Cambridgeshire.

Various shots show men of the Great Ouse Catchment Board working on a large relief model of the Fens, testing flood prevention methods. The model is complete with rivers. One of the men pours some mercury into a 'river' and watches it move downstream.

Work started on a new flood prevention scheme when Cambridgeshire suffered its worst floods for 100 years in 1947. Several shots of the men measuring water and land levels on the model, making notes and marking graphs. Shots of the machinery that controls the tides of the rivers.