most densely populated. The island has several nicknames: "Garden of the Gulf", ...

South America

* Argentina:

Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and g ...

has the Deseado ria, on the coast of Santa Cruz Province, on the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

. Also, the "bay" that is Bahía Blanca is a ría.

Consequences

The funnel-like shape of rias can amplify the effects of

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) 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 other underwater exp ...

s, as demonstrated in the seismicity of the Sanriku coast, most recently in the

2011 Tōhoku earthquake and tsunami The occurred at 14:46 JST (05:46 UTC) on 11 March. The magnitude 9.0–9.1 (M) undersea megathrust earthquake had an epicenter in the Pacific Ocean, east of the Oshika Peninsula of the Tōhoku region, and lasted approximately six mi ...

Definitions

Locations

Europe

Africa

Asia

Oceania

North America

South America

Consequences

See also

References

Further reading