The calamity in Valencia underscores a stark reality: investment in climate resilience is a matter of life and death. We have become accustomed to tropical storms and hurricanes in the Americas, Asia-Pacific and the Caribbean making headlines. But the so-called “cold drop” in the region of Valencia, Spain caught us by surprise.
This high-altitude isolated depression, also known as a DANA (Depresión Aislada en Niveles Altos), caused torrential rains and resulted in a flash flood that killed more than 200 people in the region, which recorded its driest hydrological year between October 2023 and 2024.
What is going on?
Cold drops are the explosive result of the encounter between warm Mediterranean waters and cold air coming from the North Pole. In practice, this is yet another wake-up call on the disastrous impacts of climate change induced by human activities, even in traditionally temperate regions, resulting in torrential rains or floods.
In Valencia, a year’s worth of rain fell in just eight hours, making the DANA one of the deadliest European flood events of the 21st century. The flood event confirmed – as if further proof were needed – that no country is immune to such risks. In fact, 90% of natural disasters and climate change impacts are related to water.
From 1980 to 2020, 4 588 flood disasters across 172 countries have killed more than 250 000 people and caused damages in excess of USD 1 trillion, accounting for 40% of natural catastrophe losses during the period. Between 2022 and 2050, droughts, floods and storms could wipe USD 5.6 trillion from global GDP.
Total damages from floods and storms in Europe
Source: EMDAT (2024), https://www.emdat.be/ (accessed 13 December 2024).
Learning the lessons
Cities must learn lessons from water-related disasters. After Hurricane Katrina hit New Orleans (United States) in 2005, the US federal government recognised the need for better co-ordination across levels of government for the effective management of catastrophic events, especially to respond to large-scale competing needs and insufficient resources.
In 2011, Copenhagen (Denmark) was caught off-guard by the so-called “storm of a thousand years”. Since then, the city has implemented the “Cloudburst Management Plan” consisting of 300 green and grey infrastructure projects over 20 years, from tunnels channelling rainwater to wastewater treatment plants, to “rain beds” and permeable pavements allowing rainwater to seep directly into the soil. And to respond to the constant flood risk facing the Netherlands, the Dutch government launched the “Room for the River” programme from 2013 to 2018 to widen rivers instead of reinforcing dikes. The programme boosted the flood protection of four million people living in the Netherlands’ river delta due to lower pressure on dikes when water levels rose.
Acting ahead of time
- Spend now, save later: Saving money on water security is a false economy. The cost of inaction in the future is expected to be higher than the cost of tackling climate change now. For example, in Denmark, total flood damage to homes, holiday homes, commercial buildings, transport, agriculture and tourism could amount to an estimated DKK 406 billion (EUR 54 billion) over the next 100 years. Denmark could save billions if ambitious climate adaptation measures are implemented. For instance, the cost of protection for a 100-year storm surge would be DKK 37 billion, while the potential damage costs are DKK 67 billion.
- Share and bear the risks: New urban developments sometimes occur in locations that increase exposure to flood risk and impose additional costs on water management, but those who benefit most from new urban developments (such as property developers) do not necessarily bear those additional risks and costs. Land value capture mechanisms can help governments capture the increases in land value generated by public interventions (e.g. infrastructure investments) or administrative actions (e.g. land use changes) and fund water and sewage infrastructure among others.
- Reconnect with nature: Urban sprawl is increasing at a much faster pace than population growth globally: built-up areas have more than doubled over the last 40 years. But impermeable surfaces like roads, sidewalks and parking lots prevent water from seeping back into the ground. This creates run-off, overloads sewage networks and – in the case of intense rains – causes floods. Urban planning rules can mandate shares of permeable surfaces in public spaces and new developments to avoid such floods. For example, Paris (France) just adopted a new Plan Local d’Urbanisme aiming to make 40% of public spaces permeable by 2050, to improve rainwater infiltration during severe weather events and to cool down the city during hot spells and heatwaves.
Arlene, Irma, Maria, Haiyan, Sandy, Katrina. The list of calamities is growing. But thanks to the bold and innovative measures put in place by cities across the OECD, we know what works to protect citizens and respond to emergencies. It’s time to put that into practice: real action starts today!
