Peatland ACTION - Technical Compendium
Peatland ACTION sharing good practice for peatland restoration techniques
This technical compendium of peatland restoration techniques is built on the shared experience of the Peatland ACTION Programme, since its inception in 2012, in applying peatland restoration techniques and assessing their outcomes.
It provides an overview of the procedural and technical requirements for peatland restoration in Scotland, alongside an introduction to the types of restoration interventions that have been applied to date by Peatland ACTION.
It identifies ‘families’ of techniques with shared restoration objectives and describes best practices associated with individual technique, conditions of applications, machinery requirement, intended outcomes and practical issues likely to impact on their success.
The technical compendium is intended as a guide and is not detailed prescriptive instruction. It should be used to inform the development of a peatland restoration plan, recognising that the selection of appropriate restoration techniques will always be site specific and supported by appropriate survey and baseline information. A brief overview of the basic principles of restoration of peatland hydrology is also provided to help explain the impacts, and aims, of the various restoration techniques on the water table.
The use of these techniques for other peatland habitats and peat soil restoration, reinstatement or creation may be subject to additional constraints. In all cases, it is the responsibility of the land manager to ensure that all techniques used conform to current legislation regulating their sector of activity.
This document specifically limits itself to restoration practices and their outcomes as experienced within the Peatland ACTION programme. For further information on peatlands in general, how to plan restoration or conservation projects, and best practice from other projects and partners please see Annex 1.
We are still working on further sections that introduce readers to different types of peatland systems, and which will define and explain the importance of hydrological units in different settings. These additional sections will also summarise restoration goals and how / when these are met, restoration phasing, restoration design (looking beyond the feature and thinking about hydrological pathways across a site), when not to intervene and why (including e.g., site constraints), and finally how to measure success (data and monitoring; including zones of influence of restoration activity) and lessons from failure. These sections will be compiled over the coming months and will be added to these pages in due course.
The information gathered here comes from the experiences of Peatland ACTION, with the intention that the document will be kept up to date throughout the government ambition to accelerate and transform design and delivery of peatland restoration in Scotland. This version was produced in November 2022.
For further site-specific information on how to best restore a given peatland area, please contact the Peatland ACTION team at [email protected]
1 Glossary of abbreviations
CAR Controlled Activities Regulations
DWPA Drinking Water Protected Areas
PWS Private Water Supplies
PDR Permitted Development Rights
CDM Construction (Design & Management) Regulations
HRA Habitats Regulations Appraisal
NSA National Scenic Areas
WLA Wild Land Areas
2 Restoring Peatland Hydrology
1. Basic Principles
Many of the restoration techniques discussed in this compendium can be thought of in simple terms as actions which restore the hydrology of a peatland, when it has been affected by drainage and/or alteration to its vegetation and wider surface integrity.
The height of the water table is fundamental to many of the processes within a peatland. These processes ultimately lead to either the accumulation and storage of peat (carbon sequestration), or the release of peat, carbon and other greenhouse gases to the atmosphere (Fig 1). Restoring the hydrological characteristics of a peatland to a more natural state (i.e. with a water level that is close to the surface and resilient to external climatic variation, with a low range throughout the year) will help return it to a healthy, peat accumulating, system.
The main contributor to net loss of carbon in peatlands in carbon dioxide (CO2) wherever the water table has been lowered. In near natural or rewetted peatlands, carbon dioxide pathways are generally net negative to the atmosphere, i.e., the area takes up more CO2 via photosynthesis and below-ground accumulation than is lost to the atmosphere. In such wetter peatlands, some of this net accumulation is however offset by net losses of methane (CH4). Other losses of carbon occur through the direct losses of dissolved and particular carbon through water pathways, and the indirect loss of dissolved organic carbon being re-oxidised to contribute to CO2 production. Direct loss of carbon from the surface peat via erosion is generally only observed where there is a bare peat patch or area. In cases where significant fertilisation and/or liming of peatland has occurred (generally only in intensive grassland or cropland use scenarios) there can also be significant nitrous oxide (N2O) emissions (not shown in the diagram).
