After the construction of the Glamorganshire Canal (NPRN 34425), Cardiff's shipping and maritime activities shifted towards the muddy flats to the south of the town. With the volume of traffic fast outstripping the capabilities of the sea lock and canal, the West Bute Dock (NPRN 34257) was constructed in 1832. In light of very significant tidal nature of the bay and the large deposits of mud and silt, an Entrance Channel was cut through the muddy flats from opposite Penarth Head to the dock entrance in order to facilitate access. As Cardiff Docks developed the channel was altered and extended to provide access to the the inner harbour, the Tidal Basin or Steam Packet Harbour, the Bute East Dock (NPRN 34242), Roath Dock (NPRN 34279), the Mount Stuart Dry Docks (NPRN 34267), and Queen Alexandra Dock (NPRN 34276). In 1896, the depth of the channel was described as being 43ft, 8in (13.3096m) during high-water spring tide, 5ft 8in (1.7272m) during low-water spring tide, 33ft, 8in (10.2616m) during high-water neap tide, and 15ft (4.572m) during low-water neap tide. The channel required regular dredging in order to remain navigable and in the 1920s 30,000 tons of mud were reportedly removed from the Entrance Channel each week. In 2001, the Cardiff Bay Barrage (NPRN 305755) was completed, transforming the inner harbour into a 200ha (5000 acre) freshwater lake.

(Sources: Turner, `The Bute Docks? in Barringer, Cardiff: An Illustrated Handbook (Cardiff: 1896), p. 44; Hilling, `Through Tiger Bay to Cardiff Bay ? Changing Waterfront Environment?, Transactions of the Honourable Society of Cymmordorion (1990), 183; Hutton, An Illustrated History of Cardiff Docks, vol 2 (Great Addington: 2008), pp. 128?30)
A.N. Coward, RCAHMW, 03.08.2018