One of the most current and urgent challenges is making cities sustainable and resilient to climate change. From this perspective, Nature-Based Solutions (NBSs) are well-recognized strategies for stormwater control and water cycle restoration. Urban trees are an example of NBS. However, the high degree of soil sealing typically found in urban environments limits natural processes such as infiltration and hinders the water and nutrient supply for proper root development, which weakens tree stability. Permeable pavements at the base of urban trees, on the one hand, facilitate infiltration, which helps runoff control, and on the other hand, improve stormwater retention and soil humidity, which enhance root feeding. This paper proposes an analytical-probabilistic approach to estimate the contribution of permeable pavements to stormwater management. The equations developed in this study relate the runoff probability to the storage volume, the infiltration rate into the underlying soil, and the average values of the hydrological variables in the input. The model allows us to select different runoff thresholds and considers the possibility that residual volume from previous rainfall events prefills the storage capacity. An application to a case study in Sao Paulo (Brazil) has been presented. It investigates the influence of the different parameters used in the model on the results. The comparison of the outcomes obtained using the developed equations with those obtained from the continuous simulation of measured data confirmed the effectiveness of the proposed analytical-probabilistic approach and the suitability of using permeable pavements at the base of urban trees for improving stormwater retention.

Tree stability under wind loading is a critical concern for risk management in urban and natural environments. Despite advances in assessment methods, discrepancies persist between theoretical predictions and real-world tree behaviour. This study presents results from an extensive field investigation conducted at the University of Dundee Botanic Gardens to evaluate tree uprooting stability through non-destructive static, dynamic, and uprooting tests. This paper focusses on the programme of non-destructive and uprooting tests conducted across twenty-one trees of a variety of coniferous and deciduous species. Regarding the non-destructive tests, multiple tests were carried out on the same trees, varying both the pulling direction and the pulling height. Geotechnical properties, including shear strength, water content, soil water retention behaviour, and granulometry, were characterized to assess their role in root anchorage. These characteristics were seen to be at least as important as species. The results revealed that the maximum overturning moment (M_L) occurred between a 1.6 and 2.9° inclination during uprooting for the partially saturated ground conditions at the time of testing, irrespective of species or biometric parameters. The findings contribute to refining tree stability assessments, offering practical insights for arboriculture and urban planning.

The collapse of trees, exacerbated by extreme weather events associated to climate change, has become a critical issue, particularly in urban environments where the assessment of tree stability is now an integral component of comprehensive risk management strategies. Standard methodologies for assessing tree stability commonly rely on the interpretation of on-site pulling tests, which provide insights into the mechanical response of trees subjected to lateral forces. In this context, geotechnical engineering can provide a significant contribution to evaluate the overturning resistance of trees, particularly in cases where failure mechanisms are governed by root system uprooting. Indeed, the whole root plate can be conceptualized as a shallow foundation, providing mechanical support to the tree against external loads. This paper presents an experimental campaign of pulling tests conducted on mature trees at the Botanic Garden of the University of Dundee (Scotland, UK). Mutually orthogonal loading directions, the effects of load relaxation, as well as the response to cyclic loading up to complete uprooting were systematically investigated. The experimental findings are analyzed within a geotechnical framework, drawing parallels with foundation engineering principles related to cyclic loading effects on direct foundations subjected to rocking actions. In particular, global mechanical parameters at the macro scale of the trunk collar were derived (e.g., rotational stiffness and damping ratio), and their dependence on the applied loading path systematically compared and critically commented. The results suggest the reliability of the idea of assimilating the root plate to a shallow foundation and provide novel insights into the response of trees subjected to lateral loads, contributing to a more comprehensive understanding of their toppling behaviour.

Tree stability under wind loading is a critical concern for risk management in urban and natural environments. Despite advances in assessment methods, discrepancies persist between theoretical predictions and real-world tree behaviour. This study presents results from an extensive field investigation conducted at the University of Dundee Botanic Gardens to evaluate tree uprooting stability through non-destructive static, dynamic, and uprooting tests. This paper focusses on the programme of non-destructive and uprooting tests conducted across twenty-one trees of a variety of coniferous and deciduous species. Regarding the non-destructive tests, multiple tests were carried out on the same trees, varying both the pulling direction and the pulling height. Geotechnical properties, including shear strength, water content, soil-water retention behaviour and granulometry, were characterized to assess their role in root anchorage. Results revealed that the maximum overturning moment (ML) occurred between 1.6 and 2.9° inclination during uprooting for the partially-saturated ground conditions at the time of testing, irrespective of species or biometric parameters. The findings contribute to refining tree stability assessments, offering practical insights for arboriculture and urban planning.

Urban development leads to an increment of impervious cover that drastically reduces infiltration rates and increases the risk of stormwater floods, also reinforced by the rise of extreme events due to climate change.In this context, urban trees represent a valid system for sustainable stormwater management. They decrease the runoff discharged in the sewer network and/or in the receiving water bodies.Trees impact the hydrological cycle through the processes of interception, evapotranspiration and infiltration strictly depending on several factors such as tree features, soils properties, climate, and storm event characteristics.The objective of the study is to propose an analytical-probabilistic approach to model the contribution of urban trees to the restoration of the water cycle, with particular focus on the evapotranspiration component.