There are instances when restoring a ‘near natural’ water table will be a secondary consideration, mainly when carrying out bare peat restoration. Here the prime aim of restoration is to stabilise an actively eroding area to reduce rates of erosion and peat loss. The term ‘actively eroding’ refers to where large landscape features such as haggs, gullies and peat pans have formed. It is not always possible to understand what caused these features to form, but as they are contributing to large net losses of carbon on an area basis, it is important to consider stabilising such features.
In both instances it is important to understand how water flows over and through a peatland to appreciate the potential impact of different restoration techniques. Water flows into, through and over peatland by different pathways (Fig 2). The rate of flow through these pathways can increase or decrease depending on factors such as weather, peatland condition, slope, peat composition, vegetation composition, local topography and artificial drainage. Table 1 (below) gives a simplified account of the each of the pathways of water flow and mechanism that may increase (+) or decrease (-) the water flow via these pathways.
It is important to note that restoration is not always necessarily a single-step process, in many scenarios, several phases of restoration work may be required, for example where there are multiple types of degradation features or where the surface is covered with species that are not usually found in peatlands (e.g., trees, shrub or grassland).
Factors increasing Water Flow Through Pathway (+)
Factors decreasing Water Flow Through Pathway (-)
Rainfall / snowfall
Weather / climate change - increase to precipitation intensity, rate and duration, in particular in non-growing (winter) season.
Weather / climate change - decrease to precipitation intensity, rate and duration, in particular during the growing season (summer droughts).
Precipitation that penetrates the surface and enters the peat.
Change in vegetation composition that supports faster infiltration rates, e.g., increase in cover and depth of mosses.
When peat not saturated.
Change in vegetation composition towards species that results in an overall surface that is more hydrophobic and less permeable (e.g., dense woody litter).
When peat is saturated (water does not infiltrate into peat).
Prolonged drying of peat surface (making it more hydrophobic and less permeable, thus creating increased planar flow).
Compaction by grazing, trampling and/or tracking.
Fire which has exposed, burned, and dried out the surface of peat (making it more hydrophobic and less permeable).
Infiltration Excess Overland Flow
Precipitation exceeds rate of infiltration. Water can no longer infiltrate into the soil; and so flows overland downslope.
Increases with rainfall intensity.
Hydrophobic surfaces that have reduced the water holding capacity of peat.
Lower water table; more water infiltrates peat.
Drains can intercept overland flow.
Revegetation can reduce overland flow via reduction in the speed of flow through a more complex surface structure, and, to a lesser extent, mass via increased retention in e.g. moss layers.
Saturation Excess Overland Flow
Peat becomes saturated and additional precipitation causes run-off. Run-off is mixture of rainwater and water that has penetrated peat.
On peatlands this is the most dominant overland flow pathway.
At landscape scale peat depth, watershed area, drain density, weather and local topography are major factors in determining runoff.
Higher water table. Locally, drain blocking could increase height of water table, increase saturation of peat and increase runoff.
Compaction of surface peat which has reduced the water holding capacity of peat.
Revegetation can reduce overland flow, via increased water holding capacity in the vegetative and litter layers, and ultimately newly formed peat.
Primarily water loss to the atmosphere through the process of photosynthesis (transpiration); also loss of water from vegetation and land surface (evaporation).
Increase in vegetation or change in vegetation (e.g., increased scrub and tree cover) can cause increased transpiration.
Conversely, loss of canopy can also raise evaporation from bare soil.
Removal of vegetation or a change in vegetation with reduced rates of photosynthesis, e.g. increased trampling or grazing can reduce transpiration losses from the vegetation.
Water flow through peat pipes/connected cavities within the peat.
Afforestation can cause cracking and pipe formation in subsurface layers.
Peat harvesting by pipe extrusion and drying of peat (drainage, proximity to cut edge) can also cause pipes/connected cavities to form.
