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This study conducted an in-depth analysis of the landslide problem in the loess hill and gully area in northern Shaanxi Province, selecting the loess landslide site in Quchaigou, Ganquan County, Yan'an City, as the object to assess the stability of loess slopes under the conditions of different plant root densities and soil moisture contents through field investigation, physical mechanics experiments and numerical simulation of the GeoStudio model. Periploca sepium, a dominant species in the plant community, was selected to simulate the stability of loess slope soils under different root densities and soil water contents. The analysis showed that the stability coefficient of Periploca sepium natural soil root density was 1.263, which was a stable condition, but the stability of the stabilized slopes decreased with the increase in soil root density. Under the condition of 10% soil moisture content, the stability coefficient of the slope body is 1.136, which is a basic stable state, but with the increase in soil moisture content, the stability of the stable slope body decreases clearly. The results show that rainfall and human activities are the main triggering factors for loess landslides, and the vegetation root system has a dual role in landslide stability: on the one hand, it increases the soil shear strength, and on the other hand, it may promote water infiltration and reduce the shear strength. In addition, the high water-holding capacity and permeability anisotropy of loess may lead to a rapid increase in soil deadweight under rainfall conditions, increasing the risk of landslides. The results of this study are of great significance for disaster prevention and mitigation and regional planning and construction, and they also provide a reference for landslide studies in similar geological environments. [ABSTRACT FROM AUTHOR]

Riparian softwood forests support numerous ecological functions and high biodiversity. In the context of the LIFE+ Traisen project, a non-regulated new riverbed for the lower Traisen River ("New Traisen") was created within an artificially lowered floodplain corridor. Using vegetation monitoring from 2014 to 2021, we determined (i) the role of Solidago gigantea in the establishment of softwood forests, (ii) the habitat parameters (such as flooding height, fine substrate layer thickness, and vegetation cover) that impact the establishment and growth of woody plants, and (iii) the successional phase at which woody plants become established, as well as the potential creation of new germination habitats. During early succession, the softwood species, as light-tolerant pioneer species, colonized the open sites together with S. gigantea and subsequently established a floodplain softwood forest. Unexpectedly, we observed negative forest development only when the S. gigantea cover exceeded 90%. Neither the habitat parameters nor S. gigantea cover significantly impacted tree occurrence. However, we highlight the need for optimum habitat parameters for softwood forest development in early succession phases, ideally before S. gigantea forms dense, monospecific stands. Tailored monitoring strategies are needed to guide the succession of such semi-aquatic habitats toward the development of the desired habitat type. [ABSTRACT FROM AUTHOR]

The riparian vegetation buffer zone is an important component of riverbank ecosystems, playing a crucial role in soil consolidation and slope protection. In this study, the riparian vegetation buffer zones in the Tongnan section of the Fujiang River Basin were selected as the research object. Surveys and experiments were conducted to assess the species composition and the soil and water conservation effectiveness of the riparian vegetation buffer zone. There are a total of 35 species, mainly comprising angiosperms and ferns. The dominant species include Cynodon dactylon, Setaria viridis, Phragmites australis, Erigeron canadensis, and Melilotus officinalis. The Patrick richness index (R) and Shannon–Wiener diversity index (H) are more significantly influenced by the types of land use in the surrounding area, whereas the impact on the Simpson diversity index (D) and Pielou uniformity index (E) is comparatively less pronounced. When the root diameter is less than 0.2 mm, the tensile strength of Cynodon dactylon roots is the highest. For root diameters larger than 0.2 mm, Melilotus officinalis roots exhibit the highest tensile strength. The presence of plant root systems significantly reduces erosion, delaying the time to reach maximum erosion depth by 1–4 min, decreasing erosion depth by 9–38 mm, and reducing the total amount of erosion by 20.17–58.90%. The anti-scouribility effect of Cynodon dactylon is significantly better than that of Setaria viridis. The root system notably enhances soil shear strength, delaying the shear peak by 0.26–4.8 cm, increasing the shear peak by 4.76–11.37 kPa, and raising energy consumption by 23.76–46.11%. Phragmites australis has the best resistance to shear, followed by Erigeron canadensis, with Melilotus officinalis being the least resistant. Therefore, to balance the anti-scouribility effect and shear resistance of plant roots, it is recommended to use a combination of Cynodon dactylon and Phragmites australis for shallow-rooted and deep-rooted planting. This approach enhances the water and soil conservation capacity of riverbanks. [ABSTRACT FROM AUTHOR]

The black soil region of Northeast China is the largest commercial grain production base in China, accounting for about 25% of the total in China. In this region, the water erosion is prominent, which seriously threatens China's food security. It is of great significance to effectively identify the erosion-prone points for the prevention and control of soil erosion on the slope of the black soil region in Northeast China. This article takes the Tongshuang small watershed (Heilongjiang Province in China) as an example, which is dominated by hilly landforms with mainly black soil and terraces planted with corn and soybeans. Based on the 2.5 cm resolution Digital Elevation Model (DEM) reconstructed by unmanned aerial vehicles (UAVs), we explore the optimal resolution for hydrological simulation research on sloping farmland in the black soil region of Northeast China and explore the critical water depth at which erosion damage occurs in ridges on this basis. The results show that the following: (1) Compared with the 2 m resolution DEM, the interpretation accuracy of field roads, wasteland, damaged points, ridges and cultivated land at the 0.2 m resolution is increased by 4.55–27.94%, which is the best resolution in the study region. (2) When the water depth is between 0.335 and 0.359 m, there is a potential erosion risk of ridges. When the average water depth per unit length is between 0.0040 and 0.0045, the ridge is in the critical range for its breaking, and when the average water depth per unit length is less than the critical range, ridge erosion damage occurs. (3) When local erosion damage occurs, the connectivity will change abruptly, and the remarkable change in the index of connectivity (IC) can provide a reference for predicting erosion damage. [ABSTRACT FROM AUTHOR]

Groundwater resources are essential for sustaining ecosystems and human activities, especially under the pressures of climate change. This study employed Electrical Resistivity Tomography (ERT) to assess the impact of Gully Land Consolidation (GLC) engineering on the groundwater hydrological field of small watersheds in the China Loess Plateau (CLP). Results revealed ample subsurface water storage in backfilled areas, primarily migrating along the original river path owing to topographical limitations. Although the distribution patterns of soil moisture in each backfilling block varied slightly, the boundaries of soil moisture content and variation mainly appeared at depths of 8 m and 20 m underground. Significant moisture variation occurred across the 0–20 m underground layers, suggesting the 8–20 m layer could function as a groundwater collection zone in the study area. Human activities could disturb groundwater, altering migration pathways from the original river path. An optimized "Drainage–Conveyance–Barrier" system is proposed to enhance GLC sustainability, involving upstream groundwater level control, midstream soil moisture management, and downstream hydrological connectivity improvement. These findings carry substantial implications for guiding the planning and execution of GLC engineering initiatives. The novelty of this study lies in its application of ERT to provide a detailed spatial and temporal understanding of soil moisture dynamics in the GLC areas. Future research should focus on factors such as soil types and topographical changes for a comprehensive assessment of GLC's impact on small watershed groundwater hydrology. [ABSTRACT FROM AUTHOR]

Rice terraces are crucial for agriculture in China's southern mountainous regions. Land use and land cover change (LUCC) in these areas impact hydrology, but our understanding is limited. In this study, we applied the hydrological assessment tool SWAT to a selected small watershed in the rice terrace-dense area of central Hunan province, China. This study covered four LUCC periods over the past 40 years and was simulated at annual and monthly scales. The results showed that from 1980 to 2020, the areas of paddy fields and drylands decreased by 4.19% and 5.76%, respectively, while the areas of forests and construction land increased by 1.14% and 92.48%, respectively. During the past period, LUCC led to a decrease of 1.77% and 2.49% in runoff and infiltration, respectively, and an increase of 1.03% in ET. However, the water yield remained almost unchanged, indicating that the rice terrace plays a positive role in maintaining stable watershed water yield under LUCC. The results of the sub-basin analysis indicated that the transformation of paddy fields and forests directly determines the trend of hydrological changes. Land use type had the most significant impact on the runoff of the rice-terrace watershed, with the proportions of paddy fields and forests being the most influential factors. Paddy fields significantly influenced the stability of runoff at the watershed scale, suggesting that a high paddy field ratio doesn't ensure sustainability. This study offers valuable insights for managing small watershed terraces, land use planning, and achieving sustainable development in the watershed. [ABSTRACT FROM AUTHOR]

