Down the drain: How infrastructure projects can harm farmland
© Mark Richardson/Alamy Stock Photo Standing beside a major new infrastructure project in rural Buckinghamshire on a scorching August afternoon, a lack of water seems more of an issue than too much of it.
But when the rains do return, land agent Andrew Jenkinson says a corner of the parched grass field in front of us will inevitably end up a boggy mess, saturated with water, as it did last winter.
Andrew, a rural surveyor and partner at Robinson & Hall, has many examples of the impact new infrastructure can have on farm drainage systems.
See also: What fast-track development planning will mean for farms
“In my experience of dealing with these kinds of projects, land drainage is always the biggest problem. It’s a huge legacy issue and one that the acquiring authorities just don’t seem to comprehend,” he says.
“Trying to get across a level of understanding about the importance of land drainage on the farms affected is really difficult.
“In most cases, it doesn’t seem to have been a priority during the project’s design process and can end up being a bit of an afterthought.
“Even something as basic as how soil type can impact drainage can be overlooked,” he adds.
To compound the problem, the main contractors in charge of delivering the infrastructure projects will rarely use a specialist agricultural drainage firm.
Instead, they prefer to try to do it themselves, even if it ends up costing more, says Andrew, who has advised farmers in the area affected by the HS2 rail project, East West Rail, upgrades to the A421 and A428, and major electricity cables and water pipelines.
Twin tracks
There are generally two issues, he says. “First, there is the impact of the new infrastructure itself, and then there is the effect of the works on the farm’s existing drainage system.”
On the farms we are visiting, compensation claims with the acquiring authorities are still in progress – both issues have caused problems of varying magnitudes.
Because one of the farms has been split by the project, a new bridge was required.
As new developments are not permitted to cause rainwater to enter a river or drainage channel more quickly than before, the bridge includes a system of swales on either side of the works to hold back any runoff.
A swale is a shallow drainage channel with gently sloping sides, allowing water to collect and soak away.
“It is an impressive bit of engineering, but you could argue that the drainage system has taken up much more land than it needed to.
“And because the land used for the swales was part of the compulsory purchase agreement, it means the farmer isn’t allowed access for maintenance, so what happens if they get blocked?” says Andrew.
On one of his clients’ farms, a new drain installed along the edge of a field initially included a series of manholes.
“That’s not what you really want or need running through either an arable or livestock field. It just highlights a lack of understanding of agriculture.”
© Tim Scrivener
The project also cut across part of the farm’s existing drainage system. This led to the issues that cause part of an adjacent field to flood whenever it rains heavily.
“By the time we’d discovered there was an issue, the project had been completed, and it was too late to remedy,” he says.
“Luckily, we haven’t signed off on the final compensation package, so hopefully we’ll be able to negotiate some redress, but it’s something the farm will be stuck with now.
“Frustratingly, it wouldn’t have been a problem if drainage had been considered at the beginning of the project.”
Energy issues
Although transport projects such as roads and railways are among the most prominent infrastructure developments that can affect farms, the impact of less visible schemes such as power cables, water pipes and drains should not be underestimated, warns Andrew.
He says: “The National Grid was designed to distribute power from a relatively small number of large power stations.
“Connecting the much larger number of renewable energy installations that will be needed for the government to deliver on its decarbonisation agenda will require lots more cables.”
Given the growing scale of solar and wind farms, these cables will also need wider and deeper trenches.
“Just one cable running across your farm could cut across numerous land drains, some of which might not be mapped. So the consequences could be significant if they are not replaced or repaired properly.”
How to avoid infrastructure drainage problems
© Robinson & Hall
At the outset
When talking to the acquiring authority’s agents, try to ensure that drainage issues are top of mind from the outset.
Explain the farm’s existing drainage system and how it affects the operation of the farm.
If possible, try to persuade them that it would be better, and often cheaper, to use a specialist agricultural drainage sub-contractor rather than the project’s main contractor doing the works.
During the process
During the compulsory purchase process, request that any land needed for drainage reverts to the landowner after construction is complete.
This means access will still be allowed for maintenance.
Accurate location
If your field drains aren’t accurately mapped or you no longer have the original plans, try to geotag the location of any drains whenever you find or repair them.
This will prove invaluable when dealing with future infrastructure projects, as it can be very difficult for contractors to locate old field drains.
Signing off
If the land in question has been acquired by compulsory purchase, don’t sign off on a final compensation package until it’s clear if there are going to be any potential drainage issues.
Once final compensation has been agreed, it is not possible to make any retrospective claims.
Source: Andrew Jenkinson, Robinson & Hall
The drainage expert’s view
Rob Burtonshaw, a Nuffield Scholar and director of Farm Services, a specialist land drainage contractor, says he has often been called in to remedy problems caused by infrastructure projects.
“Location is critical. If the disturbance is in the high spot of the field, then, of course, the impact is not necessarily that significant, but infrastructure projects cutting through lower sections of fields or near drainage outlets can completely compromise existing drainage systems.
“Many contractors, especially those more experienced with civil urban infrastructure, fail to recognise the intricate nature of agricultural land drains, which can function effectively for decades or even generations.
“And if they’ve only worked in areas with lighter, free-draining soils like chalk, it comes as a big shock when they get involved in projects in areas like Lincolnshire.”
A key problem is their tendency to dismiss existing drainage infrastructure, explains Rob.
“Old clay or plastic drainage pipes, which may have been functioning perfectly for 50 to 80 years, or even longer in many cases, are often overlooked or damaged during construction.
“Contractors frequently lack the specialised knowledge to identify, locate, and properly manage these existing drainage networks.”
Cross-connections – attempts to reconnect existing drains around new infrastructure – are particularly problematic, notes Rob.
“These require precise level matching, careful pipe support, and technical expertise. Improper cross-connections can lead to drainage failure, with water potentially creating significant erosion or flooding in fields.”
Smaller cross-country pipeline projects are often the worst offenders, reckons Rob, because they typically have limited budgets and less specialised drainage expertise.
However, even large infrastructure projects aren’t immune to the issues.
“The National Drainage Association provides guidelines, but many contractors remain unaware of these best practices.
“This knowledge gap means landowners often bear the cost of infrastructure-related drainage damage,” he says.
“Recognising drainage systems as critical, long-term agricultural infrastructure – comparable to railways or roads – is essential for minimising disruption and protecting agricultural productivity.”