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Soil erosion and hydrogeological risk are critical phenomena gaining increased recognition within the scientific community. Although these occurrences are naturally occurring, human activities can exacerbate their impacts. For example, deforestation consistently amplifies soil erosion. This study examines two distinct forest management strategies aimed at addressing soil erosion: the Banded Standards Method (BSM) and the Scattered Standards Method (SSM). We conducted a field experiment in two test areas located in central Italy, with one area employing the BSM and the other implementing the SSM. Two soil erosion plots were established, representing prototypes of a novel erosion monitoring apparatus called the Natural Erosion Trap (NET), or Diabrosimeter, specifically designed for forest environments. At regular intervals, particularly after significant storm events, sediment and leaf litter accumulated within the erosion plots were collected, dried, and weighed to quantify erosion rates and assess the efficacy of the silvicultural methods under investigation. The results revealed a 30.72% reduction in the eroded material with BSM compared to SSM, underscoring BSM's ability to mitigate potential hazards and preserve environmental integrity. [ABSTRACT FROM AUTHOR]

Effective proxy selection in hydrological processes is crucial in several applications. This study investigates the role of sub-basins in hydrological response, which remains unclear. Our focus is on exploring feature importance measures to identify influential sub-basins in a flood forecasting system. We use the Tiber River basin as a case study and employ a synthetic flood hydrograph dataset, consisting in approximately 20 000 simulated annual maximum hydrographs across 39 sub-basins and the basin outlet. Through this study, we present a proof of concept for ranking sub-basins based on their contribution to basin response using six feature importance measures. The results reveal eight influential sub-basins and provide guidance for strategically installing measurement instrumentation for an efficient and cost-effective flood early warning system. [ABSTRACT FROM AUTHOR]

The water-regulating capacity of nature-based solutions (NBSs) plays a crucial role in providing a full range of ecosystem services and enhancing the resilience of urban systems. This work focuses on the hydrological performance of a particular NBS, the so-called blue-green roof (BGR). The BGR is designed to collect infiltrated rainfall in a water storage layer beneath the soil to support vegetation maintenance, enhance evapotranspiration and cooling, and minimize runoff and drainage system load. The study aims to evaluate the hydrological performance of the BGR at global and event scale and, for the first time, to model climatic factors (easy to measure using common sensors) that affect its stormwater retention capacity. The data collected over 2 years and 2 months at a 5-min resolution from a pilot study in Central Italy were analysed. Additionally, a new climatic index called AWWP-x (Antecedent Wet Weather Period index) was introduced and calculated. Results show that the BGR has an overall relevant retention rate (67.1%), although the value depends on the rainfall of the observed period. Approximately 50% of the rainfall events did not produce any runoff, and during the dry season, all events were totally absorbed by the BGR. Four climatic variables were identified as significant factors for predicting BGR retention performance (R2 = 0.50). The results suggest that AWWP-130 (number of days to reach 130 mm cumulative precipitation) could be a possible proxy for the BGR stormwater retention rate. In general, this study demonstrates the potential for evaluating, planning, and designing NBSs by considering the annual and interannual climatic variability of the investigated specific location. [ABSTRACT FROM AUTHOR]

This study presents a coupled application of hydrological and hydraulic models to reconstruct a flash flood event of the ungauged watercourse of Wadi Deffa, Algeria. The objective is to compare the performances of three hydrological models (rational method, EBA4SUB, HEC-HMS) and two hydraulic bidimensional models (HEC-RAS 2D, FLO-2D) by using the Volunteered Geographic Information (VGI) data. The comparison between the observed and simulated flood areas showed satisfactorily performance of the EBA4SUB-FLO-2D approach compared to the other approaches. The analysis of the observed and simulated flood depths showed a good estimate using the approaches EBA4SUB-FLO-2D and EBA4SUB-HEC- RAS 2D. The best estimate of the two flood depth approaches is attributed to the hydrological model EBA4SUB in estimating the peak flow. The results demonstrate that the EBA4SUB-FLO-2D modeling approach can provide reliable data for the management of flood risks in the ungauged watersheds of the southwest region of Algeria. [ABSTRACT FROM AUTHOR]