The accurate assessment of discharge in vegetated floodplains during floods is a persistent challenge in river engineering due to the difficulty of acquiring hydraulic data, the variability in vegetation roughness, and the limitations of on-site vegetation characterization. This study introduces a novel approach that combines the continuous slope-area method with LiDAR-derived vegetation data and water depths measured with piezoresistive sensors to evaluate floodplain discharges while considering variations in roughness coefficients induced by arboreal vegetation. We apply this approach to a specific reach of the Piave River in Italy using data collected during the December 2020 flood event. The study demonstrates the capability of the employed measurement system to record extreme floods and emphasizes the importance of including vegetation roughness variations in floodplain discharge calculations. The proposed approach has the potential to be applied in similar scenarios, providing valuable insights for floodplain discharge estimation in vegetated areas. [ABSTRACT FROM AUTHOR]

With the limited availability of water, rain-fed horticulture is important anywhere in the world, especially in countries with arid climates. Therefore, experimental analysis is necessary to see the impact of rain-fed horticulture. Thus, it can be popularized among agricultural people if the strategies achieve better outcomes. This study aims to create a garden without irrigation in the lower regions of the Namangan hills in Uzbekistan using agrotechnical measures based on collecting natural moisture and its long-term storage due to the natural growth of some wild fruits. Soil moisture is the most important factor for plant development in arid and warm regions. The experiments were analyzed from 2013 to 2019 and promising results were found. The plant growth rate after a few years was comparable with that of irrigated agricultural lands. In addition, the yield in non-irrigated gardens was comparable with that of irrigated farms. However, a slight reduction in fruit sizes was observed (10–20%). Furthermore, the terracing and plastic and organic mulching method's efficiency is higher than terracing and organic mulching due to maintaining long-term soil moisture that can be absorbed by the plants (For May 2019, 12.7%, 7.7%, and 6.1% soil moisture levels were found in plastic and organic mulching, organic mulching, and unmulched areas). Overcoming the challenges in rain-fed horticulture experiments requires a holistic approach that integrates scientific knowledge, technological advancements, and sustainable farming practices. Collaboration between researchers, farmers, and policymakers is crucial to develop and disseminate effective strategies that address these challenges and promote resilient rain-fed horticulture systems. Therefore, this study shows the practical possibility of rain-fed horticulture in the northeastern hills in the Namangan region of Uzbekistan. Furthermore, this study provides possible agrotechnologies to practice horticulture without irrigation, which is beneficial for planners, engineers, farm managers, and agribusiness controllers. [ABSTRACT FROM AUTHOR]

Waterlogging and soil salinity issues can be handled using surface or subsurface drainage networks, soil bed elevation, and soil and crop management patterns. A properly operating and maintained drainage system is important for both rural and urban inhabitants to protect lives and property from flooding and high groundwater levels, enhance health conditions, and safeguards water purity, soil salinity, and waterlogging. It also supports and increases crop yields and consequently rural incomes. This study assessed the maintenance condition of the main surface drains (Baloza and ELFarama) located in the Tina Plain (50,000 acres) and a portion of the Southeast El-Kantara regions (25,000 acres) in North Sinai, Egypt, based on the values of the Discharge Capacity Ratio (DCR) and Manning's roughness (n). Ten measurement locations at the drain cross-section were used in the investigation. For the ELFarama Drain, the average values of n and DCR were found to be 0.029 and 86.2%, and for the Baloza Drain, they were 0.032 and 78.6%, respectively. Compared to the design values, the actual Manning's roughness was higher, indicating that the drainage canals' capacities had been reduced and that their upkeep was inadequate. In both drains, sedimentation is present and they need to be maintained, according to the hydrographic surveying results for the actual cross-sections compared to the planned cross-sections. A methodology for the channel maintenance method is presented. For removing vegetation and dredging sediment, a long-boom mechanical hydraulic excavator with a bucket is suggested and to be conducted every two years. To the results of this study, the amount of weed infestation in vegetated channels is the main factor that affects Manning's roughness coefficient value. It is now easier to calculate the proportion of weeds that are submerged in vegetated channels using echo-sound sonar technology. The DCR is an affordable and simple methodology to assess the channel maintenance status for sustainable agriculture. [ABSTRACT FROM AUTHOR]

The easy implementation of ecologically-sound remediation measures for the prompt stabilisation of burned areas may be crucial in Mediterranean forest environments. Manual in situ contour redirection of burned felled logs could aid in soil erosion control and facilitate forest self-regeneration. In this study, a plot-scale runoff/sediment yield survey was conducted in Calabria, Italy, within a Mediterranean pine forest that was affected by an extreme wildfire spanning over 15,000 hectares in the summer of 2021. The hydrological response to 24 rainfall events was analysed after one year of monitoring using nine Wischmeier and Smith 20% sloping plots, which were distributed into three plot-blocks representing different conditions (forested, burned with randomly directed fallen logs, and burned with fallen logs manually redirected along contour lines). The post-fire condition (with felled logs in random positions) exhibited a consistent overall increase (approximately four times) in runoff and sediment yield compared to the pre-fire situation. This degradation effect was mitigated by approximately 30% through the manual redirection of burned logs, which promoted early (three to five weeks) vegetation regeneration (including tree emergence) and enhanced coverage as vegetation spread from the log positions. The results obtained so far provide encouraging insights and warrant further research on steeper slopes and complementary aspects (regulatory, biological, mechanical, economic, etc.). [ABSTRACT FROM AUTHOR]

The Miyanaka Intake Dam fishway underwent improvements in 2012, and we established a new rock-ramp fishway called the Seseragi Fishway, cognizant of its utility as a passage and a habitat for bottom-dwelling and small fish with weak swimming ability. However, the fishway is occasionally submerged by floods, causing sediment accumulation that leads to changes in the vegetation composition. In addition, the arrival and inflow of seeds from upstream and the surrounding areas result in vegetation changes. In this study, the inside and outside of the rock-ramp fishway were divided into eight areas, and the vegetation succession after 2012 was determined. A correlation was observed between the results of fish catch surveys during the same period and the vegetation. Based on these results, we reported on the process of steadily operating the rock-ramp fishway while devising and improving specific management methods. Changes in vegetation, such as an increase in upright vegetation and a decrease in flow-obstructing vegetation, contributed to an increase in the population of bottom-dwellers, weak swimmers, and juvenile fish. The existence and management of appropriate vegetation are important for maintaining fishways inhabited by a variety of fish species. [ABSTRACT FROM AUTHOR]

Urban flood resilience can critically diminish the negative effects of extreme climatic conditions. In recent decades, green infrastructure has been gaining attention among researchers and authorities in terms of its use in urban contexts to enhance urban resilience. This paper tries to provide knowledge on how urban flood resilience has been recently approached through green infrastructure. To do this, the distribution of the topics of interest, authors, and sources/regions of publication are investigated through a systematic review of recent articles. Additionally, the methodological approaches and green infrastructure typologies are examined. Findings show an agglomeration of publications in developed countries. It was also observed that there is a predominance of quantitative methodological approaches and a low connectivity for some hot topics within this field of research (e.g., biodiversity). The most common green infrastructure typologies used in urban flood resilience research are also discussed. It is noticeable that more than half of the papers used general terms (e.g., urban park/open space) to describe green infrastructure rather than using technical typologies providing more information on water flow management characteristics. The outcomes are discussed to give an overview of the latest hotspots and gaps in this field of research, which gives some future directions/expectations to be followed in forthcoming investigations. [ABSTRACT FROM AUTHOR]