If peat pipes are compacted/pipes intercepted e.g., installing bunds or other ground smoothing techniques.
Peat slide/slumps destroy internal cavities.
Lateral flow of water through peat.
Greater in acrotelm and more porous peat.
And where cutting the margins of raised peat bogs.
Less in deeper more saturated catotelm and less porous peat.
Less in extensive blanket bog.
3 Procedural Requirements and Best Practice
3. Procedural Requirements and Best Practice
The following sections give a general overview of the various elements that need to be considered when planning and designing a peatland restoration project application for Peatland ACTION. These sections provide only a general introduction in addition to the specific guidance provided on our webpage for prospective applicants.
3.1 SEPA Best Practice and CAR Licensing
Peatland restoration can be subject to CAR licencing [The Water Environment (Controlled Activities) (Scotland) Regulations 2011 (as amended)]
Before carrying out any restoration activities, the potential requirement for a SEPA CAR (controlled activities regulations) licence must be considered. SEPA will not normally require authorisation for the creation of an impoundment designed to raise the water levels to restore a degraded wetland or peatland where:
a) The activity is carried out in artificial drainage channels or eroded peat (gullies, haggs, or peat pans); AND
b) The activity is not associated with an abstraction. AND
c) The impoundment is created in a watercourse less than or equal to 1 m wide
A CAR licence is therefore required where:
1. The normal width of water within the channel before restoration is >1 m (this includes any impounding dam which, by SEPA’s definition, also includes gully bunds).
2. Any watercourse (man-made or natural) which appears on a 1:50,000 scale map and is proposed for blocking will also be subject to CAR licencing regardless of the ‘normal’ width of water.
A sufficiently vegetated, undisturbed, buffer zone (minimum 5 meters to any watercourse) may be required if undertaking ground smoothing/stump flipping.
Fabric silt traps at key points on receiving watercourses and blocking forestry drains may be required.
For more information on CAR licence applicant guide and application form visit the SEPA website.
3.2 Scottish Water Drinking Water Catchments and Private Water Supplies
It is vital that peatland restoration projects do not impact water yield, trigger source water quality deterioration, or cause damage to the water supply and wastewater network infrastructures.
Scottish Water abstractions / sources are designated as Drinking Water Protected Areas (DWPA) under Article 7 of the Water Framework Directive and include land draining to reservoirs, lochs, rivers, springs and boreholes.
To exercise due diligence and establish if a peatland restoration project lies within a source water catchment or near SW assets, you must contact the Sustainable Land Management Team in the first instance / planning stages at [email protected] and provide a grid reference, map and overview of the proposal. The Sustainable Land Management Team will verify individual site constraints and advise on required site-specific precautions to protect Scottish Water assets etc. Additional Scottish Water information can be obtained from the Sustainable Land Management - Scottish Water website.
In the event of an incident occurring on peatland restoration sites that has potential to affect Scottish Water’s operational capabilities, you must notify Scottish Water immediately and reference the Sustainable Land Management Team. How to Contact Us - Scottish Water.
In Scotland, private water supplies (PWS) are defined as those that are not provided by Scottish Water. Approximately 3% of the Scottish population uses a PWS for drinking water. All PWSs have to be registered with the applicable local authority environmental health department. Therefore, the relevant authority should be contacted for additional PWS information regarding proposed restoration sites at the planning stages.
3.3 Peat Stability in Peatland Restoration
Potential peat instability is one of a range of issues considered in environmental impact assessment for upland energy generation projections, notably wind farms. Scottish Government (2017) has prepared specific guidance on best practice methods to identify, mitigate and manage peat slide hazards and associated risks to inform proposed electricity generation developments. This existing guidance, however, is a poor fit for peatland restoration activities, as it does not consider the geotechnical implications of the various restoration techniques. We commissioned a project in 2019 to investigate whether peatland restoration interventions are likely to precondition slopes or trigger failure (see Annex 2 for further information).
