Forum topic: Crews Hill and Chase Park: Why this "New Town" Is a flood risk we cannot afford to ignore

This is a long one.  I have been using ai to help with my research and this is the summary of what I have found.

Crews Hill and Chase Park: Why This "New Town" Is a Flood Risk We Cannot Afford to Ignore

Enfield's Green Belt at Crews Hill and Vicarage Farm has been named one of the government's three top-priority New Town sites, with plans for up to 21,000 homes and a new population of over 46,000 people on land that currently spans some 452 hectares of Green Belt. Before a single spade goes into this ground, residents deserve a serious, evidence-based conversation about flood risk — not just housing numbers.

This land is already doing flood-prevention work for the rest of the borough.

What isn't well known is that the north-west Enfield catchment earmarked for this development — the upper Salmons Brook and Turkey Brook area — is the same location as the Enfield Chase Restoration Project, a landscape-scale scheme converting farmland into woodland and wetland specifically to reduce flood risk, improve water quality and restore biodiversity across the borough. Enfield Council has been nationally recognised for this work, and it forms part of a wider strategy to protect areas downstream, including parts of the borough that have flooded before.

Building a town of this scale on the same land doesn't just remove Green Belt — it removes the ground doing active flood defence work for everyone downstream of it. Increasing impermeable surface area here shifts water somewhere else, and "somewhere else" in Enfield has a documented history of flooding, including the Lee Flood Relief Channel, which has come close to full capacity multiple times, in 1987, 1993 and 2000 — with the Council's own planning documents warning of continuing residual risk to areas like Edmonton and Grange Park.

The flood modelling behind these plans is out of date

Enfield's most recent Strategic Flood Risk Assessment (SFRA) was published in December 2021, and it is publicly available here: www.enfield.gov.uk/__data/assets/pdf_file/0022/11983/Level-1-strategic-flood-risk-assessment-report-2021-Planning.pdf A close read of this document raises serious questions:

• It is a Level 1 assessment — a high-level, borough-wide screening exercise. The report itself states that any specific development site, including one on the scale proposed for Crews Hill, requires a far more detailed Level 2 SFRA with site-specific modelling before it can be justified. As things stand, no evidence has been published showing this deeper assessment has been carried out for Crews Hill and Vicarage Farm.
• The river flow model covering the Turkey Brook catchment — which covers the Crews Hill area — dates from 2019, and covers fluvial (river) flooding only. It does not model surface water (pluvial) flooding at all. For that risk, the report relies on generic national Environment Agency mapping, which the SFRA itself acknowledges does not always reflect the reality of local flood risk.
• The climate change allowances used to define flood zones in this report are drawn from the Environment Agency's official guidance, which is itself derived from Met Office UKCP18 climate science. However, the modelling in this SFRA is built around the central-estimate allowance for river flow (increases of 17–27%), not the more cautious "upper end" allowance of up to 70% that the same Environment Agency guidance makes available for exactly this kind of long-term, large-scale development decision. The more severe scenario appears only as an illustrative overlay, not as a working assumption.

In plain terms: the document being relied on to judge flood risk for a development that will stand for a century or more is based on a river model that predates the pandemic, has no surface water layer for the site in question, and uses a moderate rather than cautious climate assumption. Given how consistently climate projections have needed revising upward in recent years, this is not a minor technicality — it is the difference between "safe to build" and "regret in twenty years".

There are alternatives that don't carry this risk

The government's own case for New Towns rests on the argument that England has nowhere else to put 1.5 million homes. That case deserves scrutiny too:

• England has a substantial stock of brownfield land — previously developed sites — that could absorb significant housing without touching floodplain-adjacent Green Belt or undoing existing flood defence infrastructure.
• Large numbers of underused or vacant commercial and office buildings, particularly in outer London, are realistic candidates for conversion to housing, a route that avoids new impermeable surface area entirely and reuses existing drainage infrastructure rather than overwhelming it.
• Where new flood defence is genuinely needed, natural flood management — the kind Enfield is already doing at Chase Park, including beaver reintroduction elsewhere in the UK such as in Ealing, Cornwall and Devon — is a proven, lower-cost, biodiversity-positive approach compared with concrete drainage schemes built to accommodate a development that shouldn't need to exist on this land in the first place.

