Shimna River

Shimna River
Shimna River in Tollymore Forest Park, September 2010
Location of mouth within Northern Ireland
Country	Northern Ireland
Region	County Down
Basin features
Main source	Mourne Mountains on the slopes of Ott Mountain 430 m (1,410 ft)
River mouth	Dundrum Bay, Irish Sea 5 m (16 ft)
Tributaries	Left: Trassey River Spinkwee River Tullybrannigan River Right: Burren River
Physical characteristics
Length	11.77 km (7.31 mi)

The Shimna River (Irish: Simhné, meaning river of bulrushes) is a river in County Down, Northern Ireland. It rises on the slopes of Ott Mountain, in the Mourne Mountains, and enters the Irish Sea at Newcastle, on Dundrum Bay. It is acidic and nutrient-poor, as a result of which its most common flora are mosses and liverworts, including the rare Portuguese feather-moss and Holt's mouse-tail moss. Its principal fish are salmon and sea trout, and it is managed by the Shimna Angling Club. The river is an Area of Special Scientific Interest (ASSI).

The Shimna has a history of flooding; the most serious recent flooding was in 2008. There have also been incidents of pollution, and there were serious fish kills in 2004, 2006 and 2009.

Felix Magennis, a member of the Magennis clan and relative of Hugh Magennis, Lord of Iveagh, built a castle next to the mouth of the Shimna River in 1588. The town is referred to as New Castle in the Annals of the Four Masters in 1433 so it is likely that he built on the site of an existing structure. Magennis’ castle was demolished in 1830.

The river is crossed by 16 bridges as it flows through Tollymore Forest Park. The Old Bridge, built by James Hamilton in 1726, is the oldest of the current bridges. The Ivy Bridge was built in 1780 and Foley’s Bridge in 1787. Parnell Bridge, named in recognition of Sir John Parnell who visited Tollymore in the late 18th century, was constructed in 1842. It was the last stone bridge to be built in Tollymore. The more recent footbridges are constructed from wood. Castle Bridge is located near the mouth where Main Street crosses the river. It was originally called Fearsat an Chaislein Nui (The Ford or Pass of the Newcastle) and was next to the entrance to the castle. This was replaced by a wider, straighter bridge in the 1890s.