MacDonalds's principal work in his later years also included domestic projects associated with some of the North of Scotland Hydro-Electric Board's schemes, and with the Great Ouse flood protection scheme. The latter was first considered early in 1938 following serious flooding in the Fens. Several proposals were put forward, and he was asked to formulate a protection scheme in conjunction with the River Great Ouse Catchment Board. Detailed surveys were made to determine the practicability of the works involved, and a report dealing with the whole problem was presented to the Board. The report was printed in early March 1941, but its construction was delayed by the war and until further serious flooding emphasised its urgency. In the mid-1950s the work was started in earnest under the direction of MacDonalds's firm, but he would not see its completion.