What residents can do now

The government's consultation on the seven shortlisted New Town sites, including Crews Hill and Chase Park, opened on 23 March 2026. Local campaign groups are already active and worth supporting or contacting directly:

• Action for Enfield's Future
• Better Homes Enfield
• CPRE London

Residents can also write directly to their MP and to the Ministry of Housing, Communities and Local Government, and can submit evidence of local flood history directly to the Environment Agency's Risk of Flooding from Surface Water team, who have stated they will consider it.

Building 21,000 homes is not, in itself, the objection. Building them on land that is actively protecting the rest of the borough from flooding, using flood modelling that is out of date, incomplete, and based on a moderate rather than cautious climate scenario, is the objection — and it is one the evidence supports.

Sources:

• Enfield Council, Level 1 Strategic Flood Risk Assessment, December 2021: www.enfield.gov.uk/__data/assets/pdf_file/0022/11983/Level-1-strategic-flood-risk-assessment-report-2021-Planning.pdf
• Enfield Council, Core Strategy Policy 8 (Environmental Protection and Green Infrastructure): www.planvu.co.uk/enfield/written/cs/cpt8.php
• Action for Enfield's Future: actionforenfieldsfuture.org.uk/going-going-gone-with-the-green-belt/
• Enfield Dispatch, "Enfield action group slams 'inexplicable' new town decision": enfielddispatch.co.uk/enfield-action-group-slams-inexplicable-government-new-town-decision/
• CPRE London, "'New town' poses even greater threat to Enfield Green Belt": www.cprelondon.org.uk/news/enfieldgreenbeltthreat/
• Chartered Institute of Housing, response to New Towns Taskforce recommendations: www.cih.org/news/cih-responds-to-labour-s-new-towns-announcements-chartered-institute-of-housing-cih/

I was hoping that the right eyes will see this and be able to follow up.  for reference I have written to whom I think are the relevant MP's and then needed to write a follow up letter as I found more information.  See below:

Penny Austin 
9th July 2026

Feryal Clark MP
Member of Parliament for Enfield NorthHouse of Commons, London, SW1A 0AA


CC: Rt Hon Steve Reed OBE MP, Secretary of State for Housing, Communities and Local Government
CC: Matthew Pennycook MP, Minister of State for Housing and Planning (New Towns programme)
Ministry of Housing, Communities and Local Government, 2 Marsham Street, London SW1P 4DF
CC: Joanne McCartney AM, London Assembly Member for Enfield and Haringey, Statutory Deputy Mayor —
CC: Zack Polanski AM, London Assembly, Environment Committee — : Benali Hamdache AM, London Assembly, Housing Committee — via London Assembly contact form
City Hall, Kamal Chunchie Way, London E16 1ZE

Re: Correction to my letter of 9 July 2026 — Crews Hill flood risk evidence

Dear Ms Clark, Secretary of State Reed, Minister Pennycook, Ms McCartney, Mr Polanski and Mr Hamdache,

I am writing to correct a factual error in my letter of 9 July regarding flood risk at the proposed Crews Hill and Chase Park New Town. My letter stated that no evidence had been published showing a detailed, site-specific flood risk assessment had been carried out for Crews Hill. This was incorrect, and I want to correct the record rather than leave an inaccurate claim on file.

Enfield Council in fact commissioned a full site-specific Flood Risk Assessment for the Crews Hill 'Broad location' (site reference SA27, 247 hectares), published in July 2023 by BMT Global, alongside a wider Level 2 Strategic Flood Risk Assessment the same year. It is publicly available
here: www.enfield.gov.uk/__data/assets/pdf_file/0034/54799/Flood-Risk-Assessment-Crews-Hill-Broad-Location-Planning.pdf

Having now read this document in full, I believe it strengthens rather than weakens the case for closer scrutiny of this site, for the following reasons. 

