Case study:Narborough Rehabilitation Project

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Location: 52° 41' 15.58" N, 0° 34' 41.21" E

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Project overview

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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	Environment Agency, River Restoration Centre, Natural England
Parent multi-site project
This is a parent project encompassing the following projects	No

just post works

Project summary

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River excavations and modifications took three days, the majority of one of these being import of the gravel to the ‘runs’.

Work was implemented in c1km of river. There was absolutely no gradient within the sections modified, with the river being deep and sluggish throughout. Work carried out:

• • created greater diversity of habitat by modifying both the long and cross-sections;
  • locally narrowed the channel to improve self-cleansing of the bed in these locations, and accelerated flow into pools created immediately downstream;
  • removed the unsightly deflectors by replacing them with ‘living’ features that already are doing a much more effective job than the deflectors were attempting to do;
  • the one main difference from the Castle Acre stretch was that some of the upstream ‘runs’ had a thin layer of gravel spread over them too.

Differences in character were primarily determined by the character of the river bed where pools were excavated, and the extent of reed/sedge available from adjacent to the river to add to the channel.

Where the bed was hard, and reed/sedge was plentiful, upstream narrowing could be more extensive. In all cases where the bed was hard (predominantly chalky clay), very distinct pools and upstream ‘runs’ were formed. Where-ever possible the bed of the narrowed channel upstream of the pools was shallowed by adding material dug from the pools – this could only be done where flints or firm clay formed the substrate.

Where the bed was pure soft peat, the distinction between the narrowed channel upstream, and the deepened channel downstream, was much less. Had deflectors not already been present in the channel, it would have been difficult, or impossible, to establish narrowing upstream......the deflectors now form the downstream edges of the shoulders. Without reeds/sedge from adjacent to the river being added to these areas, they could not have been expected to be retained in the long term.

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Catchment and subcatchment

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Catchment

River basin district	Anglian
River basin	North West Norfolk

Subcatchment

River name	Nar
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Site

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Name	Narborough
WFD water body codes
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WFD water body name
Pre-project morphology	Single channel, Straightened
Reference morphology	Single channel, Pool-riffle, Sinuous
Desired post project morphology
Heavily modified water body	No
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Protected species present	No
Invasive species present	No
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Project background

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Reasons for river restoration

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Mitigation of a pressure
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Measures

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Monitoring

Hydromorphological quality elements

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River Nar Rehabilitation summary by Nigel Holmes

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