Abstract. We present IT-SNOW, a serially complete and multi-year snow reanalysis for Italy (300k+ km2) covering a transitional continental-to-Mediterranean region where snow plays an important, but still poorly constrained societal and ecological role. IT-SNOW provides ∼500-m, daily maps of Snow Water Equivalent (SWE), snow depth, bulk-snow density, and liquid water content for the period 01/09/2010–31/08/2021, with future updates envisaged on a regular basis. As the output of an operational chain employed in real-world civil-protection applications (S3M Italy), IT-SNOW ingests input data from thousands of automatic weather stations, snow-covered-area maps from Sentinel 2, MODIS, and H-SAF products, and maps of snow depth from the spazialization of 350+ on-the-ground snow-depth sensors. Validation using Sentinel-1-based maps of snow depth and a variety of independent, in-situ snow data from three focus regions (Aosta Valley, Lombardia, and Molise) shows little to none mean bias compared to the former, and Root Mean Square Errors on the order of 30 to 60 cm and 90 to 300 mm for in-situ, measured snow depth and Snow Water Equivalent, respectively. Estimates of peak SWE by IT-SNOW are also well correlated with annual streamflow at the closure section of 102 basins across Italy (0.87), with ratios between peak SWE and annual streamflow that are in line with expectations for this mixed rain-snow region (22 % on average). Examples of use allowed us to estimate 13.70 ± 4.9 Gm3 of SWE across the Italian landscape at peak accumulation, which on average occurs on the 4th of March. Nearly 52 % of mean seasonal SWE is accumulated across the Po river basin, followed by the Adige river (23 %), and central Apennines (5 %). IT-SNOW is freely available with the following DOI: https://doi.org/10.5281/zenodo.7034956 (Avanzi et al., 2022b) and can contribute to better constraining the role of snow for seasonal to annual water resources – a crucial endevor in a warming and drier climate.
Abstract. The vulnerability of flood-prone areas is determined by the susceptibility of the exposed assets to the hazard. It is a crucial component in risk assessment studies, both for climate change adaptation and disaster risk reduction. In this study, we analyse patterns of vulnerability for the residential sector in a frequently hit urban area of Milan, Italy. The conceptual foundation for a quantitative assessment of the structural dimensions of vulnerability is based on the modified source–pathway–receptor–consequence model. This conceptual model is used to improve the parameterization of the flood risk analysis, describing (i) hazard scenario definitions performed by hydraulic modelling based on past event data (source estimation) and morphological features and land-use evaluation (pathway estimation) and (ii) the exposure and vulnerability assessment which consists of recognizing elements potentially at risk (receptor estimation) and event losses (consequence estimation). We characterized flood hazard intensity on the basis of variability in water depth during a recent event and spatial exposure also as a function of a building's surroundings and buildings' intrinsic characteristics as a determinant vulnerability indicator of the elements at risk. In this sense the use of a geographic scale sufficient to depict spatial differences in vulnerability allowed us to identify structural vulnerability patterns to inform depth–damage curves and calculate potential losses from mesoscale (land-use level) to microscale (building level). Results produces accurate estimates of the flood characteristics, with mean error in flood depth estimation in the range 0.2–0.3 m and provide a basis to obtain site-specific damage curves and damage mapping. Findings show that the nature of flood pathways varies spatially, is influenced by landscape characteristics and alters vulnerability spatial distribution and hazard propagation. At the mesoscale, the “continuous urban fabric” Urban Atlas 2018 land-use class with the occurrence of at least 80 % of soil sealing shows higher absolute damage values. At microscale, evidence demonstrated that even events with moderate magnitude in terms of flood depth in a complex urbanized area may cause more damage than one would expect.
