Case study:Houghton 'trout stream' enhancements

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Location: 52° 19' 30", -0° 6' 27"
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Project overview

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Status Complete
Project web site
Themes Fisheries, Hydromorphology
Country England
Main contact forename Rob
Main contact surname Clapham
Main contact user ID
Contact organisation Environment Agency
Contact organisation web site
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
Installation of a mid-channel 'v' deflector to create and maintain clean gravels

Project summary

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The Environment Agency worked with local stakeholders to improve habitat quality on a side-channel of the Great Ouse.

Like many of our rivers, the Houghton 'trout' stream, has been significantly modified over many years. These modifications include impoundment, channelization and tree clearance. These pressures have reduced the resilience of the channel to wider catchment scale pressures from water quality and sediment.

As a result of these modifications, there is insufficient flow and energy within the channel at many times of the year to move and redistribute sediment within the channel. This has meant that this 'naturally' gravelly river has an overlying layer of fine sediment. This significantly reduces the likelihood of successful spawning by species such as chub, dace and barbel, the latter of which has not been seen on the river for over a decade.

Such habitats are particularly important to retain on this side channel, as the main river is navigable, heavily impounded, and cannot provide the diversity of habitats found on this channel, all of which are vital to many species at different points in their life cycle. Furthermore, due to navigation on the main channel, options to enhance or restore it are limited.

The Environment Agency surveyed the side channel and put together a series of enhancement options to address the deterioration, which were then shared and discussed with the local Angling club and landowners. These included: Improving flow over an upstream weir, tree planting, retaining woody material, fencing, gravel jetting, and installing deflectors to keep areas of spawning gravels free from silt and excessive vegetation growth. Both landowners and Angling Club were keen to see these improvements made and offered both their time and money to see them implemented.

Partnership was vital to success of the project. Very little money was spent on these enhancements with most contributions coming from volunteer time. The angling club have helped with planting of trees (willow whips sourced from local trees), gravel jetting (using agency equipment), and will share the cost of installing fencing with the local landowners Smith & Smith. The Agencies Fisheries and biodiversity team cleared vegetation blocking an upstream weir and installed flow deflectors, again using wood sourced from locally fallen tree that identified for removal as it was blocking a nearby drainage channel.

While enhancements such as tree planting will take many years until benefits from increased cover, shelter shading, and supply of woody material to the channel are realized. Already, the benefits of the gravel jetting and flow deflectors can be seen. Following the work, the areas of clean gravels have remained, while other areas in the channel (not yet enhanced) have become covered with sediment and clogged with reed growth.

For the first time in many years, large numbers of fish have been seen congregating around the deflectors in preparation to spawn, including many large chub. Furthermore, we have also seen River Lamprey (a formerly declining species) making use of the clean gravels for spawning.

This project demonstrates that correctly targeted low-cost measures, undertaken in partnership with committed stakeholders, can make significant improvement to river channel habitat and fisheries value.

Follow link for YouTube video of spawning gravel enhancements:

Monitoring surveys and results

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Pre-enhancement fish surveys have been undertaken

The Environment Agency will continue to monitor this site through electric fishing surveys.

Lessons learnt

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Wood for construction of deflectors was sourced locally and work was undertaken by hand. Therefore the size of deflectors were limited to what could be manoeuvred by hand. Despite their size, careful consideration of the prevailing flow and sediment conditions meant they could be placed to achieve optimum benefit.

In November 2014 some of the wooden posts, used to hold deflectors in place, had to be replaced. The posts were 75 mm diameter and it is thought that the staples and screws used to secure wire to these posts were too large, causing the post to be weakened and split under load. We have since replaced posts with 20 mm re-bar drilled through the deflectors. Post diameter and staple size should be considered when planning how to secure LWD.

Image gallery


Local angling club planting trees on banktop
Example of side deflector
Chub preparing to spawn around 'v' deflector
Finished deflector in May 2014
large paired deflector

Catchment and subcatchment


River basin district Anglian
River basin Upper and Bedford Ouse


River name Ouse (Roxton to Earith)
Area category 1000 - 10000 km²
Area (km2)
Maximum altitude category Less than 100 m
Maximum altitude (m) 65
65 m
0.065 km
6,500 cm
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Arable and Horticulture
Waterbody ID GB105033047921

Other case studies in this subcatchment: Houghton 'trout stream' enhancements


WFD water body codes GB105033047921
WFD (national) typology
WFD water body name
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present No
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)
Project started
Works started
Works completed
Project completed 2014/05/01
Total cost category
Total cost (k€)
Benefit to cost ratio
Funding sources

Cost for project phases

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

Reasons for river restoration

Mitigation of a pressure Land drainage
Hydromorphology Quantity & dynamics of flow
Other reasons for the project


Structural measures
Bank/bed modifications Creation of wooden deflectors, Cleaning of spawning gravels
Floodplain / River corridor Fencing, Tree planting
Planform / Channel pattern
Non-structural measures
Management interventions
Social measures (incl. engagement)


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
Fish Yes Yes No No No

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

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Supplementary Information

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