Vrednotenje vpliva dreves na površinski odtok v urbanem okoljuAlivio, Mark Bryan (Avtor) Bezak, Nejc (Mentor) Šraj, Mojca (Komentor) Atanasova, Nataša (Član komisije za zagovor) Zupanc, Vesna (Član komisije za zagovor) Raška, Pavel (Član komisije za zagovor) built environmentdoctoral dissertationbirchpinerainfall interceptionstormwaterthroughfall partitioningnature-based solutionssoil moistureinfiltrationSWMM canopy moduleurban treesUrban stormwater management is increasingly challenged by the compounded impacts of expanding impervious surfaces and the rising frequency of localized heavy rainfall events. In response, cities are placing greater emphasis on enhancing and regenerating the capacity of urban landscapes by incorporating naturebased solutions (NbS). For cities to fully embrace trees as a strategic component of Nbs for stormwater management, there is a need for scientific evidence and a comprehensive understanding of their hydrological functions across different geographic settings, urban landscape configurations, and climates. Additionally, current stormwater models often lack the capability to simulate urban tree’s ecosystem services, particularly the stormwater runoff reduction. Hence, the dissertation aims to evaluate the impacts of open-grown birch (Betula pendula Roth.) and pine (Pinus nigra Arnold) trees on urban stormwater runoff. Targeted field measurements were conducted at an experimental urban plot to investigate the effects of species-specific interception processes on drop size distribution (DSD) changes, kinetic energy reduction, rainfall intensity attenuation, throughfall partitioning (free throughfall/FR, splash/SP, canopy drip/CD), and sub-canopy hydrological processes, including the effects on soil moisture and infiltration. Leveraging experimental measurements to obtain species/site-specific input parameters, the stormwater runoff reduction potential of birch and pine trees was modelled using the improved SWMM model with the added canopy module. Owing to rainfall interception, there is a shift in the DSD of throughfall toward larger drop diameters compared to open rainfall while also increasing the presence of smaller drop sizes. Birch, with its broad leaves, facilitates drop fragmentation and coalescence, inducing a change in throughfall DSD with peaks at smaller and larger drop sizes. The needle-like foliage of pine promotes drop coalescence, resulting in fewer but larger drops. Both species increased throughfall D50 by 8.5–26.5% (pine) and 11.7% (leafed birch), with a 5.9% reduction observed in leafless birch. This can be explained by the significant differences in the proportions of each throughfall component between tree species and phenoseasons. SP constitute over 60% of throughfall drop numbers for both species, while CD dominates throughfall volume (40% in leafed birch, > 69% in pine), except in leafless birch where FR predominates (41.8%). Both trees alter the fall velocities of raindrops, with the birch reducing the mean velocity of rainfall by 3.4% and more substantially under the pine at 42.1%. The interception effect extends beyond individual drops, with birch and pine trees reducing the rainfall kinetic energy available for soil detachment and erosion by 21.5–28.5% and 74.9– 85.3%, respectively. The birch and pine canopies further attenuate the mean event rainfall intensity by 33.9– 37.7% and 82.9–85.4%, respectively, which is crucial for regulating the distribution and delivery of rainwater to the ground to infiltrate and/or runoff. The gradual and slow release of CD under the pine leads to a more substantial reduction in KE and intensity. Local microclimatic factors such as vapor pressure deficit, temperature, and humidity further modulate the effect of the rainfall interception process on intensity attenuation and kinetic energy dissipation. These canopy-mediated processes significantly influence both the moisture response and infiltration of soil beneath the trees. Soil infiltration rates were highest in the open area (5.97 cm/hr) followed by that under the pine (5.55 cm/hr) and lowest under the birch (3.76 cm/hr). The soil under the birch exhibited a faster and higher moisture response, especially at 16 cm depth, driven by a higher volume of FR, SP, and increased throughfall intensity. Conversely, the lower throughfall volume, intensity, and more gradual delivery of CD under the pine resulted in slower increases in soil moisture. This is further substantiated by the statistically significant lagged correlations between throughfall components and soil moisture, which show that soil moisture under the birch responds more quickly and directly to SP and FR inputs, whereas under the pine, the gradual release of CD leads to a delayed and prolonged moisture response. Additionally, seasonal changes in LAI have a stronger influence on the soil moisture dynamics below the birch than pine. The application of SWMM canopy module accurately and explicitly simulated the canopy hydrological processes in both trees. This improved the representation of rainfall interception in the model. Results demonstrated that the module’s interception routine effectively captured the temporal evolution of throughfall and stemflow (Tf + Sf) under the birch and pine trees in different phenoseasons. Strong correlations were observed between the simulated and observed Tf + Sf (r = 0.97–0.99) and interception values (r = 0.72) across all storm events. The findings further indicate that implementing birch and pine trees in the study area reduces the runoff volume by 20–25% and peak flow by 16–25% across different scenarios and phenoseasons. The mixed-species tree planting scenario (Scen3 with 50% birch and 50% pine) generally achieves greater reduction benefits in both runoff volume and peak flow compared to the single-species scenarios (Scen1 with only birch and Scen2 with only pine). Analysis of the water balance from the model further emphasizes the relative contribution of canopy interception (up to 21.1%) to the stormwater reduction of birch and pine, particularly during the leafed season, small to moderate storm events, and when trees are planted over directly connected impervious areas. Moreover, infiltration + storage in the soil beneath tree canopies account for more than 20% of the water balance, especially during the leafless season and depending on the soil medium. Overall, the findings of this dissertation highlight that the ability of urban trees to manage stormwater depends on both canopy and sub-canopy level processes. To ensure that their hydrological benefits are properly credited, it is essential to comprehensively incorporate both canopy (i.e., rainfall interception, evapotranspiration) and soil hydrological processes in the analysis and modelling.[M. B. Alivio]20252025-11-04 08:45:12Doktorsko delo/naloga175552sl