On a local and regional level, climate change has had a significant impact on precipitation in the global climatic state. The purpose of this research is to examine the trend and character of urban precipitation in the world's most densely inhabited metropolis. From 1981 to 2020, 40 years of monthly and annual precipitation data from 50 major metropolitan cities throughout the world, based on population statistics, were analysed. The monthly and annual precipitation analysis was done using a homogeneity test, shifting point test, non-parametric Modified Mann Kendall test, and also through computing the magnitude of the trend using Sen's slope estimate. According to the findings of the study, the most homogeneous data was obtained in May (90 %) and the least in September (74%). In 2002, the highest number of breakpoints were found in July (9 cities) and August (8 cities). The month of January has the largest significant positive trend (10 cities) whereas annually it has 20 cities. The monthly maximum of the significant negative trend was discovered in February (4 cities) and annually in 2 main cities. In November, the maximum positive and minimum positive Sen's slope values were found to be 82% and 56%, respectively. The findings of this study are important for future water resource projections, flood or drought predictions, and engineering, scientific, industrial, agricultural, and social studies. The goal of this research is to come up with a good plan for dealing with urban flash floods and droughts as precipitation acts as the key parameter of the hydrological cycle. [ABSTRACT FROM AUTHOR]

The authors also described methods and procedures for quantify soil erosion processes (sediment sampling and water level reading in the storage tanks for total erosion measurements; profilometer, and structure from motion technique for rill erosion measurements). Merlo et al. [[11]], in turn, evaluated the relationship between soil properties (microbial biomass carbon, basal soil respiration, and metabolic quotient) and erosion in areas managed with different cropping system practices under no-tillage in the Brazilian Cerrado. Soil erosion is a process in which soil particles are first detached from the soil surface and then transported by erosive agents such as rainfall, overland flow and channelized flows in rills, ephemeral gullies and gullies [[1], [3]]. 10.3390/w15132378 15 Todisco F., Vergni L., Ortenzi S., Di Matteo L. Soil Loss Estimation Coupling a Modified USLE Model with a Runoff Correction Factor Based on Rainfall and Satellite Soil Moisture Data. [Extracted from the article]

The devastating socioeconomic impacts of recent droughts have intensified the need for improved drought monitoring in South Africa (SA). This study has shown that not all indices can be universally applicable at all regions worldwide, and there is no single index that can represent all aspects of droughts. The aim of this study was to review the performance and applicability of the Palmer drought severity index (PDSI), surface water supply index (SWSI), vegetation condition index (VCI), standardised precipitation index (SPI), standardised precipitation evapotranspiration index (SPEI), standardised streamflow index (SSI), standardised groundwater index (SGI), and GRACE (Gravity Recovery and Climate Experiment)-based drought indices in SA and provide guidelines for selecting feasible candidates for integrated drought monitoring. The review is based on the '2016 World Meteorological Organisation (WMO) Handbook of Drought Indicators and Indices' guidelines. The PDSI and SWSI are not feasible in SA, mainly because they are relatively complex to compute and interpret and cannot use readily available and accessible data. Combining the SPI, SPEI, VCI, SSI, and SGI using multi-index or hybrid methods is recommended. Hence, with best fitting probability distribution functions (PDFs) used, and with an informed choice between parametric and non-parametric approaches, this combination has the potential for integrated drought monitoring. Due to the scarcity of groundwater data, investigations on the use of GRACE-based groundwater drought indices must be carried out. These findings may contribute to improved drought early warning and monitoring in SA. [ABSTRACT FROM AUTHOR]

The purpose of the study was to collect experimental data on the vertical structure of sediment fluxes during the wave crest and trough phase over sloped bed. The first stage of the experimental work included measurements of these fluxes using the particle image method, while the second stage, measurements of sediment transport rates and granulometric distributions of sediments collected in the traps on both sides of the sloped initial area. The experimental data were compared both with the results collected previously over flat bed as well as with a theoretical analysis based on a three-layer model of graded sediment transport. This model does not take into account the effects related to the presence of fine and very fine fractions and neglects the effects related to the bed slope, i.e., to gravitational forces and to additional pressure gradients. Hence, a modification of this model is proposed that is based on four coefficients that corrected for sediment fluxes over sloped bed. The consistency of the sediment transport calculations according to the modified model with measurements was achieved within plus/minus a factor of 2 of the measurements. [ABSTRACT FROM AUTHOR]

Macroalgae are an essential basic ingredient for many industries from which numerous derived products with great economic value are manufactured. Each macroalga has a unique composition that might provide specific physical and chemical information that can be used as markers for authentication. Their compositions may differ depending on different factors, including geographical regions. Unsupervised exploratory techniques, namely principal component analysis (PCA) and hierarchical cluster analysis (HCA), and nonparametric supervised methods including support vector machines (SVMs) and random forests (RFs), were applied to the Vis-NIR spectroscopic data to standardize the quality of macroalgae based on three regional zones in Indonesia (Western, Central, Eastern). A total of 35 macroalgae samples from six islands in Indonesia were analyzed. The PCA and HCA results present a tendency for the samples to be distributed and clustered according to the type of their species. Meanwhile, the SVM successfully classified samples based on their regional zones, and when combined with five-fold cross-validation, acquired an accuracy of 82%. The RF model algorithm obtained an accuracy of 100%, 80%, and 82% for the training, test, and five-fold cross-validation, respectively. [ABSTRACT FROM AUTHOR]

Water pollution from human activities is largely a result of the discharge of wastewater and industrial waste into rivers. Phytoremediation, the technique that uses plants to remove pollutants from the polluted waters, is a growing field of research because of its various environmental advantages. This study aims to evaluate the efficiency of a constructed wetland in removing pollutants and treating the polluted waters of the Litani River in Lebanon, by means of two aquatic plants, Phragmites australis and Sparganium erectum. Results showed that the levels of the physicochemical and biological parameters measured on water samples at downstream of the wetland were lower than those obtained at upstream. Results revealed that average removal efficiency was 41% for chemical oxygen demand (COD), 54% for biological oxygen demand (BOD5), 97% for nitrate (NO3−), 40% for nitrite (NO2−), 67% for phosphate (PO43−), while it was negative (−62%) for sulfate (SO42−), indicating an increase in sulfate content in the treated effluent returning to the river. On the other hand, most of the effluent chemical and biological characteristics were within the provisional discharge limits of effluent to water body set by the Ministry of Environment (MoE) and Lebanese Wastewater Reuse Guidelines of the Food and Agricultural Organization of the United Nations (FAO). Statistical analyses also showed significant variations (p < 0.5) among the two sampling sites along the wetland. Our findings clearly demonstrate that phytoremediation is a viable solution to remove pollutants in a competitive environment and improve the quality of contaminated waters by acting as a sink for various contaminants. The gained experience may be scalable to other sites and environments across the country. [ABSTRACT FROM AUTHOR]