Of all the substances that can be present in water intended for human consumption, arsenic (As) is one of the most toxic. Many treatment technologies can be used for removing As from water, for instance, adsorption onto iron media, where commercially available adsorbents are removed and replaced with new media when they are exhausted. Since this is an expensive operation, in this work, a novel and portable plant for regenerating iron media has been developed and tested in four real case studies in Central Italy. The obtained results highlight the good efficiency of the system, which was able, from 2019 to 2023, to regenerate the iron media and to restore its capability to adsorb the As from water almost entirely. Indeed, when the legal threshold value of 10 μg/L is exceeded, the regeneration process is performed and, after that, the As concentration in the water effluent is at the minimum level in all the investigated case studies. [ABSTRACT FROM AUTHOR]

In the last decades, the Rif area in Morocco has been frequently affected by soil erosion due to intense rainfall events. In order to help farmers improve their lives and avoid damages caused by this phenomenon, a management project (the MCA Project) aiming to grow fruit trees has been realized. The objective of this study was to evaluate, in three provinces of Morocco, the effect on the hydrological response of selected erosion control management techniques combined with olive tree plantations. The investigated variables were the final infiltration (If), the imbibition of rainwater (Pi), the runoff coefficient (Kr), and the soil detachment (D). In particular, for each investigated soil utilization, three replications of a rain simulation test (80 mm/h) and soil sampling were conducted. Results for surface conditions demonstrate that under vegetation in matorral and fallow, the surface is covered at more than 75% with a high content of organic matter (OM) at 4.5% and 2.6%, respectively. Despite the compaction observed in those land uses, the surface area opened exceeded 90% in the study area. Regarding the soils physical properties, they were rich in silt at more than 40%; the rate of porosity is high where bulk density is low. At the Taounate site, low porosity was at 62% in fallow and at 55% in plowing, with high densities of 1.01 g/cm2 and 1.2 g/cm2, respectively. Tests also demonstrate that vegetation has an important role in moisture conservation in the depths of 0 to 10 cm at all sites with macroagregate stability (MA%) compared to plowing sites. In terms of soil hydrology, vegetation reduces the runoff because, under matorral (it was at 0%), it avoids soil erosion. [ABSTRACT FROM AUTHOR]

Understanding the response of a catchment is a crucial problem in hydrology, with a variety of practical and theoretical implications. Dissecting the role of sub-basins is helpful both for advancing current knowledge of physical processes and for improving the implementation of simulation or forecast models. In this context, recent advancements in sensitivity analysis tools could be worthwhile for bringing out hidden dynamics otherwise not easy to distinguish in complex data driven investigations. In the present work seven feature importance measures are described and tested in a specific and simplified proof of concept case study. In practice, simulated runoff time series are generated for a watershed and its inner 15 sub-basins. A machine learning tool is calibrated using the sub-basins time series for forecasting the watershed runoff. Importance measures are applied on such synthetic hydrological scenario with the aim to investigate the role of each sub-basin in shaping the overall catchment response. This proof of concept offers a simplified representation of the complex dynamics of catchment response. The interesting result is that the discharge at the catchment outlet depends mainly on 3 sub-basins that are consistently identified by alternative sensitivity measures. The proposed approach can be extended to real applications, providing useful insights on the role of each sub-basin also analyzing more complex scenarios. [ABSTRACT FROM AUTHOR]

