Living with drought and floods in the Anthropocene: a case study on nature-based adaptation

The projected decrease in summer precipitation and the increase of harsher weather extremes  will translate into a change in annual patterns of flood and drought (EEA, 2021); the “new normal” calls for solutions necessary to increase water resilience, ensuring water availability to preserve the ecological status of rivers, human health, and economic activities. 

In recent years, the Po basin has provided a taste of how the new climate normality in the region could look like, with more severe droughts alternated with floods and flash flood episodes. The area is vital to the Italian economy, supporting 40% of GDP, 55% of national electricity generation, and 40% of food production. Even under normal conditions, balancing water resources in the area is complex due to competing demands from agriculture, industry, energy, human consumption, and ecological preservation. 

Between 2021 and 2023 the Po basin experienced its worst drought in history: agriculture production decreased by 10%, for an estimated loss around 6 billion euros, energy production dropped by 37% with some thermoelectric plants shut down due to the lack of cooling water. Meanwhile floods and flash flood episodes have been increasing and foreseen to increase, causing fatalities and billions in damages. Between 2023 and 2024, the Emilia Romagna region experienced four devastating floods, causing 16 fatalities and damages for around 8 billion euros for the 2023 events only.

Under such a scenario, it becomes increasingly important to foster water resilience by enhancing our capacity to buffer flow extremes and sustainably retain water in the landscape. Nature-based solutions (NBS) may prove cost-effective by delivering benefits on multiple water and ecosystem processes. Natural Water Retention Measures (NWRM) in particular, are NBS that can help ‘keep the rain where it falls’ and comply with the hydraulic-hydrologic invariance (HHI) principles, which guides regional regulations. 

In this contribution, we present an analysis of how NBS may help cope with the expected hydrological extremes in the Po basin.  

We combined high-resolution data on flood risk, land economic value, and Natura 2000 to identify areas suitable for the creation of NBS. These areas could serve as a multipurpose, low-cost solution for storage, habitat restoration, and mitigating the effects of droughts and floods by storing water during high-flow events and releasing it during droughts. 

We used the LISFLOOD model (De Roo, Wesseling, and Van Deursen, 2000), configured as the European Flood Forecasting System (EFAS 5) at 1 arcminute resolution (~1.4 km), to reproduce past high/low flow events. This allowed us to estimate the extent to which high flow (flood) volumes could have been partly detained and stored to make water resources available during low flow (drought) periods.

We identify areas suitable for the implementation of NWRMs following economic, landscape-ecological and hydraulic criteria, and we simulate how these NBS placed on the suitable identified areas, could cater for the needs of water management that we expect under climate change in the coming decades.