Land use and climate change always induce significant changes in various parameters of the hydrologic cycle (e.g., surface runoff, infiltration, evapotranspiration). The Wadi El-Assiuti downstream area in the Eastern Desert of Egypt is one of the most promising areas for development that is suffering from insufficient water availability and inadequate water quality for different purposes. The main goal of this research is to evaluate the changes in groundwater quality, land use, and climate in association with geology and flooding during three periods within the years 1997–2019 in the downstream portion of Wadi El-Assiuti in the Eastern Desert of Egypt, using spatiotemporal variation associated with groundwater hydrochemical analysis and GIS techniques. About 133 groundwater samples were collected to examine groundwater quality changes over time. Different groundwater quality indices were calculated, and the results show that TDS levels of groundwater in the study area ranged between 1080–2780 mg/L, 672–4564 mg/L, and 811–6084 mg/L, while SAR levels varied within 6.15–15.34, 1.83–28.87, and 1.43–30.57 for the years 1997, 2007, and 2019, respectively. Both RSBC and SSP values exhibited significantly increasing trends over time. KR values were within 1.36–4.06 in 1997, 0.58–14.09 in 2007, and 0.35–14.92 in 2019; MAR values were within 6.9–45.2 in 1997, 20.79–71.5 in 2007, and 17.71–75.81 in 2019; and PI values were within 60.16–83 in 1997, 45.56–101.03 in 2007, and 42.51–148.88 in 2019. Across the entire study area, ongoing land use changes increased from 1.1% in 1997 to 4.1% in 2019. Findings pointed to the significant contribution of the deep Nubian Sandstone Aquifer to the groundwater aquifer at Wadi El-Assiuti through fractures and deep faults. Given the climatic conditions from 1997–2019, these changes may have affected water quality in shallow aquifers, especially with increasing evaporation. Realizing the spatiotemporal variation of the aquifer recharge system, land use development, and climate change clearly would help in water resource management. This study revealed that flooding events, deep-seated geologic structures, and land use development associated with human activities have the highest impact on groundwater quality. [ABSTRACT FROM AUTHOR]

The discharge of natural rivers is one of the important hydrological factors that are considered when responding to ice-flood disasters during ice periods. Traditionally, holes need to be dug along the cross-section on the ice cover to gauge velocity distributions along the flow depth at each hole, and to calculate the cross-sectional flow discharge by integrating velocity profiles over the entire area. This method is time consuming, costly, and inefficient. The discharge measurement can be improved using the sectional flow-depth distribution and stream-tube methods. However, the selection of both the depth-averaged–velocity-estimation method and the typical survey-point position in the cross-section affects the estimation accuracy. This study first compared the estimation methods of the depth-averaged velocity, such as the one-, two-, three-, and six-point methods, and their estimation accuracy. Furthermore, the variations in relative-unit discharge distributions in common channels with cross-sectional topographies were analyzed, and the effects of the cross-section characteristic coefficient and typical survey-point position on the flow-discharge estimation accuracy were compared. The results show that the average errors of the depth-averaged velocity estimated by the one-point method at 0.5H, new three-point method, and six-point method were 1.96%, 1.22%, and 0.45%, respectively. The new three-point method is recommended if measurement workload and accuracy are key considerations. The cross-section characteristic coefficient is considered to be 0.5 and 0.25 for the natural river and artificial channel, respectively, and the maximum-flow-depth position in the mainstream area of the cross-section is selected as the typical survey-point position. Thus, the flow-discharge estimation accuracy can be improved. In conclusion, this study provides an improved stream-tube method for the measurement of flow discharge and velocity distribution in ice periods, which can be used as a reference during practical applications. [ABSTRACT FROM AUTHOR]

Ecohydraulic models have commonly used the flow velocity, water depth, and substrate type (i3 models) as the three fundamental determinants of the distribution of freshwater biota, but a fourth determinant has largely been neglected: stream vegetation. In this study, we provide the hydraulic and habitat information required to develop vegetation-adapted ecohydraulic models (i4 models) in streams. We calculated drag forces and Manning's roughness coefficients (nV) for nine types of submerged, emergent, and overhanging stream vegetation. In addition, we developed habitat suitability curves (HSCs) for benthic macroinvertebrates for these stream vegetation types. Hydraulic modules can now be upgraded to simulate stream vegetation by including the vegetation-adapted nV values within an additive approach in which nV is added to the n value of the inorganic substrate to which the vegetation is rooted. Habitat modules can also be upgraded to include macroinvertebrate HSCs for stream vegetation, again by adding the vegetation-adapted habitat suitability to that of the inorganic substrate to which the vegetation is rooted. In combination, i4 ecohydraulic models (including vegetation) can now be designed and applied, and we suggest that ecohydraulic research should further focus on including a fifth variable (water temperature) to ultimately advance to i5 ecohydraulic models that will optimally simulate the hydroecological reality. [ABSTRACT FROM AUTHOR]

Crop yield prediction is critical for investigating the yield gap and potential adaptations to environmental and management factors in arid regions. Crop models (CMs) are powerful tools for predicting yield and water use, but they still have some limitations and uncertainties; therefore, combining them with machine learning algorithms (MLs) could improve predictions and reduce uncertainty. To that end, the DSSAT-CERES-maize model was calibrated in one location and validated in others across Egypt with varying agro-climatic zones. Following that, the dynamic model (CERES-Maize) was used for long-term simulation (1990–2020) of maize grain yield (GY) and evapotranspiration (ET) under a wide range of management and environmental factors. Detailed outputs from three growing seasons of field experiments in Egypt, as well as CERES-maize outputs, were used to train and test six machine learning algorithms (linear regression, ridge regression, lasso regression, K-nearest neighbors, random forest, and XGBoost), resulting in more than 1.5 million simulated yield and evapotranspiration scenarios. Seven warming years (i.e., 1991, 1998, 2002, 2005, 2010, 2013, and 2020) were chosen from a 31-year dataset to test MLs, while the remaining 23 years were used to train the models. The Ensemble model (super learner) and XGBoost outperform other models in predicting GY and ET for maize, as evidenced by R2 values greater than 0.82 and RRMSE less than 9%. The broad range of management practices, when averaged across all locations and 31 years of simulation, not only reduced the hazard impact of environmental factors but also increased GY and reduced ET. Moving beyond prediction and interpreting the outputs from Lasso and XGBoost, and using global and local SHAP values, we found that the most important features for predicting GY and ET are maximum temperatures, minimum temperature, available water content, soil organic carbon, irrigation, cultivars, soil texture, solar radiation, and planting date. Determining the most important features is critical for assisting farmers and agronomists in prioritizing such features over other factors in order to increase yield and resource efficiency values. The combination of CMs and ML algorithms is a powerful tool for predicting yield and water use in arid regions, which are particularly vulnerable to climate change and water scarcity. [ABSTRACT FROM AUTHOR]

Diatom identification and counting by light microscopy of permanently embedded acid-cleaned silicate shells (frustules) is a fundamental method in ecological and water quality investigations. Here we present a new variant of this method based on "digital virtual slides", and compare it to the traditional, non-digitized light microscopy workflow on freshwater samples. We analysed three replicate slides taken from six benthic samples using two methods: (1) working directly on a light microscope (the "traditional" counting method), and (2) preparing "virtual digital slides" by high-resolution slide scanning and subsequently identifying and labelling individual valves or frustules using a web browser-based image annotation platform (the digital method). Both methods led to comparable results in terms of species richness, diatom indices and diatom community composition. Although counting by digital microscopy was slightly more time consuming, our experience points out that the digital workflow can not only improve the transparency and reusability of diatom counts but it can also increase taxonomic precision. The introduced digital workflow can also be applied for taxonomic inter-expert calibration through the web, and for producing training image sets for deep-learning-based diatom identification, making it a promising and versatile alternative or extension to traditional light microscopic diatom analyses in the future. [ABSTRACT FROM AUTHOR]