Green roofs have been widely recognized as sustainable nature-based solutions to mitigate floods in urban areas, which, in the last decades, are increasing due to the combination of intense worldwide urbanization and climate change. Besides flood mitigation, green roofs provide additional benefits for the urban environment (e.g., reducing the urban heat island and ensuring energy saving for the underneath building). Moreover, green roofs facilitate the increase of urban biodiversity, attracting different species of small animals, and upgrade the city aesthetic value. Among the different types of green roofs, multilayer blue-green roofs present an additional layer to store water during rainfall events. As part of the Polder Roof field lab project, prototypes of multilayer blue-green roof developed by the Dutch company Metropolder were installed in four Italian cities: Cagliari, Palermo, Perugia, and Viterbo. The four prototypes and the experimental set up are described and the potential benefits of this innovative solution are discussed. Preliminary analyses, from December 2020 to December 2021, enable to estimate runoff reduction and thermal properties of multilayer blue-green roofs, underlying the high potential of this nature-based solution, which allows to retain most of the rainfall events and to mitigate the daily temperature variability. [ABSTRACT FROM AUTHOR]

Monitoring ephemeral and intermittent streams is a major challenge in hydrology. On-site inspections may be impractical in difficult-to-access environments. Motivated by the latest advancements in digital cameras and computer vision techniques, in this work, we describe the development and application of a stage-camera system to monitor the water level in ungauged headwater streams. The system encompasses a consumer-grade wildlife camera with near-infrared (NIR) night vision capabilities and a white pole that serves as reference object in the collected images. The feasibility of the approach is demonstrated through a set of benchmark experiments performed in natural settings. Maximum mean absolute errors between stage-camera and reference data are approximately equal to 2 cm in the worst scenario that corresponds to severe storms with intense rainfall and fog. Our preliminary results are encouraging and support the scalability of the stage-camera in future implementations in a wide range of natural settings. [ABSTRACT FROM AUTHOR]

Rainfall-runoff modelling in small and ungauged basins represents one of the most common practices in hydrology. However, it remains a challenging task for researchers and practitioners, in particular in a climate change context and in areas subject to drought risk. When discharge observations are not available, empirical or event-based approaches are commonly used. However, these schemes can be affected by several relevant assumptions. In the last years, continuous models have been developed in order to address the major drawbacks of event-based approaches. With this goal in mind, in this work we applied a synthetic rainfall generation model (STORAGE; stochastic rainfall generator), constituting the implementation of a modified version of Neymann-Scott rectangular pulse (NSRP) model, and a continuous rainfall-runoff framework (COSMO4SUB; continuous simulation modelling for small and ungauged basins) specifically designed for ungauged basins within a climate change context. The modeling approach allows one to investigate the drought hazard using specific indicators for rainfall and runoff in a small watershed located in southern Italy. Results show that the investigated area seems to tend to a mild/moderate drought in a future time period of approximately 30 years, with a decrease in seasonal water volumes availability in the range of 15–30%. Finally, our results confirm that the continuous modelling is suitable for rapid and effective design simulations supporting drought hazard assessment. [ABSTRACT FROM AUTHOR]

Transients generated by expulsion of air pockets in water pipelines represent a key issue in the management of water systems. Severe pressure surges may arise, with detrimental effects on pipelines, valves and other devices. To analyze the transient and predict the resulting pressure surge, both theoretical and experimental studies have been developed in the literature. However, most studies consider horizontal or vertical pipelines, whereas the actual profile in the real field environment is a sequence of ascending and descending pipes. Consequently, this paper summarizes laboratory experiments carried out on an undulating pipeline, with an orifice fitted at the high point to simulate an air release valve. In the experiments, the orifice diameter, the supply pressure and the air volume entrapped in the descending pipe were varied. In almost all the runs, the peak pressure was achieved during the mass oscillation transient. Water hammer only occurs because of the expulsion of air bubbles within the water column, but generally the effect on the transient is fairly negligible. Results also showed that pressure surges decrease upon increasing the orifice diameter, except for high supply pressure and small-entrapped volume, for which an intermediate 'critical' orifice diameter can be identified. [ABSTRACT FROM AUTHOR]

