Title they gently slope towards the sea. They are

 

    

    

    
      

    

    

Title

The modification of the Hesketh Out Marsh (HOM) through managed
realignment.

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Issue statement

The Hesketh Out Marsh has for centuries, been modified.
A £5 million managed realignment approach is a holistic conservation mechanism to
satisfy the demands of the coastline. The coastal marsh is a critical feature
in coastline protection and an important estuarine habitat for many species of
birdlife.

 

Background & current status

The Ribble Estuary found on the Irish
Sea coast of north-west England, consists of extensive salt marsh along its coast
and is also a site of largely grazed salt marshi.
Salt marshes develop on temperate coastlines and river mouths, where they gently
slope towards the sea. They are influenced by the tides and river inputs which
enrich the marsh with sediments and nutrients, supporting non-woody plants such
as Spartina anglica (common
cord grass)ii.
On the lower southern bank of the Ribble estuary, are the altered
coastal marshes of Hesketh Out Marsh West (HOMW) and Hesketh Out Marsh East
(HOME) (see Figure #1). As early as the 16th centuryiii,
 the coastal marsh of the Ribble Estuary has
been modified for agriculture and housing. Further conversion occurred in 1980,
when the area was drained to allow for cattle grazing and crop farming of
brassicas, wheat and potatoesiv. A
coastal embankment scheme was established as a sea defence to protect local
infrastructure from storm surges but, came with an expiration date.

 

Figure #1
A map showing the
location of the Ribble Estuary, and detailed map showing the location of
the Hesketh Outmarsh East and West within it. 
Source:  National
Geographic Map Maker Interactive (n.d.). Location of the Ribble Estuary. ESRI MapMaker, online.
Available at:
accessed 11 December 2017

Proposed
Refurbished embankment

Old
embankment

 

Altering of the marsh together with
dredging and sand extractionv
along the river and the estuary changed the sediment fluxes in this
environment. Restrictions in natural tidal flow result in biological, chemical
and physical changes as well. The transport and transformation of these
nutrients consequently affect vegetation presence, fish abundance, bird species
and effectively the entire intertidal nutrient cycling of the areavi. For
instance, vegetation composition shifted to Festuca
rubra (red fescue), as this species is adapted to drier and less saline
conditionsvii.The
native Spartina maritima (small
cordgrass), was outcompeted by the S.
anglica, reducing the habitat, for feeding and roosting waders and
wildfowl.

The Ribble Estuary is a critical habitat
for birds in the United Kingdom and maintains designations
as: Special Protection Area (SPA), Special Areas of Conservation (SAC), National
Nature Reserve (NNR), a Ramsar Wetland site and a Site of Special Scientific
Interest (SSSI) for its estuary habitats and birdsviii.
Ramsar, being the Convention on Wetlands of International Importance, seeks to
conserve wetland areas, which are important waterfowl habitat. Seventeen
species of migrating birds, waders, shorebirds and other waterfowl of
international importance utilise the site, and play a significant role in nutrient
transfer within intertidal habitats, enriching the area.

Extensive modelling shows sea level
rise to be about 20cm globally at a rate of 1.7mm/yr. since 1901ix.
Reports suggest that this rate has increased to 3.2mm/yr.x.  Modelling done for the estuary, indicates that
water levels will be amplified within the inner Ribble Estuary, making it
vulnerable to increasing flood dominance in the intertidal areasxi.
Climate change brings more intense storms, resulting in storm surges, flood
events inundating coastal settlements and coastal erosion.  Furthermore, making the existing coastal
defence structures obsolete or costly to maintain considering the changes.

The use of a Managed Realignment (MR)
scheme, is a sustainable and natural approach to cope with these challenges. The
existing structures will be breached (see Figure #1&3), allowing free tidal
flow, restoring the areas between the old defences and new embankments, to salt
marsh.

 

Discussion/analysis

The first MR site was created in the Blackwater estuary (UK), and was
flooded in 1991. Since then, fifty more MR projects have taken place xii.
The initial thrust to create the MR scheme at HOM, was to compensate for
habitat loss in a different area. Approximately 400ha of salt marshxiii,
BAP priority habitat, will be created, incorporating it into the larger Ribble
Estuary NNR, further enhancing flood protection and generating much needed
biodiversity habitat.

