The challenge of unprecedented floods and droughts in risk management.

Risk management has reduced vulnerability to floods and droughts globally , yet their impacts are still increasing . An improved understanding of the causes of changing impacts is therefore needed, but has been hampered by a lack of empirical data . On the basis of a global dataset of 45 pairs of events that occurred within the same area, we show that risk management generally reduces the impacts of floods and droughts but faces difficulties in reducing the impacts of unprecedented events of a magnitude not previously experienced. If the second event was much more hazardous than the first, its impact was almost always higher. This is because management was not designed to deal with such extreme events: for example, they exceeded the design levels of levees and reservoirs. In two success stories, the impact of the second, more hazardous, event was lower, as a result of improved risk management governance and high investment in integrated management. The observed difficulty of managing unprecedented events is alarming, given that more extreme hydrological events are projected owing to climate change .

Project(s)

HUMID Project

Land Management in Lowland Catchments for Integrated Flood Risk Reduction

Priority 1: Ecosystem Stewardship

Funder

Funder name	Awards
Ministerie van Economische Zaken en Klimaat, Netherlands
University of Saskatchewan, Canada	Global Water Futures programme
GlobalHydroPressure (Water JPI)
HUMID Project	CGL2017-85687-R - AEI/FEDER - UE
HydroSocialExtremes	HydroSocialExtremes (ERC Consolidator Grant no. 771678
Horizon 2020, Europe	MYRIAD-EU, grant agreement no. 101003276
PerfectSTORM	No. ERC-2020-StG 948601
European Regional Development Fund / Interreg Program V-A Spain-France-Andorra (POCTEFA 2014-2020)	Project EFA210/16 PIRAGUA,
Agencia Nacional de Investigación y Desarrollo, Chile	Research project no. ANID/FSEQ210001 - Research project no. ANID/NSFC190018
FP7 Security, European Union	SECurITY, grant agreement no. 787419
Austrian Science Fund, Austria / Deutsche Forschungsgemeinschaft, Germany	FWF project I 4776-N / DFG research group FOR 2416
Natural Environment Research Council, Untied Kingdom	LANDWISE, grant no. NE/R004668/1 - Grant no. NE/S013210/1
National Foundation for Science and Technology Development, Vietnam	Grant no. 105.06-2019.20
Đại học Quốc gia Hà Nội, Vietnam / Ho Chi Minh City, Vietnam
Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ, Germany