Riverbank Habitat Restoration Project

This article borrows heavily from a submission to the Broads Authority (BA) by Society member and Vice Chairman of the BA’s Navigation Committee, Phil Ollier who himself wishes to acknowledge the input of a number of Society members not least of whom is renowned conservationist Dr. Martin George OBE.

For many years, Broadland conservationists, navigators (especially sailors) locals and visitors have been aware of the encroachment of scrub at the river bank margins and the advance of overhanging trees. This is particularly noticeable in the upper reaches of the rivers where the channel has narrowed considerably.

The problems caused by riparian tree and scrub growth

There is evidence to suggest that this area was never covered by woodland to the extent that, for example, Sussex and much of the South East of England once was. However, it is not widely known that the Broadland landscape is nevertheless what we might call “industrialised” in that it was kept relatively “tree free” by the traders in their keels and wherries as well as reedcutters and coppicers who no doubt were about long before the sailors.

The natural reed margin of the river banks protected them from erosion until well into the 20th century and aided by the scrub and tree clearance of those skippers, the banks hosted a widely diverse flora and fauna.

In many places on the Broads, the water bodies were surrounded by undrained fens dominated by reedswamp species. The reeds were cut regularly for thatch and much of the growth was sent to London as “litter” for horses. This curtailed sapling growth.

The rivers also serve to disperse tree and plant seeds as well as some of the falling autumn leaves however if the offending trees/scrub were not there in the first place the sediment load would be much lighter thus aiding the dredging program. In the past, on marshland, trees and scrub were kept under control but the decline in traditional management techniques allowed scrub to invade the fens. The bulk of the resulting tree growth overhanging the waterways reduces the effective width of the channel; catastrophically so when trees fall across the navigation and require removal.

 

The larger trees, now established on the edges of the waterways cause a further problem:  the root systems undermine and loosen the banks, in many cases creating unstable overhangs which lead to the development of embayments.

 

Picture above shows the north bank of the River Bure just above the dyke leading to Black Horse Broad. The clearance done by Horning Sailing Club stops immediately above the dayboat in the middle of the three.

                              

 

                             This picture, above, is taken from below Dydler’s Mill looking towards the area covered by the shot above; it shows trees and scrub invading and reducing the reed margin.

                                      

 

                                           

The picture, above, is of a quarter mile measurement post below Dydler’s Mill on the River Bure; when erected, these were on the bank behind the reeds and visible to the ground.

                                                                                 

What became the traditional means of disposal of dredged spoil, namely “sidecasting” it onto the river banks, without spreading the material thinly, and the deliberate creation of raised flood banks provided dry areas where reeds were unable to grow thus allowing trees and scrub to take hold. Trees and scrub growing on earth floodbanks reduce access for maintenance and, by their root action, destabilise the banks.

The two main components of the marginal reedswamp, Lesser Reedmace (Typha angustifolia) and Reed (Phragmites australis) are intolerant of shade. The latter species will survive, albeit in an impoverished condition, for many years under an Alder canopy, but eventually both species will be shaded out of existence. Loss of these species and the incursion of scrub deprive a number of other species of their preferred habitat.

Research at Wallingford has demonstrated the effectiveness of riparian reed beds in protecting the river banks from erosion by waves caused both by wind and boat wash. The philosophy behind the current Broads Flood Alleviation Project (BFAP) is to replace hard engineered vertical river banks, topped by raised flood banks, with soft engineered sloping river banks backed by reeded ronds with the flood banks set back from the river edge. The soils of the river bank are then protected from erosion by reed growth in the shallower (up to 1.5m) water at the edge of the navigation. In these areas the return of scrub (and tall trees) will negate the flood alleviation project’s efforts to recreate natural reed margins to the rivers.

 

 

Examples of tree and scrub clearance in the Broads

 

BA Riverworks teams have dealt with fallen trees in the navigation and have cleared trees and scrub from the banks on an ad hoc basis during winter months.

In co-operation with Riverworks teams, Broads Society “Broadsword” volunteers have assisted with tree and scrub clearance, operating teams in both the Northern and Southern Rivers during the winter period.

The picture, above, shows the work of the Society’s Broadsword team clearing scrub from the banks of South Walsham Fleet Dyke. (Image to be updated shortly.) 

A number of sailing clubs deploy winter working parties to fell trees and scrub which blanket wind in their favoured sailing areas.

