2o As*vs'i 7.,.'} .irffi;: trix r'I R{'r\xt L.x I ',#r5F',1"--.:i"'* lr t""te BrorYn&Root ,s+,gy*#, .\t;l xt't o} RiverLittle Ouse (Brandon to Thetford) PrefeasibilityStudy Stage 1 Report: Descriptionof Investigations EnvironmentAgency Anglian Region BBR Ref 0006077/D5/135 EA ProjectRef: LVN17010 Babtie Brown & Root JV 8 The SquareMartlesham Heath lpswich Suffolk lP5 33L Tel 01473 624326 Fax 0'1473623021 '*iu*,,:,i$-l" l'\:\'! titi\)lt-:\ ! fR\ \(:r \.r{..i (l! BabtieBrcurn & Root River Little Ouse Brandon to Thetford Prefeasibitity Study - Stage 1 Report: Description of lnvestigations Purpose Draftfor Discussion Front Cover Photo AbbeyHeath Weir,River Little Ouse, Thet{ord. Ri2(}3U)00d)77EA BEndon to ThettorilA.hn\Dcumd*sux-i3i StagE1 rinat.d,oc 20/8/03 'rfi-Sl F \\'t{t{!\xt'tst auuti"tsrcrrn & Root .-s.I- 1:.1\.'| @ River Little Ouse Brandon to Thetford Prefeasibility Study - Stage 1 Reporl: Description of Investigations Tableof Contents |NTRODUCT|ON.............. .'.....'.......2 BACKGROUND............... "..""..'....2 TECHNTCALASSESSMENT.................. .............3 coNcLUstoNS............... .."....'...'..9 Appendices AppendixA - Environmentallmpact AssessmentReport Appendix B - PhotograPhs Appendix C - Works Requiredfor Navigation AppendixD - CostEstimates AppendixE - WorkingGroup Consultation Appendix F - AbstractionLicence Summaries Drawings 0006077/01/01 - StudYArea 0006077101102 - SSSI's 0006077/01/03 - SAC's 0006077/0i/04 - CurrentStructures and Prefened Lock Locations,Forest Enterprises 0006077/01/05 - River CorridorHabitat, Forest Enterprises 0006077/01/06 - PotentialEnhancement Areas, Forest Enterprises 0006077/01/07 - ScheduledAncient Monuments 0006077/D2l08 - HistoricStaunches and ExistingWeirs 0006077/D2l09 - NavigationProposals - Plan & Longsection R:12m3\0OtA77 EA Bnndoo to Tndiord\Adm\D@u@nts\D4'135 Sagts 1 Finat'doc 20/8103 I of73 i.\..1fl.ii]\\it\I r"# \{l) I-{'\ O eautreBrown & Root Rlver Little Ouse Brandon to Thetford Prefeasibility Study * Stap 1 Report; Description of lnvestigations SUMMARY 1.1 This report presentsthe initialenvironmental and technicalassessments for providing enhancementsto the environment,and navigationon the LitfleOuse between Brandon and Thetford. The areas of potentialenvironmental enhancement have been identifiedbased on informationprovided from a core list of consultees,particularly Forest Enterprises. 1.3 The key engineeringworks requiredfor the navigationto be reopenedbetween Brandon and Thetfordhave been identified. The costs for these proposalshave been assessed.work on an assessmentof the benefitsin continuing,and will be reporledon in a stage 2 report. INTRODUCTION 2.'l The River Little Ouse is at presentnavigable by small boats up from its confluencewith the River Great Ouse up to Brandonon the NorfolUsuffolkborder. There is a historyof previous navigationgoing a furtherSkms upstreamto Thetfordbut this has not been possiblefor many years. 2.2 The river between Brandonand Thetfordflows throughthe ThetfordForest, part of which is part of the BrecklandForest SSSI and part of in the Thetfordgolf courseand Marsh J55t. 2.3 The purposeof this prefeasibilitystudy is to exarninethe issuesassociated with reopening the lengthof watercoursebetween Brandonand Thetfordto navigation,and to identifyany potentialenhancements to the amenitiesin the area. The study has been preparedby Babtie Brown & Root under the NEECA framework agreement. This draft report identifiesthe key environmentalissues and the scooe of work' which would be requiredto reopen the navigation. The final reportwill provide furtherdetails of costs and benefits. BACKGROUND 3.1 The extent of the study area is shown in drawing 0006027/01101. 3.2 A descriptionof the locationis given in section 2.2 of the EnvironmentReport under AppendixA. Photographsof the siteare shownunder Appendix B. J.J There is a significanthistorical record of the developmentof this sectionof river and navigationused to go up as far as Thetford. This, however,has been disusedfor manv R12038006077 g*Ddon EA to Thetford\Arbn\Oocumedsi04..l35 Stag' I rinat.doc 20/g/03 2o173 ;';S !.\\-ili{}\\tt vi a"mi"Brouvn &Roct :\4"{i: \i i ii\ r "r S 'l River Little Ouse Brandon to Thetford Prefeasibility Study - Stage Report: Description of lnvestigations years, althoughthe openingof a lock at Brandonin 1995 has allowedsmall boats to pass upstreamof Brandonsluice to a point upstreamof the 41065 road bridgeat Brandon. There are some limitationson the size of boats that can navigateto Brandonas follows: o Limited headroomof approximately2.1m at the cut-offchannel near HockwoldCum Wilton,although it is understoodthat this is currentlybeing raised' r There is limitedwidth, length, depth and headroomat BrandonLock (4m wide, 14m long,1.2m deep and 2m headroom). 