Daniel Cook

I’m a co-owner and Director of Aegaea and a Chartered Water and Environmental Manager (C.WEM) and Chair of the CIWEM South East Branch, working in environmental consultancy since 2011. My specialist subject is flood risk policy: how the NPPF, the Sequential and Exception Tests and the Planning Practice Guidance apply to a real site, and how to build evidence that holds up when a scheme is tested at appeal, at public inquiry or in the courts.

I’ve supported over 1,000 projects in the UK and internationally, from single-house extensions to flood risk due diligence for The National Archives and Kew Gardens, and risk assessments for an international government project. I act as a flood risk and drainage expert witness, and ITV, BBC Radio, Times Radio and The Guardian have asked me to explain flood risk, from London flash flooding to where England builds its homes.

Building Aegaea

Before Aegaea I worked at Mott MacDonald, Phlorum, Ambiental, Hilson Moran and Royal HaskoningDHV, on projects across the UK and internationally. At Ambiental, a specialist in flood modelling and natural hazard analytics, I was a Director of its consulting team, Ambiental Environmental Assessment (AEA). I built that team and supported the business through its acquisition by Royal HaskoningDHV in 2019, so I came to Aegaea having already grown a consultancy team and seen it through a successful exit.

I joined Aegaea as a Director in June 2021, alongside founder Chris Cameron-Hann, and I’m a co-owner of the business. Since then I’ve been influential in Aegaea’s growth: supporting clients through complex planning decisions and building the long-term client relationships that bring them back. Together we’ve grown a team of flood risk, hydraulic modelling, drainage and civil engineering experts across England and Scotland, able to support projects from a single-house extension to a nationally significant infrastructure scheme. We also build our own digital tools, such as FloodMetric.

How I can help you

• Flood risk policy and the Sequential Test: I agree a defensible Sequential Test method with the council before the assessment starts, including on sites where earlier approvals have been legally challenged.
• Planning appeals and expert evidence: I prepare flood risk and drainage evidence, proofs of evidence and rebuttals, and present them at hearings, public inquiries and round-table sessions.
• High-risk and complex sites: Flood Zone 3 and 3b, basements, brownfield regeneration, and sites where the published flood maps don’t tell the whole story.
• Strategic land and due diligence: early advice for land promoters and developers on whether flood risk and drainage will make or break a site, including Grey Belt schemes.
• Policy change: I track NPPF and PPG updates closely and write about them on our blog, so clients know what has changed before it affects their application.

Expert witness and appeals

Selected appeals and legal challenges where I was the flood risk and drainage consultant and my evidence supported a successful outcome:

• 265 Burlington Road, Merton (Redrow): 456 homes in blocks up to 15 storeys. The 11-day public inquiry (December 2020 to January 2021) included a round-table session on flooding. The Inspector allowed the appeal in June 2021, overturning Merton’s refusal. Source
• Land west of Church Lane, Climping, West Sussex (Mulgrave Properties): an outline scheme for up to 300 homes, refused by Arun District Council in September 2017. The appeal was allowed with conditions in September 2018. Source
• Broad Lane, Beaconsfield (Hawridge Land): up to 120 homes, 50% affordable. The first inquiry in November 2024 was dismissed, the High Court quashed that decision, and permission was granted after a second inquiry in 2025. Read the case study
• Sunnyside, Nazeing, Essex (High Court): in 2014 Mr Justice Wyn Williams quashed the Secretary of State’s refusal of a traveller site. He ruled that the Secretary of State’s view on flood risk, which overrode the Inspector’s, could not stand. R (O’Connor) v SSCLG, CO/632/2014. Source
• Basement development, Barnes (Richmond): permission secured in 2017 for a basement scheme despite objections from high-profile neighbours. Source

To instruct me as an expert witness, contact me directly.

Expertise in action

• Sequential Test after a legal challenge (Southwark, SE1): for Leathermarket CBS, a community-led housing provider, I led the Sequential Test and flood risk policy work on two schemes after a court quashed an earlier council approval in the borough on flood risk grounds. We agreed the method with Southwark’s planning and legal officers before assessing, giving both schemes a defensible basis. Read the case study
• First major Grey Belt approval in Uttlesford (Little Hallingbury, Essex): flood risk assessment and SuDS strategy for 52 homes, 50% affordable, for Hawridge Land and Orchestra Land. It was the district’s first major application resolved for approval under Grey Belt policy. Read the case study
• Avoiding the Sequential Test in Flood Zone 2 (Lewisham): the pre-application advice said a Sequential Test was needed, which the site would almost certainly have failed. Detailed model outputs showed low risk from all sources, the council agreed no test was needed, and permission was granted. The client’s planner credited “the sharp-eyed Daniel Cook”. Read the case study
• Mixed-use redevelopment in Flood Zone 3b (Cheltenham): a flood risk assessment, bespoke flood model and Flood Warning and Evacuation Plan for a previously developed site in the functional floodplain. The applicant secured planning permission for mixed residential and commercial use.

In the media

• ITV, Tonight (Series 28, Episode 3), 12 February 2026: the Government’s planning overhaul and new homes. Read our article or watch on ITVX
• Times Radio, 9 February 2025: how flood legislation has evolved and will keep evolving, improvements in flood data capture, and the findings of NaFRA2 (10-minute interview). Read our NaFRA2 guide
• The Guardian, 8 February 2025: more than 100,000 homes in England could be built in highest-risk flood zones. Read the article
• BBC Radio Sussex, 17 January 2023: flooded homes: Section 19 flood investigations, the support available to residents outside the planning system, including Flood Re, and how new development must comply with the NPPF and not increase flood risk elsewhere.
• ITV London News, 14 September 2021: flash flooding in London after an intense, short-duration rainfall event. Read our article or see the ITV report

Speaking and industry roles

As Chair of the CIWEM South East Branch, I help coordinate the branch’s events programme, including webinars on groundwater and on Bewl Reservoir.

I also speak at national flood conferences:

• Flood Resilience Conference 2026 (Government Events, online): Navigating the Future of Housing: Why Better Data Means More Resilient New Builds. Topics: what NaFRA2 changed, research showing 1 in 9 new builds are in flood zones, and what the all-sources approach in the NPPF and national SuDS standards means for site layout, building design, safe access and the Sequential Test. Event page
• Flooding Resilience Conference 2025 (Government Events, online): keynote on Building Flood-Resilient Housing. Topics: using data to evaluate sites against housing targets, including sites in flood zones; building resilience and SuDS into planning; access to insurance through Flood Re; and the design options that make development possible. Event page
• Flood Expo 2017 (ExCeL London, 27–28 September): speaker while at Ambiental, at what was billed as the world’s largest flood exhibition and conference. Event preview

A bit about me

Outside work you’ll usually find me outdoors. I’ve played football at County League level and also enjoy basketball and cricket. I paddleboard, walk the South Downs with my dog Zara, an over-active French bulldog, and I’m a strictly fair-weather fisherman. With my family, I love exploring the outdoors and travelling in the UK and abroad to experience different cultures, food and more.