 

In carrying out the BFAP, Broadland Environmental Services Limited (BESL) has cleared a significant amount of scrub and willow along the Broadland river system since starting work in 2001. These include (“compartment” refers to the geographical location):-

 

River Waveney – the right hand bank (TRB) between Beccles Sailing Club and Share Drainage Mill Over 10 kilometers. (compartment 26,27 & 28)

River Waveney – the left hand bank (TLB) Long Dam Level. 2 kilometers (Compartment 24)

River Ant – TLB How Hill 1 kilometer. (Compartment 4)

River Yare – TLB Strumpshaw 800 m (Compartment 16)

River Thurne TLB Martham. 1000m. (Compartment 7)

Various conservation organisations and local landowners have carried out fen restoration projects in the Broads in recent years and management plans for some designated areas include further work of this nature.

 

Examples of work carried out include fen restoration in the Bure Marshes National Nature Reserve:-

                                                     

 

 

around Upton Broad:-

 

and on the Yare at Strumpshaw and Rockland.

 

The last five years have seen the development of techniques, largely funded by Natural England to use mechanical equipment to clear trees and scrub from former fenland and restore the reedswamp habitats. This is a Natural England project at Woodbastwick on the River Bure:-

 

While this work has had a beneficial effect on parts of the Broads, it has really only scratched the surface. In particular, it has had no effect on large areas where the BFAP places its defences well back from the edge of the waterway.

Benefits of Habitat Restoration (tree and scrub clearance from the edges of the waterway).

 

It will help to improve the biodiversity of the fen ecosystem. Although the alder woodland so characteristic of the region is of great national ecological importance, we should not want to see all the fens in the region dominated by this community – a balance between the different types of fen community is required.

 

It provides an opportunity for reedswamp species to recolonise the banks of rivers and broads. This is highly desirable as it will, inter alia, help to check the rapid rate at which the edges of the fens are being eroded by a combination of boat wash and wind-generated waves; dredging costs will thus be reduced.

 

Navigation in the upper reaches of the rivers will be improved by increasing the effective channel width, reducing the amount of sediment entering the waterways and reducing the incidence of fallen trees partially blocking the navigation, whilst sailing craft should experience clearer wind.

 

The edges of the waterways will gain a more ‘open’ and ‘natural’ appearance. The vistas will return to those not experienced since the early part of the last century.

 

 

Practical considerations

 

Tree and scrub clearance is an expensive process. On small areas, say less than 2 hectares, hand clearance and mechanical methods cost similar amounts – around £10,000 – 15,000 per hectare.

 

Surprisingly, mechanical methods cause less damage to the underlying peat layers because of the reduced tramping around and the ability of the machines to lift felled material clear, rather than dragging it across the ground. On larger areas, the mechanical methods prove more cost effective because mobilisation costs are spread more thinly.

 

For effective development of a sustainable ‘soft’ edge to the waterway it is advisable to ensure that trees growing right on the bank of the river are removed completely (rather than just felled and stumps ground out) and the edge of the waterway should be re-profiled to a slope that will allow reed growth to re-establish for a width that will allow absorption of wave energy.

 

Once clearance has been carried out and the reedswamp species have re-colonised (possibly by means of replanting but usually as a natural result of the clearance work) it will be necessary to carry out maintenance work on a regular cycle to prevent resumed scrub incursion. Given suitable equipment and planning, this should not be impossible to achieve.

 

The Society believes that there may be funding sources available for this sort of work. EU funds, Aggregates Levy and Landfill Tax seem the most likely but this is not an exhaustive list. Some of theses sources can be accessed by statutory bodies, others by private organisations, community groups or charities. Geographical restrictions are placed on some funding streams so that funds available for work in one part of the Broads might not be available for similar work elsewhere. Recent government job creation initiatives emphasising “green” outcomes might be applicable. Anyone reading this with practical experience of or suggestions for such funding is invited to contact the Society’s Administrator (see Contacts page).

 

Current BA funding streams are not sufficient to mount an effective clearance programme however, it remains the case that the objectives exist within the Broads Plan 2004 (see below).

 

Recent work carried out under a Natural England initiative has demonstrated that projects of this nature can be funded and carried out successfully in compliance with the relevant UK and European laws and objectives.

