…and What the Cranfield Study Revealed About Local Preparedness
Surface water flooding is now one of the fastest growing flood risks in England. Unlike river or coastal flooding, it occurs with little warning, can happen almost anywhere, and can overwhelm areas that may have never previously flooded.
Our 2018 Cranfield University research into Flood Groups across England highlighted just how severe and poorly understood surface water flooding had become long before it entered mainstream policy discussions. Eight years on, the findings feel even more relevant.
This blog explores what the study uncovered, why surface water flooding is so difficult to manage, and what communities and authorities can do about it.
Surface Water Flooding: The Hidden Risk the Study Exposed
Flood Groups repeatedly reported that surface water runoff was overtaking river flooding as their primary threat. They described increased impermeable cover, new developments adding hardstanding, poor drainage maintenance, undersized or ageing culverts, debris prone trash screens, rapid catchment response times and more frequent high intensity rainfall events.
What stood out was how many communities felt these surface water problems were predictable but still unaddressed. One participant described how a pair of poorly designed culverts blocked repeatedly and threatened an entire village. Even once the problem was formally recognised, funding barriers meant the upgrade never happened. This pattern appeared across multiple locations: surface water issues were obvious locally but invisible in national datasets.
Why Surface Water Flooding Is So Difficult to Manage
The Cranfield study revealed several systemic issues that combine to make surface water flooding particularly challenging.
Fragmented responsibility
Drainage responsibility is scattered across highway authorities, Lead Local Flood Authorities, district councils, water companies, riparian owners, the Environment Agency, developers and private landowners. When everyone owns a small piece of risk, no one owns the whole picture.
Inconsistent drainage maintenance
Multiple groups reported gullies not being cleared, ditches falling out of maintenance, screens clogging during storms and drainage assets with no clearly defined maintenance owner. A drain that has not been cleared can turn a minor rainfall event into a street level flood in minutes.
Outdated drainage capacity
Many drainage systems were built decades ago and were never designed for today’s climate. Groups frequently described systems becoming overwhelmed within minutes during intense storms.
Underestimation in modelling
Surface water modelling often misses micro topography, blockages, highway cambers, behaviour at road junctions and downstream restrictions. This is why local knowledge, which the study found repeatedly undervalued, is essential.
The Role of New Development in Surface Water Problems
Concerns about development were widespread across the study. Participants highlighted building on floodplains, increased impermeable surfaces, insufficient SuDS in small developments, drainage designs that failed to account for downstream capacity and developers building as soon as floodwater receded.
One LLFA reportedly only reviewed resilience measures in developments of more than ten properties, leaving smaller schemes with no meaningful scrutiny despite their cumulative runoff impact. The message was clear: planning decisions were increasing surface water risk faster than mitigation measures could control it.
This is why it is vital that developments now have a Flood Risk Assessment and Surface Water Drainage Strategy.
Local Knowledge: The Most Valuable and Most Ignored Asset
A recurring complaint in the study was that external officers, often new to the area, overlooked or dismissed local knowledge. Examples included officers unfamiliar with drainage flows, road layouts and local flood histories, misplaced interventions due to lack of on site understanding and plans that did not match real behaviour during storms.
One participant said the Environment Agency had invested in people who did not understand the area, harming project outcomes despite good intentions. Surface water flooding behaves at a hyper local scale. Communities often understand the problem more accurately than datasets do.
Why Surface Water Flooding Is Increasing in 2026
Everything the study identified has intensified. Climate change is driving more short, extremely intense downpours. Urbanisation is covering more ground with impermeable surfaces. Drainage systems have not been upgraded at the same pace. Highways drainage remains under funded and prone to blockages. Soil saturation increases runoff volumes even outside mapped floodplains.
Surface water flooding is now the type of flood most likely to catch communities off guard.
What Communities Can Do: Insights from Effective Flood Groups
The study highlighted several practical and effective community actions.
Communities can begin by mapping the problem properly. This involves walking routes, mapping flow paths, collecting photos and understanding every pinch point.
They should identify assets that repeatedly fail. Trash screens, blocked culverts and poor gully maintenance often explain the majority of risk.
They should build consistent relationships with highways teams and Lead Local Flood Authorities. Evidence based communication delivers better results than sporadic escalation.
Running practice flood events exposes gaps in communication, equipment deployment and volunteer capacity.
Developing a local flood plan helps groups respond faster and more effectively during real incidents.
Forming subgroups for drainage and surface water issues ensures technical matters are handled by people with relevant skills and interest.
Residents can also challenge planning applications for new development and review the Surface Water Drainage Strategy. If there isn’t one… challenge that.
What Authorities Need to Improve
Based on the study’s findings, authorities need better integration of local knowledge. Residents often see problems years before they appear in official datasets.
They need more consistent drainage maintenance. A single blocked drain can create a flood event.
They need stronger scrutiny of small developments, because cumulative runoff from minor schemes is a silent driver of risk.
They need clearer funding pathways. Surface water schemes were repeatedly slowed by complex and unclear processes.
The Cranfield study showed that surface water flooding was already becoming the defining flood challenge for communities. Eight years later, that prediction has proved accurate.
But the study also showed something else: surface water flooding is manageable when communities, engineers and authorities work together and when local experience is treated as valuable evidence rather than anecdote.