Case study:HLS New Forest

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Location: 50° 52' 37", -1° 37' 53"
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Project overview

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Status In progress
Project web site
Themes Habitat and biodiversity, Monitoring
Country England
Main contact forename Nick
Main contact surname Wardlaw
Main contact user ID User:nwardlaw
Contact organisation Forestry Commission
Contact organisation web site
Partner organisations
This is a parent project
encompassing the following
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Project summary

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The NF HLS is a wetland restoration scheme of huge scale and ambition with a fundamental aim to improve the condition of unfavourable SSSI units affected by historic drainage. The restoration work is perhaps unusual when compared to standard “river restorations” as the focus is on the floodplain habitat connection more than in stream habitat. The New Forest is recognised as being of outstanding importance for nature conservation in both the UK and Europe due to the size, quality and complex mosaic of habitats. The project area covers a large proportion of the New Forest SAC, SPA, SSSI and Ramsar designated land.

Over a period of approximately 150 years the mires and streams have been subjected to significant modification through drainage for varying land uses such as forestry and to enhance the potential for grazing animals. This drainage has meant that the floodplain connections are impoverished and are continuing to decline, as well as undermining the natural processes and resilience of the wetland habitats.

Due to the extensive range of drainage operations throughout the New Forest catchments, the project has delivered varying scales of restorations. At the upper end of the scale, restoration has included the re-meandering of a 3.5km stretch of straightened river on the Avon Water down to the smaller scale infilling of ~10m2 of knickpoint erosion in heathland. Approximately sixty sites have been restored since 2010.

Options for restoration on a number of the sites were drawn up based on eco-hydrological surveys and restoration plans were formed to incorporate the requirements of the unique features of the forest such as the steep stream gradients and sensitive mire ecology. The FC has led on the restoration design and implementation with input from Natural England, the Environment Agency, members of the New Forest Association, the National Park Authority and a number of consultants who have specialised in planning, ecological surveys and hydrology.

A range of restoration techniques have been used to restore the natural processes. These techniques have included: Re-meandering the watercourses into remnant meanders at the lowest point in the floodplain; re-meandering the channel within its existing planform; narrowing the channel and raising the bed level to a more natural width and depth to encourage out-of-bank flooding in high flows; infilling erosion knickpoints to prevent further headward erosion; replacing bridges with fords on forest tracks to prevent the energy being focused around the structure.

Monitoring surveys and results

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In recent years there has been extensive monitoring and evaluation of wetland sites. An independent review by the River Restoration Centre and Jonathan Cox Associates was commissioned in 2015 which evaluated eight sites that had previously been restored. The findings of this review recommended an expanded monitoring programme. In 2016 we developed a Monitoring Strategy and Delivery Plan. This details what evidence should be collected at future wetland restoration sites in the NF.

Since 2014 monitoring and surveys have been undertaken including: • pre and post work fish population surveys • invertebrate surveys and fish spawning surveys • river habitat surveys and modular river physical surveys • time-lapse photography • botanical surveys • fixed point photography • Riverfly monitoring by volunteers • water level and quality monitoring.

Alongside the restoration monitoring, species surveys have been undertaken. Whilst it is important to monitor direct impacts of the work using the methods described above, the real aim of the restoration is to increase the resilience of the habitats that are unique in the New Forest long into the future. Therefore, these species surveys are an important indicator of the health of these habitats.

Lessons learnt

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Monitoring

The New Forest has a long history of wetland restoration, with a number of studies completed prior to the HLS. As a result of this, and the nature of delivery focused agri-environment funding, it was felt that there was enough current evidence to deliver the restoration schemes in the forest. However, the previous evidence became more outdated as time progressed. Alongside this, there was an increased need for consultation with stakeholders due to needing planning permission for larger projects.

So in 2013 we developed an extensive and pioneering monitoring programme to aid with evidence for the future. In 2016 we appointed our first full time HLS monitoring officer whose sole focus is on gathering evidence to demonstrate the effects of this work.

Weather

Our in-channel restoration work takes place in a limited construction window to take account of Salmonid spawning restrictions from May until October and bird nesting season March through July.

Inclement weather has delayed a number of projects when work is suspended as a result of unsuitable ground conditions. Careful planning of work and use of resources has allowed us to undertake a large number of restorations simultaneously in the short window of opportunity.


Image gallery


Akercombe Bottom restored.jpg
Fletchers Thorns restored.jpg
Longwater Lawn restored.jpg
Soldiers Bog restored.jpg
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Catchment and subcatchment

Catchment

River basin district South East
River basin New Forest

Subcatchment

River name Avon Water
Area category 10 - 100 km²
Area (km2)
Maximum altitude category Less than 100 m
Maximum altitude (m) 82
82 m
0.082 km
8,200 cm
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Improved grassland
Waterbody ID GB107042011300



Other case studies in this subcatchment: Avon Barriers Project, Avon Barriers Project: Ferengair Weir, Holmsley Inclosure Stream Restoration


Site

Name
WFD water body codes
WFD (national) typology
WFD water body name
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body
National/international site designation
Local/regional site designations
Protected species present
Invasive species present
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) 29170
29,170 m
29.17 km
2,917,000 cm
Project started
Works started
Works completed
Project completed
Total cost category more than 10000 k€
Total cost (k€)
Benefit to cost ratio
Funding sources Higher Level Stewardship

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 more than 10000 k€ Forestry Commission
Post-project management and maintenance
Monitoring more than 10000 k€ Forestry Commission



Reasons for river restoration

Mitigation of a pressure
Hydromorphology
Biology
Physico-chemical
Other reasons for the project Improving the surrounding wetland habitats


Measures

Structural measures
Bank/bed modifications Bed raising, Removal/retreat of embankments
Floodplain / River corridor
Planform / Channel pattern Re-meandering, Re-instatement of old course
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
Channel pattern/planform Yes No Yes Yes No

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Fish: Species composition Yes Yes No Yes Yes Inconclusive
Invertebrates: Abundance 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


Monitoring documents



Additional documents and videos


Additional links and references

Link Description

Supplementary Information

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