A report about the intertidal salt marshes and mudflats in the estuary of the River Ythan in Aberdeenshire. An estuary is the lower part of a river valley where it meets the sea. It is partly filled with sediment deposited by the slow flowing river. The tides inundate an estuary twice a day creating a mix of salt and sea water described as brackish. Salt marshes can form by the slow rise and fall of the tides. Salt-tolerant plants colonise the mud, trapping material round them so that the level of the mud flats rise. Taller plants can then take hold.

First broadcast:
17 October 2007

Students could create a series of annotated diagrams showing the formation of salt marsh. They should highlight the aspects that encourage deposition, particularly slow river flow.