4.3 Minor River Floodplains

Key characteristic features

• Narrow, flat alluvial floodplains; closely follow winding alignment of river.
• Small pastures with irregular shapes.
• Curving, narrow strips of deciduous woodland along river or field boundaries.
• Overgrown hedgerows with dense tree cover; occasional ancient hedgerow oaks.
• Small farms set back on outer edge of floodplain; hamlets at bridging points.
• Narrow hump-back historic stone bridges are important local features along the River Rother.
• Horse grazing.
• Tends to have unstructured appearance.

Landform and context

The minor river floodplains of the AONB are those of the Upper Arun, to the north of Shopham Bridge, the West Sussex Rother, and the lower reaches of both the Lavant and the Ems on the margins of the chalk dip slope to the north of Chichester.

These are relatively narrow, linear landscape corridors, confined to an alluvial strip along the river so their physical context is an important influence on landscape character.

The chalk streams have a seasonal flow and are subject to flooding. Their floodplains form a flat valley floor within fairly broad, U-shaped chalk valleys. The River Rother, by contrast, flows across the highly erodible Sandgate Beds and the narrow floodplain is bounded by very gentle, rolling valley slopes which provide relatively little sense of enclosure, Within the AONB, the Upper Arun also has a narrow, flat floodplain but flows along the boundary between the landscape of the Low Weald and that of the north wooded ridges: the floodplain is enclosed by steep valley slopes on both sides.

At a local scale, the floodplain is often quite hummocky and uneven, with minor ditches, tributaries and marshy low points. The floodplain of the Rother in particular has abandoned meanders and, in places, sections of disused canal.

Land use and landscape pattern

The floodplains of the Rother and the Upper Arun are used as pasture for cattle or horses. Fields are generally small and irregular in shape, enclosed by dense, overgrown hedgerows. However, in places the hedgerow pattern has partially broken down and the pastures have an unstructured character with stock wandering freely from one field to the next. Remnants of hedgerows often seem to be freestanding within fields and there are many small, irregularly shaped copses and groups of trees which contribute a sense of randomness to this finely-grained, rather unmanaged landscape mosaic.

The curving linear strips of deciduous, woodland often mark the outer edges of the floodplain and provide a strong sense of enclosure and seclusion. They are either directly alongside the river channel itself, or mark an abandoned meander. These woodlands are principally oak, but those near the river channel or marshy parts of the floodplain contain a proportion of willow and alder. Ancient hedgerow oak trees are prominent local features, particularly along lanes or tracks.

The River Rother is constantly eroding its sandy banks and the river tends to flow within a deep channel, with freshly eroded, deeply indented banks to one side, Trampling by cattle and horses often adds to the erosion.

The historic steep hump-backed stone bridges are an important feature of the landscape along the River Rother. They are made of local sandstone and are particularly attractive and well-detailed.

The chalk streams flow within a more ordered landscape of small, rectangular flat pastures. The river channel here has a fairly open character, with little tree cover. Pastures are often edged by ditches as well as hedgerows.

Settlement

There are no settlements on the floodplain itself, but farms are often set-back on the outer edges and there are sometimes small villages or hamlets clustered on the edge of the floodplain at bridging points. There are a number of rights of way, both across and along the floodplain.

Subjective response

This landscape has a strong, distinctive character and presence, despite its narrow form. The intimate scale and organic, random quality of the pastures along the River Rother are in striking contrast to the surrounding rectangular arable fields. The river floodplain feels like a special, secluded, secretive landscape where natural forces predominate and where man's influence is relatively ineffective. The surrounding woodlands and dense hedgerows provide a strong sense of enclosure and the floodplain seems like a separate, tranquil world.

Sensitivity to change

This narrow river floodplain is unlikely to be under pressure for built development but the pastures alongside the River Rother are increasingly used for grazing horses rather than cattle or sheep, with a resultant degradation in environmental quality and visual appearance.

The random, unstructured character of the finely-grained landscape mosaic is one of the most vulnerable aspects of the minor river floodplain landscape. The scattered trees, remnant hedgerows, marshy areas and winding creeks have a special organic quality which contrasts with the surrounding, more structured arable farmland. These natural forms stem from the dynamics of the river channel itself. The River Rother is actively eroding its sandy banks but the character of its channel, and that of its associated floodplain landscape, would be threatened by engineering works designed to control its natural form.

The curving, linear strips of deciduous woodland marking the outer margins of the floodplain are another visually important, and potentially vulnerable element in this landscape. These woodlands provide a valuable sense of enclosure and seclusion and strengthen the important contrast between the landscape of the floodplain and that of the surrounding farmland.

Key issues for landscape management

Landscape mosaic

• Conserve existing small-scale irregular field pattern, all hedgerows and woodlands.
• The special, distinctive quality of these floodplain landscapes is derived from their small, intimate scale and, in particular, the finely-grained, erratic character of the landscape mosaic. This character should be enhanced by introducing more diversity of form and a wider range of habitats:
- small alder and willow copses with curved, indented natural forms; meandering, linear shapes are particularly appropriate.
- scattered single trees.
- hedgerow trees in randomly located groups.
- conversion of parts of some fields to reed beds or marshy scrapes; integrate with existing remnant ditches and channels.
- irregular planting on fringes of wetland areas to give visual emphasis to interesting natural forms.

• Encourage management of traditional water meadows and reintroduce management of farmland as seasonally wet pastures wherever this is possible, particularly on the floodplain landscapes of the chalkland streams.
• Reduce intensity, extent and visual impact of horse grazing.
• Encourage expanded hinterland on either side of the river floodplain to act as a buffer zone and to extend the visual and ecological influence of the river floodplain landscape.
• Study erosion pattern of the River Rother. Allow natural erosion to occur as far as possible in areas where rights of way are not affected. Reintroduce spiling with willow stakes as a traditional technique for reinforcing the eroding banks of the river channel where appropriate.
• Conserve the historic stone bridges along the River Rother.
• Pollard existing willows, where this is possible, to contribute to the distinctive visual character of the landscape and, in particular, to give the river a stronger visual influence in the wider landscape. Plant new willow trees with a view to future pollarding in appropriate locations.

Priorities for action

• Habitat creation schemes on a small, finely-grained scale to enhance visual and ecological value of riverside meadows.
• Reduce scale and visual impact of horse grazing.
• Buffer zones and planting to encourage broader river landscape corridor wherever possible.

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