A backwater to boost the Teise

A backwater to boost the Teise

Anglers have already reported seeing small fish using a new backwater on the River Teise in Kent just days after it was created by the South East Rivers Trust.

Taking just over a week to construct in September, the backwater has created a refuge for aquatic life taking cover from high flows or pollution incidents emanating from the main river.

A natural depression had formed in the land
A natural depression had formed in the landscape

A natural depression in the landscape, which might actually have been the original course of the river, proved the perfect place to construct this new backwater, near Goudhurst.

The depression was dug out to a size of 20×8 metres by our contractors FGS Pilcher. They used two diggers and four dumpers to create the full depth of the wetland.

The deepest section was created where it would be fed by the river and then a slope was built to the far end. This will prevent fish becoming trapped and that the backwater will always hold water, even during low flow conditions.

It is always a bonus when materials can be reused. We placed root plates and large pieces of timber within the backwater to provide additional habitat. The complex root plates provide great cover for juvenile fish, while the large pieces of timber may be used by amphibians accessing or exiting the backwater, or as a perch for birds.

We also have plans for other large pieces of timber generated during the construction works. We will be returning to the site to introduce some of these big bits of wood into the river, to help increase habitat diversity within the Teise itself.

We have begun to plant the backwater's edge with ferns
We have begun to plant the backwater’s edge with ferns

We have recently planted some of the backwater edges with ferns and other flora sourced from the riverbank nearby. These have been supplemented with a natural pond/wetland seed mix to attract insects and birds when they grow next spring. These will help the backwater become a haven for dragonflies and damselflies.

The work, supported by the Environment Agency, is part of our mission in the Teise Habitat Improvement project to improve this sub-catchment of the River Medway.

In recent years we have removed four concrete weirs to allow fish to reach different habitats and added woody materials such as deflectors to improve river habitat.

We have also worked closely with the Teise Angling and Conversation Society to improve the course of a heavily modified and dredged river and improve the habitats for brown trout, rainbow trout and grayling which frequent the watercourse.

The completed backwater on the Teise
The completed backwater on the Teise

Going down the drain in the name of plastic research

As part of our Preventing Plastic Pollution (PPP) project, the South East Rivers Trust carried out a trial by putting guards under drains in public streets, to collect and assess the types of litter that are ending up in rivers.  Hannah Dry, our Plastics Project Officer, reports.

Trialing new ways to prevent plastic pollution

Drain guards trial
Opening a drain guard to see what litter has been captured

Our work over the past three years for the Preventing Plastic Pollution project has involved many cleanups and litter categorising events, education sessions and workshops and setting up a River Guardians scheme.

These were to make the public aware of the problems caused by plastic in rivers and oceans and to help communities think about how they might reduce their reliance on single-use items, which accounts for 50% of the of the plastic that reaches oceans via rivers.

Another principal aim of PPP, however, was to investigate and trial innovative ways to prevent plastic reaching rivers in the first place.

One way in which we did this on the River Medway,  our section of the 18-partner PPP project, was to trial the use of drain guards on public streets. What goes down these public drains goes straight into the river. The idea was to capture litter, to see what types were common and to examine the scheme’s potential – if scaled up – to preventing litter reaching rivers.

We worked in partnership with Kent County Council to put in six drain guards around Maidstone town centre, installing them for a nine-month trial.

The problem with drains

Potential for scaling up drain guards
Monitoring took place regularly during the nine-month trial

Drainage pipe networks are complex. Ownership is fragmented between different organisations such as local authorities, water companies, internal drainage boards, highways authorities, businesses and private individuals. These bodies only maintain the drain, but the responsibility of preventing pollution sits with no one.

What we do know is that rainwater drainage systems are a source of pollution directly into rivers – and a lot of this pollution is plastic. Once in the river, it is difficult to remove, resulting in immense damage to the environment, organisms and affecting water quality – and finally ending in marine ecosystems.

Last June, we installed drain guards to capture the debris, not just to prevent it reaching the river network but giving us the chance to see what types of litter were common.

