If you look at Downpatrick today, it's hard to imagine that it was once a seaside town.
Up until the middle of the 18th century, tidal waters stretching from Strangford Lough almost encircled the town and at one time the hill on which Down Cathedral stands was virtually an island, connected to nearby land by a narrow causeway.
In an effort to reclaim land from the sea, local landowner Edward Southwell erected the first tidal barrage across the Quoile river in 1745, at a site near the bridge on the old Belfast road. Marshes were drained and land that was once swamped by seawater was turned into fertile agricultural ground.
Then in 1934 the construction of new tidal gates took place in an effort to provide even greater protection against flooding. These gates were equipped with self-acting sluices which closed when the tide of Strangford Lough began to rise and opened again at low tide to release flood water.
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In time, however, even this barrier proved to be inadequate and a new barrage was constructed in 1957 at Hare Island, close to the mouth of the Quoile river.
The permanence of the new barrier meant that Downpatrick was closed off to sea traffic forever. Quoile Quay and Steamboat Quay, which once provided berths for visiting ships from across the British Isles, were rendered completely useless by the construction of the barrage.
Although the barrier cut off Downpatrick's sea trading links, it did mean that the town would be protected from all but the most severe of winter floods.