Coordinates: 49°29′13″N 2°32′06″W / 49.487°N 2.535°W
The Braye du Valle is the area between the main Island of Guernsey and Le Clos du Valle, which was a tidal island to the north.
The original reason for the separation of the north of the Island of Guernsey may relate to seismic disturbances or changes in the sea level. The rise and fall of the tide in Guernsey is over 10 metres (33 ft) which creates energy to move loose materials.
The Braye was open to the sea and the shoreline moves with the waves and the tides. Gravel and sand are deposited onshore, only to be swept back offshore. Storms batter the coast, and tides flood areas on a daily basis. The premiere forces that shapes the coastal landscape, however, are waves. Beaches are not fixed features, they are dynamic environments.
At the eastern end an iron age fort, later to become the castle of Saint Michael where in 1117 there was a large ceremony to celebrate the finalisation of major works. Granite walls and gate were added in the 15th century, barracks in the 18th century, and the name "Vale Castle" is now the common name.
It is likely that at one time a land bridge connected the two sections next to the Vale church, before the sea broke through. In 1204 it is reported that the Royal Court of Guernsey visited the Braye du Valle to replace boundary markers that had been washed away.
The Braye covered around 350 acres of sand, gravel, clay and bog. Water channels one or two feet deep ran its entire length. Salterns and marshy meadows that flooded at high tide formed the sides. Saltpans operated on the southern side. 1,600 metres (5,200 ft) long, up to 750 metres (2,460 ft) wide and 3 metres (9.8 ft) to 9 metres (30 ft) deep at high water.
A leper hospice founded to care for returning crusaders in the 12th century, who had contracted the disease was located at Maladerie Road in St Sampsons, with the cemetery on the edge of Braye du Valle, now covered by L'Islet road. It closed when the disease faded away in the 16th century.