CORE UNIT: PATTERNS AND PROCESSES IN THE PHYSICAL ENVIRONMENT
The North and South Bull Walls were built between 1818 and 1824 to prevent Dublin Port choking with silt. The walls increased the tidal flow in and out of the harbour which kept the port clear of sand. However, the North Bull Wall blocked the movement of sediment by longshore drift. As a result sand was deposited against the North Bull Wall. This deposition resulted in the creation of sand dunes and a salt marsh up against the North Bull Wall. Over time this deposition created the North Bull Island.
O Fig. 44 Map of North Bull Island
The island now extends five km in length and is about one km wide. A well-developed dune system is established which runs along the length of the island. On the seaward side is Dollymount strand, on the leeward side is a lagoon and salt marsh. At low tide the bed of the lagoon is exposed as mudflats which provide vital winter feeding grounds for migratory wildfowl such as Brent Geese from the Canadian Tundra and Iceland.
North Bull Island is still growing but storms can erode the seaward edge.
The main human pressure on the island is erosion of the sand dunes due to visitor traffic. Anything between 1,500 and 4,000 people visit per day in summer.