There were plans to increase the depth of the canal to , to allow through working from the Lagan Navigation, but the start of the First World War in 1914 changed the economic climate, and the canal faced increasing competition from road transport once the war was over. The canal, along with the Lagan Navigation and the Ulster Canal, was under the direct control of the British Government from 1 July 1917, but shared an improvement grant of £19,000 with the Lagan Navigation when it was returned to private ownership. Despite competition, traffic in building sand, grain and coal continued to increase through the 1920s, reaching 57,000 tons in 1931, when tolls raised £1,634, and the company made a profit of £650. After that, traffic fell rapidly, with the company making less than £50 in 1939. Very little traffic used the canal during the Second World War, and all traffic ceased in 1946. In April 1954 the canal was officially abandoned and relegated to the status of a drainage ditch, when control of it passed to the Ministry of Commerce. It subsequently came under the jurisdiction of the Ministry of Finance from 1962.