Pistyll Rhaeadr

Site of Special Scientific Interest · 52.8527, -3.3769

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Powys County

Climate exposure

This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.

Peatland

Peat habitats store centuries of carbon and depend on a stable, waterlogged water table. Warmer, drier summers dry out peat, making it far more vulnerable to wildfire and to carbon release — a pressure that can undo years of restoration work regardless of how well the site is otherwise managed.

Habitats

Fast flowing river and stream

Geology & landscape

Landscape processes: Fluvial, Peatland / Mire

Description

Description Pistyll Rhaeadr is of special interest due to its fluvial geomorphology. The site lies on the southern slopes of the Berwyn mountain about 6 km north-west of Llanrhaeadr ym Mochnant. The site contains the waterfall of Pistyll Rhaeadr, the highest in Wales at 75 m, together with stretches of the Afon Disgynfa above and Afon Rhaeadr below the falls. The river runs from north-west to south-east and drops from an altitude of 400 m as it runs through the moorland above the falls to about 260 m. Pistyll Rhaeadr marks the boundary between an upland, boulder-lined channel originating in peat and a downstream reach with point bars as characteristic depositional features. Associated with the falls are a series of plunge pools and an arch. The importance of the site lies not only in the waterfall and related features, but also in the geomorphologically significant contrast between the mountain torrent of the Disgynfa upstream of the fall and the wider valley section occupied by the Afon Rhaeadr downstream which demonstrates more lateral activity and depositional features.

Plant communities

A9 — Fast flowing river and stream, Marginal and inundation, Pond ditch and canal, Sluggish river and stream

Potamogeton natans community

Schoenoplectus lacustris, Juncus bulbosus, Sparganium angustifolium, Sparganium erectum, Sparganium minimum, Alisma plantago-aquatica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Elodea canadensis, Lemna minor, Lemna trisulca, Nymphaea alba, Callitriche platycarpa, Callitriche stagnalis, Littorella uniflora, Potamogeton natans, Ranunculus trichophyllus, Glyceria fluitans, Chara subspinosa

A14 — Fast flowing river and stream

Myriophyllum alterniflorum community

Isolepis fluitans, Juncus bulbosus, Fontinalis antipyretica, Lobelia dortmanna, Equisetum fluviatile, Myriophyllum alterniflorum, Lemna minor, Callitriche stagnalis, Littorella uniflora, Potamogeton filiformis, Potamogeton gramineus, Potamogeton natans, Ranunculus peltatus, Chara spp., Nitella hyalina

A17 — Chalk river and stream, Fast flowing river and stream

Ranunculus penicillatus ssp. pseudofluitans community

Berula erecta, Nasturtium officinale, Elodea canadensis, Lemna minor, Callitriche stagnalis, Veronica beccabunga, Polygonum amphibium, Polygonum hydropiper, Potamogeton crispus, Potamogeton pectinatus, Ranunculus penicillatus ssp. pseudofluitans

A18 — Fast flowing river and stream

Ranunculus fluitans community

Fontinalis antipyretica, Fontinalis squamosa var. curnowii, Myriophyllum alterniflorum, Myriophyllum spicatum, Elodea canadensis, Mentha aquatica, Lemna gibba, Lemna minor, Potamogeton perfoliatus, Ranunculus fluitans, Glyceria fluitans, Phalaris arundinacea