Case study:New Forest LIFE project

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Location: 50° 52' 21", -1° 37' 33"
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Project overview

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Status Complete
Project web site http://www.newforestlife.org.uk/
Themes Flood risk management, Habitat and biodiversity, Land use management - forestry, Monitoring
Country England
Main contact forename Sarah
Main contact surname Oakley
Main contact user ID
Contact organisation Forestry Commission
Contact organisation web site http://www.forestry.gov.uk/
Partner organisations Environment Agency, University of Southampton
This is a parent project
encompassing the following
projects
Highland Water at Warwickslade Lawn, Holmsley Inclosure Stream Restoration, Markway Stream Restoration
Project picture

Project summary

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In the past, the Highland Water and Blackwater channels have been straightened and cleared of large woody debris (LWD), leading to disconnection of the channel from its floodplain, increased headward erosion and downcutting, high sediment transport rates and rapid progression of flood peaks.

The New Forest LIFE III project was proposed to improve the ecological potential of the catchments, increase habitat diversity and mitigate flood risk. Restoration began in 2003, with a 'test restoration' on the Blackwater, followed by Highland Water, reaching completion in 2006. The project involved remeandering of the channel and the introduction of LWD dams and CWD - providing habitats for fish and macroinvertebrates, while increasing flow resistance and the frequency/magnitude of overbank flow (which in turn would supply additional LWD for dam creation. LWD dams also increase the frequency of pool-riffle sequences - improving bed complexity.

Many aspects of the projects were deemed to be a success, with a clear increase in delay of the flood peak, post-restoration. The frequency and duration of overbank flow was also observed to increase appreciably.

Works included: Introduction of LWD to increase flow resistance - increasing frequency/magnitude of overbank flow, delaying flood peaks for flood mitigation and creating habitat for aquatic organisms. Bed-level raising with gravel addition.

Monitoring surveys and results

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Lessons learnt

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Image gallery


The old course of the stream
Restored channel with large wood incorporated, Blackwater
Meander development on the Blackwater
New restored channel on the Blackwater
Fallen trees left in place to increase diversity, Blackwater
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Catchment and subcatchment

Catchment

River basin district South East
River basin New Forest

Subcatchment

River name Highland Water
Area category 10 - 100 km²
Area (km2)
Maximum altitude category 100 - 200 m
Maximum altitude (m) 121
121 m
0.121 km
12,100 cm
Dominant geology Siliceous
Ecoregion Great Britain
Dominant land cover Broadleaved Woodland
Waterbody ID GB107042016720



Other case studies in this subcatchment: Highland Water at Warwickslade Lawn


Site

Name Highland Water/Blackwater
WFD water body codes GB107042016720
WFD (national) typology Low, Small, Siliceous
WFD water body name Highland Water
Pre-project morphology Straight
Reference morphology Sinuous, Pool-riffle
Desired post project morphology
Heavily modified water body Yes
National/international site designation EU - Special Area of Conservation
Local/regional site designations SSSI (Site of Special Scientific Interest)
Protected species present No
Invasive species present No
Species of interest
Dominant hydrology Quick run-off
Dominant substrate Barton clays and plateau gravels.
River corridor land use Plantation forestry, Woodland
Average bankfull channel width category 2 - 5 m
Average bankfull channel width (m)
Average bankfull channel depth category 0.5 - 2 m
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient 0.0066
Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 3000 m
3 km
300,000 cm
Project started 2003/06/01
Works started 2005/06/01
Works completed 2006/08/01
Project completed
Total cost category more than 10000 k€
Total cost (k€)
Benefit to cost ratio
Funding sources EU LIFE III

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 Flood mitigation
Hydromorphology Width & depth variation, Flow velocities, Increase sinuosity.
Biology Improve channel:floodplain connectivity, to increase wetting and provide further habitat opportunities.
Physico-chemical
Other reasons for the project Bank erosion, Landscape enhancement


Measures

Structural measures
Bank/bed modifications Introducing large woody debris, Habitat restoration, Bed raising, Gravel augmentation
Floodplain / River corridor Floodplain reconnection, Floodplain spillways
Planform / Channel pattern Re-meandering
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
Width & depth variation Yes Yes Yes No No Improvement
Flow velocities Yes Yes Yes No No Improvement

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Fish Yes Yes No Yes Yes Inconclusive

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
Frequency of overbank flow Yes Yes No Yes No Improvement
Lag in propagation of flood peak Yes Yes No Yes No Improvement


Monitoring documents



Additional documents and videos


Additional links and references

Link Description
http://www.newforestlife.org.uk/life3/PDFs/PDFs/LaymansReport.pdf Layman's Report
http://www.newforestlife.org.uk/life3/PDFs/PDFs/C-V2EndofProjectHydroRpt.pdf Hydrological Report
http://www.geog.soton.ac.uk/school/staff/profiles/das/Life.pdf New Forest LIFE III Monitoring Report
http://www.natura.org/DOC/uk newforest panels.pdf Sustainable Wetland Creation in the New Forest
http://www.coastms.co.uk/resources/6a99ddc3-5955-4605-9f30-76f182f80153.pdf Presentation: Practice and impacts of wet woodland restoration in lowland headwater streams in the New Forest SAC.

Supplementary Information

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