WILD TROUT TRUST The Chalkstream Habitat Manual introduction.pdf · who supplied photographs, and to Nigel Holmes who proof-read the document This document was written under contract

WILD TROUT TRUST

The ChalkstreamHabitat Manual

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Introduction to the manual

Following on from the successful 'Wild TroutSurvival Guide', the Wild Trout Trust identified a need for more detailed and practical guidance on habitat enhancementtechniques specific to river types, in this case,chalkstreams.

After considerable discussion, the Trust hasadopted a web-based Portable Document Format(PDF), with guidance arranged in easy to read sections.

This approach has a number of advantages: • information can be viewed on-line,

(requires Adobe Acrobat Reader®, which can be downloaded free fromhttp://www.adobe.com/products/acrobat/readstep2_allversions.html), or saved to hard disc as required (free of charge);

• it can be emailed to other organisations orindividuals, or printed out as a hard copy for use on site;

• it can be easily updated and reviewed in line with new legislation or practice.

THE CHALKSTREAM HABITAT MANUAL sheet 1 of 5

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ents The production of this manual has been supported by the Environment Agency,

Natural England and the River Restoration Centre.

The Wild Trout Trust would like to thank the following individuals who made up the project steering group:

•Allan Frake and Lawrence Talks (Environment Agency)

•Simon Johnson, Tim Jacklin and Andy Thomas (Wild Trout Trust)

•Martin Janes (River Restoration Centre)

We would like to extend a special thanks to all individuals and organisations who supplied photographs, and to Nigel Holmes who proof-read the document

This document was written under contract by Vaughan Lewis, Windrush AEC Ltd. Design of the document and production of original artwork was undertaken by Robert and Rhoda Burns/Drawing Attention.

Introduction

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The information available in this manual is not intended to be comprehensive or definitive; in particular, details or topics relevant to particular circumstances may well not be included. Readers areadvised to seek full professional advice before considering acting on any of the recommendations in this manual, and the WTT does not accept any liability for its content.

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THE CHALKSTREAM HABITAT MANUAL Introduction sheet 2 of 5

How to use the PDFs

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The information contained within each section isaimed at practitioners. The Trust receive largenumbers of calls and emails from a wide range ofindividuals and organisations, seeking detailedadvice on any number of 'how to' issues: How do Iinstall a groyne? Which way should it face? Howcan I improve spawning for trout? We haveattempted to answer these and many other questions in these PDF sheets.

Each section is a stand alone document, cross-referenced to others where appropriate. For ease of use we have used ‘Bookmarks’ (whichappear as an icon or tab on the left side of thePDF viewer window). By clicking on them, these enable the reader to jump to any section.Photographs and explanatory diagrams areincluded to illustrate points made in the narrative.Plan views of a 'typical' river have been included,both to show the range of problems oftenencountered and possible ways of resolving them. Links to useful websites, contacts, and further reading are provided.

Whilst these guidelines are very practically basedit is important to realise that there are a numberof over-arching river processes that help to shapechalk rivers. Many of these are covered in detailin the Trust's 'Wild Trout Survival Guide'. Thosethat particularly affect chalk rivers include thelarge number of sluices and impoundments erected over time for milling, water meadowdrowning, and fisheries purposes. Their impacton chalk river habitat is very significant and must never be overlooked when planning anyenhancement or restoration scheme.

Even more fundamentally, it is imperative that atall times we should work with natural riverprocesses, rather than against them. Carefulobservation of your river, and consultation withprofessional ecologists and fisheries specialists(including of course the Wild Trout Trust) willinform future decisions. In some cases, the bestapproach to restoration may be to do nothing, bepatient and let the river naturally repair pastdamage. However, in many instances, affirmativeaction is required to assist natural recovery.


List of sections

Legal considerationsIn a complex world, there are inevitably a numberof legislative considerations for any project.This section highlights key areas that must beaddressed at the planning stage, including landdrainage consenting, and species protection.

Health and Safety is everyone's responsibility.No project should be undertaken without due H&S planning and the development ofappropriate risk assessments. The main areasthat must be covered by this planning andassessment are examined.

Restoring over-wide channelsOver-wide channels are a feature of many chalkstreams. They are often a consequence ofexcessive dredging in the past, or due to areduction in river flow as a result of abstractionor climate change. The benefits of channel nar-rowing are examined in this section, along witha range of techniques proven to be effective.The benefits and drawbacks of the techniquesare examined.

