Mudflats (also mud flats, tidal flats, tide flats, etc.) 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.

Mudflats are typically important regions for wildlife, supporting a large population, although levels of biodiversity are not particularly high. They are often of particular importance to migratory birds. 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.

Several especially shallow mudflat areas, such as the Wadden Sea, can be used for the sport of mudflat hiking.

Major example areas

• Arcachon Bay, France
• Wadden Sea: Netherlands, Germany, Denmark
• Bridgwater Bay and Morecambe Bay, United Kingdom
• Banc d'Arguin, Mauritania
• Snettisham Norfolk England, United Kingdom
• Belhaven East Lothian Scotland, United Kingdom
• Lindisfarne Island, England, United Kingdom
• Port of Tacoma, United States
• Cape Cod Bay, United States
• Minas Basin, Nova Scotia, Canada
• Yellow Sea, China, Korea
• Cook Inlet, United States
• West coast of Andros Island, Bahamas

See also

• Wetland
• Coastal wetland (foreshore)
• Intertidal zone
• Estuary
• Humphrey the whale
• Bay mud