Intense Rainfall Events Research Articles

Problem Tree Analysis for Farm Communities along Bicol River Basin, Camarines Sur, Philippines

In the past decades, climate change has become a disruptive issue in agriculture. This paper provides a brief problem analysis of the current status of selected agricultural farmlands along Bicol River basin (BRB) in the province of Camarines Sur. Six barangays from initially identified vulnerable municipalities were assessed on their respective community’s agricultural problems. Two barangays from each from the municipality in Baao, Canaman and Minalabac, were targeted as participating sites in the Participatory Rural Appraisal (PRA). The paper aimed to survey insights into the dynamics of problems in agriculture-based problems of these communities and to identify priorities needed for the improvement of farm productivity. A problem tree analysis revealed that sixty-seven percent (67%) of the sites claimed that problem’s root cause was the absence of water source for efficient farming irrigation. Oppositely, thirty-three percent (33%) of the participating communities pinpointed the base problems to prolonged flooding that hampers the ideal farm yield. Other problems mentioned included unavailability of advanced farming technologies, low harvest rates due to climate shift, high cost of farming inputs such as fertilizers and labor, access to farm to market roads, low farm gate price of harvested products and lack of trees to aide in flood prevention. The study further revealed that either water scarcity or effects of rainfall intensities are the key problems faced by agricultural communities in the selected areas.

The impacts of exceptional rainfall on phosphorus mobilisation in a mountain agroforestry catchment (NE, Spain)

Erosion causes significant soil and nutrient losses that can reach streams and degrade habitats. Phosphorus (P) is among the nutrients of greatest concern for water pollution. Due to the increase in the number of storm events over the last decade, which could rise further under climate change scenarios, a more in-depth analysis of the effect of rainfall on the behaviour of P in fragile environments is needed. Little is known about the mobilisation and export of P in mountainous Mediterranean agroecosystems. To contribute to this knowledge, this research analysed the variability of P in the sediments of streambeds of different orders in an agroforestry area of the Northern Ebro Basin (Aragón, Spain) following an exceptional rainfall event; the implications of different land uses were also explored. Sediment composition was assessed before and after the rainfall event in three nested subcatchments and then related to soil properties. Phosphorus was mostly linked to the mineral fraction (mainly to silicates), while the links between P with clay and organic matter (P-clay, P-OM) were very weak. The P-OM links occurred only in the soils of forested areas. Agricultural lands, which are prone to erosion and had the highest P concentrations, contribute to P release. However, the streambeds and the lateral erosion of channel banks by floods triggered by the rainfall event should be considered as the main contributors to the export of P. The high intensity rainfall event led to 35% and 60% reductions in clay and OM, respectively, and to an enrichment of P in the sediments, the concentrations of which were lower in the headwaters than downstream. This means that the P in streambeds remains exposed in relatively high concentrations following extreme rainfall events with implications for the P cycle and water pollution.

Variable storage behavior controlled by rainfall intensity and profile structure upon saturation excess overland flow generation

The effects of rainfall intensity and terrain structure on hillslope storage behavior upon saturation excess overland flow (SOF) generation are not yet fully understood. Analytical solution techniques that provide direct insights into the hillslope storage behavior were adopted in this study. The Threshold of StOrage (TSO) at critical rainfall intensity N0 (the minimum rainfall intensity to generate SOF) and the storage upon SOF generation (SO) at rainfall intensity N (>N0) were derived using analytical solutions of the kinematic wave equation over unit-width shallow sloping aquifers. The derived analytical solutions match the results of the numerical models of the Boussinesq equation for 25 idealized hillslopes under various rainfall intensities. It was found that as N = N0, TSO is determined by hillslope structures, i.e., TSO on the convex hillslopes is always greater than that on concave hillslopes with the same gradient, and TSO on convex and concave hillslopes gradually approaches as the gradient increases. As N > N0, hillslope storage dynamics is characterised by variable storage behavior as rainfall intensity increasing, i.e., SO increases with N. An inflection point of rainfall intensity N1, below which the curvature of the bedrock profile has a limited effect on SO, was found. Although N1 was greater on steeper hillslope, the corresponding values of SO1 on hillslopes under different gradients are close, which means that the effects of rainfall intensity and profile structure on SO is balanced at N = N1. This study helps to deepen our understanding of the quantitative role of rainfall intensity and profile structure in the process of runoff generation, and has the potential to improve the free storage capacity parameter in conceptual models.

