Case study:Longstreet A 91a

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Location: 51° 15' 35", -1° 48' 1"
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Project overview

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Status Complete
Project web site http://www.environment-agency.gov.uk/homeandleisure/wildlife/119594.aspx
Themes Fisheries, Habitat and biodiversity
Country England
Main contact forename Mike
Main contact surname Porter
Main contact user ID
Contact organisation Environment Agency
Contact organisation web site http://www.environment-agency.gov.uk
Partner organisations
Parent multi-site project

Case_study:Strategic Framework for Restoration of the River Avon (SFfRRA)

This is a parent project
encompassing the following
projects
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Project summary

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This reach is located to the south of Enford and is 1535m in length. The original reach has been sub-divided into two due to the overall length of the reach (1.5km) and differing channel characteristics. This note therefore refers to the upstream section only, between Enford Bridge and Enford Grange, approximately 0.5km in length. The reach is designated SSSI and SAC. There reach is privately fished. Downstream of Enford Bridge the channel has been altered in the past due to dredging and straightening. The channel is deep and flow is slow and uniform, which is causing the deposition of silt within the channel, obscuring the gravel bed below. The reach is also affected by an impoundment caused by a wooden board and stone weir at Enford Grange. This structure impounds the river for at least 150m upstream and possibly further, resulting in uniform flow conditions and drowned out riffles. The left bank is also being undercut and eroded in a number of places along the reach.

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Lessons learnt

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Image gallery


Impoundment - Before
Impoundment - After
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Catchment and subcatchment

Catchment

River basin district South West
River basin Hampshire Avon

Subcatchment

River name Hampshire Avon (Upper)
Area category 100 - 1000 km²
Area (km2)
Maximum altitude category 200 - 500 m
Maximum altitude (m) 212
212 m
0.212 km
21,200 cm
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Arable and Horticulture
Waterbody ID GB108043022350



Other case studies in this subcatchment: Gunville Phase I, River Avon Habitat Enhancement, Fifield, River Avon at East Chisenbury, West Amesbury


Site

Name
WFD water body codes GB108043022350
WFD (national) typology
WFD water body name Hampshire Avon (Upper)
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) 575
575 m
0.575 km
57,500 cm
Project started
Works started
Works completed
Project completed 2013/01/01
Total cost category 10 - 50 k€
Total cost (k€) 34
34 k€
34,000 €
Benefit to cost ratio
Funding sources Environment Agency

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 Impoundments (not hydropower)
Hydromorphology Width & depth variation, deposition of silt, erosion
Biology
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Gravel berms, Riffle creation, Bank reprofiling
Floodplain / River corridor
Planform / Channel pattern Lowering of impoundment, Introducing large woody debris, Tree management
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

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Before measures After measures Qualitative Quantitative


Monitoring documents



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Additional links and references

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Supplementary Information

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