Historic Landscape Characterisation

The Middle Wye Valley

The Nautral Landscape

The Middle Wye Valley historic landscape occupies a well-defined topographical area, with the dramatic escarpment of the Black Mountains to the south and with the lower and more gently sloping sandstone hills of Brecknock to the west and of Radnorshire to the north, the overall topographical range falling between about 700m above Ordnance Datum on the crest of the Black Mountains to about 80m on the floor of the valley. The Old Red Sandstone which underlies most of the area shows considerable variation, and includes red marls, siltstones, flaggy mudstones, grits and some conglomerates, green Senni Beds, red and purple Brownstones, and thin beds of limestone. The sandstone strata have been selectively exploited in the past as sources of building stone for houses, barns, walls and other structures, and for stone roofing tiles. The beds of limestone have been quarried for the production of agricultural lime.

The landscape was shaped during the last glaciation when ice flows moving south-eastwards, along the upper Wye valley, merged with a glacier moving north-eastwards along the Llynfi valley, the ice eventually escaping into the Herefordshire plain to the east of Hay. Glaciation created the broad and flat-bottomed valleys of the Llynfi and the Wye and also left a legacy of landforms and drift deposits which have had a significant effect upon natural vegetation, human settlement and land-use. Notable amongst these features are the substantial recessional moraine which partly blocks the valley between Clyro and Hay, the partly drift-covered foothills of the Black Mountains south of Talgarth, and the gravelly till composed of red marls on parts of the floor of the Llynfi and Wye valleys. Some of these fluvioglacial deposits have been exploited in the past as sources of both gravel and clay.

The drainage pattern established following the glaciation is based upon the Wye and the Llynfi rivers which merge at Glasbury. The Llynfi, originating at and deriving its name from the late glacial lake at Llangorse, is joined by the eastward-flowing Dulas at Bronllys and by several streams occupying steep-sided valleys running off the northern escarpment of the Black Mountains, notably the Nant yr Eiddil which joins it near Trefecca, the Ennig which joins it near Talgarth, and the Felindre Brook which joins it near Three Cocks. The northern slopes of the Black Mountains are deeply incised by a number of other streams which form tributaries to the Wye, including the Nant Ysgallen, Digedi Brook, Cilonw Brook and Dulas Brook. The Wye follows a meandering course along the floor of the valley, with numerous oxbows, cutoffs and palaeochannels emphasising the constant deposition and reworking of alluvial deposits that has taken place since the last glaciation. The floodplain of the Wye is up to about 1 kilometre wide though there are three natural crossing points within the historic landscape area at Llyswen, Glasbury and Hay, where higher land approaches the river more closely upon either side. Between Clyro and Hay the Wye has cut a narrow channel only a matter of a few hundred metres wide through the 50m-high glacial moraine which otherwise blocks the valley at this point.

A wide variation in soil types is to be found within the historic landscape area, depending upon hydrology, the underlying geology and the presence of drift deposits or alluvium. Apart from some areas of impeded drainage with cambic stagnogley soils, high up on at the foot of the Black Mountain escarpment, the foothills of the Black Mountains and the lower hills to the north and west are largely covered with relatively well-drained brown earths, which in the past have permitted cultivation to be carried on at relatively high altitudes above sea level. There is greater local variation in soil types along the base of the Llynfi and Wye valleys, essentially depending upon whether they overlie clayey marls, gravel deposits, or river alluvium. Most of the lower-lying soils are well-drained and easily worked, though some are affected by seasonal waterlogging and flooding.

Little paleoenvironmental analysis has been undertaken on deposits within the historic landscape area itself, but work at Rhosgoch Common and a number of other upland and valley bottom sites in the region indicate that by a date of about 6000 BC the local vegetation would have been dominated by oak woodland, with widespread local occurrences of lime, elm, ash, birch, hazel and alder, the woodland extending to altitudes of up to perhaps 600m above Ordnance Datum. There are indications that this natural woodland cover was already beginning to be affected by human activity by the Mesolithic period, and there is evidence of local cultivation for cereal production in the early Neolithic period, from a date of about 4000 BC. Progressive woodland clearance took place throughout the prehistoric, Roman and medieval periods, and it seems likely that by the later medieval period the extent of woodland cover resembled that of the present day, with areas of semi-natural mixed deciduous woodland largely confined to the steeper and less accessible hillslopes and stream valleys.