Case study:West Lexham Rehabilitation Project

This case study is pending approval by a RiverWiki administrator.

Approve case study

 

0.00

(0 votes)

To discuss or comment on this case study, please use the discussion page.

Location: 52° 43' 9.81" N, 0° 43' 14.84" E

Edit location

Loading map...

{"format":"googlemaps3","type":"HYBRID","minzoom":false,"maxzoom":false,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"limit":50,"offset":0,"link":"all","sort":[""],"order":[],"headers":"show","mainlabel":"","intro":"","outro":"","searchlabel":"... further results","default":"","import-annotation":false,"width":"auto","height":"400px","centre":false,"title":"","label":"","icon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"visitedicon":"","wmsoverlay":false,"zoom":14,"layers":[],"controls":["pan","zoom","type","scale","streetview","rotate"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"resizable":false,"kmlrezoom":false,"poi":true,"cluster":false,"clustergridsize":60,"clustermaxzoom":20,"clusterzoomonclick":true,"clusteraveragecenter":true,"clusterminsize":2,"imageoverlays":[],"kml":[],"gkml":[""],"searchmarkers":"","fullscreen":false,"scrollwheelzoom":false,"showtitle":false,"hidenamespace":true,"template":"Location map popup","userparam":"","activeicon":"","pagelabel":false,"ajaxcoordproperty":"","ajaxquery":"","locations":[{"text":"\u003Cp\u003E\u003Cbr /\u003E\n\u003C/p\u003E\u003Cp\u003E\u003Cb\u003EProject Title:\u003C/b\u003E West Lexham Rehabilitation Project\n\u003C/p\u003E\u003Cp\u003E\u003Cb\u003ECountry:\u003C/b\u003E \u003Ca href=\"/wiki/index.php?title=England\" title=\"England\"\u003EEngland\u003C/a\u003E\n\u003C/p\u003E\u003Cp\u003E\u003Cb\u003EProject Status:\u003C/b\u003E Complete\n\u003C/p\u003E\u003Cp\u003E\u003Cb\u003EThemes:\u003C/b\u003E Habitat and biodiversity\n\u003C/p\u003E\u003Cp\u003E\u003Cbr /\u003E\n\u003C/p\u003E","title":"West Lexham Rehabilitation Project","link":"","lat":52.71939191292,"lon":0.72079002857208,"icon":"/wiki/images/c/ce/Green_marker.png"}]}

Left click to look around in the map, and use the wheel of your mouse to zoom in and out.

Project overview

Edit project overview

Status	Complete
Project web site
Themes	Habitat and biodiversity
Country	England
Main contact forename	Nigel T.H.
Main contact surname	Holmes
Main contact user ID
Contact organisation
Contact organisation web site
Partner organisations	River Restoration Centre, Environment Agency, Norfolk County Council, Natural England
This is a parent project encompassing the following projects

site location of works

Project summary

Edit project overview to modify the project summary.

A half day work to remove the impounding influence of a weir, and in the channel upstream four pools and runs were dug. A second weir, between two bridges c35m downstream of the one shown in the images, was also removed. This structure had minimal impact on habitat, but was an impediment to easy migration of fish etc. wishing pass upstream.

The structure within the meadow that was impounding the Nar upstream had some archaeological interest. For this reason there was a ‘watching brief’ from Norfolk County Council to ensure there was no damage done to any known existing interest features, and to record anything else of interest should this be revealed during the removal of the impounding structure. To minimise damage to the historical elements of the bridge, the concrete ‘boards’ were removed with great care, leaving the central pillar and upper lintel in place, yet drawing the bed down to the required level.

The effect of centuries of impoundment has been to create a sluggish/non-existent flow in the river upstream with the resultant deposition of thick layers of mud. Pools were created by widening the channel locally. To help keep the pools clear in the future, the channel was narrowed upstream. Due to the extreme depth of soft mud, narrowing was achieved by pushing in one side of the existing river edge with the back of the bucket, and the void created behind this was filled with the arisings from creating the pools. Four pools and upstream ‘runs’ were created, with the run formed upstream of the second pool from the top having a small amount of gravel spread on the bed – this was won from the bed of the river in the pool downstream.

Monitoring surveys and results

This case study hasn’t got any Monitoring survey and results, you can add some by editing the project overview.

Lessons learnt

This case study hasn’t got any lessons learnt, you can add some by editing the project overview.

Catchment and subcatchment

Select a catchment/subcatchment

Edit the catchment and subcatchment details
(affects all case studies in this subcatchment)

Catchment

River basin district	Anglian
River basin	North West Norfolk

Subcatchment

River name	Nar
Area category
Area (km2)
Maximum altitude category
Maximum altitude (m)
Dominant geology
Ecoregion
Dominant land cover
Waterbody ID

Site

Edit site

Name	West Lexham
WFD water body codes
WFD (national) typology
WFD water body name
Pre-project morphology	Single channel, impounded, straightened
Reference morphology	Single channel, Pool-riffle, Sinuous
Desired post project morphology
Heavily modified water body	No
National/international site designation
Local/regional site designations
Protected species present	No
Invasive species present	No
Species of interest
Dominant hydrology
Dominant substrate
River corridor land use
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)

Project background

Edit project background

Reach length directly affected (m)
Project started	2011/02/28
Works started
Works completed
Project completed	2011/03/04
Total cost category
Total cost (k€)
Benefit to cost ratio
Funding sources

Cost for project phases

Phase	cost category	cost exact (k€)	Lead organisation	Contact forename	Contact surname
Investigation and design
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance
Monitoring

Reasons for river restoration

Edit reasons for restoration

Mitigation of a pressure
Hydromorphology
Biology
Physico-chemical
Other reasons for the project

Measures

Edit Measures

Structural measures
Bank/bed modifications
Floodplain / River corridor
Planform / Channel pattern
Other
Non-structural measures
Management interventions
Social measures (incl. engagement)
Other

Monitoring

Hydromorphological quality elements

Edit Hydromorphological
quality elements

Element	When monitored		Type of monitoring		Control site used	Result
	Before measures	After measures	Qualitative	Quantitative

Biological quality elements

Edit biological
quality elements

Element	When monitored		Type of monitoring		Control site used	Result
	Before measures	After measures	Qualitative	Quantitative

Physico-chemical quality elements

Edit Physico-chemical
quality elements

Element	When monitored		Type of monitoring		Control site used	Result
	Before measures	After measures	Qualitative	Quantitative

Any other monitoring, e.g. social, economic

Edit Other responses

Element	When monitored		Type of monitoring		Control site used	Result
	Before measures	After measures	Qualitative	Quantitative

Monitoring documents

Upload monitoring documents

Image gallery

Edit Image gallery

Additional documents and videos

Upload additional documents

River Nar Rehabilitation summary report by Nigel Holmes

Additional links and references

Edit links and references

Link	Description

Supplementary Information

Edit Supplementary Information