Influence of Vegetation Filter Strip on Slope Runoff, Sediment Yield and Nutrient Loss

It is an important branch of erosion research to control soil erosion on eroded gullies and slopes by using vegetation filter strip. Several simulated rainfall experiments were carried out in soil tanks filled with loess sandy loam taken from a typical eroded gully area with less vegetation coverage in Yanghe hilly basin in Xuanhua District, Zhangjiakou City, Hebei Province. The soil and water conservation effects of two different vegetation setting modes were compared under the same vegetation strip width and different rainfall intensities and slopes. During the rainfall process, the changes of runoff and sediment yield and nutrient loss were not stable, but the same erosion index had similar variation trends under different combinations of rainfall intensity, slope and vegetation coverage. Multiple regression results showed that runoff and sediment production in eroded gully can be effectively reduced through vegetation filter strips, which are jointly affected by rainfall intensity and slope. There was no significant difference in the amount of runoff and sediment yield between the two vegetation setting modes. Rainfall intensity and slope gradient showed different strengths of impact on nutrient loss. Through cluster analysis, the results showed that the impacts of rainfall intensity, slope gradient and vegetation setting modes on soil and water loss on slope can be equal or offset. In general, setting vegetation filter strips can offset the effects of rainfall intensity and slope, but vegetation regulation of erosion was not obvious under extreme rainfall and steep slope conditions. What’s more, rainfall intensity had a dominant effect on erosion. The results in this research may provide reference for practical application of vegetation filter strips on eroded slopes.

INVESTIGATION ON HYDROLOGIC PERFORMANCE OF PERVIOUS CONCRETE PAVEMENT BY FINITE ELEMENT ANALYSIS

Pervious concrete pavement has been used widely as an effective practice for water management in low-impact development techniques. The hydrologic performance of pervious concrete pavement depends significantlyon the rainfall intensity and the designed slope. This study assessed the hydrologic performance of pervious concrete pavement by evaluating the time for surface ponding via finite element analysis. A series of simulations were carried out to explore the relationship between hydrologic performance and pervious concrete pavement by the Hydrus 2D program. The research’s results showed that as the slope increased, the time of surface ponding also increased. The data indicated that the slope variable had a low impact on the water level in pervious concrete pavement under a constant rainfall intensity. Observation of the effect of rainfall intensity showed that when the rainfall intensity increased twofold, the time for surface ponding dropped about two times. Furthermore, when surface ponding appeared, pervious concrete pavement at higher rainfall intensity had lower water content. The rainfall intensity also significantly affects the hydrologicperformance of the pervious concrete pavement. This study only assessed the hydrologic performance by using the time for surface ponding via finite element analysis. Further experimental studies should be conducted to examine the relationship of other factors to the hydrologic performance of pervious concrete pavement.

Soil water infiltration evaluation from punctual to hillslope scales.