 

Tree and scrub clearance is one of the few activities that will attract support from most groups of Broads stakeholders. Conservationists, navigators, anglers, ramblers, landscape artists and government departments with interests and duties in the area should all support an initiative to increase activity of this nature; most have been contacted and all are positive.

 

 

The Habitat Restoration Project

 

A number of Broads Society Committee members and Phil Ollier have taken a close interest in this subject. The Committee members involved decided to ask the full Committee for permission to work towards a fully funded project. This was granted and an initial steering group comprising Paul Howes, Phil Ollier and Richard Baguley was set up and tasked to take preparatory steps.

 

On May 15th the Society organised a meeting at Horning Sailing Club to which it invited a wide range of people from all groups of Broads Stakeholders, including Natural England, the Environment Agency, Norfolk Wildlife Trust, Broads Authority members and staff, local politicians, conservationists, navigators, riparian owners and technical experts.

 

Of these an excellent, representative group took a trip on the River Bure between Horning and Salhouse. This allowed people to see sections of river bank that had been cleared by sailing club volunteers and other sections that had been cleared under the Natural England initiative. It was possible easily to contrast these areas with those that which remains overgrown. The effects on the landscape, navigation and wildlife were clearly visible.

 

During the river trip many of those on board contributed their technical knowledge; our thanks go to Martin George, Rick Southwood, Martin Broom as well as our own Paul Howes and Phil Ollier.

 

 

Paul Howes & Phil Ollier listen to Dr. Martin George OBE (centre)

The large river boat used allowed a fine view of both banks: the northern one being largely overgrown above Black Horse Broad notwithstanding the efforts of the sailing club whilst the southern bank opened up wonderful vistas across the fen to Woodbastwick Decoy Broad. The comparison was illuminating and the difference clear to all. Above Dydler’s Mill (northern bank) both sides of the river were more and more overgrown until, just before entering Salhouse Broad, it was obvious how narrow the river has become.

 

 

                                                

Looking across the cleared fen towards Woodbastwick Decoy Broad.

 

A meeting held after the river trip identified wide support for the sort of clearance work that had been observed and discussed a number of possible sources and mechanisms for funding and carrying out the work.

 

 

Current situation (mid July 2009)

 

The Broads Authority has agreed that it should take a more pro-active role in delivering the 5-year priority objectives TR16 and TR17 in the Broads plan 2004.

 

The Broads Authority has appointed staff to work in partnership with the Society (Phil Ollier, initially) and other interested parties to identify appropriate funding streams, to facilitate the application of those funds to the purpose of clearing trees and scrub and the re-establishment of reeded ronds to appropriate sections of the waterways and to provide practical help and assistance where necessary.

 

The Authority was asked to consider that any direct financial contribution from the Authority in support of this work should be drawn in appropriate proportions from the General Fund and the Navigation Account as the outcomes will support all three of the Authority’s statutory objectives. The Authority has agreed initial funding details of which may be found here:- http://www.broads-authority.gov.uk/authority/meetings/broads-authority/2009/06-26.html at 4(3)(iii).

 

 

 

 

Notes:-

 

In July 2005 the Broads Authority published “River Corridor Tree and Scrub Management Guidance – A Guide for managers in theBroads” which provides quick reference to key relevant legislation, reasons for removal and retention of trees, best practice and case studies.

 

The BA has also published a pamphlet entitled “Broads Design & Management Information. Environment & Landscape. How do I plan and manage trees and scrub alongside rivers?”

 

The Broads Authority’s Broads Plan 2004:-

 

The Broads Plan 2004 contains the following statements:-

 

Issue: Bank erosion is a recurring problem for landowners and impacts on water quality. A range of bank protection measures is used, and the Authority promotes ‘soft’ or natural engineering solutions where possible.

 

20-year aim: Bank erosion will be minimal, with sustainable and where practicable natural or ‘soft’ engineering solutions used to protect the more vulnerable stretches of waterways.

 

5-year priority objectives:

TR16 Minimise bank erosion where caused by boating activity.

TR17 Protect and restore vulnerable banks and ronds.

 

The 5 year action plan picks up on this objective in the following terms: “restore river-banks by removal of excessive tree and scrub growth, and maintain through routine clearance/coppicing.

 

These objectives do not provide measures for identifying their achievement within the identified timescale but they do provide a justification for action by the Authority to address the problems caused to the navigation and the environment by riparian tree and scrub growth.