Application of bioengineering techniques as geo-hydrological risk mitigation measures in a highly valuable cultural landscape: Experiences from the cinque terre national park (Italy)

In this work, experiences from the use of bioengineering techniques as geo-hydrological risk mitigation measures within the territory of Cinque Terre National Park (Eastern Liguria, Italy) after an extreme rainfall event that occurred on 25 October 2011 are described. This rainstorm was responsible for intense erosive processes and triggered numerous shallow landslides, causing severe structural and economic damage. After this disastrous event, many bioengineering interventions were planned to stabilize the most unstable slopes and the most problematic streams. Based on multidisciplinary studies and field surveys, an inventory of the executed bioengineering works was compiled. Subsequently, on the basis of expert judgement, both the efficiency and effectiveness of the works three years after their construction were examined. Furthermore, the compliance of the executed works with the design requirements was analysed. This study revealed that some of the investigated works lack post-intervention maintenance and require the adoption of remedial measures aimed at improving the biotechnical functions of live materials, which are often ineffective. This case study highlights the importance of technical aspects that should be considered during the design phase of bioengineering works, especially when implemented within protected areas. Specifically, it would be greatly helpful to define instructions for post-intervention maintenance and monitoring and to perform vegetational studies. Considering the great cultural and natural heritage of the study area, the obtained results are expected to provide useful information for the definition of guidelines for the best practices to be adopted when future bioengineering works are planned for geo-hydrological risk management purposes.