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. 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.
Tidal flats, along with intertidal salt marshes and mangrove forests, are important ecosystems. 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, mollusks and fish. 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.
Selected example areas
- Arcachon Bay, France
- Banc d'Arguin, Mauritania
- Great Rann of Kutch, India
- Belhaven, East Lothian Scotland, United Kingdom
- Bridgwater Bay and Morecambe Bay, United Kingdom
- Cape Cod Bay, Massachusetts, United States
- Cook Inlet, Alaska, United States
- Lindisfarne Island, England, United Kingdom
- Minas Basin, Nova Scotia, Canada
- Padilla Bay, Washington, United States
- Plymouth Bay, Massachusetts, United States
- Port of Tacoma, Washington, United States
- Skagit Bay, Washington
- Snettisham Norfolk England, United Kingdom
- Wadden Sea: Netherlands, Germany, Denmark
- West coast of Andros Island, Bahamas
- Yellow Sea, China, Korea
- Moreton Bay, Queensland, Australia
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