Since the initial output of this project in late 2020, Peatland ACTION officers have been able to carefully consider the potential effects of restoration on peat stability. The risks can now be evaluated using both qualitative and quantitative approaches to ensure that appropriate techniques are applied in the context of site and peat conditions.
The approach taken enables Peatland ACTION officers and other restoration designers, to:
• assess baseline stability at a site-scale,
• identify ‘modified’ stability given selected restoration groundworks, and;
• determine risk based on receptors within, downslope and downstream of proposed restoration sites. Receptors in this context are defined as ecological, e.g., watercourses, species or habitats, or artificial, such as infrastructure.
Our peat stability risk assessment tool will be published later in 2022/23. In the interim, please see Annex 2 for further information.
3.4 Considerations on Livestock, Wildlife Densities and Muirburn
Appropriate, light, grazing can help to maintain peatland habitats in good condition. The overall impression of a peatland in good condition is one where the ground is wet enough for you to need to wear wellingtons to walk across even in summer and is too wet for trees and shrubs to grow (with the exception of bog woodland habitat).
Blanket and raised bog vegetation comprises of a mix of Sphagnum mosses, short heather, cross-leaved heath, cotton grass, amongst other species. Tall heather, shrubs and isolated trees tend to be suppressed and have a stunted growth form in a well-functioning peatland. If there are signs of trampling then this would suggest that the grazing level is too high and we would recommend reducing the grazing level.
By grazing a bog with appropriately low numbers and types of stock/ wild herbivores, tall heather, shrubs and rushes will be lightly browsed, which will keep light penetration to the moss layer high enough, allowing Sphagnum and other mosses to grow optimally. Fen vegetation is dominated by sedges and mosses. Light grazing of fens similarly may help to keep the landscape open and reduce potentially invasive tree and scrub species. See Annex 1 for more detailed documents on bog and fen management.
Key guidance on our website documents
- Information on grazing densities
- Information on deer densities (coming soon)
- The connection between peat and deer management a case study.
- The Muirburn Code
Check for updates on muirburn on the NatureScot website (coming soon).
3.5 Considerations on protected areas
Peatland restoration improves peatland condition and often brings wider benefits for nature, water and landscapes. It can however be a disruptive activity, causing temporary damage to land and indirect and/or temporary disturbance to wildlife. At the design stage of any project, potential impacts on habitats, species and landscapes need to be considered, no matter where the project is located, and these impacts mitigated for as best as possible. For those projects, which have the potential to impact on the features of a designated site, there are formal processes that need to be worked through to ensure potential impacts are fully assessed and mitigated for if necessary.
The main designations that need to be considered are:
• Sites of Special Scientific Interest
• Special Areas of Conservation
• Special Protection Areas
• Landscape designations - National Scenic Areas and Wild Land Areas
Sites of Special Scientific Interest (SSSI)
SSSIs are those areas of land and water that we consider best represent our natural heritage in terms of their flora, fauna, geology, or geomorphology. Scotland has 1,422 SSSIs, covering around 1,011,000 hectares or 12.6% of Scotland’s land area.
When undertaking peatland restoration on or adjacent to an SSSI it is likely, given the typical nature of restoration work, that the project will require consent from NatureScot to proceed. Each SSSI has a list of Operations Requiring Consent associated with it; these operations have the potential to damage the features of the site. If any are required to be undertaken as part of the restoration then consent from NatureScot must be sought and received prior to work commencing. For more information about SSSI’s and the consent process please visit the NatureScot website.
Special Areas of Conservation (SAC) and Special Protection Areas (SPA)
As a suite of sites, SACs and SPAs form a network of protected areas that stretch across the European Union and the UK. They are known as European Sites. SACs protect one or more special habitats and/or species. SPAs protect one or more rare, threatened or vulnerable bird species.
