Building a flood-resilient Ireland

Recent storms, such as Storm Babet that caused devastating flooding in Midleton in 2023, highlight the severe impacts that climatic events can have on our communities. Attribution studies, that assess the degree to which climate change may be influencing these events, are concluding that climate change is making such storms more likely and more severe.

As our climate continues to change, it is affecting weather patterns and driving sea level rise. As a result, flood risk presents an increasing threat to Irish communities, infrastructure, our economy, and natural ecosystems. Over the coming decades, we can expect significant impacts from the effects of climate change, such as rising sea levels, increased winter rainfall, more heavy rain days, and more intense storms.

While global mitigation of climate change remains essential, Ireland must also adapt to these impacts.

To manage a risk, it is first necessary to understand that risk. How will climate change influence flooding, to what degree, how fast, and where? To answer these questions, the Office of Public Works (OPW) has been undertaking flood mapping and flood risk assessment programmes over the past 20 years that assess potential future risk as well as that which we face today.

Through the initial National Catchment-based Flood Risk Assessment and Management (CFRAM) Programme, followed by the national predictive flood mapping programmes, flood maps have been prepared for all streams and rivers in the country with a catchment area of more than 5km2, as well as for the entire national coastline.

The flood maps have been prepared based on existing conditions, but also for future scenarios that include allowances for the potential impacts of climate change. For example, for coastal conditions flood maps have been prepared for four future scenarios with allowances for a mean sea level rise of 0.5m up to 2m above existing levels. The future scenarios used have been informed by international and national publications and research, and are in line with the most recent projections of the Intergovernmental Panel on Climate Change.

The flood maps, publicly available on the OPW’s FloodInfo portal (www.floodinfo.ie), show the areas prone to flooding and form the basis of flood risk assessments that determine the level of risk and potential damages different floods can cause under each scenario, providing a solid evidence base for action.

Based on our understanding of current and future risks, adaptation actions are needed to help Ireland build resilience to climate change and extreme weather events. Two points do however need to be taken into account:

• While our understanding continues to improve through ongoing research and assessments, significant uncertainty remains around the pace and scale of change in rainfall intensities and flood magnitudes that may occur.

• Climate change is already increasing flood risk, but its full impacts, such as sea level rise, will unfold gradually over the coming decades. It is projected that it will be the end of the century before sea level rise is expected to reach 0.5-1.0m, and potentially up to 2m, above current levels.

Tidal defences along the River Liffey, that include an allowance for sea level rise.

Therefore, adaptation must plan for a range of possible futures, not a single fixed outcome at a defined point in time, recognising that we do not need to design and build today for a change that may or may not materialise at the end of the century. Instead, we must use an adaptive management approach in our investments today, taking account of a range of possible futures. This approach informs our decisions on what needs to be done now to address existing risks while also providing for future, cost-effective adaptation and further investment that might be required over the years and decades to come, depending on how climate change unfolds.

Future adaptation measures for flood protection may include nature-based measures. These measures can help attenuate the increased overland run-off and flow into rivers that are expected with climate change, which in turn can reduce flood risk downstream.

Adaptation has been mandated as part of the design process for all recent OPW flood protection schemes, with a requirement to prepare a Scheme Adaptation Plan. These Plans set out what provisions have been made for climate change in the design and construction of the Scheme, what future adaptation measures are foreseen or available, and when future interventions may be required.

A programme of work is also underway to prepare Adaptation Plans for the existing Schemes that have been completed in the past. This programme will examine what adaptation measures may be required to maintain a standard of protection for the benefitting communities, and will also assess the potential need for tidal barriers or similar works to protect our major cities and surrounding areas in the event of more extreme sea level rise.

The decisions we make today on development and infrastructure will have long-term consequences. Housing and major investments will most likely remain in place through significant future climate change. It is therefore essential that infrastructural planning and design and spatial planning and development management processes integrate climate change and flood risk considerations to ensure our built environment is adaptable and resilient to these challenges.

The Sectoral Adaptation Plan for Flood Risk Management, prepared by the OPW, has set out a range of specific actions to help build Ireland’s resilience to the potential impacts of climate change on flooding and flood risk. These include further reinforcing the foundation of our understanding of potential future risk through further research and ongoing assessment and mapping. Building on this, the priority is to ensure that decisions made today for long-term investments are fully informed by the risks and facilitate the range of necessary adaptations that may be required in the future.

Further information on climate adaptation for flood risk is available from the Sectoral Adaptation Plan for Flood Risk Management:

W: www.gov.ie/en/office-of-public-works/policy-information/climate-adaptation