 

Climate change adaptation is chief priority, and MR is a critical
strategy in reducing inundation and limiting development within HOM1. With
sea levels set to rise possibly more than 1m by 2100xiv,
the current structure will no longer offer coastal protection, as it will not
withstand wave overtopping (see figure #2). At risk, will be 12,200 residential
and 700 non-residential properties together with 10,300ha of agricultural landxv. By
allowing seawater back onto the land, developing salt marsh can store
floodwater and absorb impacts of the higher sea levels and increased storm
surges, resulting from climate changexvi.
The annual value of flood protection for property and agriculture, was
estimated to be £164,905, if flood defences are rectifiedxvii.

                                                                                                                                    

 Figure #2
The Ribble Estuary area
including HOM. The highlighted areas show “Flood risk from rivers or the sea. High risk means that each
year this area has a chance of flooding of greater than 3.3%. This
considers the effect of any flood defences in the area. These defences reduce
but do not completely stop the chance of flooding as they can be
overtopped, or fail.”
Source: Environmental Agency, 2017. Long Term Flood Risk Information.
online Available at: Accessed 11 December 2017

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ecosystem Services (ES) incorporates natural functions and are the
conditions that sustain life. Salt marshes, habitats provide significant ES
such as:

·       
carbon
sequestration in accreting sediments,

·       
flood
defences for coastal communities,

·       
habitat
provisioning for wildfowl, and

·       
nursery
areas for commercially-caught fishxviii.

 

Establishing a saltmarsh area means it will sequester enormous amounts of
carbon, an important factor in mitigation against rising atmospheric carbon
dioxide (CO2). It is estimated that if all HOMW was mature salt
marsh before disruption, it would have current carbon store of 56,929txix.
The HOM salt marsh also provides critical habitat for the wintering population
of 161,500 waders and 57,000 wildfowl, on average.xx  These include amber red listed birds as
recorded by the British Trust for Ornithology (BTO)2
(see table #1)3.

Table #1

Categorises
the birds that utilise the salt marsh at HOM and Ribble estuary.
*Red is the highest conservation
priority, with species needing urgent action. Amber is the next most
critical group, followed by green.

Read
more at
https://ww2.rspb.org.uk/birds-and-wildlife/bird-and-wildlife-guides/bird-guide/status_explained.aspx#BxCElqgFD3F75s4G.99
 

 

The saltmarsh will have saline lagoons and the river morphology will be
improved, creating a suitable area for the diverse birdlife (See Figure #3). Increasing
the tidal flow into the area will support:

·       
submerged
aquatic vegetation growth,

·       
deeper
channels,

·       
fish
habitat and food sources for marsh birdlife.

 

As changes in the marsh happen over
time, birds will have more nesting and foraging areasxxi.
Further to this, the locale gains a recreational amenity and an asset, catering
to birding enthusiasts and tourists. Annually, this birdlife is monitored as
part of the national Wetland Birds Survey (WeBS) facilitated by British Trust
for Ornithology, Wildfowl & Wetlands Trust, the Royal Society for the
Protection of Birds and the Joint Nature Conservation Committeexxii.

 

Figure #3
Site map of the HOM area
illustrating the proposed flow of sea water back into the existing area and
lagoon creation through Managed realignment.

 
Source: Environmental Agency, 2013. Hesketh Out Marsh East Managed
Realignment Environmental Statement: Non-Technical Summary. pdf.
Bristol: Environmental Agency. Available at:
Accessed 11 December 2017

Coastal salt marsh is
protected under the European Habitats Directive, and the UK’s Post-2010
Biodiversity Framework (BF) aims to prevent net losses to the area of priority
habitats, including salt marsh. Salt marshes are also considered in the
Biodiversity Action Plan (BAP) which aims to protect and enhance habitats for
endangered species. In restoring the HOM area, it will achieve the BF strategic
goal of utilising the ecosystem approach to restore the ecosystem services
derived from coastal areas. It will provide a suitable flood and coastal
defence, whilst ensuring the biodiversity of the salt marsh habitat is
restored.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The future is built on a holistic approach to
management, where economic, social and ecological factors are aligned. Working
with natural processes will realise a wider range of benefits through habitat
creation, biodiversity enhancement and climate change mitigation and restoration
of disconnected areas.

