Cymraeg / English
Historic Landscape Characterisation
The Making of the Middle Usk Valley Landscape
ENVIRONMENTS AND BOUNDARIES
The Natural LandscapeThe Middle Usk Valley historic landscape area is bounded to the north by Mynydd Epynt, by Mynydd Troed and Mynydd Llan-gors on the western edge of the Black Mountains to the east, and by the eastern flanks of the Brecon Beacons to the south.
The underlying solid geology throughout the area is of Silurian and Devonian Old Red Sandstone. The principal ice flow down the Usk valley during the last glaciation was divided by the western end of the Black Mountains near Llan-gors in the eastern part of the area, one branch turning south-eastwards down the Usk towards Crickhowell and the other continuing to the north-east across the Llynfi lowland to the Wye valley between Glasbury and Hay-on-Wye. Llangorse Lake, the largest natural lake in Breconshire, is of glacial origin. It is up to 8.5 metres deep and probably cut into solid rock at its lowest point. Water in the lake is retained by a barrier of glacial gravel together with more recent alluvial deposits, brought down by streams rising on the hills to the east. Other glacial deposits including morainic debris are present in the Usk valley in the Gilestone/Llansantffraed and Brynich/Groesffordd areas. The slight valley at Pennorth, was formed as a glacial meltwater channel running southwards from the direction of Llangorse Lake in the direction of the Usk valley.
The historic landscape area falls into a number of distinct topographical areas. The areas bordering the river Usk are generally flat and low-lying and between about 120-60 metres above sea level. On the east is the slightly elevated shallow basin around Llangorse Lake enclosed by gently undulating hills rising to a height of about 270 metres but with the isolated ridge of Allt yr Esgair between the Usk valley and the lake which rises to a height of 390 metres above sea level. The area to the north-east of Brecon is again gently undulating and generally between about 140-270 metres. The topography of the area to the north of the Usk and to the north-west of Brecon is more diverse, broken down into a number of distinct stream valleys and small isolated hills such as Coed Fenni-fach and Pen-y-crug which reach heights of about 300 metres. Brecon itself occupies a relatively level area bordering the flood plain of the river, between about 130-80 metres above sea level.
The soils throughout the area are predominantly well-drained, coarse reddish loamy soils overlying the sandstone bedrock, with fine, reddish silty alluvium along the flat flood plain of the river Usk, and with clayey, silty and loamy soils subject to seasonal waterlogging on the north-western margin of Llangorse Lake. Modern land use throughout the area is mostly permanent pasture, but with some arable and fodder crops and conifer plantations on steeper and less accessible land such as Allt yr Esgair and Coed Fenni-fach.
The historic landscape area is drained by a number of distinct streams and rivers. On the north-west are the Nant Brān, Afon Ysgir and Afon Honddu which join the Usk at Aberbrān, Aberyscir and Brecon (Aberhonddu) respectively, bringing water down from the southern flanks of Mynydd Epynt. To the north the Afon Brynich drains land to the south and west of Llan-ddew, joining the Usk just to the east of Brecon. To the south is the Afon Tarell which enters the Usk at Llanfaes and the Afon Cynig which joins it at Abercynrig. The Usk itself occupies a broad alluvial floodplain between Brecon and Talybont-on-Usk, with a complex and active system of river meanders and cutoffs. The eastern part of the area, however, is principally drained by the Afon Llynfi and its tributary streams such as the Nant Tawel at Llanfihangel Tal-y-llyn and the Nant Cwy at Llan-gors which feed Llangorse Lake and drain northwards to join the watershed of the river Wye near Talgarth.
From early times the Middle Usk Valley has occupied an important nodal point in lines of communication linking south-east Wales along the Usk valley and midland England via the Wye valley with south-west Wales, a route occupied successively by the Roman roads of the 1st to 4th centuries, the turnpike roads of the 18th and 19th centuries, the railways of the later 19th and 20th centuries, and by modern trunk roads.
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