River Restoration in Thessaly, Greece

Thessaly is a region in Greece facing frequent floods, water scarcity, declining water quality, soil degradation, and loss of natural habitats. The most productive agricultural region in Greece, over 50% of the region’s land is used for farming. As the climate changes, Thessaly is expected to become hotter and drier, and flooding is set to worsen.

In 2020, a devastating cyclone known as Medicane Ianos hit Greece, bringing more rainfall in 48 hours than some areas receive in a whole year. Floods inundated cities like Karditsa, destroyed harvests, washed away bridges, and lives were lost. Damage to the region is estimated to have amounted to over EUR 700 million.

We partnered with Global Infrastructure Basel (GIB) Foundation, WWF Greece and the European Investment Bank (EIB), using our Sustainable Asset Valuation (SAVi) methodology to map out the environmental, social, and economic outcomes of a nature based approach to the issues Thessaly is facing, comparing this to a traditional grey infrastructure solution. Our assessment combines a spatially explicit analysis, system dynamics model, and financial analysis to quantify the outcomes of three scenarios:

1. Nature-based infrastructure (NBI): Riparian forests and floodplain restoration are implemented.
2. Hybrid infrastructure: Riparian forests and floodplain restoration are implemented, and small dams are built upstream to reduce sedimentation.
3. Grey infrastructure: New dikes are built along the river channel.

Our assessment found that the NBI intervention has the highest benefit-to-cost ratio over the next 25 years. The benefit-to-cost ratio of the NBI is 2.9, compared to 2.4 for the hybrid and 1.5 for the grey infrastructure.

Even without considering the avoided flood damages, the additional benefits, such as increased agriculture production and avoided costs of emissions, are sufficient to justify the investment in the NBI. The net benefits would be even larger when considering avoided flood losses, particularly from extreme events.

The carbon storage value of NBI, which is equal to EUR 12.8 million, is, on its own, larger than the costs of the NBI (EUR 6.8 million) and of the hybrid infrastructure (9.3 million). The NBI would also improve habitat quality and support biodiversity, which could provide recreational opportunities and improve agricultural productivity.