 

Anticipated
questions

Projects
may encounter obstacles that could either be addressed or fester into bigger
problems. Some constraints are considered here.

1.     
How will the community and their losses be
addressed?

2.     
Will the MR be a success?

3.     
What is the period for salt marsh recovery?

 

Suggested response         

1.      Community:

a.     
involved
in the process (stakeholder consultation)

b.     
local
materials used

c.     
Social
and recreational benefits (including access to areas)

d.     
Land
(agri.) protection by the new embankment.

e.     
Affected
landowners can access agri-environmental schemes such as Countryside Stewardshipxxiii.

 

2.       

a.     
It
is a long-term solution, aligned with the principles of sustainable
development.

b.     
Monitoring
vegetation and biodiversity changes repeatedly, will assess the future of the
site.

c.     
 Learn and adapt from similar MR projects-
Thorngumbald on the Humber
Estuary, Brancaster on the north Norfolk Coast and Halvergate on the River Yare
(Norfolk Broads)xxiv.

 

3.      Recovery is dependent on:

a.     
Length
of time and severity of tidal restriction which influences vegetation, soil properties
other limits.xxv

b.     
Salt
intolerant and non-marsh plants will die off at first.

 

(Words:1342)

 

References (endnotes)

1
Section 1.3 Managing Coastal Flood Risk of the Report, Future of the Sea: Current and Future Impacts of Sea Level Rise on the
UK- “Adaptation measures can reduce all three
aspects of risk: reducing the probability of inundation, through defences and
managed realignment of coastlines; reducing exposure, by limiting development
in flood-prone areas; and reducing vulnerability, through improved flood
forecasting and warning, or individuals, organisations and communities
improving their own protection levels”.

2
Birds of Conservation
Concern 4 (BoCC), 2015. BOCC Summary Leaflet. pdf. online Available at Accessed 12 December
2017

3
The Royal Society for
the Protection of Birds (RSPB), 2015. Red,
amber and green explained. online Available at:< https://ww2.rspb.org.uk/birds-and-wildlife/bird-and-wildlife-guides/bird-guide/status_explained.aspx#zDcEqAOiJPhtxmXf.99> Accessed: 12 December
2017

 

i
Pillai, S., 2003. Information Sheet on Ramsar Wetlands
– Ribble and Alt Estuaries. online Ramsar, Available at:
Accessed 11 December 2017.

 

ii
Pillai, S., 2003. Information Sheet on Ramsar Wetlands – Ribble and Alt
Estuaries. online Ramsar, Available at:
Accessed 11 December 2017.

 

iii
Halcrow Group Ltd., 2013. North West Estuaries
Processes Reports Mersey Estuary. pdf. online Sefton Council. Available at:
  Accessed 11 December 2017

 

iv
Tovey, E.L., Pontee, N.I. and Harvey, R. (2009).
Managed Realignment at Hesketh Out Marsh West. Proceedings of the Institution
of Civil Engineers – Engineering Sustainability, e journal. Online
162:223–228. Available at:
<://www.icevirtuallibrary.com/doi/10.1680/ensu.2009.162.4.223> Accessed
11 December 2017

 

v
Halcrow Group Ltd., 2013. North West Estuaries Processes
Reports Mersey Estuary. pdf. online Sefton Council. Available at:   Accessed 11 December 2017

 

vi
Roman, C.T. and Burdick, D.M. ed., 2012. Tidal Marsh Restoration A Synthesis of
Science and Management. online Washington D.C.: e book Islandpress.
Available through: Academia
Accessed 11 December 2017.

 

vii
Tovey, E.L., Pontee, N.I. and Harvey, R. (2009). Managed Realignment at Hesketh
Out Marsh West. Proceedings of the Institution of Civil Engineers – Engineering
Sustainability, e journal. Online 162:223–228. Available at:
<://www.icevirtuallibrary.com/doi/10.1680/ensu.2009.162.4.223> Accessed
11 December 2017

 

viii
Halcrow Group Ltd., 2013. North West Estuaries Processes Reports Mersey
Estuary. pdf. online Sefton Council. Available at:   Accessed 11 December 2017

 

ix
Edwards, T. (2017). Future of the Sea: Current and
Future Impacts of Sea Level Rise on the UK. Available at:   Accessed 11 December 2017.

