Case study:Malltraeth Marsh

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Location: 53° 12' 53", -4° 19' 42"
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Project overview

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Status Complete
Project web site
Themes Habitat and biodiversity
Country Wales
Main contact forename Ian
Main contact surname Hawkins
Main contact user ID
Contact organisation RSPB Cymru
Contact organisation web site http://www.rspb.org.uk/reserves/guide/m/malltraethmarsh/
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
Wetland and open water restoration, Malltraeth Marsh.

Project summary

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The channel was canalised, embanked, and virtually featureless carrying highland water from upstream across a flat lowland valley. Marsh either side is grazing land designated as SSSI. Aims of the project: • To restore the open water characteristics of remnant cut-off channels of the Cefni that were being to be lost through drying and reed/rush/sweet-grass invasion. • Combined with local restoration of high water tables, these measures ensured that the wildlife interests which gave rise to its notification as an SSSI are maintained and enhanced. Works carried out: • excavation of drying relic meanders and other open water areas • sluices on drains/ditches to raise water levels in summer • sluices and/or bunds to raise winter water levels • willow/scrub control and other vegetation management • improved bank profiles to the many ditches that traverse the floodplain

Monitoring surveys and results

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Catchment and subcatchment

Catchment

River basin district Western Wales
River basin North West Wales

Subcatchment

River name Cefni - tidal limit to Ceint
Area category 10 - 100 km²
Area (km2)
Maximum altitude category Less than 100 m
Maximum altitude (m) 87
87 m
0.087 km
8,700 cm
Dominant geology Siliceous
Ecoregion Great Britain
Dominant land cover Improved grassland
Waterbody ID GB110102058670



Site

Name Malltraeth Marsh
WFD water body codes GB110102058670
WFD (national) typology
WFD water body name Cefni - tidal limit to Ceint
Pre-project morphology Embanked, Straightened
Reference morphology Wetland marsh
Desired post project morphology
Heavily modified water body No
National/international site designation UK - Site of Special Scientific Interest
Local/regional site designations Special Area of Conservation
Protected species present No
Invasive species present No
Species of interest
Dominant hydrology
Dominant substrate
River corridor land use Wetland, Rough unimproved grassland/pasture
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
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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) 7000
7,000 m
7 km
700,000 cm
Project started 1993
Works started
Works completed
Project completed 1996/01/01
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Cost for project phases

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Investigation and design
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Reasons for river restoration

Mitigation of a pressure Impoundments (not hydropower)
Hydromorphology
Biology
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications excavation of historic channels, Bed raising
Floodplain / River corridor Creation of wetland, Floodplain reconnection
Planform / Channel pattern
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
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Physico-chemical quality elements

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Monitoring documents



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Supplementary Information

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