<div> <div> <div> <p><strong>Context. </strong>Water is the most proximal concept for all human beings, and yet many of us struggle to realize the importance of proper water resources management, as well as the breadth and depth of growing water conflicts in a warming climate. This is particularly true for young students, since they will see impacts of climate change first-hand.</p> <p><strong>Goal and recipients. </strong>Within &#8220;Water and Us&#8221;, we educate next generations on the correct (and incorrect) ways in which water is currently managed. This is done to instill the need for a sustainable use of water resources, in the hope that this will help neutralize incorrect policies, economic conflicts and tensions around water. Current recipients are high school students, but we are also experimenting with elementary students and adult audiences.</p> <p><strong>Method.</strong> Rather than providing ready-to-use recipes or a traditional, lecture-style approach, the signature of Water and Us is to put students at the center of a participatory, laboratory- based process geared towards the evaluation of new solutions for water management. Through a process of learning by doing, we reflect on recurring questions like <em>&#8220;what does it mean to manage water resources? How do human activities affect the water cycle? What are the expected impacts of climate change and the associated solutions for sustainable development in a warmer world?&#8221;.</em></p> <p>Structure. The first module is dedicated to understanding the water cycle &#8211; a cycle that will be &#8220;rewritten&#8221; with the students themselves based on their own experience and knowledge. The goal is to show how the same term &#8220;water resource&#8221; has many different meanings, sometimes even in conflict with each other. The second module will be dedicated to to sharpen students&#8217; understanding of the most common and recurring terms and expressions surrounding the issue of water resources and climate change: an opportunity to confer a more precise meaning to expressions like the Paris Agreement, droughts, water conflicts, Next Generation EU, which are used almost daily in the media but that are not always easy to place in the overall picture. The <em>third </em>module, finally, is a synthesis of the previous ones and focuses on the still little-known theme of socio-political, juridical, and technical water conflicts and how they are increasingly fuelled by the effects of climate change.</p> <p>Innovativeness. Each meeting starts with a real-life story, lasting about 20 minutes, and then moves on with a workshop lasting about 30 minutes, so that listeners can immediately put themselves at the centre of the problem. This method promotes awareness on the issue of water management and stimulates the design of consensus-based, innovative solutions for community&#8217;s benefit.</p> <p>In this presentation, we will share lessons learned by the first pilots of &#8220;Water and Us&#8221; in Liguria, Italy, as well as plans to upscale and export this experience to other audiences.</p> </div> </div> </div>
<p>Extensive knowledge of hydrological processes occurring during droughts is required for a sustainable water resources management, especially in a changing climate. Large-sample analyses are particularly informative in this sense, because they allow us to extend the understanding beyond specific catchments. Data from experimental catchments and observatories showed that water stored within the catchment can sustain evapotranspiration and discharge during dry periods and previous multi-catchments studies on droughts highlighted the storage control on hydrological drought characteristics, through the quantification of hydrological signatures and catchment properties. However, few studies have explicitly quantified across different climates and catchment types the contribution of subsurface storage changes (&#916;S) in the annual water balance, in drought propagation (from the meteorological to the hydrological one), and in drought recovery. Here, we assembled a dataset blending ground-based precipitation and discharge data, and remote-sensed actual evapotranspiration data to study drought propagation and recovery in a water-balance and data-based perspective for 102 catchments across various climatic and morphological properties in Italy. This region experienced severe drought years over the study period (hydrological years 2010 - 2019), as detected by the Standardised Precipitation Index for an accumulation period of 12 months. This large-sample analysis revealed that (i) subsurface storage is a non-negligible term in the annual water balance, as &#916;S mean annual value represents on average the 11% of precipitation across the catchments, (ii) its depletion sustains discharge during drought years (median annual &#916;S anomaly equal to -97 mm for catchments attenuating the hydrological drought with respect to the meteorological one), and (iii) it recovers from precipitation deficits over shorter time scales than evapotranspiration, but similar as those of discharge. These findings emphasize the need of explicitly considering subsurface storage in drought analyses to properly inform policy makers and water managers, as it is a key driver in drought propagation and recovery across climates and catchment properties.</p>
<p>Evaluating historical extreme flood events is fundamental due to their socioeconomic impacts. In this context, the spatial distribution of the event has a key role and the univariate approach, based on the analysis of local flood frequency on a single site, is not the proper one.</p><p>For this reason, in the recent past, an increasing amount of research has focused on the regional characterization of flood events, trying to describe their temporal and spatial distribution. The main objective of this work is the comparison of two different methods widely used for the selection and characterization of spatially distributed flood events for risk assessment purposes. Both methods were applied to the Italian territory and compared in terms of parameters used, results obtained, and technical analogies and differences.&#160;</p><p>The two methodologies reveal similar results, comparable with a list of extreme events produced as a collection of historical flood reports. The results show that floods co-occurring in several basins are unevenly distributed, with a higher number of selected events occurred in Northern and Central Italy, where the largest Italian basins are located.</p>
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