Quantifying infiltration and surface runoff at the hillslope scale is indispensable for soil conservation studies. However, the spatial and temporal variability of infiltration imposes a major constraint on surface runoff estimation. Point infiltration values do not fully express the complexity of the surface runoff in the landscape. Considering the need to improve the estimation of runoff volume from infiltration data, this study aimed to measure the apparent infiltration at hillslope-scale and compare it with two methods of infiltration estimative derived from point information. The study was carried out in six hydrological monitoring units paired. A set of hyetographs and hydrographs allowed the determination of apparent infiltration [Formula: see text] to each monitoring unit as a function of precipitation rate P. The measured [Formula: see text] values were used: (1) to evaluate the efficiency of the different land management in increasing infiltration; and (2) to evaluate the efficiency of two methods of hillslope-scale infiltration estimation based on point data: (a) derived from concentric rings method ([Formula: see text]), and (b) derived from a physically-based modeling ([Formula: see text]). Regarding the differences in land managements, terraces proved to be the most efficient land management practice, followed by phytomass addition. Regarding the methods, for precipitation rates greater than 40 [Formula: see text] the point infiltration-based [Formula: see text] underestimates apparent infiltration [Formula: see text] with PBIAS ranging from [Formula: see text] to [Formula: see text]. Even so, [Formula: see text] proved efficient in representing [Formula: see text] at less intense rainfall events. Nonetheless, the point infiltration-based method [Formula: see text] properly represented [Formula: see text] to all rainfall intensities (Nash-Sutcliffe coefficient [Formula: see text]).

The influence of seed-drill choice on crop performance in a semi-arid production region of South Africa

A seed-drill should facilitate seed placement in an environment conducive to uniform seedling emergence. In semi-arid rain-fed production regions, low rainfall intensity and erratic rainfall events can result in non-uniform emergence. Evaluation of seed-drills is necessary to supply small grain producers with potential solutions to combat non-uniform seedling emergence. The aim of this study was to investigate the influence of three seed-drills on seeding depth, crop emergence, biomass production and yield over the duration of two growing seasons. Barley, canola and wheat were established with three seed-drills, each equipped with a different opener. Seed-drills contained either double disc openers, tine openers, or a combination of both tines and single discs. Crops responded variably to seeding equipment under different climatic conditions. For example, accuracy of seeding depth varied between the three seed-drills utilised. Seed-drills, together with their associated seed placement characteristics, influenced crop emergence. Biomass production was variable over the course of the growing season. Biomass production of crops established with the double disc seed-drill tended to be higher than that of crops established with tine seed-drills. Additional research about adaptations of agronomic practices and seed-drill openers may increase resilience to adverse climatic conditions in semi-arid small grain production regions. Various factors, including soil physical conditions, environmental conditions, economic feasibility and practical applications must be taken into consideration when selecting a seed-drill.

Interactive Effects of Rainfall Intensity and Initial Thaw Depth on Slope Erosion

Seasonal freeze–thaw processes have led to severe soil erosion in the middle and high latitudes of the world, so understanding the freeze–thaw erosion process is of great significance for soil and water conservation as well as for ecological engineering. The area affected by freeze–thaw erosion in China exceeds 13% of the national territory. However, there is little data regarding the impact of rainfall intensity and initial thaw depth on soil erosion. Here, the effects that different rainfall intensities (0.6 mm/min, 0.9 mm/min and 1.2 mm/min) and different initial thaw depths (0 cm, 2 cm, 4 cm and 6 cm) had on the soil erosion process on the loess slope were studied under simulated rainfall conditions. The results showed that the infiltration rate decrease with prolonged runoff time, and then stabilized. Runoff occurred more quickly during increasingly intense rainfall, especially when little soil had thawed. The variation in runoff and sediment yield occurred in two stages: slow growth and rapid growth. As soil thawed to greater depths, rainfall intensity had less influence on the sediment. A linear relationship existed between the cumulative runoff and the sediment yield of all treatments. (R2 > 0.92, p < 0.01). Rainfall intensity and thaw depth had interacting effects on erosion. At low rainfall intensities, the initial thaw depth played a leading role in the erosion process, but at higher rainfall intensities, rainfall intensity played a larger role. Stage II erosion amount accounted for more than 90% of the total erosion across all treatments. The results of this research provide a guide for furthering the understanding of the soil water erosion mechanism of thawing slopes.

