Hertfordshire data centre hydrology, flood risk, and drainage consultancy

This represents one of the UK’s most ambitious data centre projects, with a hyperscale campus planned on a sensitive site in Hertfordshire. The development, comprising two large data centre buildings and associated infrastructure, is located on land classified as ‘Grey Belt’ – an area with both environmental value and planning constraints. The scale of the project, combined with its proximity to existing communities, watercourses, and green infrastructure, presented significant challenges in terms of hydrology, flood risk, and drainage management.

The site’s development required a robust understanding of local hydrological conditions to ensure that the new data centre would not increase flood risk to the surrounding area or compromise the integrity of local water resources. The planning process demanded a comprehensive flood risk assessment, the design of sustainable drainage systems (SuDS), and the integration of climate resilience measures. Additionally, the project needed to demonstrate that it could deliver substantial biodiversity net gain and landscape enhancements, while also managing the operational water demands and potential runoff from a large, impermeable footprint.

Arthian was appointed to deliver a full suite of hydrology, flood risk, and drainage consultancy services. Our approach began with a detailed hydrological assessment, using industry-standard methods and modelling tools to analyse rainfall, runoff, and catchment characteristics. This enabled us to quantify the baseline flood risk from all sources – including fluvial, pluvial, and groundwater flooding – and to identify key receptors both on and off site.

We prepared a comprehensive Flood Risk Assessment (FRA) in line with national planning policy, ensuring that the proposed development would remain safe from flooding throughout its lifetime and would not increase flood risk elsewhere. Our team designed a site-wide drainage strategy that incorporated sustainable drainage systems (SuDS), including permeable surfaces, attenuation basins, and controlled discharge to local watercourses. These measures were carefully integrated with the site’s landscape and ecological masterplan, supporting our clients commitment to a 135% biodiversity net gain and the creation of a new country park.

Throughout the planning and design process, Arthian worked closely with the client  statutory consultees, and local stakeholders to ensure that all hydrological and drainage solutions were robust, resilient, and aligned with best practice. Our live project management tools and transparent reporting enabled rapid responses to emerging challenges and ensured that all regulatory requirements were met.

The outcome was a set of hydrology, flood risk, and drainage strategies that not only secured planning consent for this nationally significant data centre, but also set a benchmark for sustainable infrastructure development in sensitive locations. Arthian’s expertise helped the client deliver on its vision for economic growth, environmental stewardship, and climate resilience.