Estuary
Pictured above is the estuary of the River Teifi (Afon Teifi).
There are many different variations of an estuary, but in most basic terms it is defined as the tidal mouth of a river where the tide and stream meet. It is semi-enclosed and is connected to the sea, so estuaries generally contain seawater (or coastal brackish water) mixed with freshwater that has drained from the land. However, some estuaries - particularly those along freshwater lakes before connecting to the sea and so may not mix with seawater.
Estuaries often have an identifiable ecosystems and act as natural filters for runoff to support plant, bird, fish and other animal communities by providing food, breeding grounds and places to rest during migration. They can be susceptible to degradation based on conditions such as erosion, overdevelopment and pollution.
As transition zones between freshwater and seawater, estuaries display oceanic properties, experiencing rising tides and waves and registering saltwater content. They also mimic the properties of rivers by registering freshwater flow and producing sediment.
The four most common types of estuaries classified by their geology are:
Estuaries can also be classified by their water circulation patterns. The most common types are salt wedge, partially mixed, well-mixed, inverse and intermittent.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
We're expanding our collaborative mission by launching DB Intelligence, an exclusive market research advisory panel. Built environment professionals can now get paid to share their expertise on industry trends, products and services.
Panel members receive direct financial incentives for participating in research projects like short surveys, 1-2-1 interviews and focus groups. Register today to shape the future of the construction sector.
Planning condition discharge in England and Wales
A brief exoplanation from a building compliance expert, with further links.
Overheating guidance and tools for building designers
Guidance for dealing with element of building fabric control that have increasing importance.
Shading for housing, a design guide
From the Good Homes Alliance and British Blind and Shutter Association.
UK Standard Skills Classification (SSC)
A shared framework for describing skills needs.
Social media ban consultation comes to close
CIOB urges UK Government to consider social media’s role in careers guidance in ban debate.
The latest of eight Skills England apprenticeship units
The addition of battery manufacturing welcomed by ECA with a warning about the risks of fast-tracked apprenticeship units.
Building Control Independent Panel final report
A precis of a key report led by Dame Hackitt with full recommendations and link to the government response.
Building Safety recap April, 2026
A short and longer run-through of the month, with links to further information and sources.
CIAT May 2026 briefing.
From medieval scribes to modern word art.
ECA welcomes crackdown on late payment and push for clean energy, whilst CIOB seek fixed cladding removal timeframes.
Cyber Security in the Built Environment
Protecting projects, data, and digital assets: A CIOB Academy TIS.
Managing competence in the built environment
ITFG publishes new industry guide on how to meet the ICC principles.
The UK's campaign to reduce noise pollution: Mythbusting, articles and topic guides.