When undertaking peatland restoration on or adjacent to a European Site, potential impacts need to be assessed as per Habitats Regulations. The Habitat Regulations require that any plan or project that may damage a European site is assessed and it may only go ahead if certain strict conditions are met. This process is known as a Habitats Regulations Appraisal (HRA). All restoration plans which might impact on a European Site need to go through this process.
For more information about European Sites and the HRA process please visit the NatureScot website.
Note that many SSSIs are also designated as European sites, whether as Special Areas of Conservation or Special Protection Areas or both, giving these areas multiple designations.
National Scenic Areas (NSA) and Wild Land Areas (WLA)
NSAs and WLAs are a network of site across Scotland recognised for their nationally important landscapes. Whilst peatland restoration projects often result in long term improvements to these landscapes, restoration works can have an impact. Most restoration techniques disappear into the landscape over time so any impact they have is generally short term. If projects have certain elements, such tracks and fencing, these can have longer term impacts.
All potential impacts need be considered at the design stage. NatureScot have produced guidance, Peatland restoration projects in protected landscapes, to help project designers to plan projects in a way that will minimise any possible impacts.
Where to find more information about Scotland’s designated sites?
NatureScot’s SiteLink is an online map-based tool which can be used to check whether a project is located within or close to a designated site. Site details e.g., site features, citation, lists of Operations Requiring Consent can also be accessed there.
3.6 Considerations Regarding Species Protection
All peatland restoration work needs to consider the potential effects on Scotland’s wildlife. Restoration work needs to ensure that no offenses in relation to disturbance, killing or taking of wild birds, other animals and to the survival of protected plants & fungi are committed. Some offences are specific and others more general. For more information about the relevant pieces of legislation pertaining to species protection see our species licensing legislation web page.
More detail about Scotland’s protected species and the offences that must be avoided when carrying out peatland restoration is available in our handy protected species A to Z guide
Although the default position is that working during the bird breeding season should be avoided, it may be possible in some circumstances to carry out restoration work inside the bird breeding season. Working inside the Bird Breeding Season for Peatland ACTION-supported projects guidance set out a protocol that all parties involved in peatland restoration are required to follow to ensure that they stay within the constraints of the law.
Similarly, measures to avoid disturbance to e.g., otters or reptiles may need to be implemented during restoration works. Our team can advise on these aspects.
3.7 Permitted development rights and Prior Notification to Local Authorities
On 1 April 2020 The Town and Country Planning (General Permitted Development and Use Classes) (Scotland) Amendment Order 2020 introduced Class (20A), which specifies permitted development rights (PDR) for peatland restoration projects.
Permitted development rights remove the need to apply for planning permission where proposals comply with the terms of the rights. Unlike applications for planning permission and other types of permission, prior notification is a procedure where, in this instance, the ‘restorer’ (i.e., those pursuing peatland restoration projects) must tell the planning authority about their proposals before taking advantage of permitted development rights. The result will be a decision that ‘Prior Approval’ is or is not needed. The intention is that proposals with no obvious risk of any negative impacts should be allowed to proceed without further consideration.
Class 20A grants planning permission for the carrying out of works on peatland for the restoration of that peatland. This includes works for the stabilisation, revegetation and re-profiling of bare peat and related drainage works, and the extraction of peat from within a peatland site for the sole purpose of the use of such peat in the restoration of peatland within that peatland site.
The prior notification/prior approval (PN/PA) process is a two-stage process which allows a planning authority to consider whether a proposal requires closer scrutiny and approval of some aspects of a proposal (in this case a peatland restoration scheme, see below) which is subject to PDR. This process must be completed before the restoration works can begin.
Firstly, the restorer needs to seek a view from the planning authority as to whether the authority's prior approval is required – the prior notification stage. In doing so, the restorer must submit:
(i) a peatland restoration scheme (see below),
(ii) a map showing the location of the peatland site to be restored,
(iii) the relevant fee required to be paid.
Once the Peatland Restoration Scheme (PRS) is submitted, the planning authority has 28 days to give a view on the need for prior approval. If a decision has not been issued within the 28 days, approval is deemed granted and the proposal can proceed.
