Case study:Little Waltham Meadows Back Channel creation: Difference between revisions

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|Multi-site=No
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|Project picture=Back channel at LW.jpg
|Project picture=Back channel at LW.jpg
|Project summary=This is a multi-pronged project aimed at improving in channel morphological diversity, reducing diffuse pollution and sedimentation entering the main river Chelmer and Provide improvements to the riparian habitats and enhance the resilience of the wet woodland.  
|Project summary=This was a multi-pronged project aimed at improving in channel morphological diversity, reducing the amount of diffuse pollution and sedimentation entering the main river Chelmer. It will also increase the amount of riparian habitat along the River Chelmer and enhance the resilience of the wet woodland.  


Funded by the Catchment restoration fund, as part of the Essex Healthy headwaters scheme, the earthworks will take place in late Summer, early Autumn 2014.  
Funded by the Catchment restoration fund, as part of the Essex Healthy headwaters scheme, the earthworks took place in late Summer, early Autumn 2014.
 
This aims of this project were achieved in the first instance by the creation of a new 280 backwater channel with a new sluice/water control structureinstalled which allows water in to the new back channel at times of high flows. This is an effective tool in providing refuges for fish and Macrophytes during high flow events and also enhances habitat variability  by creating additional riparian habitat along the Chelmer. It also proved effective at providing space for emergent vegetation and new bank side vegetation.
 
The existing land drain which previously fed directly into the Chelmer was redirected to feed into three new settlement ponds which are filtering out pollutants by allowing it to settle with the added benefit of nitrate and phosphate stripping by the reed and other developing vegetation. These new settling ponds then allow water to feed into the new back channel.
 
Additional habitat was created in the north end of the reserve by installing a new water control structure. Unlike the other sluice this captures rain water and holds it back on the land re-wetting an existing piece of woodland to historical levels. Over time this should allow an expansion of the wet woodland and increase in the amount of wet woodland found on the River Chelmer.
|Monitoring surveys and results=Monitoring of water quality in the nearby Chelmer is underway, a pre baseline level has been established and a post project level will be taken. Overtime it is hoped that some kind of monitoring of the back channel vegetation will be undertaken to look at establishment dynamics.
|Lessons learn=Several lessons have been learnt, in the wet woodland enhancement, sometimes the simplest solution is the easiest. The drop board sluice has a habit of leaking and it may be that a simple clay bund with a a pipe and 90 degree collar may have sufficed.


This aims of the project will be achieved by creating a new 280 backwater channel to provide refuges for fish and Macrophytes during high flow events. This will also enhance habitat variability  by creating additional space for emergent vegetation and new bank side vegetation. An existing land drain which currently feeds directly into the Chelmer will be redirected to feed into two new settlement ponds which will filter out the diffuse pollution by a method  of delay, settle out and filter. This land drain will then feed into the new backwater channel.


Additional habitat will be created by installing a new sluice to re-wet an existing piece of woodland to historical levels. Extra woodland will be planted on the river side to create shading of the river and the new channel. Water to the new back channel will be controlled via a new water control structure, maintaining the flows of the River Chelmer.
|Monitoring surveys and results=Monitoring of water quality in the nearby Chelmer is underway. As is monitoring of vegetation in the back channel and bay.
|Lessons learn=For the wet woodland enhancement, sometimes the simplest solution is the easiest. The drop board sluice has a habit of leaking and it may be that a simple clay bund with a a pipe and 90 degree collar may have sufficed.
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Revision as of 15:15, 17 November 2014

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Location: 51° 46' 26.36" N, 0° 28' 50.59" E
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Project overview

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Status Complete
Project web site
Themes Habitat and biodiversity, Hydromorphology
Country England
Main contact forename Kieren
Main contact surname Alexander
Main contact user ID User:KierenAlexander
Contact organisation Essex Wildlife Trust
Contact organisation web site http://www.essexwt.org.uk
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects 		No
Project picture

Project summary

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This was a multi-pronged project aimed at improving in channel morphological diversity, reducing the amount of diffuse pollution and sedimentation entering the main river Chelmer. It will also increase the amount of riparian habitat along the River Chelmer and enhance the resilience of the wet woodland.

Funded by the Catchment restoration fund, as part of the Essex Healthy headwaters scheme, the earthworks took place in late Summer, early Autumn 2014.

This aims of this project were achieved in the first instance by the creation of a new 280 backwater channel with a new sluice/water control structureinstalled which allows water in to the new back channel at times of high flows. This is an effective tool in providing refuges for fish and Macrophytes during high flow events and also enhances habitat variability by creating additional riparian habitat along the Chelmer. It also proved effective at providing space for emergent vegetation and new bank side vegetation.

The existing land drain which previously fed directly into the Chelmer was redirected to feed into three new settlement ponds which are filtering out pollutants by allowing it to settle with the added benefit of nitrate and phosphate stripping by the reed and other developing vegetation. These new settling ponds then allow water to feed into the new back channel.

Additional habitat was created in the north end of the reserve by installing a new water control structure. Unlike the other sluice this captures rain water and holds it back on the land re-wetting an existing piece of woodland to historical levels. Over time this should allow an expansion of the wet woodland and increase in the amount of wet woodland found on the River Chelmer.

Monitoring surveys and results

Edit project overview to modify the Monitoring survey and results.


Monitoring of water quality in the nearby Chelmer is underway, a pre baseline level has been established and a post project level will be taken. Overtime it is hoped that some kind of monitoring of the back channel vegetation will be undertaken to look at establishment dynamics.

Lessons learnt

Edit project overview to modify the lessons learnt.


Several lessons have been learnt, in the wet woodland enhancement, sometimes the simplest solution is the easiest. The drop board sluice has a habit of leaking and it may be that a simple clay bund with a a pipe and 90 degree collar may have sufficed.


Image gallery


The back channel comes together.jpg


ShowHideAdditionalImage.png


Catchment and subcatchment

Catchment

River basin district Anglian
River basin Combined Essex

Subcatchment

River name Chelmer (Upper)
Area category 10 - 100 km²
Area (km2)
Maximum altitude category 100 - 200 m
Maximum altitude (m) 124124 m <br />0.124 km <br />12,400 cm <br />
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Arable and Horticulture
Waterbody ID GB105037041200



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) 400400 m <br />0.4 km <br />40,000 cm <br />
Project started 2012/10/01
Works started 2014/09/22
Works completed 2014/11/21
Project completed 2015/03/31
Total cost category
Total cost (k€)
Benefit to cost ratio
Funding sources Catchment Restoration Fund

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design Essex Wildlife Trust Kieren Alexander
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure
Hydromorphology Reduce diffuse pollution
Biology
Physico-chemical
Other reasons for the project Biodiversity, Landscape enhancement, flood alleviation


Measures

Structural measures
Bank/bed modifications New sluice structures
Floodplain / River corridor Creation of backwaters, Creation of wet woodland, Riparian enhancement
Planform / Channel pattern
Other
Non-structural measures
Management interventions
Social measures (incl. engagement) Local volunteers planted the trees and learnt about Natural Flood Management
Other


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

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

Edit Supplementary Information


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