This study seeks to clarify the content characteristics, spatial distribution, potential sources and ecological risks of nitrogen, phosphorus and some heavy metals (As, Hg, Cd, Cr, Cu, Pb, Zn and Ni) in the sediments of Yueliang Lake. Nitrogen, phosphorus and heavy metals were analyzed in the surface and core sediments of Yueliang Lake. The present situation of heavy metal pollution and the degree of potential ecological risk in sediments was evaluated by the geo-accumulation index (Igeo) and potential ecological risk index (RI). The correlation (CA) and principal component analysis (PCA) methods were used to analyze the potential sources of the main pollutants among the heavy metals. The results show that the total nitrogen (TN = 2305 mg/kg) and total phosphorus (TP = 530 mg/kg) in the surface sediments of Yueliang Lake are at medium and low levels, respectively. The average content of organic matter was 2.17%, and the nutrient ratio was 6.90–11.92, which was significantly higher in the northwest than in the middle and east of Yueliang Lake, indicating that the organic matter was a mixture of endogenous aquatic plants and exogenous terrestrial plants in the sediments. From two evaluation indices (RI and Igeo) calculated using element contents, the heavy metals in the surface sediments were at a moderate ecological risk level. The level of Hg was moderately polluted, Pb and Cd were at the mildly polluted level, and Cu, Zn, As, Cr and Ni were at pollution-free levels. Except for Hg, the other elements in the core sediment are basically not polluting, and the whole is at the level of slight ecological risk. The sources of heavy metals in the sediments are roughly divided into three categories. The first category is natural sources, including Cr, Ni, As, Zn and Cu. The second category includes Cd and Hg and the main sources are highly related to energy development and agricultural activities. The third category is light Pb pollution caused by vehicular traffic and coal-related industrial activities. Therefore, the pollution problems caused by tourism development and agricultural activities should be considered in the future development of the Yueliang Lake area. [ABSTRACT FROM AUTHOR]

The diversion of large flows of water in open channels, which exceed safe water levels, into water storage systems is the focus of this paper. We focused upon the middle route of the South-to-North Water Transfer Project and the ancient canal gate 4 drainage pool. We estimated the water storage quantity and the amount of compensation this offered. We used the improved PID algorithm to the study 20 disturbance flow water pipe heads. The results show that the storage compensation algorithm can suppress the fluctuation of water level to a certain extent, but, for the disturbance caused by large flows, the maximum fluctuation of water level in front of Shahei sluice gate that the storage compensation control algorithm is capable of is more than 0.3 m, which is much larger than the water level constraint of the middle line channel pool, where the rate of the drop in water level should not exceed 0.15 m per hour. However, in the case of large flow disturbance, the variation of water level in front of all the control gates in the study area is not more than 0.1 m, which meets the severe water level constraint of the middle line project, and the water level control effect is good, which protects the operation safety of the canal pool. [ABSTRACT FROM AUTHOR]

Low fluvial terraces present azonal spatialization, encompassing several geomorphological compartments and climate zones in Brazil. Their genesis is directly related to river dynamics. When influenced by allogenic forces, such as Holocene climate pulses, it results in channel incision and posterior abandonment of the floodplain. Relatively plain landforms at different altimetric levels identified between the current floodplain and hillslope (low river terraces) are a result of these processes. Previous works using Optically Stimulated Luminescence (OSL) in low terraces of several rivers in Brazil have indicated morpho-chronologic similarities between depositional events, raising the hypothesis of feedbacks and fluvial adjustments relatively simultaneous to Holocene climate events. Considering these dynamics, this study employed OSL to obtain absolute dating information for 114 samples taken from distinct levels of the low river terraces of 30 rivers in Brazil, integrating the database of the IG-UNICAMP laboratory of Geomorphology and Environmental Analysis. Based on the data and statistical analysis (cluster and correlation analysis), this study aimed to identify relationships between different variables which might have controlled spatial homogenous and heterogeneous feedbacks during distinct paleoenvironmental contexts. The proposed methodology tested a fundamental hypothesis of the regional climatic geomorphology, and the results obtained may contribute to future discussions on the relationship between low river terraces and anthropic occupation. [ABSTRACT FROM AUTHOR]

The many hydrodynamic implications associated with the geomorphological evolution of braided rivers are still not profoundly examined in both experimental and numerical analyses, due to the generation of three-dimensional turbulence structures around sediment bars. In this experimental research, the 3D velocity fields were measured through an acoustic Doppler velocimeter during flume-scale laboratory experimental runs over an emerging sand bar model, to reproduce the hydrodynamic conditions of real braided rivers, and the 3D Turbulent Kinetic Energy (TKE) components were analyzed and discussed here in detail. Given the three-dimensionality of the examined water flow in the proximity of the experimental bar, the statistical analysis of the octagonal bursting events was applied to analyze and discuss the different flume-scale 3D turbulence structures. The main novelty of this study is the proposal of the 3D Hole Size (3DHS) analysis, used for separating the extreme events observed in the experimental runs from the low-intensity events. [ABSTRACT FROM AUTHOR]

Riparian phreatophytes in hyperarid areas face selection pressure from limiting groundwater availability and high transpiration demand. We examined whole-plant water use and hydraulic traits in Populus euphratica and Tamarix ramosissima seedlings to understand how they adapt to groundwater variations. These species coexist in the Tarim River floodplain of western China. Measurements were performed on 3-year-old seedlings grown in lysimeters simulating various groundwater depths. P. euphratica had relatively greater leaf area-specific water use due to its comparatively higher sapwood area to leaf area ratio (Hv). A high Hv indicates that its sapwood has a limited capacity to support its leaf area. P. euphratica also showed significantly higher leaf-specific conductivity (ksl) than T. ramosissima but both had similar sapwood-specific conductivities (kss). Therefore, it was Hv rather than kss which accounted for the interspecific difference in ksl. When groundwater was not directly available, ksl and Hv in P. euphratica were increased. This response favors water loss control, but limits plant growth. In contrast, T. ramosissima is more capable of using deep groundwater. Stomatal sensitivity to increasing leaf-to-area vapor pressure deficit was also higher in P. euphratica. Overall, P. euphratica is less effective than T. ramosissima at compensating for transpirational water loss at a whole-plant level. For this reason, P. euphratica is restricted to riverbanks, whereas T. ramosissima occurs over a wide range of groundwater depths. [ABSTRACT FROM AUTHOR]

Floodplain vegetation is characterized by its ability to resist deformation and destruction and to deform elastically and plastically under the influence of external mechanical forces. The force of water that presses on the plant induces stress and deformation in it, but once the force is removed, the elastic properties of the vegetation return it to its original state. It regains its original size, shape, and volume. In this paper, the deflection arrow was analysed based on the field tests conducted, and then the modulus of elasticity of natural shrub vegetation was determined. Measurements were made at different plant heights. Analysis was carried out at different growing periods to estimate the variation of plant elasticity with growth, development, and season. The results confirm the loss of flexibility during winter for all the shrubs analysed. Based on the measurements carried out, the elastic modulus E of the shoots was estimated. The average modulus of elasticity ranged from about 2100 to about 4000 MPa and showed high variability, reaching even µ = 50%, both within a given shrub and depending on the measurement season. The results presented here indicate a high natural variability of mechanical parameters even within the same plant. [ABSTRACT FROM AUTHOR]

Due to large-scale geological deposition processes, slope structures are often stratified, which means that the spatial distribution of the parameters involved in slope reliability evaluation is statistically anisotropic. This paper studies the effect of the statistical anisotropy of undrained shear strength on the probability of slope failure (pf) based on the Monte Carlo simulation. The results show that for the horizontally layered slope, the larger the horizontal correlation scale of undrained shear strength (λx) is, the larger pf is, especially when λx is smaller than the slope length; for the vertically layered slope, the larger the vertical correlation scale (λy) is, the smaller pf is, especially when λy is smaller than the slope height. Additionally, the mechanism of the above results is discussed by analyzing the displacement distribution at different correlation scales. The findings indicate that in the reliability evaluation of undrained slopes in stratified structures, either underestimation of λx or overestimation of λy leads to an unconservative estimate of pf, resulting in an overestimation of the slope stability. [ABSTRACT FROM AUTHOR]