Increase in rainfall intensity promotes soil nematode diversity but offset by nitrogen addition in a temperate grassland

Precipitation regime in arid and semi-arid regions is exhibiting a trend of increase in rainfall intensity but reduction in frequency under global climate change. In addition, nitrogen (N) deposition occurs simultaneously in the same regions. Nematodes are the dominant soil biota in terrestrial ecosystems and are involved in various underground processes. How the diversity of nematode communities responds to changing precipitation regime and how N deposition regulates the responses remain unclear. Here, we performed a field experiment initiated in 2012 to examine the effect of changes in the precipitation regime (2 mm precipitation intensity, 5 mm precipitation intensity, 10 mm precipitation intensity, 20 mm precipitation intensity, and 40 mm precipitation intensity) and N addition (10 g N m−2 yr−1) on soil nematode community in a semi-arid grassland in Inner Mongolia of China. We found that the abundance and diversity of nematodes increased under the treatments with fewer but stronger precipitation events (the largest abundance of total nematodes was 1458.37 individuals/100 g dry soil occurred under 40 mm intensity treatment). However, N addition reduced nematode diversity under these treatments, which largely offset the positive effects of increased rainfall intensity alone. Soil pH and plant belowground biomass were the main factors affecting nematode diversity. Our results imply that, as a consequence of global climate change, an increase in the intensity of rainfall events in the coming decades may favor the nematode communities within arid and semi-arid ecosystems. However, this positive effect may be largely offset by soil acidification in the regions experiencing heavy N deposition.

Review of water safety planning processes and options for improved climate resilient infrastructure in Vanuatu

Abstract Vanuatu is a small island state ranked the most at-risk for natural hazards globally. Access to safe and secure water is limited, particularly for poor and rural residents. It is projected that climate change will increase temperatures, sea level, cyclone intensity, and extreme rainfall events in Vanuatu. As the impacts of climate change become clearer, it is becoming easier to predict the consequences of those changes on water infrastructure. The Government of Vanuatu, Department of Water Resources (DoWR) wants to support communities to enhance the resilience of community water supply infrastructure, despite the additional challenge of climate change. Since 2013, DoWR has adapted Water Safety Plans to the local context with Drinking Water Safety and Security Plans (DWSSPs). An analysis of actions taken after 199 DWSSPs, site visits and interviews, revealed an opportunity to integrate climate change more into existing community risk planning processes. The analysis also identified many potential problems with existing water infrastructure that increase their exposure to climate risks as well as possible improvements to decrease those risks. As a result, adjustments were made to the current water safety planning approach, so that communities review hazards associated with climate change and identify resilient infrastructure improvements.

Investing in Urban Blue–Green Infrastructure—Assessing the Costs and Benefits of Stormwater Management in a Peri-Urban Catchment in Oslo, Norway

Cities are challenged by climate change impacts, such as extreme rainfall events that affect conventional urban water management systems via increased sewage water overflows resulting in water quality deterioration and urban floods causing infrastructure damage. Investments in blue–green infrastructure (BGI) are increasingly considered to address these issues. However, these should be cost-effective. In this study, the effectiveness of five different BGI strategies and one grey strategy are assessed for a peri-urban catchment area in Oslo (Grefsen) using a cost–benefit analysis. The strategies include (i) wadis; (ii) green roofs; (iii) raingardens, rain barrels and wadis; (iv) infiltration crates; (v) water squares, and (vi) a separate sewage system. Besides economic effectiveness, the study also aims to identify the proper protection level by comparing cost–benefit ratios and net benefits for 60-min rainfall events occurring once every 5, 20, and 100 years (M5, M20, and M100), concerning both the current situation and under future climate change (using the Representative Concentration Pathway 8.5). The analyses revealed the highest BC ratios for wadis (12.0–17.3), separate sewage systems (7.7–15.1), and a combination of raingardens, rain barrels, and wadis (1.6–2.3). Strategies dimensioned for less frequent but more intensive rainfall events yielded higher BC ratios. Results for infiltration crates were difficult to interpret and were found to be very sensitive to input parameters. The other strategies implied a negative BC ratio. The study concludes that investments in BGI in Grefsen, Oslo, can be positively judged from a social–economic perspective and provide suitable information for water-related decision makers to decide upon the strategy selection and the appropriate flood protection level.

