By Louise Walsh

Published 25 January 2023

With a changing climate and rising sea levels putting cities at risk of flooding, it’s crucial for planners to increase their cities’ resilience. A new tool has been developed to help them – and it started with the throwing of a thousand virtual hexagons over Hull.

Low lying, at risk from the sea, river and surface water, the UK’s second biggest flood risk after London… It’s little wonder that decision makers, environmental agencies and residents are worried about the long-term sustainable future of the city of Hull.

On 5 December 2013, the largest tidal surge ever was recorded in the Humber. Around 1,100 properties and over 7,000 hectares of land were flooded, impacting industry and infrastructure around the estuary, and affecting trade, transport and production.

Before that, on 25 June 2007, the city’s drainage systems were overwhelmed on the wettest day in one of the wettest months in living memory. More than 10,000 homes were evacuated, almost all of Hull’s 98 schools were damaged and a life was tragically lost. The cost of repair across the city was put at more than £40m.

“These ‘once-in-a-lifetime’ flooding events will become more frequent as sea levels rise and we experience more storms,” says Mike Dobson, who works for Arup, global specialists in the sustainable built environment, and spent 15 years working in the Humber area for the Environment Agency.

“Fortunately there’s a wealth of climate data available,” says Professor Tom Spencer, Director of the Cambridge Coastal Research Unit in the Department of Geography. “Ideally you’d feed this high-spec climate science modelling into informed decision making.”

But that’s not straightforward, Spencer explains: “It’s a very complex set of tasks which requires a lot of resource – and most organizations just don’t have that. So what tends to happen is everything is over-simplified and only a small number of possible scenarios are considered – not enough to build in the uncertainties of the climate changes we face.”

Dobson and Spencer, together with Steven Downie, a Fluid Dynamics specialist in Arup’s Technology and Research team, plus researchers at the National Oceanography Centre, set out to change this.

They developed a new digital tool to communicate the impact of sea-level rise on flood risk. Developed as a web-based portal, the sea-level rise tool can be used to understand the economic impact of tens of thousands of potential scenarios of rising seas and mitigation activities. It’s the first time the full scope of the Intergovernmental Panel on Climate Change (IPCC) sea-level rise projections can be seen in an interactive way.

The team was supported by the Environment Agency, which acted as stakeholder and provided vital data to enable a case study based on Hull.