The assessment of rainfall extremes at sub-hourly scales is generally hindered by a lack of rainfall data at small timescale resolutions. This study proposes a methodology for assessing mean annual maximum rainfall at the sub-hourly scale by blending historical time series of annual maxima recorded by mechanical stations (operating at hourly scales) up to the end of the past century with newer time series of annual maxima at higher time resolutions recorded by automatic stations installed over the past twenty years. A linear correlation was found at the regional scale between the shape parameter controlling the dependency of rainfall maxima with a duration longer than one hour and the shape parameter of the dependency of rainfall maxima with the durations shorter than one hour. Thanks to this correlation, data recorded at the mechanical stations could be exploited to assess sub-hourly mean annual maxima. The proposed hybrid procedure was verified and was found to provide estimates with an accuracy close to those obtained with the high-resolution data, i.e., our best estimates. Moreover, the proposed procedure outperforms what could be achieved by spatially interpolating the best estimates at those locations where only hourly data are available. [ABSTRACT FROM AUTHOR]

The prediction of ocean waves is a highly challenging task in coastal and water engineering in general due to their very high randomness. In the present case study, an analysis of wind, sea flow features, and wave height in the southern coasts of the Caspian Sea, especially in the off-coast sea waters of Mazandaran Province in Northern Iran, was performed. Satellite altimetry-based significant wave heights associated with the period of observation in 2016 were validated based on those measured at a buoy station in the same year. The comparative analysis between them showed that satellite-based wave heights are highly correlated to buoy data, as testified by a high coefficient of correlation r (0.87), low Bias (0.063 m), and root-mean-squared error (0.071 m). It was possible to assess that the dominant wave direction in the study area was northwest. Considering the main factors affecting wind-induced waves, the atmospheric framework in the examined sea region with high pressure was identified as the main factor to be taken into account in the formation of waves. The outcomes of the present research provide an interesting methodological tool for obtaining and processing accurate wave height estimations in such an intricate flow playground as the southern coasts of the Caspian Sea. [ABSTRACT FROM AUTHOR]

The paper studies four newly implemented terraced sites in Ethiopia, highlighting how agricultural terracing can enhance the soil water content in terraced areas. In the last few years, terraced landscapes have been receiving renovated interest all over the world (e.g., dry-stone walls named UNESCO heritage in November 2018). Given these premises, the aim of the present Special Issue was to gather studies dealing with hydrological-geological risk mitigation given by terraced landscapes, with the potential hazards induced by degraded and/or abandoned terracing, and with effective terrace management strategies. Sound terracing implementation and terraced landscape restoration can contribute to reduce hydrological and hydrogeological hazards, as well as soil erosion and land sliding [[5]]. [Extracted from the article]

Agricultural terraces are an important element of the Italian landscape. However, abandonment of agricultural areas and increase in the frequency of destructive rainfall events has made it mandatory to increase conservation efforts of terraces to reduce hydrological risks. This requires the development of new approaches capable of identifying and mapping failed or prone-to-fail terraces over large areas. The present work focuses on the development of a more cost-effective alternative, to help public administrators and private land owners to identify fragile areas that may be subject to failure due to the abandonment of terracing systems. We developed a simple field protocol to acquire quantitative measurements of the degree of damage—dry stone wall deformation—and establish a damage classification system. This new methodology is tested at two different sites in Tuscany, central Italy. The processing is based on existing DTMs derived from Airborne Laser Scanner (ALS) data and open source software. The main GIS modules adopted are flow accumulation and water discharge, processed with GRASS GIS. Results show that the damage degree and terrace wall deformation are correlated with flow accumulation even if other factors other than those analyzed can contribute to influence the instability of dry stone walls. These tools are useful for local land management and conservation efforts. [ABSTRACT FROM AUTHOR]

Due to the development of the scale of tractor-ploughed terraces, terraces have been increasing in number, while global climate change is causing frequent extreme rainfall events in the Loess Plateau, resulting in many terrace landslides. To study the mechanism and process of shallow landslides and deep slip surface of terraces induced by extreme rainfall in loess hill and gully area, we conducted a laboratory model test of a terrace under artificial rainfall and used the Swedish arc strip method. The research results are as follows. The mechanism of shallow landslides in terraces is rill erosion accelerating rainfall infiltration, suspending the slope, and increasing its bulk density. The destruction process of shallow landslides can be roughly divided into six processes, and the earth volume of the landslide is 0.24 m3. The mechanism of the deep sliding surface in terraces occurs under the combined action of water erosion and gravity erosion. The soil moisture content increases, which decreases the anti-sliding moment and increases the sliding moment, and the safety factor becomes less than the allowable limit for terraces. The deep sliding deformation area of the terrace was 0~1.0 m below the slope surface, slip surface radius was 1.43 m, the slip surface angle was 92°, and the deep sliding surface began to form earlier than terraced shallow landslides. The displacement of the characteristic points increased from the slope top, to the slope center, and to the slope foot, with maximum displacements of 40.3, 15.5, and 6.0 mm, respectively. [ABSTRACT FROM AUTHOR]

Hillslope viticulture has a long history in Mediterranean Europe, and still holds important cultural and economic value. Steep hillsides have widely been levelled by terraces, in order to control surface water flow and facilitate cultivation. However, under unsustainable management and growing rainfall aggressiveness, terraced vineyards have become one of the most erosion-prone agricultural landscapes. The Valcamonica valley in Lombardy (Italy) presents a typical example of an ancient wine production region where rural land abandonment has previously caused widespread degradation of the traditional terracing systems. Recently, a local revival of wine production led to restoration plans of the terraces and their drainage functioning, to safeguard productivity and hydrogeologic safety. In this study, an Unmanned Aerial Vehicle (UAV) survey was carried out to reconstruct an accurate and precise 3D terrain model of a Valcamonica vineyard through photogrammetry. The resulting high-resolution topographic data allowed insights of surface flow-induced soil erosion patterns based on the Relative Path Impact Index (RPII). Three diverse drainage networks were designed and digitally implemented, allowing scenario analysis of the costs and benefits in terms of potential erosion mitigation. The presented methodology could likely improve the time-efficiency and cost-effectiveness of similar restoration plans in degraded landscapes. [ABSTRACT FROM AUTHOR]

Due to the reduction in the prices of oranges on the market and social changes such as the ageing of the population, traditional orange plantation abandonment in the Mediterranean is taking place. Previous research on land abandonment impact on soil and water resources has focused on rainfed agriculture abandonment, but there is no research on irrigated land abandonment. In the Valencia Region—the largest producer of oranges in Europe—abandonment is resulting in a quick vegetation recovery and changes in soil properties, and then in water erosion. Therefore, we performed rainfall simulation experiments (0.28 m2 ; 38.8 mm h−1) to determine the soil losses in naveline orange plantations with different ages of abandonment (1, 2, 3, 5, 7 and 10 years of abandonment) which will allow for an understanding of the temporal changes in soil and water losses after abandonment. Moreover, these results were also compared with an active plantation (0). The results show that the soils of the active orange plantations have higher runoff discharges and higher erosion rates due to the use of herbicides than the plots after abandonment. Once the soil is abandoned for one year, the plant recovery reaches 33% of the cover and the erosion rate drops one order of magnitude. This is related to the delay in the runoff generation and the increase in infiltration rates. After 2, 3, 5, 7 and 10 years, the soil reduced bulk density, increase in organic matter, plant cover, and soil erosion rates were found negligible. We conclude that the abandonment of orange plantations reduces soil and water losses and can serve as a nature-based solution to restore the soil services, goods, and resources. The reduction in the soil losses was exponential (from 607.4 g m−2 in the active plot to 7.1 g m−2 in the 10-year abandoned one) but the water losses were linear (from 77.2 in active plantations till 12.8% in the 10-year abandoned ones). [ABSTRACT FROM AUTHOR]