Minimum Rainfall Inter-Event Time to Separate Rainfall Events in a Low Latitude Semi-Arid Environment

Water scarcity in dry tropical regions is expected to intensify due to climate change. Characterization of rainfall events is needed for a better assessment of the associated hydrological processes, and the proposition of adaptation strategies. There is still no consensus on the most appropriate method to separate rainfall events from a continuous database, although the minimum inter-event time (MIET) is a commonly used criterion. Semi-arid regions of low latitudes hold a distinct rainfall pattern compared to their equivalent at higher latitudes; these seasonally dry tropical forests experience strong spatial–temporal variability with intense short-duration rainfall events, which, in association with high energy surplus and potential evaporation, leads to an atmospheric water deficit. In this study, we identified the most adequate MIET based on rainfall data continuously measured at 5-min intervals over the last decade (2009–2020) in the semi-arid northeast of Brazil. The rainfall events were grouped according to different MIETs: 15 min, 1 h, 2 h, 3 h, 6 h, 12 h, and 24 h to determine rainfall depth, duration and intensity at intervals of 5, 30, and 60 min, time between events, and respective temporal distribution, with and without single tip events. Including single tip events in the dataset affected the number of rainfall events and respective characteristics up to a MIET of 3 h. A MIET of 6 h is the most appropriate to characterize the rainfall distribution in this tropical semi-arid region. Three classes were defined based on rainfall depth, duration, and intensity: I-small events (77% below 40 mm and 32 mm/h), II-high intensity events (3% between 36 and 76 mm/h), III-longer events of higher depth (20%). This study is useful for understanding how the MIET relates to other ecohydrological processes and provides more precise information on the rainfall characteristics at the event scale.

A comparative study of riverine 137Cs dynamics during high-flow events at three contaminated river catchments in Fukushima

This study presents the temporal variations in riverine 137Cs concentrations and fluxes to the ocean during high-flow events in three coastal river catchments contaminated by the Fukushima Daiichi Nuclear Power Plant accident. River water samples were collected at points downstream in the Niida, Ukedo, and Takase Rivers during three high-flow events that occurred in 2019–2020. Variations in both the dissolved and particulate 137Cs concentrations appeared to reflect the spatial pattern of the 137Cs inventory in the catchments, rather than variations in physico-chemical properties of water and suspended solid. Negative relationships between the 137Cs concentration and δ15N in suspended solid were found in all rivers during the intense rainfall events, suggesting an increased contribution of sediment from forested areas to the elevation of particulate 137Cs concentration. The 137Cs flux ranged from 0.33 to 19 GBq, depending on the rainfall erosivity. The particulate 137Cs fluxes from the Ukedo River were relatively low compared with the other two rivers and were attributed to the effect of the Ogaki Dam reservoir upstream. The percentage of 137Cs desorbed in seawater relative to 137Cs in suspended solids ranged from 2.8% to 6.6% and tended to be higher with a higher fraction of exchangeable 137Cs. The estimated potential release of 137Cs desorbed from suspended solids to the ocean was 0.022–0.57 GBq, and its ratio to the direct flux of dissolved 137Cs was 0.12–6.2. Episodic sampling during high-flow events demonstrated that the particulate 137Cs flux depends on catchment characteristics and controls 137Cs transfer to the ocean.

Comprensión de la sensibilidad a las propiedades del suelo y condiciones de lluvia de dos modelos de estabilidad de taludes basados en la física

Physically-based models have been used to assess landslide susceptibility, hazard, and risk in many regions worldwide. They have also been regarded as valuable tools for landslide prediction and the development or improvement of landslide early warning systems. They are usually validated to demonstrate their predictive capacity, but they are not deeply studied regularly to understand the sensitivity of the input variables and the behavior of the models under many different rainfall scenarios. In this research paper, we studied two distributed physically-based models for shallow landslides: SLIP and Iverson. For this, the first-order second-moment (FOSM) method was used to calculate the contribution of random input variables (soil strength, unit weight, and permeability parameters) to the variance of the factor of safety. Different intensity and duration rainfall events were simulated to assess the response of the models to those rainfall conditions in terms of the factor of safety and failure probability. The results showed that the shear strength (cohesion and friction angle, in order of significance) parameters have the largest contribution to the variance in both models, but they vary depending on geological, geotechnical, and topographic conditions. The Iverson and SLIP models respond in different ways to the variation of rainfall conditions: for shorter durations (e.g. ≤ 8 h), increasing the intensity caused more unstable areas in the SLIP model, while for longer durations the unstable areas were considerably higher for the Iverson model. Understanding those behaviors can be useful for practical and appropriate implementation of the models in landslide assessment projects.