3.5 There is considerableexisting amenity value along the length of river between Brandon and Thetford,and there are several environmentaldesignations covering this area (see AppendixA). use is made of the watercoursefor canoeingand there are other recreationaluses of the area. The ThetfordForest Enterpriseshave extensiveresponsibilities for the managementof land adjacentto the river,and are keen to improvethe water level managenrentso as to improvesome of the existingland uses. 3.7 Consultationswith the seven rnembersof the workinggroup have been undertaken during the periodof this study. These are reportedon in Appendix F' 3.8 Historicalsurvey informationhas been used to look at the engineeringrequirements to allow water depths to be increasedfor navigation. These changes in water depth would need to be achievedwith a combinationof raisingwater levels and excavationldredgingol the existingbed. Detailsof these works are given in the followingsections. TECHNICALASSESSMENT CurrentWater Level ManagementRegime 4.1.1 A Water Level ManagementPlan exists for the ThetfordGolf Courseand Marsh SSSI. This SSSI containsthe only survivingtrack of BrecklandHeath known as Thetford Wanen. 4.'1.2 Much of the river corridoralso compriseswetland habitat,although no specificwater level managementplan has been identifiedfor these other areas. 4.1.3 The EnvironmentAgency canies out dredgingof the river as required,and weed cutting twice a year (in June and September). Furtherdetails of the resultsof the currentwater level managementare coveredin AppendixA' 4.1.4 The locationof the five historicalstaunches which used to exist on the river between Brandonand Thetfordare shown on drawing0006077/D2i08. These stauncheswere used to impoundwater above them to allow sufficientdepth for navigation. While there Rj2OO3\0006077EAgmndonloTheltordlArtm\O@umonts\I)4-135StagE1rtnar.dcA)/8/03 3of73 I i ili;r\ lli \ ,: i1r' /fr\ _ i{ir:tr'\ f_}l eabtietsrourn& Root River Little ouse Brandon to Thetford Prefeasibility Study - stage 1 Report: D€scri6ion of lnvestigations may be traces of the staunchesremaining. they have no practicalaffect on the current water levels. 4.1.5 The drawing(0006077/D2l08) also showsthe locationof the weirslsluicesalong this stretchof river,which have been built to replace these historicstaunches. ln additionto controllingwater levels,it is understoodthat these structuresalso act as gauging stations to measureflows. 4.1.6 The Agency have advisedthat the current retentionLevels are; o BrandonSluice > upstreamwater level = 3.4 mAOD . Abbey Heath Weir > upstreamwater level approx = 7.4 mAOD o ThetfordNo1 Sluice > upstreamwater level = g.6 mAOD Requirements for Navigation 4.2.1 The existingriver bed level (and subsequentwater level) rises by approximately7.5 m along the 6 km betweendownstream of BrandonSluice and Thetfordtown centre,which will necessitatethe constructionof locks to enable boats to reach rhetford. 4.2.2 There are essentiallytwo differentnavigation standards that could be adopted;one which would limit the size of the boats to the navigationstandard of the cunent Brandon Lock; and anotherthat would allow largervessels to reach Thetford,but this would necessitate the enlargemenVreconstructionof the BrandonLock. These two standardsare tabulated below: ExistingStandard I t.gS m *" Equivalent to navigation standard of Denver Retief Channet Lock Following discussionsw;th the EA, it was agreed that the above higher standardwould be too onerous,since 90% of the boats using this stretchof rjver only had a draft of 1.2m or less. lt was also acceptedthat the minimum headroomfigure of 3.0 m could be reducedto 2.7m to avoid raising/reconstructingthe A1065 Brandon(Arch) Road Bridge.Therefore, the two navigationstandards considered by this study are as follows: 2.0m I lmprovedStandard 1.35m 2.Vm 4.2.3 The width of the River LittleOuse within the study area generallyvaries between 12 and 15 m for muchof its length,with localwidening to approximately20 m at Brandon.and Rl2m3$00f177 EA BEndon io 135sbsn 1 rinal.oe 20/8103 4o173 l.:;'r't id{r\\t}.1;'l a"mi"Erown & Root \i I i:\r \ @ River Little Ouse Brandon to Thetford Prefeasibility Study - Stage 1 Report: Ilescri$ion of Investigations reducedwidths of I and 10 m at Thetfordtown centre and Two Mile Bottom respectively. These widths would appear to be sufficientfor navigationup to Thetford. 4.2.4 To facilitatenavigation up to Thetfordwill requirea combinationof raisingwater levels and bed excavationldredging.Raised water levels will be requiredalong the sectionof river betvveenSanton Downhamand Abbey Heath Weir - where the cunent water depths are limited.There will also be a requirementto raise some of the existingbridges over the riverto accommodatethe minimumheadroom