I2-RED: A Massive Update and Quality Control of the Italian Annual Extreme Rainfall Dataset

The collection and management of hydrological data in Italy has been dealt with at national level, initially, by the National Hydrological Service (SIMN), and at regional level in the last 40 years. This change has determined problems in the availability of complete and homogeneous data for the whole country. As of 2020, an updated and quality-controlled dataset of the historical annual maxima rainfall in Italy is still lacking. The Italian Rainfall Extreme Dataset (I-RED) has recently been created to allow studies to be performed with a homogeneous dataset at a national level. In this paper, the methodological approach adopted to build an improved and quality-controlled version of I-RED (in terms of both the rainfall depth values and the position of the rain gauges) is presented. The new database can be used as a more reliable research support for the frequency analysis of the rainfall extremes. This new I2-RED database contains rainfall annual maxima rainfall of 1, 3, 6, 12 and 24 h from 1916 until 2019, counts 5265 rain gauges and has been corroborated by a re-positioning and elevation-checking of 15% of the stations. A descriptive analysis of the maximum values of the stations, which provides an additional quality check and reveals different intriguing spatial features of Super-Extreme rainfall events, is also presented

A local regression approach to analyze the orographic effect on the spatial variability of sub-daily rainfall annual maxima

In this work we investigate the spatial variability of sub-daily rainfall extremes over Italy considering the influence of local orographic effects. We consider the average annual maxima computed from the recently-released Improved Italian – Rainfall Extreme Dataset (I2-RED) in about 3800 time series with at least 10 years of data (1916–2020 period) and we analyze the orographic effects through a local regression approach which gathers stations in a grid cell-centered area of 1 km resolution. Several constraints are considered to tackle problems determined by the low data density of some areas and by the extrapolation at low/high elevations. Different criteria for selecting the local sample are examined. This work confirms with increased detail previous findings, such as a generally positive gradient of the 24 h average annual maxima and the evidence of negative gradients in large mountainous areas for the 1 h maxima. The use of a local regression approach allows to identify the areas showing the reverse orographic effect, providing material for future investigations on the physical explanation of this evidence. Moreover, the reconstructed maps will allow to apply more accurate approaches in works related to the spatial variability of other rainfall statistics, such as the quantiles required for hydrologic design

ANALISI PRELIMINARE A SCALA URBANA DEL RISPARMIO DI ACQUA POTABILE CONSEGUENTE ALLA CAPTAZIONE E ALL’USO DI ACQUA PIOVANA PER FINI DOMESTICI

• Usare acqua piovana nelle case di Torino ridurrebbe il prelievo d’acqua potabile del 27% annuo • Gli edifici con grandi superfici di tetto pro-capite risultano essere i più efficienti • Il volume ottimale del serbatoio di raccolta è legato all’area del tetto e agli abitanti dell’edificio • È comunque necessaria un’analisi che unisca ai costi economici i vantaggi sociali e ambiental

Water savings and urban storm water management: evaluation of the potentiality of rainwater harvesting systems from the building to the city scale

The main potential benefits of rainwater harvesting, namely water saving and storm water management, are easily evaluable at a building scale when well-known behavioral models are used. However, the evaluation is often more complex at an urban scale, due to a lack of building characteristics and demographic data. In the present paper, we propose a method, which is based on the representative building concept that can be used to quantify the potential benefits of rainwater harvesting at different scales, that is, from the building scale to the district and city scales. Particular attention has been paid to the sizing of the system so that it can be used for different rainwater collection purposes. The method has been applied to the city of Turin (Italy) considering different scenarios: 1) domestic use (e.g., toilet flushing and the washing machine), where buildings are independent of each other, and 2) two public uses (the irrigation of public green areas and street washing), for which we have hypothesized that the rainwater collection takes place at a district scale. The non-potable water saving for domestic use varies across the city from 29% to 62%, according to the characteristics of the buildings, while the reduction of the flow peak conveyed to the sewerage system, during extreme storms, is quite constant (in the 57–67% range). Irrigation and street washing require a lower amount of water, thus about 80% of water can be saved, but the retention efficiency is low, and a slight reduction in the flow peaks can be expected. The aim of the methodology presented in this work is to provide a suitable decision-making tool for policy makers and urban planners to evaluate the capability and efficiency of rainwater harvesting systems for buildings, districts, and cities

Numerical analysis of phreatic levels in river embankments due to flood events

A 2D saturated–unsaturated unsteady-flow numerical study has been carried out to analyze the behavior of levees stressed by flood events. The investigation has involved: i) simulation of the seepage process in a simplified levee over a long period of river flows; ii) the use of a synthetic design hydrograph to be utilized as an alternative to a long-term history of river stages and iii) the influence of the unsaturated parameters on the maximum saturation depth in the levee soil. The results of the analysis show that the statistical properties of the maximum annual phreatic levels are different from those of the corresponding river levels, and that the tested synthetic design-hydrograph is able to guarantee a well-balanced, conservative margin. The analysis shows that the role of the unsaturated zone is also very important. Furthermore, a comparison of the piezometric levels, computed by means of the numerical model, with those computed through simplified solutions, shows that the latter ones may not be conservative