Historic Landscape Characterisation

The Vale of Clwyd

THE NATURAL LANDSCAPE

The historic landscape area of Dyffryn Clwyd lies at the southern end of the Vale of Clwyd, a flat lowland area formed in a down-faulted trough enclosed by hills, rising steeply up to the fault scarp of the predominantly Silurian shales of the Clwydian hills on the east and up to the ridge of Carboniferous limestone which forms a band on the west side of the valley. The floor of the valley, between about 2-5km across, rises in height from about 30m near Denbigh to about 100m at the head of the valley. The underlying geology here is of soft, red Triassic sandstones and marls which are mostly masked by later glacial and alluvial deposits but are exposed in areas of elevated ground as at Ruthin and Hirwaen.

At the present day a typical cross-section of the vale from west to east would cut through the following topographic regions: limestone hills on the west, reaching a height of about 200m; a relatively narrow band of sloping ground above the valley bottom, between about 1km wide; the flat, 1ow-lying and seasonally waterlogged land on the valley bottom, up to about 2km wide; a broad band of gently-sloping ground on the eastern side of the vale, about 2km wide, extending from the valley floor to the foot of the Clwydian hills; the more steeply sloping ground up to about 1km across, extending up to the top of the hill scarp; and finally the flatter ridge along to the top of the Clwydian hills, rising to a height of up to about 550m. This pattern is repeated again and again and broken only by the steep-sided valleys of the streams and valleys, entering the vale from the east and west. As a consequence each of the communities in the vale have their own quota of waterlogged meadows, better-drained sloping pastures and arable land, upland meadows and moorland in the relatively short transects from valley bottom to hill top.

During the last glaciation, about 18,000 years ago (dated locally by the radiocarbon age of a mammoth bone from Ffynnon Beuno Cave, near Tremeirchion), the northern ice sheets advanced up the vale to within about 5km of Denbigh, creating a terminal moraine forming a line of low hills across the vale at Trefnant. A glacial lake known as Lake Clwyd formed by meltwaters dammed up against the moraine, stretching inland about 10km, to the south of Llanfair Dyffryn Clwyd. Deltas 1-3km across were built up where the eastward flowing rivers and streams from the Denbigh Moors entered the lake, in the area to the east of Denbigh by the Afon Ystrad, in the area of Llanrhaeadr by the Nant-mawr, in the area of Llanfair by the Afon Clywedog, and at Aberchwiler by the Afon Chwiler, drainage from the vale having initially been eastwards, 'uphill' through the valley of the Afon Chwiler. Once the moraines in the Trefnant area had been breached the drainage pattern assumed its present pattern on the floor of the vale.

The floor of the vale is generally good agricultural land, a strip of better-drained land on the eastern terrace between Llanbedr Dyffryn Clwyd on the south and Aberchwiler on the north being classed as Grade 1 land and much of the lower-lying land, often subject to seasonal waterlogging, being classed as Grade 2, the grading of the hill-side and hill-top land to the either side of the vale generally diminishing with height. The vale has less than 30 inches of rain but has a comparatively low proportion of the cropland in wheat, largely due to the nature of the soils which though rich tend to maintain a high water table, especially in winter, and discourage cereal production today. Present-day land-use is therefore predominantly pastoral, with limited cereals and fodder crops on better-drained ground and areas of woodland and forestry plantation generally limited to the steeper hill slopes and poorly drained lowland areas.

Few pollen studies have been carried out within the vale, and although our knowledge of post-glacial environmenal history is therefore limited, it is assumed that native woodland gradually extended over the whole of The Vale of Clwyd as the climate gradually ameliorated following the last glaciation, and that this was progressively felled by human activity from the prehistoric periods up to the recent past, with only relatively small areas of natural woodland surviving to the present day. It is uncertain when Lake Clwyd finally became infilled with sediment, but it seems probable that small lakes and areas of alder carr survived until at least the 5th millennium BC, when the first evidence of human activity on open sites in the vale can be detected.