First, baseline Environment Agency mapping, which excludes the effect of flood defences, shows parts of the site reaching Flood Zone 3b, the most severe classification, and confirms the site has previously flooded, with multiple recorded groundwater and sewer flooding incidents nearby. 

Second, the report's climate change modelling uses only a 17 percent increase to fluvial and surface water flow, the lower end of the range, despite the report itself noting that Environment Agency guidance sets an upper-end allowance for the Thames basin of up to 54 percent by the 2080s. That higher scenario is never modelled. 

Third, and most significantly, the report's own author notes that its climate-adjusted fluvial flood map, which shows only minimal risk, is inconsistent with the baseline flood zone maps for the same site, and explicitly advises this should be treated with caution. The equivalent climate-adjusted surface water map is likewise flagged in the report as inconsistent with the baseline surface water mapping. Based on the data available, the report also states the development would have failed the sequential test, a core planning safeguard, though it suggests this may be resolved through further site-specific work. 

Fourth, this assessment was produced in 2023 against a Local Plan figure of around 9,200 homes for Crews Hill and Chase Park combined. The New Towns proposal now under consideration is for up to 21,000 homes, more than double that figure, and it is not clear whether the flood risk evidence base has been revisited to reflect this substantially increased density.I would be grateful if my original three requests could now be read in light of this corrected evidence: first, whether the discrepancy the Council's own assessment identifies between its climate-adjusted and baseline flood maps has since been investigated with more detailed hydraulic modelling; second, whether the flood risk evidence base will be revisited given the New Towns proposal's substantially greater density than the site assessed in 2023; and third, whether the upper-end climate change allowance of 54 percent, rather than the 17 percent estimate used in 2023, will be applied given the scale and expected lifespan of this development. 

I apologise for the earlier inaccuracy and appreciate your patience in receiving this correction. 

Yours sincerely,
Penny Austin

SourceEnfield Council, Flood Risk Assessment: Crews Hill Broad Location (SA27), BMT Global, July 2023: www.enfield.gov.uk/__data/assets/pdf_file/0034/54799/Flood-Risk-Assessment-Crews-Hill-Broad-Location-Planning.pdf]link
 

Hi, I downloaded the 2021 flood risk assessment document PDF referred to in the article above but cannot see the maps listed on p88. They seem to have disappeared off the side of the page. However I do have a copy of the 2013 Upper Lea Valley Opportunity Area Report produced by the then Mayor Of London which clearly shows the extent of the flood risk areas across three full page maps as attached which I hope are relevant to the article.

I'd fully expect the Council to be regularly updating their Strategic Flood Risk Assessment particularly if they continue to plan for a New Town (or e Development Corporation does, should that be the route the Mayor and the Government tske now the Council has withdrawn).  Data on this changes regularly - for instance, surface water flooding data, incorporating climate change allowances, has just been published.  It's a constantly moving area of data. 

Objectors always point to the 'alternatives' that exist to a new town, but I'm sceptical that they're wholly realistic, and there are issues with bringing these forward.  The point of looking at a new town (and I really have no alliance for or against Crews Hill) is to ensure a long term supply of housing for future generations.  We won't see delivery there for at least ten years.  Brownfield sites, empty offices and the like can't be relied on to deliver this particularly if the Council has to demonstrate a five year supply (and I'm not au fait with where the Council is on this).  In addition, long term planning of a large site ensures that the provision of strategic infrastructure (including SUDs and flood alleviation) can be built into the planning, something that just can't be achieved with a piecemeal brownfield approach where sites aren't identifiable or guaranteed to be deliverable beyond five years.  And I'd expect many brownfield sites in the borough to be known to the Council and many may already be allocated, committed or contributing to the expected windfall.  Further, brownfield sites developed in this way aren't likely to deliver the type and range of houses required by current and future needs.  I wish there was some slightly wider thinking on this.  And as for green belt - well, it only has five purposes, and it doesn't include protecting open land, or wildlife sites or access to recreation; and some of it is brownfield land / grey belt.