Peatland Restoration Scheme
This refers to the production and submission of a scheme (plan) that sets out the restoration activities within an area of peatland identified by the scheme, and includes details in respect of any measures to mitigate:
- impacts of the proposed development on archaeology,
- the risk of contamination or flooding as a result of the development on the peatland site,
- the impacts of the proposed development on soil, and
- the removal, felling, lopping or topping of any trees,
In addition to the above, the PRS should include the date, or latest date by when restoration works will be completed on the peatland site; and information on any engagement with regard to funding under Peatland ACTION or registration under the Peatland Code, in order to assist the planning authority's decision making.
3.8 Assessment of impacts on scheduled monuments or archaeological remains
Scotland has a rich historic environment both above and below ground. Peatlands are of enhanced historic environment significance because of the nature of the archaeological resource they may contain and owing to the unique preservation qualities of the peat.
Peatland restoration is taking place at the scale of thousands of hectares per year and is spread across the entire country often in remote locations. Despite the significant historic environment record held for Scotland we do not have a detailed understanding of all interest in all places. Restoration work has the potential to impact on these interests and those involved in designing and delivering projects need to consider potential impacts. In addition to possible negative impacts, restoration projects also have the potential to identify new interests and help to protect them.
Ensuring we adequately consider these interests are built into the permitted development prior notification process. To help with this the Association of Local Government Archaeologists have published guidance on how to assess sites. It sets out an informed procedure to secure the protection of heritage and historic environment features within peatland restoration projects from the design stage through to the project delivery stage.
To ensure on site health and safety and to avoid risk of damage to any infrastructure, a search for utilities that may be located either on or down slope/catchment of the planned restoration site and access routes must be undertaken. Typically, direct impacts on utilities can be caused by machinery during excavation. However, consideration should also be given to the risk that large restoration projects, that have the potential to create a change in flood risk, can have on surrounding infrastructure.
The search should check for both over ground and underground utilities. Any planned new infrastructure on, or in the vicinity of, the area to be restored should be identified during the projects development phase.
Typical over ground utilities are:
- Electricity transmission or distribution lines
- On-shore electricity generation infrastructure
- Telecommunication lines
Typical underground utilities include:
- Water supply and sewer infrastructure, including pipelines (this should include consideration of off-grid domestic supplies as well as Scottish Water infrastructure)
- Gas pipelines
- Electricity transmission and distribution lines
- Telecommunication and data cables
Over ground utilities are plain to see so a site visit will identify these. Electricity-related infrastructure in place is also marked on Ordnance Survey Maps which can be used to highlight the hazard when mapping proposed restoration works and associated access routes. Any planned new infrastructure on the area to be restored should be identified during the projects development phase.
The route of underground pipelines are in some cases e.g. gas pipelines identified through a series of above ground markers. Other underground utilities are not marked as clearly in all cases. Individual utility network companies can be contacted for information on potential assets they may have in the area. There are also online searches that can be used to search for multiple utilities in an area.
The possibility of future infrastructure across the site e.g. to support on-shore wind should be considered at the project development stage in discussion with land owners and local Planning Authorities.
Utility providers in Scotland
The following hyperlinks take you to the web page of each utility network provider which explains how to find out information about the network in the area you are working.
- Water and Sewers - Scottish Water
- Gas - Scottish Gas Network
- Electricity - SP Energy Networks
- Scottish and Southern Electricity Networks
- Telecommunications - Openreach
For projects that have potential to affect utilities in England, the Peatland ACTION officer would be able to advise on contacts with relevant utilities.
3.10 Health and Safety in Peatland Restoration
Peatland restoration is an inherently dangerous activity, often carried out in remote areas, using heavy machinery, on difficult terrain. It is also classed as a form of construction, and therefore requires compliance with the Construction (Design & Management) Regulations 2015 or “CDM (2015).”
