Case study:River Tat Restoration Scheme: Difference between revisions

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|Subcatchment=Tat
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{{Site}}
{{Site
|WFD water body code=GB105034051140
|Heavily modified water body=No
|Protected species present=No
|Invasive species present=No
}}
{{Project background
{{Project background
|Project started=2013/05/01
|Project started=2013/05/01

Revision as of 13:36, 1 September 2015

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Location: 52° 49' 3.92" N, 0° 45' 26.84" E
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Project overview

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Status Complete
Project web site
Themes Fisheries, Flood risk management, Habitat and biodiversity, Hydromorphology, Land use management - agriculture, Monitoring
Country England
Main contact forename Adam
Main contact surname Thurtle
Main contact user ID
Contact organisation Environment Agency
Contact organisation web site http://www.environment-agency.gov.uk/
Partner organisations Water Management Alliance, Natural England, Atkins, Pynkney Hall Estate
Parent multi-site project

Case_study:Wensum River Restoration Strategy

This is a parent project
encompassing the following
projects
No
Restored section of River Tat, March 2014

Project summary

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The River Tat is a tributary of the River Wensum and forms part of the River Wensum Site of Special Scientific Interest. The planform and channel geometry has historically been subjected to significant modification including diversions, straightening, widening and the construction of an online lake system. The aim of the restoration work was to ‘kick start’ natural morphological processes throughout the reach.

A design report was written for the site which outlined the range of restoration measures that could be used. However, the design was extremely flexible and the location of different features was determined by a combination of expert judgement and working with existing channel features. On the ground works were delivered by an experienced Environment Agency Field Services team who have become skilled at delivering this type of restoration work.

In locations where a gravel bed was present, albeit beneath a layer of sand/silt because of the homogeneous character of the water course, gravel glides have been restored by re-distributing the bed material to form glide-pool sequences. The water velocity has been increased by narrowing the channel, using features such as earth berms and woody debris, resulting in a clean gravel bed. Deep pools have been dug to introduce variations in bed levels, providing flow diversity and creating resting areas for fish.

A key restoration measure has been the installation of Large Woody Debris (LWD). Reducing tree cover in heavily shaded areas, by selective coppicing, provides a sustainable source of material. This also allows light onto the river, promoting marginal vegetation to establish. LWD has introduced flow diversity, helping keep the gravels free from silt and providing overhead cover for fish.

Monitoring surveys and results

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Lessons learnt

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Catchment and subcatchment

Catchment

River basin district Anglian
River basin Broadland Rivers

Subcatchment

River name Tat
Area category 10 - 100 km²
Area (km2)
Maximum altitude category Less than 100 m
Maximum altitude (m) 6868 m <br />0.068 km <br />6,800 cm <br />
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Arable and Horticulture
Waterbody ID GB105034051140



Site

Name
WFD water body codes GB105034051140
WFD (national) typology
WFD water body name
Pre-project morphology
Reference morphology
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

Reach length directly affected (m)
Project started 2013/05/01
Works started
Works completed
Project completed 2014/07/01
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

Mitigation of a pressure
Hydromorphology
Biology Improving SSSI site, Fish: Abundance
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Cleaning of spawning gravels, Creation of pools and riffles
Floodplain / River corridor Installing riverside fencing
Planform / Channel pattern Introducing large woody debris, Introduction of LWD deflectors
Other
Non-structural measures
Management interventions
Social measures (incl. engagement)
Other


Monitoring

Hydromorphological quality elements

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

Biological quality elements

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

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

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


Monitoring documents



Additional documents and videos


Additional links and references

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Supplementary Information

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