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The environmental group Thames 21 has issued a progress report on one of its north London projects - the Salmons Brook Healthy River Challenge.   During 2015 work was continued in Grovelands Park and along the Houndsden Gutter.

What is the Salmons Brook Healthy River Challenge?

love the lea logoThe Salmons Brook Healthy River Challenge is part of Thames 21's Love the Lea programme of work to improve the quality of the water in the River Lea, some of which is used to provide drinking water and some of which continues downriver to the Thames.

Thames21 has been working with Enfield Council, The Environment Agency and Thames Water to improve the health of the Salmons Brook using systems inspired by nature and the energy of local people who live close to the river.

Why the Salmons Brook?

The Salmons Brook starts near Potters Bar and flows through Enfield to join the River Lea in Edmonton. The Salmons Brook is failing standards for water quality set out by the EU and needs new approaches to help clean it up.

Enfield has a separate sewage system, meaning that surface water and wastewater are carried in two separate pipes.  As a result, pollutants enters the Salmons Brook in a number of different ways, through misconnected plumbing, road run-off and dumping of household and industrial waste into surface water drains.

What are the aims of the project?

This project consists of a number of key elements:

1. Creating a range of wetland systems to help treat polluted water before it is allowed to enter the Salmons Brook
2. Promoting local behavioral change through education about the urban water cycle
3. Allowing more people to access and benefit from their local waterways and wetland systems
4. Assessing the impact of the wetlands created and of local behavioral change on the health of the Salmons Brook

Read more about the Salmons Brook project

Below we reproduce some extracts from the 2015 summary.

Grovelands Park Reed bed


The lake in Grovelands Park is the centrepiece of a beautiful and grand landscape designed in the 18th century.  Sadly the lake is afflicted with pollution from a number of surface water drains, bringing oils and metals from roads and foul water from plumbing misconnections into the lake.  Toxic algal blooms are common in summer.  This pollution limits the lake’s potential as a wildlife habitat and as park visitors will know, it can be unsightly and smelly too. 

In June 2015 we created a reed bed in the south western end of the lake.  The reeds will naturally break down these pollutants and increase oxygen levels in the water, as well as providing a new habitat for birds and insects.  The reeds, rushes, sedges and colourful purple loosestrife and yellow flag iris are establishing well, protected from grazing birds by netting.

Within just a few months of installing the reed bed we began to see an improvement in water quality.

Grovelands Boardwalk


Also in Grovelands Park the boardwalk through the woods between Seaforth and Branscombe Gardens has been replaced, giving a more pleasant and safer route through this lovely area of woodland to view the rainscape and stream.  The rainscape itself is developing very nicely, with the sedges gaining lush growth and doing a great job to clean the water here. 

Rainwater Only! Drains to River


Have you spotted these markers?  Road drains around the project sites have been marked up by volunteers. These drain markers raise awareness that the drains lead straight to local rivers, and shouldn't be used to dump any paints, chemicals etc. More drains will be marked this year, and other information about the Salmons Brook and SuDS, as well as how we can care for the stream, will be designed for each site too.

Houndsden Spinney Sustainable Drainage System (SuDS)

photoIn autumn we worked with the London Borough of Enfield to create two SuDS to improve the water quality in the Houndsden Gutter.  They have been designed to treat water that runs off Houndsden Road every time it rains, taking with it oils and heavy metals into the stream.

In the first run-off is directed along the verge in a shallow ditch (known as a swale) and into the natural woodland basin of the Spinney, where polluting chemicals are naturally and safely used by plants to grow or broken down by bacteria in the soil.  The swales have been planted with sedges and native grasses to slow water flow and begin the treatment, and the woodland basin planted with suitable native seed mixes.  In the second system the water is treated in basin on the verge.  Water will then naturally soak into the soil, recharging the water table.  This is particularly important during times of summer drought.  

The stream supports a small fish population, and fish are seriously impacted by road contamination such as oils and heavy metals, so reducing the pollutant levels in the stream is of great importance.

2016 will see tree and bulb planting here, plus the replacement of the dangerous boardwalk through the Spinney.        

Rain Planters

photoThames21’s SuDS education programme visited schools around the Salmons Brook, with our first rain planter created at Churchfield Primary School, Edmonton.  These planters collect rain from roofs, storing rainwater and helping to prevent flooding.  They're also great for biodiversity.

We've trained some volunteers to make rain planters, and further water quality, rain garden creation and SuDS maintenance training will be offered in 2016.  Get in touch if you're interested in joining a course.


Future Project Focus

This year we'll be finishing off at Houndsden Spinney with some more planting and replacing the boardwalk.

We have funding for some creative information at the SuDS sites, and marking more road drains to stop dumping.

We'll also be picking up a focus again at the Glenbrook, making further improvements and striving again to tackle the water quality issues here.  Our water quality tests show that the rainscape is working, especially to reduce nitrates and e-coli bacteria, even bringing them to guideline acceptable levels.  But the water coming into the system is still so poor and we need to continue to collaborate with Thames Water to sort this.

Work will soon start on the Bury Lodge wetlands, a great project spearheaded by Enfield Council to help the Salmons Brook right by the A10.  We'll be assisting with this project too.

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