Peatland ACTION and all of the delivery partners take health and safety very seriously. Achieving programme-wide compliance with the CDM (2015) regulations helps to ensure the safe working of all involved. All participants in the development, design and delivery of a restoration project have a responsibility in ensuring safe and effective work takes place on the ground. Key duty holders must be appointed, and specific documents produced at different stages of the restoration project.
4 Restoration - Artificial drains
Guidance on Artificial drains
Included in this series are the following key techniques:
1 Peat dams
2 Plastic piling dams
3 Wooden and composite dams
4 Drain re-profiling in combination with drain blocking
5 Wave dams
6 Zipping / zippering
5 Restoration - Bunding interventions above and below ground
Guidance on Bunding interventions above and below ground
Included in this series are the following key techniques:
5.1 Deep Bunding
5.2 Surface Bunding
6 Restoration - Gully and Bare peat restoration: Flow management
Guidance on Gully and Bare peat restoration: Flow management
Included in this series are the following key techniques:
1. Using surface bunds in gullies
2. Stone dams
7 Restoration - Gully and Bare Peat Restoration: Stabilisation and Revegetation
Included in this series are the following key techniques:
7.1 Hag / Gully / Peat bank / reprofiling
7.4 Whole turving
7.5 Borrow pits
7.6 Transplanting propagules
8 Restoration - Forest-to-Bog restoration
Guidance on Forest-to-Bog restoration
Included in this series are the following key techniques:
8.1 Tree harvesting
8.2 Tree Mulching, stump grinding and "Deep” Mulching
8.3 Furrow blocking
8.4 Ground smoothing
9 Restoration - Scrub removal
Guidance on Scrub removal
Included in this series are the following key techniques:
9.1 Removing scrub from peatlands
10 Restoration - Track Removal or Reinstatement
Guidance on Track Removal or Reinstatement
Included in this series are the following key techniques:
10.1 Track Removal or Reinstatement
Annex 1: Further guidance
Additional resources for the Peatland ACTION programme and further information on peatlands, their management following peatland restoration, data collected through the duration of the project and case studies are available on the NatureScot Peatland ACTION webpages.
The Peatland ACTION YouTube playlist also showcases additional restoration videos for specific techniques, which may be useful to anyone interested in carrying out restoration.
Annex 2: Further information on peat slides
A key observation made in Peatland ACTION is that landslides in peat are relatively rare occurrences in Scotland, given the extensive peat cover. A second key observation, derived from an updated peat landslide database held by Dr Andy Mills, is that peat landslides are often spatially clustered, i.e., they occur on the same hillslopes as previous failures.
This implies that if an area on a peatland has already experienced peat instability, there is a higher likelihood of recurrence than in nearby areas without evidence of peat land-sliding. This is logical, since there are likely to be intrinsic physical and hydrological properties that make some peat more susceptible to landslides than others.
Landslides are generally considered to occur in response to long term preconditioning factors and triggers. Preconditioning factors reduce the stability of a slope (Table 2) while triggers (Table 3) cause the landslide.
In relation to restoration, it is important to understand what groundworks may act to precondition slopes or trigger failure.
Peatland ACTION is currently implementing a peat slide risk assessment tool for all new applications, in order to identify projects where a risk of peat instability may exist. We are hoping to add this information soon.
