The Solway Mosses Rehabilitation of lagg fen

1
The Solway Mosses Rehabilitation of lagg fen

• English Nature (Natural England)
• Peatlands for People project 2001 to 2007.
• Frank Mawby (Independent Consultant - formerly
  English Nature)
• Alasdair Brock (Natural England formerly
  English Nature)

2

• Lagg Fen Rehabilitation Key Issues
• Essential to locate water flows and volumes
• Water often drains through shallow peat and flows
  at the interface with the mineral soil
• Good survey detail and preparation.
• Hydrology, topography of surface and mineral
  soil, condition of peat and types of mineral
  soil.
• Dams and bunds/berms will often need to be built
  on top of the mineral soil to ensure a good seal
  and should be substantial. Shallow dry peat is
  poor construction material.
• Maintain control of water flow and distribution.
• Cracks and deep fissures are a significant
  problem and may cause instability when peat is
  re-wetted.

3
Solway Firth Estuary
Location
Ecosse
They hold most of the remaining primary intact
active mire in England. UK total is 470ha of
which 280ha is on these four mosses
4
Bowness Common

• Bowness Common was least affected by peat
  cutting.
• Badly damaged by drainage, agriculture, a railway
  and fires.

5
Glasson Moss

• Commercial cuttings
• Agricultural encroachment through drainage and
  land improvement

6
Drumburgh
Drumburgh Moss was extensively cut for peat both
for domestic use and commercial in the early 1900s
7
Mire boundaries
The mire boundaries are almost all against land
cleared of peat, drained and improved for
agriculture (or caravan parks). Some areas of
shallow peat remain within the site boundary
8
The Project Working together

• Three Conservation bodies worked in partnership.
• English Nature (now Natural England)
• The RSPB
• Cumbria Wildlife Trust
• They all owned or leased substantial areas of
  each bog.

9
The Project -Site Selection

• Sites were selected because the work could be
  achieved in the time.
• The work could be done within a site boundary.
• The area was within the ownership of one of the
  conservation bodies.
• The main 2001-2004 project was time limited to 3
  years. Cost 1 million pounds sterling
• The 2007 project cost 70,000 pound sterling

10
Employing consultants

• To achieve the project and the spend within the
  timescale consultants were employed to do
• Surveys topographic, mineral soil base, peat
  depth
• Hydrology
• Obtain consents
• Plans and Specification
• Contracts and Contract management
• Professional expertise.

11
The condition of the mire edge

• Mire edge peat is dry and free draining
• Very shallow or no peat on mineral soil that may
  vary from clay to estuarine deposits of sand and
  gravel
• It is essential determine water flows and
  catchments on mire margins

12
Glasson Moss North boundary

• Close to original lagg position
• Old peat cuttings
• Drainage in two directions
• No ownership constraints

13
Glasson Moss North
Existing peat cutting compartments used as
bunds The drainage could not be changed for legal
reasons Plastic pile dams were inserted in the
north drain Trees were left
14
Glasson Moss North
Cracks and fissures were a problem this bund/berm
has polythene sheet membrane in shallow peat and
Plastic pile used to seal fissures in deep peat
15
Glasson Moss North

Plastic Pile dam in northern drain
16
Glasson Moss North-August 2007

• New Lagg after 3 years of restored hydrology
• Sphagnum growth
• Betula dying - being replaced by Salix, Alnus

17
Glasson Moss South West
Problems with old peat cuttings Dry, cracked
peat Narrow margin of trees and scrub between
mire and boundary drain 2 to 3 metre height
difference in levels
18
Glasson Moss South West
Bund/berm problem - Some sphagnum development,
but water leaking away through free draining
peat under the berm to mineral soil
19
Glasson Moss South West (2007)
Successful only criticism, water is overtopping
the bund/berm, which should have been 30 cm higher
20
Glasson Moss South West (2003)
Plastic pile barrier across corner of deep peat,
aimed to seal cracks and fissures 3 metres deep
to mineral soil Has not worked water is leaking
through or under the pile Possibly causing a
problem by creating its own new crack/fissure
21
Bowness Common Rogersceugh

• Much of the land is on peat converted to
  agricultural land in the mid 1800s.
• The farm is surrounded by the moss and all drains
  cut through the moss.
• Had the owners attempted to deepen the drain
  English Nature would have objected because of the
  damage to the moss.
• RSPB purchased the farm in partnership with
  English Nature.

22
Bowness Common Rogersceugh

• Eutrophication from farmland nutrients was the
  main issue.
• The ideal solution would have been to pipe the
  drain through the moss and backfill over it -
  Very expensive.
• The actual solution was to dam the drain at every
  30cm of fall and allow a period of nutrient
  flushing before raising water levels to maximum.
  Could take up to 10 years.
• Possible addition is a phragmites reed bed to
  soak up nutrients

23
Bowness Common Rogersceugh
Clay imported from nearby to form a seal round
the pipe
24
Bowness Common Rogersceugh
Dam built with peat and water levels controlled
by fixing 90 degree elbow to pipe.
25
Bowness Common Rogersceugh
Main drain dammed with peat dams and 600 mm
diameter outlet pipes with water level control
and adjustment.
26
Drumburgh Moss
Area owned by Cumbria Wildlife Trust All the peat
cleared over a substantial area mostly by
commercial cutting in early 1900s
27
Drumburgh Moss
Mineral soil of estuarine origin Old creeks may
even be draining the intact mire
28
Drumburgh Moss

• Bunds constructed with mineral soil
• Main bunds also provide access for maintenance
  and public access
• One problem the clay was dry and blocky and
  difficult to compact

29
Drumburgh Moss
Old peat face was re-profiled to a slope of 1 in
20 A continuous 2 metre deep pile wall was
inserted at the foot of the slope. Aim to stop
water movement in the mineral soil
30
Drumburgh Moss - problems

• Outlets became blocked, water level rose and wave
  action breached the main bund/berm
• The first inner bund failed because the clay was
  dry and difficult to compact
• Rectified by inserting polythene sheet membrane

31
Drumburgh Moss. August 2007
32
Glasson Mossnorth, March 2007
Paddy field layout of small compartments. Small
compartments (100-200m2 ), bunds/berms covered
with coir mat to prevent wave erosion, and
assist re-vegetation. Water cascades over
bund/berm.
33
Glasson Mossnorth, March 2007
34
Wedholme Flow
Steel piling in 4 metre deep drain at mire edge
35
Some Conclusions

• Each section of mire edge presents different
  problems
• Problems with adjacent landowners, they are
  concerned that plans to wet up lagg will impact
  on farmland
• Acquisition may be possible but very costly
• A natural lagg will rarely be achieved
• The hydrology of the main peat body should be
  enhanced by any lagg work.