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General sketch-map of a tidal plain, showing the typical tripartition in supratidal, intertidal and subtidal zones. The most apparent character of the area is the development of tidal channels, affecting mainly the intertidal zone. In this case, the tidal flat is protected seaward by a beach barrier, but in many cases (low-energy waves and longshore currents) the tidal flats may directly pass into a shallow marine environment.

Mudflats or mud flats, also known as tidal flats, are coastal wetlands that form when mud is deposited by tides or rivers. They are found in sheltered areas such as bays, bayous, lagoons, and estuaries. Mudflats may be viewed geologically as exposed layers of bay mud, resulting from deposition of estuarine silts, clays and marine animal detritus. Most of the sediment within a mudflat is within the intertidal zone, and thus the flat is submerged and exposed approximately twice daily.

In the past tidal flats were considered unhealthy, economically unimportant areas and were often dredged and developed into agricultural land.[1] Several especially shallow mudflat areas, such as the Wadden Sea, are now popular among those practising the sport of mudflat hiking.

On the Baltic Sea coast of Germany in places, mudflats are exposed not by tidal action, but by wind-action driving water away from the shallows into the sea. These wind-affected mudflats are called windwatts in German.


Mudflats near Oban on Stewart Island, New Zealand

Tidal flats, along with intertidal salt marshes and mangrove forests, are important ecosystems.[2] They usually support a large population of wildlife, and are a key habitat that allows tens of millions of migratory shorebirds to migrate from breeding sites in the northern hemisphere to non-breeding areas in the southern hemisphere. They are often of vital importance to migratory birds, as well as certain species of crabs,[3] mollusks and fish.[4] In the United Kingdom mudflats have been classified as a Biodiversity Action Plan priority habitat.

The maintenance of mudflats is important in preventing coastal erosion. However, mudflats worldwide are under threat from predicted sea level rises, land claims for development, dredging due to shipping purposes, and chemical pollution. In some parts of the world, such as East and South-East Asia, mudflats have been reclaimed for aquaculture, agriculture, and industrial development. For example, around the Yellow Sea region of East Asia, more than 65% of mudflats have been destroyed over the past 50 years.[5][6]


Mudflat sediment deposits are focused into the intertidal zone which is composed of a barren zone, marsh and salt pan. Within these areas are various ratios of sand and mud that make up the sedimentary layers.[7] The associated growth of coastal sediment deposits can be attributed to rates of subsidence along with rates of deposition (example: silt transported via river) and changes in sea level.[7]

Barren zones extend from the lowest portion of the intertidal zone to the marsh areas. Beginning in close proximity to the tidal bars, sand dominated layers are prominent and become increasingly muddy throughout the tidal channels. Common bedding types include laminated sand, ripple bedding, and bay mud. Bioturbation also has a strong presence in barren zones.

Marshes contain an abundance of herbaceous plants while the sediment layers consist of thin sand and mud layers. Mudcracks are a common as well as wavy bedding planes.[7] Marshes are also the origins of coal/peat layers because of the abundant decaying plant life.[7]

Salt pans can be distinguished in that they contain thinly laminated layers of clayey silt. The main source of the silt comes from rivers. Dried up mud along with wind erosion forms silt dunes. When flooding, rain or tides come in, the dried sediment is then re-distributed.[7]

Selected example areas[edit]

Mudflats in Brewster, Massachusetts, United States, extending hundreds of yards offshore at the low tide. The line of seashells in the foreground indicates the high-water mark.
Gulls feeding on mudflats in Skagit Bay, Washington.


  1. ^ Dredging Indian River Lagoon Wetlands 1920 - 1950s
  2. ^ Tidal flat habitats
  3. ^ Mud crab (Scylla serrata) culture in tidal flats with existing mangroves
  4. ^ Manko - Tidal Flat, Mangrove Forest
  5. ^ MacKinnon, J.; Verkuil, Y.I.; Murray, N.J. (2012), IUCN situation analysis on East and Southeast Asian intertidal habitats, with particular reference to the Yellow Sea (including the Bohai Sea), Occasional Paper of the IUCN Species Survival Commission No. 47, Gland, Switzerland and Cambridge, UK: IUCN, p. 70, ISBN 9782831712550 
  6. ^ Murray, N.J.; Clemens, R.S.; Phinn, S.R.; Possingham, H.P.; Fuller, R.A. (2014), "Tracking the rapid loss of tidal wetlands in the Yellow Sea", Frontiers in Ecology and the Environment 12 (5): 267–272, doi:10.1890/130260 /
  7. ^ a b c d e Reineck, H.E, and I.B Singh, Deposistional Sedimentary Environments, 2nd Ed. New York: Springer-Verlag Berlin Heidelberg, 1980, pp. 418-428

External links[edit]

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Mudflat — Please support Wikipedia.
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2247 news items

Wicked Local

Wicked Local
Mon, 25 Apr 2016 11:43:44 -0700

More than 500 members of the community packed Mudflat Pottery School in Somerville on April 16 during its third annual Empty Bowls event, a benefit for local food rescue organization Food For Free. The event raised $15,000 for the nonprofit, which ...

Tavistock Times Gazette

Tavistock Times Gazette
Wed, 13 Apr 2016 01:37:30 -0700

A VERY special cricket match took place on Saturday when a pitch magically appeared from under the Tamar River at Weir Quay due to an exceptionally low tide. Cargreen Yacht Club had challenged Weir Quay Sailing Club to a match on the sandbank, just ...

BBC News

BBC News
Sun, 10 Apr 2016 04:03:45 -0700

River Tamar mudflat cricketers make most of low tide. 10 April 2016 Last updated at 12:08 BST. Cricketers have been having fun on a muddy pitch that appears only at very low tides on the River Tamar. Two teams from sailing clubs on either side of the ...


Sat, 30 Apr 2016 23:56:15 -0700

It feeds on saltmarsh periwinkle, a snail that grazes on marsh grasses and that could turn the wetlands into a mudflat if it had no such predator, he said. "Harvesting of the terrapins is just another threat, especially since New Jersey is one of the ...
Fremont Bulletin
Sat, 30 Apr 2016 23:56:15 -0700

Alameda: Mother's Day will be celebrated with a "Moms on the Mudflat" program from 9:30 to 11 a.m. May 8 at Crab Cove Visitor Center in Alameda, led by naturalist Morgan Dill. Bring your mud boots to learn what crabs, lugworms and other moms are doing ...


Tue, 26 Apr 2016 15:34:23 -0700

Check the Shorebird Festival website (www.shorebirdfestival.com) for tours with such titles as "The Turkey Vulture: Love at Second Sight" and exhibits like: "Mudflat Meals -- See what shorebirds have for dinner." The Grays Harbor National Wildlife ...

The Indian Express

The Indian Express
Fri, 29 Apr 2016 13:58:46 -0700

The good news is that the mudflat, which stretches from Airoli in the eastern suburbs of Mumbai to Sewri in Central Mumbai, has transformed itself into a beautiful mangrove forest. The Brihanmumbai Municipal Corporation (BMC) has included the newly ...

Trinidad Guardian

Trinidad Guardian
Sat, 30 Apr 2016 19:37:30 -0700

Since the main highway to the sea was the Caroni River, a landing place with a tiny garrison of half-starved soldiers was stationed on a mudflat where later the town was to be built. Three years later, Sir Walter Raleigh, the intrepid English privateer ...

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