Terracing and vegetation are an effective practice for soil and water conservation on sloped terrain. They can significantly reduce the sediment yield from the surface area, as well as intercept the sediment yield from upstream. However, most hydrological models mainly simulate the effect of the terraces and vegetation on water and sediment reduction from themselves, without considering their roles in the routing process, and thus likely underestimate their runoff and sediment reduction effect. This study added the impact of terraces and vegetation practice on water and sediment routing using the time-area method. The outflow in each travel time zone was revised in each time step by extracting the watershed of the terrace units and the vegetation units and calculating the water or sediment stored by the terraces or held by the vegetation. The revised time-area method was integrated into the Land change Model-Modified Universal Soil Loss Equation (LCM-MUSLE) model. Pianguanhe Basin, in the Chinese Loess Plateau, was chosen as the study area and eight storms in the 1980s and 2010s were selected to calibrate and verify the original LCM-MUSLE model and its revised version. The results showed that the original model was not applicable in more recent years, since the surface was changed significantly as a result of revegetation and slope terracing, while the accuracy improved significantly when using the revised version. For the three events in the 2010s, the average runoff reduction rate in routing process was 51.02% for vegetation, 26.65% for terraces, and 71.86% for both terraces and vegetation. The average sediment reduction rate in routing process was 32.22% for vegetation, 24.52% for terraces, and 53.85% for both terraces and vegetation. This study provides a generalized method to quantitatively assess the impact of terraces and vegetation practice on runoff and sediment reduction at the catchment scale. [ABSTRACT FROM AUTHOR]

Detailed modeling of floodplain flows and associated processes requires data on mixed, heterogeneous vegetation at river reach scale, though the collection of vegetation data is typically limited in resolution or lack spatial information. This study investigates physically-based characterization of mixed floodplain vegetation by means of terrestrial laser scanning (TLS). The work aimed at developing an approach for deriving the characteristic reference areas of herbaceous and foliated woody vegetation, and estimating the vertical distribution of woody vegetation. Detailed experimental data on vegetation properties were gathered both in a floodplain site for herbaceous vegetation, and under laboratory conditions for 2-3 m tall trees. The total plant area (Atot) of woody vegetation correlated linearly with the TLS-based voxel count, whereas the Atot of herbaceous vegetation showed a linear correlation with TLS-based vegetation mean height. For woody vegetation, 1 cm voxel size was found suitable for estimating both the Atot and its vertical distribution. A new concept was proposed for deriving Atot for larger areas from the point cloud attributes of small sub-areas. The results indicated that the relationships between the TLS attributes and Atot of the sub-areas can be derived either by mm resolution TLS or by manual vegetation sampling. [ABSTRACT FROM AUTHOR]

The historical agrarian landforms (AL) represent man-made features that alter the hydrological process on cultivated hillslopes. Soil water content (SWC) and its spatial and temporal variability represent an important state indicator for understanding of these processes. In order to assess the differences between individual AL in terms of SWC stability, continuous soil moisture measurements at five different monitoring localities characterized by a specific combination of AL and environmental factors were performed. Temporal SWC stability was evaluated using mean relative difference (MRD) and its standard deviation (SDRD). Differences in mean SWC and MRD values demonstrated the difference between saturated inner part of the AL and external parts such as terraced slopes and mounds, soil depths, and slope positions. In order to analyze the relationship between SWC and environmental variables, the methods of constrained ordination were applied. The most influential factors that regulate SWC variability during the periods of rain were identified as: stone content, sand fraction content, slope orientation, type of agrarian landform, and its orientation against the contour lines. Results also pointed to the fact that different factors predominate among individual localities and, therefore, SWC variability reflects the effect of combination of various environmental factors rather than effect of single parameter. Besides the improved understanding of SWC variability, our results also highlight the importance of AL in regulating the hydrological processes at historical agricultural landscape of the West Carpathian region. [ABSTRACT FROM AUTHOR]

This paper is devoted to a mathematical model for phenol and p-cresol mixture degradation in a continuously stirred bioreactor. The biomass specific growth rate is presented as sum kinetics with interaction parameters (SKIP). A discrete time delay is introduced and incorporated into the biomass growth response. These two aspects—the mutual influence of the two substrates and the natural biological time delay in the biomass growth rate—are new in the scientific literature concerning bioreactor (chemostat) models. The equilibrium points of the model are determined and their local asymptotic stability as well as the occurrence of local Hopf bifurcations are studied in dependence on the delay parameter. The existence and uniqueness of positive solutions are established, and the global stabilizability of the model dynamics is proved for certain values of the delay. Numerical simulations illustrate the global behavior of the model solutions as well as the transient oscillations as a result of the Hopf bifurcation. The performed theoretical analysis and computer simulations can be successfully used to better understand the biodegradation dynamics of the chemical compounds in the bioreactor and to predict and control the system behavior in real life conditions. [ABSTRACT FROM AUTHOR]

Flood hazard mitigation in urban areas crossed by vegetated flows can be achieved through two distinct approaches, based on structural and eco-friendly solutions, referred to as grey and green–blue engineering scenarios, respectively; this one is often based on best management practices (BMP) and low-impact developments (LID). In this study, the hydraulic efficiency of two green–blue scenarios in reducing flood hazards of an urban area crossed by a vegetated river located in Central Tuscany (Italy), named Morra Creek, were evaluated for a return period of 200 years, by analyzing the flooding outcomes of 1D and 2D unsteady hydraulic simulations. In the first scenario, the impact of a diffuse effect of flood peak reduction along Morra Creek was assessed by considering an overall real-scale growth of common reed beds. In the second scenario, riverine vegetation along Morra Creek was preserved, while flood hazard was mitigated using a single vegetated flood control area. This study demonstrates well the benefits of employing green–blue solutions for reducing flood hazards in vegetated rivers intersecting agro-forestry and urban areas while preserving their riverine ecosystems. It emerged that the first scenario is a valuable alternative to the more impacting second scenario, given the presence of flood control areas. [ABSTRACT FROM AUTHOR]

The effect of vegetation in hydraulic computations can be significant. This effect is important for flood computations. Today, the necessary terrain information for flood computations is obtained by airborne laser scanning techniques. The quality and density of the airborne laser scanning information allows for more extensive use of these data in flow computations. In this paper, known methods are improved and combined into a new simple and objective procedure to estimate the hydraulic resistance of vegetation on the flow in the field. State-of-the-art airborne laser scanner information is explored to estimate the vegetation density. The laser scanning information provides the base for the calculation of the vegetation density parameter ωp using the Beer–Lambert law. In a second step, the vegetation density is employed in a flow model to appropriately account for vegetation resistance. The use of this vegetation parameter is superior to the common method of accounting for the vegetation resistance in the bed resistance parameter for bed roughness. The proposed procedure utilizes newly available information and is demonstrated in an example. The obtained values fit very well with the values obtained in the literature. Moreover, the obtained information is very detailed. In the results, the effect of vegetation is estimated objectively without the assignment of typical values. Moreover, a more structured flow field is computed with the flood around denser vegetation, such as groups of bushes. A further thorough study based on observed flow resistance is needed. [ABSTRACT FROM AUTHOR]

Rainfall infiltration is the primary triggering factor of slope instability. The process of rainfall infiltration leads to changes in the water content and internal stress of the slope soil, thereby affecting slope stability. The soil water retention curve (SWRC) was used to describe the relationship between soil water content, matric suction, and the water retention characteristics of the soil. This characteristic is essential for estimating the properties of unsaturated soils, such as unsaturated hydraulic conductivity function and shear strength. Thus, SWRC is regarded as important information for depicting the properties of unsaturated soil. The SWRC is primarily affected by the soil pore size distribution (PSD) and has unimodal and bimodal features. The bimodal SWRC is suitable for soils with structural or dual-porous media. This model can describe the structure of micropores and macropores in the soil and allow the hydraulic behavior at different pore scales to be understood. Therefore, this model is more consistent with the properties of onsite soil. Few studies have explored the differences in the impact of unimodal and bimodal models on unsaturated slopes. This study aims to consider unimodal and bimodal SWRC to evaluate the impact of unsaturated slope stability under actual rainfall conditions. A conceptual model of the slope was built based on field data to simulate changes in the hydraulic behavior of the slope. The results of seepage analysis show that the bimodal model has a better water retention capacity than the unimodal model, and therefore, its water storage performance is better. Under the same saturated hydraulic conductivity function, the wetting front of the bimodal model moves down faster. This results in changes in the pressure head, water content, and internal stress of the soil. The results show that the water content and suction stress changes of the bimodal model are higher than those of the unimodal model due to the difference in water retention capacity. Based on the stability of the slope, calculated using the seepage analysis, the results indicate that the potential failure depth of the bimodal model is deeper than that of the unimodal model. [ABSTRACT FROM AUTHOR]

