There are several watercourses around the Thames in Cookham which play an important role in drainage and flood recovery, and are habitats for wildlife. The River Thames splits into four channels downstream of Cookham Bridge: Odney Weir, the Cookham Lock Cut, Cookham Weir and the southernmost channel is called Lullebrook. West of these channels, the Fleet Ditch/Strande Water runs roughly north-south from Cock Marsh to Widbrook Common, running under the Moor Road (and over it during a flood) next to the NT car park. South of Cookham are the White Brook, which runs through Widbrook Common and under Sutton Road (or over it during a flood), and the Northtown/Maidenhead Ditch.
If you own land adjacent to a watercourse you have rights and responsibilities associated with it. In many cases the responsibilities include clearing vegetation and fallen trees. The EA has published a "Living on the edge" guide explaining what landowners must and can do. It has also published advice on how and when to clear vegetation from watercourses.
The EA maintains parts of the main river and publishes its work programme on the gov.uk River and Coastal Maintentance Programmes page.