by Adam Bayliss
At this time of year you may see Environment Agency workers out and about cutting grass on embankments. When you see us you might wonder, is it really necessary? Especially when amongst the grass there may be pollinator friendly wildflowers and habitat for nesting birds. As the manager of a team that looks after flood defences in Yorkshire, I’m going to explain why we do this, the detailed planning behind it and how we’re always working to create a better place in everything we do.
Our flood defences come in a range of shapes and sizes. Some are large moving barriers (like the Thames Barrier), others are made of glass, steal or concrete and many are natural looking earth embankments. Often found in scenic locations, these embankments are great places to go for walk, spend time with friends and family and be close to nature.
What many people don’t realise is that the embankments are manmade – usually from clay, covered with soil and then grass – they help protect our villages, towns and cities from flooding during storm surges and times of high rainfall.
Just like any piece of engineering, they need regular maintenance to ensure they work when they need to. Some of our most important defences are our flood storage reservoirs, each one holds more than 25,000 tonnes of water. Maintenance of these reservoirs has to be done to a high standard because the consequence of the embankment failing could potentially put people’s lives at risk and result in flooded communities. Grass has to be kept short on the banks to ensure it forms dense grass sods. These create a consistent root network, making the banks more resilient to erosion from waves, over topping and heavy rain.
Dense sods are just one part of it. Keeping the grass short means we can monitor it for defects - often an early warning sign of something more significant. Shorter vegetation also discourages vermin from digging into the bank. Embankments with badger or rabbit warrens in them leak like a sieve, meaning they can collapse when water runs through them.
I know that for some people the sight of swathes of grass being cut can be distressing, especially when you take into account pollinators and nesting birds, so I wanted to assure you that it’s not an activity we do lightly. All our engineering and maintenance is guided by independent research and best practice borne out of a number of independent reports over the years. We have team of biodiversity specialists whose role it is to advise throughout the year on the best time to carry out our maintenance work.
When carrying out the work we use specialist industrial mowers which are quieter than domestic lawn mowers. Before mowing the machine operator will walk over the site to try and identify any nesting birds or other habitat or hazards. Our staff are diligent and will stop work if they see something of interest to get further advice.
It’s not all cut cut cut though. Across the country we work closely with organisations to create biodiversity. Here are just a few examples of the work that’s taking place in Yorkshire.
- Working with Sheffield and Rotherham Wildlife Trust we have funded the planting of wildflowers and 50 trees on land behind a reservoir.
- We’ve worked with the RSPB at Houghton reservoir on the River Dearne to plant 4ha of trees and 600m of hedgerows, the RSPB then planted a further 1ha of wet woodland to create a valuable wildlife resource.
- With the Yorkshire Farming and Wildlife Partnership we’ve funded 2.hectares of trees and 370m of hedgerow.
- This year we’ve planted over 16 hectares of trees and 1.7km of hedgerows in Yorkshire alone, and have done similar in 2019, 2018.
- And as part of Defra’s national pollinator strategy to establish pollinator-friendly vegetation management, we have identified land that we own which we can seed with that will hopefully flourish into wildflower meadows.
Further afield, in south west London, work taking place on the River Hogsmill has seen trees and large branches - which could have caused a flood risk downstream - cut back and refitted into the river channel as deflectors. These deflectors slow the river and create a more meandering habitat perfect for invertebrates and other ecology. In Essex and Suffolk, on parts of the sea walls we delay cutting until the end of September to protect the active nests of rare bumblebees
The list of initiatives my team are working on to increase biodiversity is almost endless and this is being replicated across the country.
I hope this gives you an insight into why we maintain our flood embankments in the way we do and sheds some light on lots of the work you might not see.
If you want to find out more please follow us on twitter where you’ll find links to all the Environment Agency twitter account near you.
16 comments
Comment by Helena Smalman-Smith posted on
That's really interesting, thank you! P.S. I think you mean "steel" not "steal" 🙂
Comment by Adam Bayliss posted on
Thanks for taking the time to read it and glad you liked it. I knew i'd make at least one error!
Comment by Ray Walton posted on
Hi Adam..all sounds good as usual...so nothing to do with legal and illegal Water and Sewage Company discharged 'Raw Sewage' and 'Hazardous Waste' debris (ie: toilet paper, nappy liners, contraceptives, sanitary towels, condoms, sharps etc). being caught up in the grass, riverbank vegetation and overhanging trees, thus exposing the dire EA/Govt legalised situation to the public and river users including anglers, swimmers, boaters etc. putting everyone at risk of disease and contamination and infection. It is becoming common knowledge that this is the real reason, so you don't need to hide it anymore...I like the wild flowers though but you need to stop the mass felling of Riverbank healthy trees and mass vegetation clearance in the guise and reasoning for 'Flood Defence' which is now proven by yourselves and others to be flawed and out of date. Best Regards... Ray Walton
Comment by Adam Bayliss posted on
Hi Ray,
In Yorkshire we have about 1200km of engineered earth embankment last time I checked and I manage a decent chunk of these. I can honestly say that we maintain the embankments for the reasons set out in the blog.
