SHIFTING SANDS: Community-based Bathymetry of Isola Sacra (Fiumicino, Italy)

The SHIFTING SANDS project (funded by the program Impetus for Citizen Science) was implemented in cooperation with the Mujeres in Mare community, the network of local committees and associations Tavoli del Porto, inhabitants of Fiumicino and surrounding areas, and professional scientists from the network Scienza Radicata (overall more than 130 participants). The aim was to monitor and map seafloor changes at Isola Sacra (Fiumicino, mouth of the Tiber river, Italia). The goal was to assess and disseminate siltation rates in the bay, within the broader context of the critical issues surrounding the new Fiumicino cruise port project. A six-month community science campaign in 2025 was organized, including training, data collection and analysis, dissemination, and engagement with a wider audience. Project outings were conducted on foot, by sailboats, and by an inflatable boat, using a combination of low-cost, open-source tools. The campaign's results include: (i) monthly in-situ measurements of the seafloor depth at Isola Sacra; (ii) mean bathymetric profile of the lighthouse bay for the year 2025; (iii) Estimation of the mean annual linear and volumetric siltation rate (0.15 m/year and 81000 m³/year) in the bay itself. These empirical estimates are compatible and comparable with siltation rates derived from numerical modeling methods, demonstrating the validity and potential of the participatory science approach developed and integrated with statistical geospatial analysis. The methodology realistically captures non-homogeneous spatial changes in sediment accumulation; however, it reflects the inherent limitation of using temporally averaged values to calculate sedimentation rates, a common feature of many numerical studies. This approach may lead to underestimating future siltation rates, as it does not consider the non-linear effects that may occur in response to time-varying external perturbations, such as dredging operations or extreme weather events. Despite this, the method developed and tested allows for straightforward measurement of sedimentation rates and monitoring of siltation over time, thanks to the highly accessible tools used. The project also promoted local ecological knowledge among citizens and the transparency of research methodologies for environmental impact assessments of the port project.

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SHIFTING SANDS is co-funded under the IMPETUS project, itself funded by the European Union's Horizon Europe program and implemented by King's College London, Ars Electronica, EUSEA, Nesta, Science for Change, T6 Ecosystems srl, Zabala Innovation Consulting.

It is produced by RIZOMI.LAB in collaboration with Seasters, Ponentino ASD, and Scienza Radicata.