Flood Risk Assessments in Kent

The River Medway is Kent’s largest river. Its floodplain through Tonbridge, Yalding, East Peckham, Wateringbury, West Farleigh and Maidstone generates significant Flood Zone 2 and 3 areas and a substantial volume of FRA work. The Medway catchment is complex – the Teise, Beult and Eden all contribute, and the Leigh Flood Storage Area upstream of Tonbridge plays a central role in managing peak flows through the Medway valley. Any FRA for a Medway catchment site must engage with EA Medway model data and understand the storage area’s operation and its implications for defended and undefended scenarios. The Medway tidal estuary from Rochester to the Thames creates additional tidal risk through the Medway towns of Rochester, Chatham, Gillingham and Strood.

The River Stour drains the north Kent plateau through Canterbury and Sandwich to Pegwell Bay, with tidal influence extending upstream from Fordwich. The Stour catchment includes a distinctive groundwater flooding risk from the chalk geology of the North Downs. The Nailbourne, Little Stour and Elham Valley Bourne are winterbourne streams – intermittent chalk streams that flow only during periods of high groundwater – and groundwater flooding in the villages of the Elham Valley, Barham, Bridge and Bishopsbourne is a documented and planning-relevant risk. Groundwater flooding in Kent’s chalk geology is not captured by the standard fluvial flood zone maps and requires specific assessment.

Romney Marsh in the south of the county is a low-lying coastal plain protected by sea walls and a network of drainage ditches maintained by the Romney Marsh Internal Drainage Board. Development on or near the Marsh requires IDB consultation and must address the managed drainage system alongside tidal coastal risk. The North Kent Marshes – Sheppey, the Isle of Grain and the Thames estuary marshes – are similarly reliant on ageing tidal defences that are subject to the Medway Estuary and Swale flood and coastal risk management strategy.

• Development in Flood Zone 2 or 3 along the Medway, Stour, Darent, Eden, Teise, Beult or any tributary
• Development in the Medway tidal estuary area from Rochester to Sheerness where combined tidal and fluvial risk applies
• Development on or near Romney Marsh or the North Kent Marshes where IDB consultation and tidal risk assessment are required
• Development where groundwater flooding from chalk geology is a planning consideration in the Elham Valley or North Downs
• Development of 1 hectare or more in Flood Zone 1
• Coastal development in Folkestone, Dover, Margate, Whitstable or Herne Bay where Channel coastal and wave risk applies

We understand Kent’s varied flood risk mechanisms – fluvial Medway, tidal Thames, groundwater chalk, Romney Marsh IDB and Channel coastal – and the specific SFRA evidence that applies to each location across the county. We are familiar with the Sevenoaks Level 2 SFRA 2025, Medway Council’s SFRA and the requirements of Kent County Council as LLFA.

Our FRAs engage with EA Medway, Stour and Darent model data and address groundwater flood risk where it is material. We cover all Kent districts and Medway unitary authority.