Chichester Ship Canal

Chichester Ship Canal

Background

The Chichester Ship Canal is a leisure waterway linking historic Chichester to the sea. The canal runs 4 miles from the Basin to the Harbour at Birdham and, today, the 2 miles as far as Donnington is navigable.

It is valued by local residents and holidaymakers who enjoy the many activities – narrow boat trips, rowing, canoeing, rambling, fishing, and cycling. Management of the activities and maintenance of the canal is the responsibility of Chichester Ship Canal Trust, who lease the canal from West Sussex County Council.

The Canal Trust is a registered charity with c 450 members, whose aims are the preservation, maintenance and improvement of the navigation between Chichester and the harbour – a historical monument to the transport revolution in Britain in the 19th century. The Trust is entirely manned by around 140 volunteers who crew the boats, run the shop, bailiff the angling and carry out maintenance and restoration work.

Project Brief

The trust manages a busy waterway featuring Scheduled boat trips and charter cruises on their canal cruiser ‘Kingfisher’. The increased use of leisure craft on the canal, however, was causing significant erosion. By 2010 much of the canals 2m grassy verge had been lost to erosion and in many places the towpath itself was indented with erosion embayments causing significant health and safety concerns about pedestrian traffic.

Cain Bio-Engineering was the successful bidder to undertake the repair works using a two staged ‘coirnet’ revetment. The technique jointly reinstates the lost upper bank margin with the main retaining revetment and eliminates boat wash and erosion into the long term with the lower terrace which is constructed close to the water’s edge.

The finished structure is designed to fully vegetate and provide both aesthetic, wildlife and health & safety benefits into the long term.

The Solution

Before

Images down the canal bank show the extent to which the 2m wide grassy verge has been almost entirely eroded away  with the new bank edge hard up against the towpath itself.

2 meters of grassy verge eroded away.

Original verge eroded away.

Original verge eroded away.

Stakes mark the new outer bank.

During

Work now commenced to stake out the original outer bank line with hardwood posts to form both an inner high-level and outer low-lying terrace close to the waters edge.  Geotextiles are fitted and the subsequent cavities back-filled with dredged sediment from the canal bed. The completed terraces are planted with a selection of native canal and wetland species.

Outer bank line staked out.

Geotextiles are fitted and cavities back-filled.

Cavity back-filled with dredged sediment.

Project manager ‘Mikey Bee’ showing detail of ‘dredged arisings’

Project completion showing two-tier revetment.

 

After

Images below show the vegetated structure at various times following project completion, from 7 months to 7 years. Even only 7 months after project completion there was rapid growth of plant cover which provided valuable winter habitat on the low-level marginal shelf.

7 months after - showing valuable winter plant cover.

13 months after project completion, full summer bloom.

After 7 years marginal vegetation has fully colonised the terraces.