Monitoring ephemeral and intermittent streams is a major challenge in hydrology. While direct field observations are best to detect spatial patterns of flow persistence, on site inspections are time and labor intensive and may be impractical in difficult-to-access environments. Motivated by latest advancements of digital cameras and computer vision techniques, in this work, we describe the development and application of a stage-camera system to monitor the water level in ungauged headwater streams. The system encompasses a consumer grade wildlife camera with near infrared (NIR) night vision capabilities and a white pole that serves as reference object in the collected images. Time-lapse imagery is processed through a computationally inexpensive algorithm featuring image quantization and binarization, and water level time series are filtered through a simple statistical scheme. The feasibility of the approach is demonstrated through a set of benchmark experiments performed in controlled and natural settings, characterized by an increased level of complexity. Maximum mean absolute errors between stage-camera and reference data are approximately equal to 2cm in the worst scenario that corresponds to severe hydrometeorological conditions. Our preliminary results are encouraging and support the scalability of the stage-camera in future implementations in a wide range of natural settings. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to study the effect of the spatio-temporal changes of Land Use/Land Cover (LULC) within the hydrologic regime of the Cervaro basin in Southern Italy. LANDSAT Thematic Mapper (TM) imagery acquisition dates from 1984, 2003, 2009, and 2011 were selected to produce LULC maps covering a time trend of 28 years. Nine synthetic bands were processed as input data identified as the most effective for the Artificial Neural Network (ANN) classification procedure implemented in this case study. To assess the possible hydrological effects of the detected changes during rainfall events, a physically-based lumped approach for infiltration contribution was adopted within each sub-basin. The results showed an increase in flood peak and a decrease of the rangelands, forests, and bare lands between 1984 and 2011, indicating a good correlation between flooding areas and land use changes, even if it can be considered negligible in basins of large dimensions. These results showed that the impact of land use on the hydrological response is closely related to watershed scale. [ABSTRACT FROM AUTHOR]

One of the main issues arising during the rapid filling of a pipeline is the pressure transient which originates after the entrapped air has been expelled at the air release valve. Because of the difference in density between water and air, a pressure transient originates at the impact of the water column. Many authors have analyzed the problem, both from the theoretical and the experimental standpoint. Nevertheless, mainly vertical or horizontal pipelines have been analyzed, whereas in real field applications, the pipe profile is a sequence of ascending and descending pipes, with air release/vacuum valves at high points. To overcome lack of knowledge regarding this latter case, laboratory experiments were carried out to simulate the filling of an undulating pipeline, initially empty at atmospheric pressure. The pipe profile has a high point where an orifice is installed for air venting, so as to simulate the air release valve at intermediate high point of a supply pipeline. In the experiments, the diameter of the orifice and the opening degree of both upstream and downstream valves were varied, in order to analyze their effect on the pressure transient. The experiments were also carried out with a longer descending pipe, in order to assess the effects on the pressure surge of the air volume downstream of the orifice. [ABSTRACT FROM AUTHOR]

Soil erosion caused by intense rainfall events is one of the major problems affecting agricultural and forest ecosystems. The Universal Soil Loss Equation (USLE) is probably the most adopted approach for rainfall erosivity estimation, but in order to be properly employed it needs high resolution rainfall data which are often unavailable. In this case, empirical formulas, employing aggregated rainfall data, are commonly used. In this work, we select 12 empirical formulas for the estimation of the USLE rainfall erosivity in order to assess their reliability. Moreover, we used a Stochastic Rainfall Generator (SRG) to simulate a long and high-resolution rainfall time series with the aim of assessing its application to rainfall erosivity estimations. From the analysis, performed in the Rieti province of Central Italy, we identified three equations which seem to provide better results. Moreover, the use of the selected SRG seems promising and it could help in solving the problem of hydrological data scarcity and consequently guarantee major accuracy in soil erosion estimation. [ABSTRACT FROM AUTHOR]

