Key characteristic features

• Valleys have developed strongly hierarchical, branching pattern.
• Marked variations in form, scale and character of valleys.
• Landform contrasts often emphasised by land use; woodland/scrub and pastures on steeper valley sides and arable fields on gentler slopes.
• Principal chalkland settlements are sheltered within valleys.
• Roads follow main valleys.

The surface of the chalk dip slope is furrowed by extensive branching dry valley systems. There are several hypotheses for their evolution, but most are generally thought to be the traces of early drainage patterns which have been abandoned as the level of the water table in the chalk fell. These dry valley systems occur throughout the chalk landscapes of the AONB but they have greater visual influence within the east open chalk uplands, where even the shallower dry valleys provide a degree of contrast to the surrounding, windswept fields of the chalk uplands.

Many of the chalk valleys show evidence of periglacial activity which would have occurred during particularly cold spells in the Pleistocene period. Solifluction deposits are found on most of the valley floors and it is thought likely that the valleys were generally deepened and enlarged by periglacial erosion.

The enclosed west chalk uplands also includes most of the minor dry valley systems which have eroded it but here the complex landscape mosaic of woodland, forest, farmland and parkland does not vary noticeably in response to such minor variations in relief. However, this area is subdivided by the large chalk valleys of the River Lavant and the River Ems, both of which support rivers on their lower reaches. The Lavant valley is aligned longitudinally across the dip slope, following a structural fold in the chalk. This, and the Ems valley further west, form very broad, relatively deep channels within the chalk, creating a particularly strong hierarchy of landform in the west chalk landscapes of the AONB.

On a still larger scale, the principal chalk valleys landscape type includes the valleys of the four rivers - the Arun, Adur, Ouse and the Cuckmere - which have eroded right through the South Downs creating 'water gaps'. Also included are the relatively large, dry north-south valleys containing the villages of Findon, Pyecombe and Jevington, the Birling Gap and the broad longitudinal valley from the village of Falmer to that of Glynde which, like that of the Lavant, has taken up the alignment of a structural fold in the chalk dry slope. While the river floodplains are described as a different landscape type (ref. principal river floodplains and brooks pastures), these larger valleys all share similar visual characteristics.

In summary, the chalk valley landscapes of the AONB are subdivided into three separate landscape types:

• Principal chalk valleys
• East chalk valley systems
• West chalk valley systems

Previous - Next