Shimna River

Overview

The Shimna River (Irish: An tSionna) is a short, spate river that rises on the slopes of Ott Mountain in the Mourne range and empties into the Irish Sea at Newcastle, County Down. Designated an Area of Special Scientific Interest (ASSI), the river is celebrated for its dramatic geology, nutrient‑poor acidic waters and a suite of rare mosses and liverworts that cling to its banks. Its clear, fast‑flowing sections are a haven for Atlantic salmon and sea trout, while the lower reaches broaden into a shallow boating pond that frames the historic town of Newcastle.

History

Human interaction with the Shimna stretches back millennia. Flint artefacts dating to the Mesolithic and Bronze Age have been recovered from the river’s floodplain, hinting at early settlement. In 1588 Felix Magennis erected a castle near the river’s mouth; the structure was demolished in 1830, but the site remains a reminder of the river’s strategic importance.

The river runs through Tollymore Forest Park where it is crossed by sixteen stone bridges, the oldest being the 1726 Old Bridge built by James Hamilton. Notable bridges include the Ivy Bridge (1780), Foley’s Bridge (1787) and the 1842 Parnell Bridge. The Hermitage, a small stone shelter designed by Hamilton in the 1770s, provided a genteel refuge for ladies while men fished the waters below.

In the 1960s the Fofanny Dam was constructed on the Shimna to supply water to Banbridge, Portadown and Newry. A modern underground treatment plant now processes the water, but the dam and its reservoir remain largely hidden from view, preserving the river’s natural character.

Geology & Ecology

The upper Shimna cuts through granite formed around 50 million years ago, while the lower reaches flow over Silurian shale and dark basalt bands created by volcanic intrusions 60 million years ago. This varied bedrock produces a mix of riffles, pools, cascades and step‑gorges that support a unique assemblage of plants.

The river’s oligotrophic (base‑poor) waters host an exceptional range of bryophytes. In addition to the Portuguese feather‑moss (Platyhypnidium alopecuroides) and Holt’s mouse‑tail moss (Isothecium holtii), the ASSI citation records species such as compressed flapwort, filamentous green algae, water earwort, flagellate feather‑moss, bulbous rush, long‑beaked water feather‑moss, Alpine water‑moss, greater water‑moss, claw brook‑moss, rusty feather‑moss, fox‑tail feather‑moss, yellow‑fringe moss and the liverwort overleaf pellia. Many of these are found nowhere else in Northern Ireland.

Oak, beech, ash and birch line the banks, interspersed with rhododendron, elderberry and ivy. The woodland is mainly acidic, with downy birch, hazel, goat willow and hawthorn dominating the riparian scrub.

The river supports Atlantic salmon, brown trout, sea trout, minnow, stone loach, three‑spined stickleback and eel. Otters are a regular sight near the mouth, and the banks attract dippers, grey wagtails, kingfishers, grey herons and the feral Mandarin duck that has lived on the river since 1978.

Angling & Recreation

The Shimna is managed jointly by the Department of Culture, Arts and Leisure and the Shimna Angling Club. Its salmon and sea‑trout runs are among the best in Northern Ireland; a record 16 lb 6 oz sea trout was landed in 1983. The fishing season runs from 1 March to 31 October. Anglers must obtain a permit, which can be purchased at the Newcastle Visitor Information Centre (10‑14 Central Promenade, Newcastle, BT33 0AA) or directly from the Shimna Angling Club.

The river’s spate nature means water levels rise quickly after rain, creating exciting fast‑flowing runs for experienced anglers.

Filming & Culture

The dramatic gorge and historic bridges have attracted film crews; the Shimna River featured as a backdrop in the television series Game of Thrones.

What to See & Do

Tollymore Forest Park, covering almost 630 ha at the foot of the Mournes, offers a network of marked trails that showcase the Shimna’s natural and cultural attractions.

• River Trail – Starting at the Azalea Walk, the path follows the tree‑lined Shimna upstream past the Hermitage, crossing at Parnell Bridge where a 10‑metre cascade drops spectacularly. Detailed information is available on the Tollymore Forest Park River Trail page.
• Arboretum Path – This gentle walk skirts the lower edge of the arboretum, winding through semi‑mature broad‑leaved trees before entering experimental forest plots that host exotic species such as monkey‑puzzle and eucalyptus.
• Mountains & Drinns Trail – A longer loop that weaves through conifer and broad‑leaf woodland, passing duck ponds, historic bridges and points of interest like the 18th‑century stone arches. The optional Drinns loop adds a modest challenge for keen walkers.

Along the routes visitors can admire the 16 historic bridges, the stone‑built Hermitage shelter, and the dramatic shale and basalt outcrops that frame the river. Bird‑watchers often spot kingfishers darting over the water, while photographers love the mist‑filled cascades after rain. In summer, the park hosts a “Wild River Dipping” event (dates vary) that lets families experience the river’s cool waters up close.

Practical Information

The Shimna River itself is free to explore, but most visitor facilities are centred in Tollymore Forest Park. The park is open daily from 10:00 until sunset; admission charges are displayed at the entrance. On‑site parking is available for a modest fee, and the park accepts all major credit and debit cards. Toilets, baby‑changing facilities and picnic areas are provided, and the park can accommodate coach parties.

The river is easily accessed from Newcastle via the A2 coastal road. Local bus services (e.g., Translink Goldline) stop in Newcastle, providing a convenient public‑transport link for those without a car. The nearest airports are Belfast International and City of Derry.

For anglers, permits are obtained through the Shimna Angling Club or at the Newcastle Visitor Information Centre (10‑14 Central Promenade, Newcastle, BT33 0AA). The fishing season runs March‑October.

The Shimna’s coordinates are 54.22455 N, 5.9403 W, making it easy to locate on a GPS device. Whether you are an angler chasing a trophy trout, a naturalist hunting rare mosses, a fan of Game of Thrones, or a walker seeking historic stone bridges amid forest scenery, the Shimna River delivers a uniquely Irish outdoor experience.