Trend Pattern of Heavy and Intense Rainfall Events in Colombia from 1981–2018: A Trend-EOF Approach

The Andes mountain range divides Colombia into various climatic regions over the country, as the Andean, Caribbean, Pacific, Amazon, and Orinoco regions. Given this scenario, knowing the current change in total precipitation and their extremes values are relevant. In this study, the main goal is to assess the spatio-temporal trends of heavy and intense rainfall at a seasonal scale during the last 38 years (1981–2018) using the trend empirical orthogonal function (TEOF). An increase in maximum precipitation during five consecutive days (RX5day), Simple daily intensity index (SDII), and the number of days with precipitation above 20 mm (R20mm) and 30 mm (R30mm) during December–February and March–May was observed in most of the Colombian territory, except for the Amazon region for RX5day. A decrease in total rainfall in June–August was observed in the Andean, the Caribbean, and southern Pacific regions, while, in the northern Pacific, it increased, consistent with the trend patterns of RX5day, SDII, and R20mm. During September–November, there was a reduction in rainfall in the Amazon region and the South Pacific, and an increase in RX5day, SDII, R20mm, and R30mm in the Andean, the Caribbean, and North Pacific regions. The TEOF showed more pronounced spatial trend patterns than those obtained with the traditional Mann–Kendall test. The findings offer a better understanding of the climate extremes impacts in tropical latitudes and help planners to implement measures against the future effects of climate change.

Effects of rainfall intensities and slope gradients on nitrogen loss at the seedling stage of maize (Zea mays L.) in the purple soil regions of China

Loss of soil nitrogen has been reported to reduce soil productivity and result in eutrophication. The objective of this work was to understand the mechanisms of nitrogen loss at the maize seedling stage from purple soil in the sloping farmlands of southwest China. The characteristics of nitrogen loss were explored in experiments simulating rainfall conditions during the maize seedling stage at different rainfall intensities (60 mm/h, 90 mm/h, and 120 mm/h) and slope gradients (10°, 15°, and 20°). The results showed that the runoff and sediment yield increased with time. The surface runoff and sediment yield increased with the rainfall intensity and slope gradient. Nitrogen losses increased in the surface runoff and sediment but decreased in the interflow as the rainfall intensity and slope gradient increased. Dissolved total nitrogen (DTN) was the main form of nitrogen in the surface runoff and interflow, and nitrate nitrogen (NO3-N) was the main form of DTN. The surface runoff and sediment accounted for less than half of the TN losses. Thus, interflow was the main pathway for nitrogen loss. The regression lines between the surface runoff and forms of nitrogen losses in the runoff and interflow were linear. The results indicated that an increasing rainfall intensity and slope gradient generally increased the surface runoff, sediment, and their nitrogen losses. However, the opposite trend was observed for the interflow and its nitrogen losses. Keywords: forms of nitrogen, surface runoff, interflow, sediment yield, slope gradient, rainfall intensity DOI: 10.25165/j.ijabe.20221502.6015 Citation: He S Q, Gong Y B, Zheng Z H, Luo Z T, Tan B, Zhang Y Q. Effects of rainfall intensities and slope gradients on nitrogen loss at the seedling stage of maize (Zea mays L.) in the purple soil regions of China. Int J Agric & Biol Eng, 2022; 15(2): 142–148.