One of the main signatures of short duration storms is given by Depth–Duration–Frequency (DDF) curves. In order to provide reliable estimates for small river basins or urban catchments, generally characterized by short concentration times, in this study the performances of different DDF curves proposed in literature are described and compared, in order to provide insights on the selection of the best approach in design practice, with particular reference to short durations. With this aim, 28 monitoring stations with time series of annual maximum rainfall depth characterized by sample size greater than 20 were selected in the Northern part of the Puglia region (South-Eastern Italy). In order to test the effect of the investigated DDF curves in reproducing the design peak discharge corresponding to an observed expected rainfall event, the Soil Conservation (SCS) curve number (CN) approach is exploited, generating peak discharges according to different selected combinations of the main parameters that control the critical rainfall duration. Results confirm the good reliability of the DDF curves with three parameters to adapt on short events both in terms of rainfall depth and in terms of peak discharge and, in particular, for durations up to 30 min, the three-parameter DDF curves always perform better than the two-parameter DDF. [ABSTRACT FROM AUTHOR]

Soil erosion during rainfall events is affected by several factors, such as topography, soil type, land management, and vegetation cover. In this study, a series of tests investigates the influence of selected perennial herbaceous plants with a deep and strong rooting system, called MC1, on runoff generation and soil erosion. The tests on the investigated nature-based solution have been performed in the Cape Fear experimental hillslope with natural and artificial rainfall and for different vegetation heights. For all the experiments, runoff, soil moisture, and erosion data were observed and collected. The results obtained in this study suggest the following conclusions: (1) MC1 is effective in terms of soil erosion reduction already with a minimum vegetation height equal to 30 cm; (2) MC1 maximum efficiency, in terms of soil loss reduction, has been reached for a vegetation height equal to 70 cm; (3) In terms of the eroded material, the use of MC1 allows for a reduction of soil loss up to 300 times higher than the bare soil condition; (4) The use of MC1 allows for a reduction in the runoff coefficient up to 1/3 of the corresponding value in the bare soil condition. [ABSTRACT FROM AUTHOR]

Land use/land cover (LULC) maps are a key input in environmental evaluations for the sustainable planning and management of socio-ecological systems. While the impact of map spatial resolution on environmental assessments has been evaluated by several studies, the effect of thematic resolution (the level of detail of LU/LC typologies) is discordant and still poorly investigated. In this paper, four scenarios of thematic resolutions, corresponding to the four levels of the CORINE classification scheme, have been compared in a real case study of landscape connectivity assessment, a major aspect for the biodiversity conservation and ecosystem service provision. The PANDORA model has been employed to investigate the effects of LULC thematic resolution on Bio-Energy Landscape Connectivity (BELC) at the scale of the whole system, landscape units, and single land cover patches, also in terms of ecosystem services. The results show different types of impacts on landscape connectivity due to the changed spatial pattern of the LULC classes across the four thematic resolution scenarios. Moreover, the main priority areas for conservation objectives and future sustainable urban expansion have been identified. Finally, several indications are given for supporting practitioners and researchers faced with thematic resolution issues in environmental assessment and land use planning. [ABSTRACT FROM AUTHOR]

Devastating floods are observed every year globally from upstream mountainous to coastal regions. Increasing flood frequency and impacts affect both major rivers and their tributaries. Nonetheless, at the small-scale, the lack of distributed topographic and hydrologic data determines tributaries to be often missing in inundation modeling and mapping studies. Advances in Unmanned Aerial Vehicle (UAV) technologies and Digital Elevation Models (DEM)-based hydrologic modeling can address this crucial knowledge gap. UAVs provide very high resolution and accurate DEMs with low surveying cost and time, as compared to DEMs obtained by Light Detection and Ranging (LiDAR), satellite, or GPS field campaigns. In this work, we selected a LiDAR DEM as a benchmark for comparing the performances of a UAV and a nation-scale high-resolution DEM (TINITALY) in representing floodplain topography for flood simulations. The different DEMs were processed to provide inputs to a hydrologic-hydraulic modeling chain, including the DEM-based EBA4SUB (Event-Based Approach for Small and Ungauged Basins) hydrologic modeling framework for design hydrograph estimation in ungauged basins; the 2D hydraulic model FLO-2D for flood wave routing and hazard mapping. The results of this research provided quantitative analyses, demonstrating the consistent performances of the UAV-derived DEM in supporting affordable distributed flood extension and depth simulations. [ABSTRACT FROM AUTHOR]