We all work off independent research that supports the grass cutting which is primarily in the CIRIA Report 116 and the British Dams Society guidance (although there is a lot more). This report talks about the impact long and unmaintained grass has on embankment stability particularly in overtopping events, which is when they're most vulnerable.
Certainly in my area we don't undertake 'mass felling' of tree's on riverbanks, we undertake an Environmental Action Plan (EAP) which includes colleagues from our biodiversity team, external contractors and frequently independent specialists, to remove tree's we must justify each one and all be in agreement giving it formal sign-off. In addition to this each year we undertake a mitigation which involves fresh tree planting, environmental enhancements etc.
If you have specific concerns about maintenance standards in your area i'd recommend getting intouch with your local Asset Performance Team and speaking to them about it. I'm (and colleagues) are always open to discussion on why we do things certain ways.
Regards,
Adam
Comment by Dean posted on
This is an interesting and useful read. One thing stuck out though - it doesn't seem appropriate to refer to the animals that try to burrow into riverbanks as 'vermin', seeing as many of these creatures are suffering from habitat degredation. The actions you take to check the banks indicate care for them, but the use of this term suggests a negative attitude rather than one of care and management.
Comment by Mark posted on
Thanks. I Googled specifically for an answer to this question. I also wondered how will tree roots impact flood bunds? I live by a river that has a bund and loads of treeless flat space between the river and the bund, space that I thought could instead be a tree line about 3-6, well spaced out trees wide. Also the marshes are surrounded by around two miles of barbed wire fencing. Why is it not 2 miles of mixed native hedging? The edges of the marsh are dry most of the year so cutting would be easy. Is it the cost? Could we not create a 'hedge fund' lottery? Surely the trees and hedging would help flooding downstream and locally, perhaps reducing the need to cut as often. Would if hurt the bunds if you just adhered to No Mow May?
Comment by Mark posted on
Thanks. I Googled specifically for an answer to this question. I also wondered how will tree roots impact flood bunds? I live by a river that has a bund and loads of treeless flat space between the river and the bund, space that I thought could instead be a tree line about 3-6, well spaced out trees wide. Also the marshes are surrounded by around two miles of barbed wire fencing. Why is it not 2 miles of mixed native hedging? It's a SSSI and would surely benefit from being surrounded by plants useful to wildlife rather than barbed wire. The edges of the marsh are dry most of the year so cutting would be easy. Is it the cost? If so, could we not create a 'hedge fund' lottery? Surely the trees and hedging would help flooding downstream and locally, perhaps reducing the need to cut as often. Would if hurt the bunds if you just adhered to No Mow May?
Comment by Adam Bayliss posted on
Hi Mark,
Often tree's along the river can sometimes be beneficial from an FCRM perspective as it can stabilise the riverbank and reduce foreshore erosion, plus it doesn't really impact on the embankment operation, tree planting can improve water quality by increasing shading, offering fish habitat etc but it depends on the location.
The options for 'site security' vary massively from site to site so its not a one size fits all option unfortunately. Likewise sometimes hedgerows aren't ideal because if an area of 'wetland' is surrounded by hedges then it can dry the wetland out further, there is research to show that a wetland area is a greater carbon store than tree planting so it really is on a case by case basis.
However you are right in some places that a mixed hedgerow can be a really good option instead of fences, for example at one of the reservoirs that my team manage we planted a hedgerow to supplement a wooden fence a few years ago which now offers us greater site security and biodiversity benefits.
Regards,
Adam
Comment by Sarah Stille posted on
I am not convinced that a dense grass sward is more effective for consolidating banks and bunds than naturally-occurring scrub boundaries. Especially as you say that trees on the banks encourage meandering and slow the rate of flow. There's far too much interference in natural processes in the name of conservation/land management.
Comment by Adam Bayliss posted on
Hi Sarah,
There is loads of independent research that shows how much more effective the dense sward is. Its primary benefit is its erosion protection as it doesnt tend to give any preferential flow paths or obstruction like woody vegetation does.
The key research is documented in CIRIA Report 116 but is replicated in a number of other research documents and CIRIA R116 is supported by the British Dams Association where its referenced as best practice.
Thanks,
Adam
Comment by Ann Orchard posted on
Would it be possible to cut a section through a bund, at an above-ground level if one was hoping to create a pedestrian footpath from one side to the other?
Comment by eileenroffe posted on
Please call our customer contact center on: 03708 506 506. Thank you in advance
Comment by kim Routen posted on
Good morning, Please can you advise on the time table for cutting the grass on the keadby Amcotts River Trent defence.
Thanks
Comment by eileenroffe posted on
Good morning - please see the link to our maintenance programme: https://www.gov.uk/government/publications/river-and-coastal-maintenance-programme - ^Eileen
Comment by Zita McCarthy posted on
Could you tell me when the banks will be cut on the river trent in Collingham Newark Nottinghamshire. NG237LZ. Many thanks
Comment by eileenroffe posted on
Good morning, you can view our river and coastal maintenance programme here https://www.gov.uk/government/publications/river-and-coastal-maintenance-programme and search using your postcode. Or you can call oru national customer contact centre on 03708 506 506 Eileen