Assessing Nature-Based Solutions for Water Resilience Using Sentinel-2 and PlanetScope Imagery: Traditional Stone Weirs in Sifnos Island (Greece)

Nature-based solutions (NBS) harness natural processes to address climate-related risks and evolving environmental challenges, providing sustainable and cost-effective alternatives to conventional grey infrastructure. Traditional stone weirs represent multifunctional and environmentally friendly structures that contribute to ecosystem sustainability while enhancing protection against water-related hazards. This type of NBS has demonstrated significant potential in regulating surface runoff by controlling water flow and retaining sediments, thereby reducing flow velocity and erosion during high-discharge events. Through these mechanisms, stone weirs support the enhancement of community resilience under changing climatic conditions. Within the framework of the CARDIMED project, a network of 120 traditional stone weirs was being developed and implemented on Sifnos Island (Greece). These structures are strategically distributed along two main stream networks with the objectives of improving water regulation, supporting aquifer recharge, enhancing biodiversity, and facilitating small-scale agricultural water use. The design and deployment of the weirs are tailored to the specific hydrological and ecological characteristics of the arid island environments of the eastern Mediterranean.

This study presents an integrated assessment of the effectiveness of stone weir nature-based solutions (NBS) in quantifying climate adaptation benefits, with a particular focus on stormwater regulation, using Sifnos Island (Aegean Sea, Greece) as a case study. The analysis adopts a multi-source monitoring framework that combines Earth observation data with in situ measurements collected through fixed monitoring stations, low-cost sensor deployments, and participatory crowdsourcing campaigns. Remote sensing techniques based on Sentinel-2 imagery are employed to derive key vegetation and water-related indices, including the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Water Index (NDWI), allowing the evaluation of vegetation condition, soil moisture availability, and land surface dynamics. To enhance spatial and temporal detail, PlanetScope imagery is integrated through the Copernicus Contributing Missions (CCM) programme, providing observations at 3 m spatial resolution. The near-daily revisit frequency of PlanetScope enables the monitoring of short-term dynamics and the computation of indices during hydrologically critical periods. Earth observation products are validated using in situ data acquired from monitoring systems installed at strategically selected locations, delivering high-resolution measurements of hydrological, meteorological, and ecological variables under varying climatic conditions. Overall, the proposed methodology offers a robust framework for quantifying the impacts of stone weir implementation and supports the evaluation of their scalability as effective, sustainable solutions for enhancing climate resilience on the regional scale.

Aknowledgments:

PlanetScope © Planet (2025) provided under Copernicus by European Union and European Space Agency.

This research has been funded by European Union’s Horizon Europe research and innovation programme under CARDIMED project (Grant Agreement No. 101112731) (Climate Adaptation and Resilience Demonstrated in the MEDiterranean region).