Instream structuresChalkstreams can often lack feature, with a uniformity of channel form offering poor habitat for trout and other species. The use ofsimple instream structures can be used toimprove habitat diversity and availability. Thissection examines the use of naturally occurringmaterials to create such structures, with advantages of each technique examined.

Gravel rehabilitation/restorationThe concept of the 'habitat bottleneck' hasbecome well understood with respect to troutpopulation dynamics. All too often, bottlenecksin chalkstreams occur at the spawning habitatlifestage. By careful restoration and rehabilitationof existing gravel spawning areas, and the creation of additional sections, spawning successcan often be improved. This can allow a reduction in the intensity of stocking with fishfarm reared trout, and an increase in wild trout.

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Tree managementTrees have a major impact on the morphologyand ecology of chalkstreams. The balance oflight and shade cast by their canopies influencesthe growth of instream and marginal vegetation,whilst their roots provide protection from erosionand cover for trout. Careful management ofriparian trees and shrubs can therefore be usedto optimise habitat conditions for trout. Thissection examines the range of managementtechniques available, and their efficacy.

Protecting marginal habitatDamage to marginal habitat, particularly fromgrazing agricultural stock, can result in increasedrates of erosion, often to the detriment ofchalkstream habitat. Controlling grazing by the use of fencing can reduce this damage significantly.

Influencing land managementMuch of the management of chalkstreams focus-es on the channel and adjacent banks. However,many of the processes that drive the formationof the channel and its ecology take place in the wider catchment. This section identifies themost important of these processes, and detailsmechanisms to address a range of potentiallydamaging impacts that can arise on a catchment scale.

Management of riparian andinstream vegetation

Weed cutting, both instream and bankside, is a long-standing component of chalkstream management. It is also a hugely controversialone. This section examines the benefits andpotential pitfalls of weedcutting, and offers abalanced view of its place in the fisheries management toolbox

Use of Large Woody Debris (LWD)For a long time, large branches and trees thatfell into chalkstreams were regarded as littlemore than a nuisance, and were routinelyremoved. However, the contemporary view ofLWD has changed dramatically. There is clearevidence that LWD is a key component ofchalkstream ecology and as such, should bemore carefully and sympathetically managed.Guidance is provided as to the most effectiveway of achieving optimum benefit to trouthabitat from LWD.

Erosion controlErosion is a natural and necessary part of riverine processes. Without it, there would beno pools and gravel shallows, no deep runs orsilty margins. However, at times, erosion can beexcessive, generally due to the impact of mans'activities. It may then be necessary to reducethe rate of erosion to something nearer to a natural level. This section examines when itmay be appropriate to control the rate of erosion, and how best to do so.

Case study: The River Glaven:The Wild Trout Trust is proud of the high levelof uptake of its advice by recipients of AdvisoryVisits. One of the most outstanding projectsundertaken by volunteers, with the assistance of the Trust, was the enhancement of the RiverGlaven at Letheringsett, Norfolk. The case study chronicles the planning, design and implementation of this scheme, with successesand failures clearly identified. The high qualityof the work, and its benefits to the river's ecologywere recognised by the award of first prize in the amateur category to the River GlavenConservation Group at the 2007 Wild TroutTrust conservation awards.

Further informationThis guide does not claim to be comprehensive.Despite the detailed advice it provides onchalkstream management, there will inevitablybe times when more information is required.This section provides a wide range of web-basedlinks, written text and contacts to other groupsthat the Wild Trout Trust believes will be of benefit.

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Section of overgrazedand eroded bank

Poor land managementcausing soil to enter the river,increasing sediment build-up in the channel, and clogging

spawning gravels

Heavily overshadedchannel with no

marginal vegetation

Overwide channelwith deposited fine silt

Heavily cut banks and channelwith little marginal or instream

vegetation remaining

Over deep slow sectionof river with little gravel

due to past dredging

DAMAGED CHALKSTREAM.

Feedback is both useful and informative. Overtime, the Trust hopes to improve and develop thecontent of the PDF's. Inevitably, we won't get itright first time. Your input could help us to

improve and update their content. Comments canbe sent to [email protected]

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WILD TROUT TRUST The Chalkstream Habitat Manual introduction.pdf · who supplied photographs, and to Nigel Holmes who proof-read the document This document was written under contract