Stodmarsh: The River’s in Trouble, but There’s Money in the Pollution Crisis
Six years after Natural England raised the alarm over pollution at Stodmarsh, a market in nutrient credits is helping developers move forward. Millions in public funding have been committed, private mitigation schemes promise to unlock thousands of homes, and a council-owned company has published its first accounts. But new Environment Agency figures raise an uncomfortable question: when will Stodmarsh itself recover?
Two pounds. Ninety years.
Those are two of the numbers buried in the first accounts of Stour Environmental Credits Ltd (SEC), the company established by Ashford Borough Council and Canterbury City Council to help developers offset pollution from new housing.
The £2 represents its net assets. Not its bank balance, which stood at £3.6 million, but what remained on paper after accounting for its liabilities.
The 90 years concern environmental arrangements intended to keep nutrient mitigation operating long after today’s developers, councillors and perhaps even the companies involved have disappeared.
Meanwhile, the Environment Agency has published new modelling showing that, despite anticipated improvements, the river system serving Stodmarsh is expected to remain above important nutrient targets in 2030.
So what exactly is East Kent’s growing nutrient-credit market buying, and who will ensure the promises are kept?
The river has not read the business plan
On 9 October 2026, the Environment Agency published its updated catchment pollution assessment, accompanied by a 14-page report specifically examining Stodmarsh.
Its findings make uncomfortable reading.
Using a model calibrated against historical data, the agency estimates a phosphate concentration of 0.275 milligrams per litre, against a converted target of approximately 0.039. That’s about seven times the target.
Nitrate is estimated at 7.931 milligrams per litre, against a target of 1.5 — more than five times the target.
These are modelled concentrations based on the 2014–2020 period, not fresh water samples collected in October 2026. Nor do they establish that pollution has increased sevenfold since the previous report; the earlier assessment used a different presentation of the phosphorus benchmark.
The more revealing figures concern what happens next.
Even under the agency’s optimistic 2030 scenario, phosphate remains at 0.102 milligrams per litre and nitrate at 5.057. Both remain substantially above their respective targets.
The agency estimates that historical phosphate inputs came predominantly from point sources, including sewage-treatment discharges, at 56.9%, followed by rural land use at 23.2% and urban sources at 17%.
For nitrate, rural land use accounts for 54.3%, with point sources contributing 39.3%.
But there is another important qualification.
On page four, the agency acknowledges that its modelling excludes additional nutrient contributions from future development, including housing.
Those additional loads are intended to be dealt with through planning assessments and environmental permitting. Their exclusion does not mean developers can disregard them.
Nevertheless, it means the published 2030 scenarios are not comprehensive forecasts of every future housing contribution.
That matters in a catchment where thousands of additional homes are proposed and millions are being committed to mitigation.
How a pollution warning became a business opportunity
The story began in July 2020 when Natural England advised councils that new development in the Stour catchment (in yellow below) needed to demonstrate nutrient neutrality.






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