The growing concentration of population and the related increase in human activities in coastal areas require numerical simulations to analyze the effects of flooding events that might occur in susceptible coastal areas in order to determine effective coastal management practices and safety measures to safeguard the inhabited coastal areas. The reliability of the analysis is dependent on the correct evaluation of key inputs such as return period of flooding events, vulnerability of exposed assets, and other risk factors (e.g., spatial distribution of elements at risk, their economic value, etc.). This paper defines a methodology to assess the effects of flooding events associated with basin run-off and storm surge in coastal areas. The assessment aims at quantifying in economic terms (e.g., loss of assets) the risk of coastal areas subject to flooding events. The methodology proposed in this paper was implemented to determine the areas subject to inundation on a coastal area in Southern Italy prone to hydrogeological instability and coastal inundation. A two-dimensional hydraulic model was adopted to simulate storm surges generated by severe sea storms coupled with intense rainfalls in order to determine the areas subject to inundation in the low-land area along the Adriatic coast object of this study. In conclusion, the economic risk corresponding to four different flooding scenarios was assessed by correlating the exceedance probability of each flooding scenario with the potential economic losses that might be realized in the inundated areas. The results of the assessment can inform decision-makers responsible for the deployment of risk mitigation measures. [ABSTRACT FROM AUTHOR]

Airborne remote sensing systems are increasingly used in engineering geology and geomorphology for studying and monitoring natural hazardous scenarios and events. In this study, we used two remote sensing monitoring techniques, i.e., light detection and ranging (LiDAR) and unmanned aerial vehicles (UAV) to analyze the kinematic evolution of the Montescaglioso landslide (Basilicata, Southern Italy), a large rain-triggered landslide that occurred in December 2013. By comparing pre- and post-event LiDAR and UAV DEMs and UAV orthomosaics, we delineated landslide morphological features and measured horizontal displacements and elevation change differences within landslide body. Analysis of two subsequent post-events digital terrain models (DTMs) also allowed the evaluation of the evolutionary behavior of the slope instability, highlighting no signs of reactivation. The UAV-derived digital surface models (DSMs) were found consistent with the LiDAR-DTMs, but their use was in addition highlighted as highly effective to support geomorphic interpretations and complement LiDAR and field-based data acquisitions. This study shows the effectiveness of combining the two UAV-LiDAR methodologies to evaluate geomorphological features indicative of the failure mechanism and to interpret the evolutionary behavior of the instability process [ABSTRACT FROM AUTHOR]

Estimating economic losses caused on buildings and other civil engineering works due to flooding events is often a difficult task. The accuracy of the estimate is affected by the availability of detailed data regarding the return period of the flooding event, vulnerability of exposed assets, and type of economy run in the affected area. This paper aims to provide a quantitative methodology for the assessment of economic losses associated with flood scenarios. The proposed methodology was performed for an urban area in Southern Italy prone to hydrogeological instabilities. At first, the main physical characteristics of the area such as rainfall, land use, permeability, roughness, and slopes of the area under investigation were estimated in order to obtain input for flooding simulations. Afterwards, the analysis focused on the spatial variability incidence of the rainfall parameters in flood events. The hydraulic modeling provided different flood hazard scenarios. The risk curve obtained by plotting economic consequences vs. the return period for each hazard scenario can be a useful tool for local authorities to identify adequate risk mitigation measures and therefore prioritize the economic resources necessary for the implementation of such mitigation measures. [ABSTRACT FROM AUTHOR]