Estimating the main hydrodynamic features of real vegetated water bodies is crucial to assure a balance between their hydraulic conveyance and environmental quality. Riparian vegetation stands have a high impact on vegetated channels. The present work has the aim to integrate riparian vegetation's reflectance indices and hydrodynamics of real vegetated water flows to assess the impact of riparian vegetation morphometry on bulk drag coefficients distribution along an abandoned vegetated drainage channel fully covered by 9–10 m high Arundo donax (commonly known as giant reed) stands, starting from flow average velocities measurements at 30 cross-sections identified along the channel. A map of riparian vegetation cover was obtained through digital processing of Unnamed Aerial Vehicle (UAV)-acquired multispectral images, which represent a fast way to observe riparian plants' traits in hardly accessible areas such as vegetated water bodies in natural conditions. In this study, the portion of riparian plants effectively interacting with flow was expressed in terms of ground-based Leaf Area Index measurements (LAI), which easily related to UAV-based Normalized Difference Vegetation Index (NDVI). The comparative analysis between Arundo donax stands NDVI and LAI map enabled the analysis of the impact of UAV-acquired multispectral imagery on bulk drag predictions along the vegetated drainage channel. [ABSTRACT FROM AUTHOR]

Rainfall-induced shallow landslides represent a serious threat in hilly and mountain areas around the world. The mountainous landscape of the Cinque Terre (eastern Liguria, Italy) is increasingly popular for both Italian and foreign tourists, most of which visit this outstanding terraced coastal landscape to enjoy a beach holiday and to practice hiking. However, this area is characterized by a high level of landslide hazard due to intense rainfalls that periodically affect its rugged and steep territory. One of the most severe events occurred on 25 October 2011, causing several fatalities and damage for millions of euros. To adequately address the issues related to shallow landslide risk, it is essential to develop landslide susceptibility models as reliable as possible. Regrettably, most of the current land-use and urban planning approaches only consider the susceptibility to landslide detachment, neglecting transit and runout processes. In this study, the adoption of a combined approach allowed to estimate shallow landslide susceptibility to both detachment and potential runout. At first, landslide triggering susceptibility was assessed using Machine Learning techniques and applying the Ensemble approach. Nine predisposing factors were chosen, while a database of about 300 rainfall-induced shallow landslides was used as input. Then, a Geographical Information System (GIS)-based procedure was applied to estimate the potential landslide runout using the "reach angle" method. Information from such analyses was combined to obtain a susceptibility map describing detachment, transit, and runout. The obtained susceptibility map will be helpful for land planning, as well as for decision makers and stakeholders, to predict areas where rainfall-induced shallow landslides are likely to occur in the future and to identify areas where hazard mitigation measures are needed. [ABSTRACT FROM AUTHOR]

Flood protection is considered one of the crucial regulating ecosystem services due to climate change and extreme weather events. As an ecosystem service, it combines the results of hydrological and ecosystem research and their implementation into land management and/or planning processes including several formally separated economic sectors. As managerial and economic interests often diverge, successful decision-making requires a common denominator in form of monetary valuation of competing trade-offs. In this paper, a methodical approach based on the monetary value of the ecosystem service provided by the ecosystem corresponding to its actual share in flood regulating processes and the value of the property protected by this service was developed and demonstrated based on an example of a medium size mountain basin (290 ha). Hydrological modelling methods (SWAT, HEC-RAS) were applied for assessing the extent of floods with different rainfalls and land uses. The rainfall threshold value that would cause flooding with the current land use but that would be safely drained if the basin was covered completely by forest was estimated. The cost of the flood protection ecosystem service was assessed by the method of non-market monetary value for estimating avoided damage costs of endangered infrastructure and calculated both for the current and hypothetical land use. The results identify areas that are crucial for water retention and that deserve greater attention in management. In addition, the monetary valuation of flood protection provided by the current but also by hypothetical land uses enables competent and well-formulated decision-making processes. [ABSTRACT FROM AUTHOR]

Vegetation on the banks and flooding areas of watercourses significantly affects energy losses. To take the latter into account, computational models make use of resistance coefficients based on the evaluation of bed and walls roughness besides the resistance to flow offered by vegetation. This paper, after summarizing the classical approaches based on descriptions and pictures, considers the recent advancements related to the analytical methods relative both to rigid and flexible vegetation. In particular, emergent rigid vegetation is first analyzed by focusing on the methods for determining the drag coefficient, then submerged rigid vegetation is analyzed, highlighting briefly the principles on which the different models are based and recalling the comparisons made in the literature. Then, the models used in the case of both emergent and submerged rigid vegetation are highlighted. As to flexible vegetation, the paper reminds first the flow conditions that cause the vegetation to lay on the channel bed, and then the classical resistance laws that were developed for the design of irrigation canals. The most recent developments in the case of submerged and emergent flexible vegetation are then presented. Since turbulence studies should be considered as the basis of flow resistance, even though the path toward practical use is still long, the new developments in the field of 3D numerical methods are briefly reviewed, presently used to assess the characteristics of turbulence and the transport of sediments and pollutants. The use of remote sensing to map riparian vegetation and estimating biomechanical parameters is briefly analyzed. Finally, some applications are presented, aimed at highlighting, in real cases, the influence exerted by vegetation on water depth and maintenance interventions. [ABSTRACT FROM AUTHOR]

In the meandering riverbank of the Upper Yellow River (UYR), the native alpine swamp meadow (AS) has continuously degenerated into an alpine meadow (AM) due to climate change and intensified grazing. Its implication on river morphology is still not well known. This study examined this effect by in situ measurings of (1) physical properties of roots and their distribution in the soil-root mixture of the upper bank layer, and (2) the tensile strength in terms of excavating tests for triggering cantilever collapses of AS and AM riverbanks. The results showed that the root number in AS was significantly greater than that in AM, though the root distribution in both was similar. Also, the average tensile strength of individual roots in AS was 31,310 kPa, while that in AM was only 16,155 kPa. For the soil-root mixture, it decreased from 67.39 to 21.96 kPa. The weakened mechanical property was mainly ascribed to the lessened root number and the simpler root structure in the soil-root mixture of AM that reduces its ability to resist the external force. These findings confirmed that healthy AS can enhance bank stability and delay the development of tensile cracks in the riverbank of the meandering rivers in the UYR. [ABSTRACT FROM AUTHOR]

Nitrate pollution remains an unsolved issue worldwide, causing serious effects on water quality and eutrophication of freshwater and brackish water environments. Its economic costs are still underestimated. To reduce nitrogen excess, constructed wetlands are usually recognized as a solution but, in recent years, interest has been raised in the role of ditches and canals in nitrogen removal. In this study, we investigated the environmental and economical sustainability of nitrogen removal capacity, using as a model study a lowland agricultural sub-basin of the Po River (Northern Italy), where the role of aquatic vegetation and related microbial processes on the mitigation of nitrate pollution has been extensively studied. Based on the Life Cycle Assessment (LCA) approach and costs and benefits analysis (CBA), the effectiveness of two different scenarios of vegetation management, which differ for the timing of mowing, have been compared concerning the nitrogen removal via denitrification and other terms of environmental sustainability. The results highlighted that postponing the mowing to the end of the vegetative season would contribute to buffering up to 90% of the nitrogen load conveyed by the canal network during the irrigation period and would reduce by an order of magnitude the costs of eutrophication potential. [ABSTRACT FROM AUTHOR]