Influence on stability
Increase in mass (peat formation)
Increase shear stresses acting downslope, long term and progressive where these are occurring naturally; may occur in the short term where peat spoil is stored on the peat surface
Increase in mass (water content)
Increases shear stresses acting downslope, may occur in response to re-wetting e.g., through peat restoration or naturally occurring drain blocking (sidewall collapse)
Increase in mass (loading by trees)
Increases shear stresses acting downslope, medium term and may occur where root plates are within peat rather than onto substrate
Reduction in shear strength
Reduction in shear strength of peat or substrate through changes in physical structure (either remoulding by progressive creep or vertical fracturing), reduction of frictional contact (e.g., through increasing buoyancy as water table rises), chemical or physical weathering (e.g., clay dispersal by organic acids or weathering of rock substrate)
Loss of tensile strength
Loss of tensile strength by dieback of vegetation, e.g., from burning, air pollution or in extreme cases of grazing and/or poaching
Increase in buoyancy
Increase in buoyancy through formation of subsurface water pools (e.g., to form quaking bog) or filling and/or blocking of natural pipe networks (e.g., through pipe ceiling collapse or excess rainfall)
Influence on stability
Causes development of transient high pore-water pressures along pre-existing or potential rupture surfaces (e.g., at the discontinuity between peat and substrate)
Causes development of high pore-water pressures
Rapid ground accelerations (earthquakes)
Causes a decrease in shear strength
Unloading by fluvial incision
Reduces support to upslope material
Alteration to drainage patterns
Focusses drainage and generates high pore-water pressures along pre-existing or potential rupture surfaces (e.g., at the discontinuity between peat and substrate)
Blocking of pipes by drain reprofiling / damming
Rapid ground accelerations (blasting / vehicles)
Causes an increase in shear stresses
Plant operations during restoration works
Unloading by excavations
Reduces support to the upslope material (e.g., during track construction)
Reprofiling activities on transverse drains
Loading by plant or overburden
Causes an increase in shear stress
Plant operations during restoration works (failure to use low ground pressure excavators)
As part of a technical report completed on behalf of Peatland ACTION, a study was undertaken in order to evaluate the effects of restoration activities on the stability of some Peatland ACTION sites. This report is currently being reviewed by external exports and will be added to this section once the review process has been completed.
A spatial database of Peatland ACTION project locations was reviewed against publicly available satellite imagery in Google EarthTM. The objectives were as follows:
- To determine whether satellite data are of sufficient resolution to identify restoration work.
- To determine whether restored sites show any signs of accelerated geomorphological processes (such as erosion), pre-failure indicators (such as cracking or ground displacement) or peat landslides.
- To provide evidence-based context with which to evaluate the potential for restoration to precondition or trigger peat landslides.
Sites considered comprised all Peatland ACTION projects since inception of the initiative in 2012 up to May 2019.
Inspection of each site at maximum resolution (typically an “eye altitude” of c. 1 km) indicated the vast majority to show no signs of instability, landslides, drain offsets, tension cracks / tearing, enhanced erosion of gullies or drains, excessive ponding or waterlogging.
- A shallow landslide present between blocked drains in non-afforested blanket peatland (Caithness): inspection of historical satellite imagery indicated the failure to have taken place prior to drain blocking and therefore restoration was not likely to have been a contributory factor.
- Margin failure of a restored lowland raised bog at Moss Band (Lanarkshire): this location was observed to have failed subsequent to restoration and was one of the events contributing to the request of the current study.
- Margin failure of a restored lowland raised bog at Greenhead Moss (Lanarkshire): this failure occurred subsequent to restoration and also contributed to the request for this study.
Since the report was completed, we also have received observations of:
- Tensile cracking on the margin of an upland blanket bog on the Isle of Arran, where there was heavy rainfall following restoration works, saturating the ground, and where the drain pattern also focussed water. Remedial action was taken and no further movement has occurred, even following further heavy rainfall events.
- Cracking and slumping on a restored lowland raised bog at Black Loch Moss. The site is not a Peatland ACTION site but has had restoration work carried out by other parties in the past. An investigation into the causes of the failure indicated that it is unlikely that the restoration contributed to the failure, since the movement occurred some distance away from the main restoration interventions.
From investigations so far, it is clear that although restoration has been carried out in a wide range of settings, from lowland raised bogs to hillslopes in blanket bog, ground instability is rarely observed, certainly in comparison to groundworks in other settings (such as quarrying, track or wind farm construction).
Further Guidance & Support
Further Guidance & Support:
Peatland ACTION Project Officers are available to help you with your project. Please contact us as at [email protected] to be put in touch with your local Officer.