The guards – which were nicknamed witches’ hats because of their triangular shape – are made from a geotextile material and designed to sit beneath a drain grill to act as a filter, catching plastic litter and debris that are washed in through runoff.

Monitoring these drain guards every few months, we found that we had to fit new models in three of the drains after four months because of issues with cigarette burn holes. Emptying and categorisation of the litter occurred at every monitoring session throughout the trial. The purpose of the trial was to assess the feasibility and effectiveness of the drain guards in preventing litter getting into the drainage network and to assess their potential to provide a long-term solution for stopping plastic pollution from point source discharge outlets into the Medway.

What we found

Litter in a drain guard
Cigarette butts were the most common find when emptying drain guards during our trial

There is no doubt that plastic litter falls into our drainage networks from roads and pedestrian walkways. Plastic was found in every drain guard during every monitoring session. Over the course of the trial, the guards caught and removed more than 774 items.

The locations to trial the drain guards were chosen based on the footfall and on their proximity to amenities such as bar and pubs. That was exactly where we found the highest volume of litter, the biggest number of cigarette butts and bits of rubbish that can be directly linked to the consumer – such as lemon slices, plastic straws, and beer bottle lids.

This gave us the chance to assess the influence of amenities with the volume of litter in the drain as well as giving an opportunity to engage with passers by on site and to use the information later on to engage directly with pub/bar goers and owners.

The most frequent litter type, by far, was cigarette butts (423). Their filters are made from a chemical compound – usually cellulose acetate, a type of synthetic fibre. It takes years to break down.

The next most common item that we found were unidentifiable plastic items (172). These were too small to be categorised or too degraded, having been out in the environment too long. The strangest things we found were half a toothbrush handle and metal magnetic balls.

We also found 74 pieces of used chewing gum. It is common for chewing gum to contain plastic polymers such as polyvinyl acetate, which gives chewing gum its elasticity. Again, this means it will take a very long time to break down.

The items we found in the guards varied drastically between locations. Bottle tops, cigarette butts, straws and were all found in the guards outside pubs, whereas the guards placed on the high street next to shops typically collected items such as receipts and sweet wrappers.

Is there potential for scaling up?

Hannah before opening a drain guard
Hannah before opening a drain guard

The theory behind installing drain guards is sound – stopping pollutants before they become an issue for river ecosystems. However, the wider use of drain guards still, arguably, addresses the symptom rather than the cause of plastic pollution.

Consistent categorisation of litter during every emptying of drain guards is unrealistic, as it is time consuming and requires multiple people. Therefore, it is likely they would only be used to prevent plastic debris from entering river catchments. Yet this is still a very valuable function and something that we as a society must consider if we are to have any effect on the amount of plastic entering our rivers.

The complex nature of drain ownership and tailoring the size and shape to different sized drains, to ensure litter is collected more reliably, are also challenges that would need to be overcome.

And then there was the glamour factor…

This trial was not a glamorous one. A lot of the time was spent inspecting drains and counting very degraded and contaminated piece of litter that many people would find very disgusting. Not to mention the smell of the drains! Imagine sewers.

Yet it is necessary. Only by counting and categorising what we find down these drains can we then begin to understand the type and scale of the items and begin to think of ways to prevent it getting there in the first place.

There is too much plastic flowing into our rivers. Once it finds its way into a river, it is very difficult to remove. We need all stakeholders to take responsibility for the drainage networks and monitor and stop what is falling into them.

This trial provided data about what is entering the drainage network and how this differs between locations. It has tested different technologies to address this issue and highlighted areas where it could be feasible long term.

Sign up for our Plastic-Free Community Action Plan

The South East Rivers Trust has launched a new scheme to encourage groups to protect rivers from plastic, by cutting their reliance on single-use items. It is called the Community Action Plan and is part of our Preventing Plastic Pollution project. Below, Hannah Dry, our Plastics Project Officer, outlines the concept and how you can get involved.