Case study:Little Waltham Meadows Back Channel creation

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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

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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

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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

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Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this 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 Edit 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 Edit 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 Edit reasons for restoration Mitigation of a pressure Hydromorphology Reduce diffuse pollution Biology Physico-chemical Other reasons for the project Biodiversity, Landscape enhancement, flood alleviation Measures Edit 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 Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Physico-chemical quality elements Edit 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 Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description Supplementary Information Edit Supplementary Information