Unprecedented flooding in Spain highlights urgent climate risks and infrastructure resilience lessons

By Bernard Rizk

Media Relations Advisor, uOttawa

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Valencia, Spain
Valencia, Spain - Credit: pexels.com
The October 2024 flood in Valencia, Spain, stands as one of the most severe flooding events in recent history, with record-breaking rainfall and extensive impacts across southern and southeastern Spain. Triggered by an unusual cut-off low-pressure system, the storm brought intense and prolonged rainfall to the region, overwhelming natural and urban drainage systems. Some areas received hundreds of millimeters of rainfall within mere hours—equivalent to the average annual precipitation—leading to rapid runoff and widespread inundation.

In the eastern Júcar Basin, a key area for water resources in the region, rainfall accumulation reached an extraordinary 610.9 mm over just four days, from October 29 to November 1, 2024. This immense amount of rain generated an estimated flood volume of 4.453 billion cubic meters of water, severely straining river systems and reservoirs and causing them to exceed their capacities.

By learning from extreme events like the Valencia floods, Canada and other countries can better understand the severe risks of climate change, preparing for a future in which extreme weather events are likely to become more frequent and more severe.

The media team asked Hossein Bonakdari, Associate Professor at the Faculty of Engineering, about lessons from the extreme climate phenomenon and future prevention strategies.

Q1. How did land management practices contribute to the flood severity, and what changes could reduce future risks?

Bonakdari : Rapid urban development in coastal cities has significantly contributed to flood severity by increasing impermeable surfaces, such as roads and buildings, which prevent water from being absorbed into the ground. This increased runoff overburdens drainage systems, leading to more severe flooding. In rural areas, practices like soil compaction from agricultural expansion and deforestation have reduced the landscape’s ability to naturally retain water, causing rapid runoff that intensifies downstream flooding. Given that this region has experienced previous floods, and with climate change expected to increase such events, focusing on land management is crucial for future risk reduction.

Green infrastructure uses natural processes to manage water and reduce flood risks by identifying flood-prone areas, increasing permeable surfaces, restoring floodplains and wetlands, investing in flood-adaptive features like bioswales, and creating natural barriers. Gray infrastructure focuses on engineered solutions to control water flow, including upgrading drainage systems, reinforcing flood barriers, building resilient transportation and water networks, enhancing stormwater management with retention basins, and guiding safe land-use through zoning regulations. Together, these approaches provide a balanced strategy for sustainable flood resilience. Combining these green and gray infrastructure strategies offers a comprehensive approach to reducing the adverse impacts of future floods, enhancing both natural and engineered resilience against climate-driven flood risks.
 

Q2. What key engineering lessons were learned for infrastructure resilience in flood-prone areas, and what design changes could help?

Bonakdari: Infrastructure must be adaptable and robust to build flood resilience in climate-impacted regions. Key lessons from Valencia include:

  1. Enhanced Drainage Capacity: Traditional drainage systems should be upgraded with larger pipes, detention basins, and permeable surfaces to handle increased precipitation levels.
  2. Integrating Green and Gray Infrastructure : Combining green solutions (like rain gardens and wetlands) with gray infrastructure improves water absorption and reduces runoff.
  3. Protecting Critical Infrastructure : Elevating and flood-proofing essential services (energy, transport, water) ensures they remain operational during floods.
  4. Flexible Urban Planning: Enforcing zoning restrictions in high-risk areas and creating flood zones can limit exposure to flood risks.
  5. Strengthening Building Codes: Updated codes requiring flood-resistant materials and construction techniques will improve resilience.
  6. Early Warning and Monitoring Systems: Real-time monitoring and early warning networks enable proactive responses, reducing property damage and protecting lives.
  7. Redundant Infrastructure Systems : Redundancy in power, water, and transportation systems ensures essential services are maintained during extreme events.

Resilience requires a multifaceted approach, blending engineering, adaptive planning, and nature-based solutions to help communities withstand future climate-driven floods.
 

Q3. What are the potential long-term environmental impacts, like soil erosion and habitat loss, and how can these be mitigated?

Bonakdari : Each flood event brings long-term environmental impacts, including soil erosion and degradation, as floodwaters accelerate soil loss, reducing fertility and agricultural productivity; habitat loss and ecosystem disruption, displacing wildlife and impacting biodiversity; water quality degradation, introducing pollutants harmful to human health and aquatic life; altered hydrology, which changes river courses, decreases groundwater recharge, and heightens future flood risks; and coastal ecosystem impacts, with floodwaters carrying sediments and pollutants that damage sensitive marine habitats. Mitigation strategies can be applied to counter these effects, such as using revegetation, buffer strips, soil conservation practices, and retention basins to stabilize soil and reduce erosion; restoring habitats with native vegetation, establishing floodplain reserves, and creating ecological corridors to support wildlife; implementing riparian buffer zones, restoring wetlands as natural filters, and adopting sustainable agricultural practices to reduce runoff pollutants.
 

Q4. How can policymakers and engineers collaborate to support recovery and build community resilience against future floods?

Bonakdari : In flood-prone regions like Canada, where climate variability and extreme weather events are increasing, collaboration between policymakers and engineers is essential for effective flood recovery and long-term resilience. Policymakers and engineers can establish data-driven policies by integrating engineering assessments, climate projections, and historical flood data, guiding the creation of flood-resistant building codes and infrastructure standards. Policymakers secure funding for both green (e.g., wetlands) and gray (e.g., levees) infrastructure while engineers design and implement solutions to optimize water retention and runoff control. Collaborative community outreach and flood preparedness programs help educate residents, with early warning systems and real-time monitoring further supporting proactive responses. Resilient land use planning and zoning regulations reduce exposure by restricting development in high-risk areas, while post-flood assessments allow policymakers and engineers to learn from past events, improving standards and infrastructure. Supporting flood management research and technology innovation enhances resilience through pilot projects and adaptive designs, positioning Canada as a leader in flood resilience strategy.
 

Q5. How do these floods relate to climate change and offer insights into future extreme weather impacts globally, including in Canada?

Bonakdari : The October 2024 floods in Valencia exemplify the intensifying impact of climate change on extreme weather, underscoring the global trend toward more frequent and severe flooding as sea surface temperatures (SSTs) rise. Warmer SSTs in the North Atlantic fueled atmospheric moisture, resulting in unprecedented rainfall as a moisture-laden cut-off low-pressure system stalled over the region. Canada faces similar risks, with coastal SSTs in the Pacific and Atlantic contributing to increased moisture and more intense storm patterns. Canadian climate trends, including heightened rainfall, heat waves, and wildfire frequency, reflect the broader global shifts observed in Valencia. Key lessons for Canada include bolstering infrastructure resilience by upgrading drainage systems, incorporating green infrastructure, and improving emergency response capabilities to handle higher runoff volumes. Developing early warning systems using real-time data from satellite monitoring can enhance preparedness, while sustainable land-use practices, such as zoning restrictions in high-risk areas, can mitigate flood impacts. Valencia’s flood offers insights for Canada on adapting urban planning to integrate green spaces and buffer zones, improving ecosystem resilience through reforestation and wetland restoration, and investing in adaptive infrastructure to accommodate these climate-driven shifts. The Valencia event thus highlights the importance of global collaboration, proactive adaptation, and infrastructure resilience to address the growing challenge of climate-induced extreme weather.