Climate change is exposing the UK to higher seas, greater rainfall, and more intense short-duration storms. Roger Smith, managing director of Hesselberg Erosion Protection, explores the extra demands this places on hydraulic infrastructure, and the need for proactive planning and maintenance.
Erosion has always been a design consideration in UK hydraulic engineering. However, much of our coastal, river and water-control infrastructure was designed and built based on historical climate patterns. Today’s warming climate is driving greater rainfall intensity, peak river flows, discharge overflows and sea levels, meaning that critical water infrastructure now faces water volumes, velocities and erosive forces for which it was never designed.
Infrastructure such as reservoir embankments, spillways, flood storage areas and coastal abstraction assets are increasingly exposed to hydraulic loading well beyond the assumptions embedded in legacy design standards. Our sewerage and waste water systems cannot cope with higher water volumes from a greater number and intensity of high-rainfall events, leading to the widely reported discharge of untreated waste into England’s rivers and seas.
This potent combination of factors has become a core and urgent infrastructure challenge for asset owners and operators.
National risk and investment alignment
The Environment Agency’s National Assessment of Flood and Coastal Erosion Risk confirms that both flooding and coastal erosion exposure are expected to rise significantly over coming decades, driven primarily by sea level rise and intensified rainfall regimes.
This changing risk profile is now being matched by unprecedented public and regulated investment, as recognition grows that infrastructure resilience must keep pace with accelerating climate pressures. The Environment Agency’s Collaborative Delivery Framework (CDF), the primary funding route for flood and coastal defence projects in England, has seen its budget expand from £2.6 billion in the 2015–2021 period, to £5.2 billion for 2021–2027.
Alongside this, regulated water sector investment is entering a major delivery phase. Through Asset Management Plan 8 (AMP8), water companies are collectively investing around £88 billion between 2025 and 2030, overseen by Ofwat and the Environment Agency. This programme contains several programmes specifically targeted at improving resilience, including spending of £10 billion to reduce storm overflow spills by 44% compared with 2021 levels, and £1.4 billion specifically allocated to catchment- and nature-based solutions.
In parallel, Government approval of updated Water Resources Management Plans has unlocked £7.9 billion of additional investment over the next five years, including major reservoir developments near Abingdon and in the Fens. For those of us involved in erosion management, this is an opportunity to which we must respond with long-term thinking, and the use of climate-resilient design.
Changing hydraulic drivers and erosion mechanisms
Climate projections from the Met Office UKCP18 programme show clear trends towards more intense rain storms, increased winter rainfall, higher peak river flows and continued sea level rise.
For erosion processes, these shifts translate into increased boundary shear stress, longer periods of saturation, more frequent overtopping events, and accelerated material fatigue. That means that across water infrastructure portfolios, we’re more likely to see worsening:
Toe scour at embankments and flood defences
Overtopping-induced surface erosion of reservoir dams
Erosion due to out-of-channel flow along spillways
Progressive bank retreat along rivers and navigation corridors
Loss of sediment buffers, exposing structural foundations
Increased internal erosion risk during prolonged high-water conditions
What’s key is that, rather than isolated failures, these mechanisms increasingly act in combination, which can compound asset vulnerability.
Reservoirs, embankments and climate-adjusted performance
While the UK’s reservoir safety framework remains among the most robust globally, erosion continues to represent a leading cause of long-term degradation. In our changing climate, we’re seeing an increase in upstream face wave erosion under prolonged storm loading, and erosion of the downstream slope due to exceedance flows and overtopping. There’s also an increase in scour at spillway transitions and outlet structures, and the degradation of historic protection systems installed under outdated design assumptions.
Modern erosion protection approaches are increasingly designed for climate-adjusted hydraulic loading scenarios that reflect probabilities, and modelled future conditions. They may use elements such as high-durability rock armour systems with improved interlock, enhanced filter layers designed to control internal erosion, and scour-resistant toe stabilisation to prevent progressive undermining.
Erosion protection approaches increasingly incorporate open stone asphalt (OSA), both for extending the life of existing infrastructure and to protect new assets. First used for dam erosion protection in 1991, OSA has a 35-year maintenance-free record on dams, and has been used by all the UK’s major water companies. For asset owners and inspection engineers, asphalt is a very ‘honest’ material, as it follows settlements and voids beneath. This gives earlier warning of hidden danger when compared to traditional rigid systems such as concrete.
Crucially, these systems are now designed for future flow and wave conditions rather than historic averages, reducing the likelihood of flood events, breaches and repeated retrofit cycles.
From reactive repair to predictive erosion management
It’s been consistently shown across national adaptation reporting that anticipatory action delivers better safety and economic outcomes than reactive intervention. Newer technologies including LiDAR and topographic surveys, bathymetric monitoring, remote sensing of shoreline movement, or ground-based deformation and saturation sensors allow erosion progression to be measured and modelled with increasing precision. This supports early-stage intervention before structural integrity is compromised.
From a whole-life cost perspective, this preventative approach is almost always more effective. Reactive repairs typically involve constrained access, urgent mobilisation, environmental permitting complexity and operational disruption, all of which are incurred at a great cost. Planned reinforcement, by contrast, can be integrated into asset management programmes at substantially lower cost and risk.
Alongside hard engineering for critical assets, there’s an important role for complementary measures such as reconnecting floodplains to attenuate peak flows, or stabilising riverbanks through targeted vegetation. Sediment nourishment can help protect structural toes, while restoring wetlands and saltmarsh works to reduce incoming wave energy. Here it’s also important to consider the role of erosion protection in the natural habitat, for example by encouraging biofilms such as seaweeds on solutions situated within intertidal zones. Seeding the surface of solutions such as OSA and asphalt-filled geomats encourages biodiversity, and supports the ability of the solution to prevent erosion.
When underpinned by robust modelling and sediment management, these approaches can materially reduce erosive loading, while delivering demonstrable biodiversity and carbon benefits.
Canals and navigation assets under growing pressure
Erosion isn’t just a consideration along the UK’s coastline: our inland navigation network faces its own challenges. With annual income of roughly £200 to £240 million, the Canal & River Trust manages around 2,000 miles of canals and rivers across England and Wales, maintaining embankments, heritage structures and flood-sensitive corridors.
In a changing climate, the trust faces increasing erosion and hydraulic stress across ageing infrastructure, with funding uncertainty beyond 2027 adding further resilience challenges. Many canal embankments were constructed long before modern hydraulic understanding, making their proactive erosion reinforcement increasingly critical.
As with other public and private bodies charged with maintaining critical water infrastructure, the Canal & River Trust must manage erosion in the context of regulatory compliance, service continuity, climate resilience commitments and brand reputation. On top of this, all owners and operators must balance their public safety obligations against the need to prioritise finite capital and resources.
As our climate warms and changes, the hydraulic pressures on UK infrastructure will continue to intensify. Given this reality, it’s incumbent on those who manage coastal, waterway and water supply assets to evolve towards predictive, climate-adjusted resilience planning. Erosion risk must be factored into monitoring regimes, design standards and long-term capital programmes. Those designing and building solutions must ensure they are fit for future scenarios, calling on natural and complementary measures where possible. In this way, the UK will be far better positioned to control whole-life costs and maintain infrastructure performance in a changing climate.
Common Erosion Failure Modes and Critical Hydraulic Thresholds in UK Water Infrastructure
Understanding how erosion initiates and propagates is central to designing resilient protection systems. Across reservoirs, flood defences, canals and river assets, failure rarely occurs from a single mechanism. Instead, progressive degradation under repeated hydraulic loading leads to threshold exceedance and rapid loss of stability.
