The integrated system of Nature-based Solutions to mitigate floods and drought risks in the Serchio River Basin (Italy)

The Serchio River Basin is a basin of national interest under Italian law; its lower part includes the Lake Massaciuccoli sub-basin, within the Regional Natural Park of Migliarino-San Rossore-Massaciuccoli, a Natura 2000/RAMSAR site of high biodiversity value. 20th-century agricultural and urban development transformed the territory, which now faces extreme drought and water deficit (May-September), flood risk from the river and lake, water pollution, erosion/soil loss, subsidence, and degraded ecosystem/biodiversity quality -- pressures compounded by climate change, including rising temperature, high-variability rainfall shifts, and Mediterranean drought trends projected to worsen (up to +0.7 events/decade by 2040-2070 under RCP8.5 versus 1980-2015), with river-flood frequency also projected to rise by 2070.

The EU Horizon 2020 'Phusicos -- According to Nature' project aimed to demonstrate that Nature-based Solutions (NbS) can be economically and environmentally sustainable ways to reduce flood and drought risk in rural landscapes, improve the Massaciuccoli Lake area's hydrogeological and ecological condition, and test a 'Living Lab' participatory approach to cooperative NbS planning, as part of a broader Serchio basin risk-reduction and ecosystem-restoration plan, with an eye to post-COVID-19 rural revitalisation and replicability elsewhere.

The intervention plan comprises: a 45 ha phyto-depuration plant (15 ha built and active, remainder under construction, targeted completion 2021, designed to treat about 135,000 m3/day); vegetated buffer strips along two secondary canal-network areas to limit erosion, trap sediment and filter nutrients/pollutants; conservation agriculture (reduced tillage, cover crops such as Lolium multiflorum, sod-seeding) trialled on about 60 ha at two farms; a roughly 4.0 ha sedimentation basin (under construction) at the sub-catchment outflow before the pumping station, reducing particulate transport and nutrient loads while also acting as a flood/drought buffer reservoir; and 'gentle management' of canals (widening the trapezoidal cross-section with a one-bank floodplain while retaining bank vegetation) to restore morphological/ecological function and allow natural flood expansion, approved and financed but still in planning as of the 2021 update. Living Labs engaging farmers and local stakeholders followed three phases: understand/investigate/plan/explore; creative co-design/refinement; and evaluation/testing. An interdisciplinary monitoring programme covers soil sampling, precipitation/temperature trends, hydrogeological/geochemical characterisation, solid-transport monitoring and crop productivity.

Expected outcomes include slower pollutant discharge to the lake, improved ecological status and biodiversity, reduced soil erosion and solid transport, and greater basin-wide hydraulic resilience to flood and drought, alongside socio-economic co-benefits (tourism/recreation such as birdwatching and kayaking, wellbeing, green-economy jobs in sustainable agriculture, stakeholder cooperation/ownership, climate-risk awareness) and climate-mitigation co-benefits from expanded vegetated, carbon-sequestering area. The NbS package is partly funded by the EU Horizon 'Phusicos' project (1,425,000 EUR), with additional funding from the Tuscany Region (phyto-depuration and other NbS, via the PIT-Pianura Pisana project) and Italy's national environment ministry (hydraulic network improvement).

Success factors include the integrated approach tackling climate risks (drought, flood) alongside non-climate pressures (eutrophication, pollution, erosion, biodiversity loss) in a high-value ecological area, the choice of synergistic 'no regret' NbS, and the Living Lab process's full farmer/stakeholder involvement, which tailored solutions locally and built learning and acceptance. A detailed multidisciplinary monitoring programme is expected to support transferability elsewhere. Limiting factors are bureaucratic and administrative: Italian law treats NbS as naturalistic-engineering works requiring lengthy approval, and extensive Living Lab meetings were needed to build relationships with stakeholders and trade associations.