 

x
Edwards, T. (2017). Future of the Sea: Current and Future Impacts of Sea Level
Rise on the UK. Available at:
Accessed 11 December 2017.

 

xi
Halcrow Group Ltd., 2013. North West Estuaries Processes Reports Mersey
Estuary. pdf. online Sefton Council. Available at:   Accessed 11 December 2017

 

xii Pendle,
M., 2013. Estuarine and coastal managed realignment sites in England
Estuarine and coastal managed realignment sites in England. pdf.online
Available at:
.Accessed
11 December 2017

 

xiii
Environmental Agency, 2013. Hesketh
Outmarsh East Managed Realignment Scheme. pdf Preston: Environment
Agency.  Available at:< http://heskethbankcouncil.uk/wp-content/uploads/Articles/EA%20Outmarsh%20East.pdf>
Accessed 11 December 2017

 

xiv
Zsamboky, M., Fernández-Bilbao, A., Smith, D., Knight, J. and Allan, J., 2011. Impacts
of climate change on disadvantaged UK coastal communities. pdf Joseph
Rowntree Foundation. online Available at:
Accessed 11 December 2017.

 

xv
Halcrow Group Ltd., 2013. North West Estuaries Processes Reports Mersey
Estuary. pdf. online Sefton Council. Available at:   Accessed 11 December 2017

 

xvi
European Climate Adaptation Platform, 2016. Saltmarsh
recreation by managed realignment, Hesketh Out Marsh – UK (2014) online
Available at:
Accessed 11 December 2017

 

xvii
MacDonald, M.A., de Ruyck, C., Field, R.H., Bedford, A.
and Bradbury, R.B., 2017. Benefits of coastal managed realignment for society:
Evidence from ecosystem service assessments in two UK regions. Estuarine,
Coastal and Shelf Science, e
journal. online Available at:
Accessed 11 December 17

 

xviii
MacDonald, M.A., de Ruyck, C., Field, R.H., Bedford, A. and Bradbury, R.B.,
2017. Benefits of coastal managed realignment for society: Evidence from
ecosystem service assessments in two UK regions. Estuarine, Coastal and
Shelf Science, e journal.
online Available at:
Accessed 11 December 17

 

xix
MacDonald, M.A., de Ruyck, C., Field, R.H., Bedford, A. and Bradbury, R.B.,
2017. Benefits of coastal managed realignment for society: Evidence from
ecosystem service assessments in two UK regions. Estuarine, Coastal and
Shelf Science, e journal.
online Available at:
Accessed 11 December 17

 

xx
Tovey, E.L., Pontee, N.I. and Harvey, R. (2009). Managed Realignment at Hesketh
Out Marsh West. Proceedings of the Institution of Civil Engineers – Engineering
Sustainability, e journal. Online 162:223–228. Available at:
<://www.icevirtuallibrary.com/doi/10.1680/ensu.2009.162.4.223> Accessed
11 December 2017

 

xxi
Roman, C.T. and Burdick, D.M. ed., 2012. Tidal Marsh
Restoration A Synthesis of Science and Management. online Washington D.C.: e
book Islandpress. Available through: Academia
Accessed 11 December 2017.

 

xxii
Pillai, S., 2003. Information Sheet on Ramsar Wetlands – Ribble and Alt
Estuaries. online Ramsar, Available at:
Accessed 11 December 2017.

 

xxiii
Defra, 2002. Managed Realignment Review. pdf DEFRA Flood Management Division.
Available at: .
Accessed 11 December 2017

 

xxiv
Defra, 2002. Managed Realignment Review. pdf DEFRA Flood Management Division. Available at: .
Accessed 11 December 2017

 

xxv
Roman, C.T. and Burdick, D.M. ed., 2012. Tidal Marsh Restoration A Synthesis of
Science and Management. online Washington D.C.: e book Islandpress.
Available through: Academia
Accessed 11 December 2017.

 

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