According to the IPCC report from Working Group I, global warming is expected to drive rising sea levels, and lead to more frequent extreme precipitation events that will intensify the risk of coastal, river and pluvial floods. Victoria Naipal, climate scientist and risk expert at EcoAct, discusses the latest knowledge of exposure and impacts of flooding due to climate change, and shares her recommendations.
How does climate change lead to more flooding events?
About river and pluvial floods
The number of flooding events has already increased over the last few decades. Currently, 58 million people are exposed to river flooding globally, more than half of whom live in Asia.
Climate change affects river and pluvial flooding in two ways:
- By increasing the frequency of extreme precipitation events, leading to more pluvial and river flooding
- By increasing “rare” extreme precipitation events. This means events with a high return period, e. g. 100-year precipitation events are occurring more frequently, leading to more extreme pluvial and river flooding
The IPCC report from Working Group 1 warns that this could occur across most regions of the world for global warming scenarios > 2°C. At 3 °C warming, minimum exposition risk is 90-186 million people could be affected by river flooding (SSP5 – fossil fuel development scenario), with maximum exposition risk 113-241 million people (SSP3 – regional rivalry scenario). Meanwhile, the global population exposed to extreme river flooding with a 100-year return period is projected to increase 2.5-3% by mid-Century for global warming scenarios above 2°C.
For Europe, projections show extreme precipitation increase (including in the Mediterranean regions), occurring in winter, spring and autumn to be highly likely. Europe is expected to witness the largest increase in river flood risk. Events with peak river discharge above a 100-year return period have already increased significantly and will most likely continue to do so, especially in West and Central Europe. In July 2021, catastrophic floods in Germany caused 184 deaths due to heavy rainfall.
About sea level rise and coastal floods
Globally, around 148 million people in low-lying coastal cities are exposed to episodic coastal flooding. The latest IPCC report from Working Group I concluded that sea level is extremely likely to continue rising across all continents and will increase the risk of coastal flooding under high tides, also increasing the impacts from waves and storm surges.
Sea level rise is a slow but continuous and certain process that may lead to 186cm increase in the Extreme Total Water Level in Europe by the end of the century in a business-as-usual scenario (climate scenario leading to a warming between 3° and 4°C by end of the century). In the absence of better coastal protection, this sea level rise will increase the frequency of extreme coastal floods in Europe up to a factor 1000 depending on the location and climate scenario.
Global projections show that in the business-as-usual scenario, the area of global land inundated by coastal flooding may increase by 15%, leading to a 17% increase in population exposure, and a 16% increase in exposed assets.
Compound events leading to catastrophic floods
Extreme precipitation events in highly urbanized and low-lying coastal areas together with coastal flooding may have catastrophic consequences, such as the floods in Venice in November 2019. These compound flooding events will be exacerbated by climate change. In Europe, as extreme precipitation events increase, the Mediterranean is the most exposed region to compound flooding.
Loss and damage due to flooding
Floods can result in costs not only for damage and loss of assets, but also costs associated with recovery, insurance, flood adaptation, and mitigation measures.
For example, episodic coastal flooding is estimated to threaten around $7.8tn worth of assets globally; sea level rise under the business-as-usual scenario could push this figure up to $11tn by 2050. In Europe, expected annual damage from extreme sea level rise is estimated to be around €1.25bn at present day and may increase by mid-century to €39bn in the business-as-usual scenario.
Flood adaptation and mitigation recommendations
Flood management through adaptation or mitigation is a way to prevent or reduce the risk of flooding. Several countries and organisations have a multiple-layer safety approach in place for the development of flood mitigation and adaptation measures.
Flood protection measures
There are “grey” and “nature-based” flood protection measures. “Grey” flood protection measures include construction works such as dikes, levees, channels and reservoirs. “Nature-based” flood protection measures use natural means to slow water flow such as providing space for flood water (e.g. not building in floodplains of rivers) and planting trees (such as mangroves). Even though the grey flood protection measures can be effective on the short term, they are usually very costly, have high maintenance costs and destroy biodiversity. Natural solutions often take more time to implement, but have many co-benefits such as increasing biodiversity, improving water quality and sequestering carbon.
Floodproof spatial planning
Flood proofing includes waterproofing existing structures (using waterproof materials), raising of structures to prevent damage, changing building use, or even relocating structures to a non-flood prone zone.
Early warning systems are an important part of disaster management and include flood monitoring, forecasting and early warnings for local communities. Another important part of flood disaster management is the emergency response plan, and a continuity plan for businesses. Both need to be prepared in advance and reviewed with all key stakeholders.
Flood risk, its damage and protection costs should not be underestimated in the near and mid-term future. Every organisation should be able to assess their current and future risk to flooding and know how to adapt to and mitigate this risk. It’s also important to not only combat flood risk at an organisational level, but also to help communities become flood resilient by raising awareness and investing in flood risk adaptation & mitigation projects at a local, regional, and national level.
As experts of climate change adaptation and mitigation, EcoAct can help your business to prepare for future flood risk, feel free to contact us to find out more!
 Dottori et al. (2018) in Nature Climate Change
 Yukiko et al. (2021) in Scientific Reports
 Values in brackets are for the SSP3 scenario (regional rivalry scenarios), and the normal values are for SSP5 (fossil fuel development scenario)
 de Bruijn et al.(2019) in Scientific Data
 Kirezci et al. (2020) in Scientific Reports
 Vousdoukas, M, I. et al. (2018) in Nature Climate Change
 EEA report (2016): Flood risks and environmental vulnerability