Estimation of rainfall erosivity factor in Italy and Switzerland using Bayesian optimization based machine learning models

This study aimed to evaluate the estimation accuracy of rainfall erosivity (R-factor) in Italy and Switzerland through five Machine learning (ML) models (Decision Tree (DT), K-Nearest Neighbors (KNN), Random Forest (RF), Gradient Boosting (GB), and eXtreme Gradient Boost (XGB)) tuned with optimal hyperparameters. To build the ML model, high temporal resolution (HTR) rainfall data were collected from 297 rain-gauge stations located in the study area. To estimate the RUSLE-based R-factor through the models, the rainfall amount for each rainfall event, the rainfall duration, and the maximum 60-min intensity were used as input data. The datasets for training/validation and testing consisted of rainfall data from 287 and 10 stations, respectively. In a second phase, each ML model was trained through 10-fold cross validation based on training and validation data. For hyperparameter adjustment, the models were optimized using the Bayesian optimization algorithm (BOA). The R-factor estimation performance of each ML model through cross validation improved from 6.1% to 62.8% as hyperparameters were optimized through BOA. In particular, ensemble models such as RF, GB, and XGB were superior to other models with an accuracy performance of 0.9 or even more. And the RF showed an excellent estimation performance (R2 = 0.965, NSE = 0.958, RMSE = 44.993 MJ mm ha−1h−1, and MAE = 13.901 MJ mm ha−1h−1) for test stations, followed by GB and XGB with similar performance. However, the R-factor for the extremely intense rainfall event estimated by the ML models showed a significant difference from the RUSLE-based R-factor. This result implies that although the ML model built in this study can reasonably estimate the R-factor in the general rainfall event, additional training and validation through securing various rainfall event data is required to improve estimation accuracy on an extreme rainfall event.

The Effects of Rainfall, Soil Type and Slope on the Processes and Mechanisms of Rainfall-Induced Shallow Landslides

Landslides are a serious geohazard worldwide, causing many casualties and considerable economic losses every year. Rainfall-induced shallow landslides commonly occur in mountainous regions. Many factors affect an area’s susceptibility, such as rainfall, the soil, and the slope. In this paper, the effects of rainfall intensity, rainfall pattern, slope gradient, and soil type on landslide susceptibility are studied. Variables including soil volumetric water content, matrix suction, pore water pressure, and the total stress throughout the rainfall were measured. The results show that, under the experimental conditions of this paper, no landslides occurred on a 5° slope. On a 15° slope, when the rainfall intensity was equal to or less than 80 mm/h with a 1 h duration, landslides also did not happen. With a rainfall intensity of 120 mm/h, the rainfall pattern in which the intensity gradually diminishes could not induce landslides. Compared with fine soils, coarser soils with gravels were found to be prone to landslides. As the volumetric water content rose, the matrix suction declined from the time that the level of infiltration reached the position of the matrix. The pore water pressure and the total stress both changed drastically either immediately before or after the landslide. In addition, the sediment yield depended on the above factors. Steeper slopes, stronger rainfall, and coarser soils were all found to increase the amount of sediment yield.

Alternatives how to mitigate urban flooding and CSO in urbanized areas used in European cities and towns

Urban flooding and combined sewer overflow in city, or town areas represents potential risk in environmental, economic, or social aspects. The goal of this study is to process and evaluate efficiency of individual solutions to reduce occurrence of flooding in urban areas caused by intense rainfall events. The known conventional solutions are stormwater chambers, or storage drains. The new trend in reduction of stormwater drainage into combined sewer system are parts of blue-green infrastructure. Blue-green infrastructure represents environmental urban infrastructure which consists of sensitively selected urban vegetation combined with ingenious hydrological elements of urban city drainage. The study also deals with experimental usage of decentralized real time control, based on a gossip-based algorithm of moveable gates in sewage network. Experiment was proposed for drainage system of the city of Cosenza in Italy. Evaluation will assess application value of individual proposed solutions for the reduction of combined sewer overflow for Slovak republic and its urban cities, or towns.

Comparative Evaluation of the Rainfall Erosivity in the Rieti Province, Central Italy, Using Empirical Formulas and a Stochastic Rainfall Generator

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.