Rainwater Infiltration Research Articles

Stability analysis of rainfall-induced landslides: A case study of a hilly area in Bangladesh

Rainfall-induced landslides stand as the prevailing geohazard in tropical and subtropical regions. The ongoing global climatic changes have introduced a wave of anomalous rainfall events across the world. These abnormal weather patterns have triggered numerous landslide incidents, resulting in significant loss of life and property. To develop early warning systems for such threats to people in mountainous areas of Chittagong, Bangladesh, it requires an in-depth understanding of the geo-environmental properties of soil slopes under heavy rainfall. Historical records reveal that rainfall in total exceeding 150–250 mm has resulted in both localized slope collapses and debris floods. When it rains heavily, rainwater infiltrates initially unsaturated slopes, elevating the degree of saturation while decreasing soil suction. Consequently, the reduced shear strength along the critical slip surface diminishes the factor of safety (FoS), and slope failure occurs. As a result, studies of soil-water characteristics have been conducted, followed by laboratory testing at the impacted sites, and the study found that rainfall and soil type (fine-grained silt) were the most critical factors behind landslides. The mechanism of slope failure is also demonstrated using a simple numerical infiltration model and a slope stability equation. The soil characteristics, the saturated volumetric water content (θs), closely match the field water holding capacity (θf), with a minor difference of 4-8%, and the drainage condition at the bottom of the slope appear to be important factors. Application of these test results to an early warning system for landslides and flash floods is finally demonstrated based on some simplifying assumptions.

Analysis of the impact of green infrastructure on surface runoff from urban areas

Current construction methods and the marked increase in urbanisation are contributing to a high proportion of impermeable surfaces in built areas. Such surfaces reduce the infiltration of rainfall into the ground, which in turn leads to high amounts of surface runoff, which can have negative consequences in terms of flood safety. The introduction of green and hybrid infrastructure seeks to improve the characteristics of urban areas in terms of increasing the infiltration of rainwater and reducing stormwater runoff. In this study, we considered the larger industrial area of Rudnik in Ljubljana. Based on data on rainfall characteristics and soil properties, we calculated the surface runoff for the current situation and the situation when the improvements were introduced, where we took into account green roofs, tree planting and porous ground surfaces. Having analyzed the data, measurements, and calculations, we found that green infrastructure contributed positively to the reduction of surface runoff in urban areas, with differences of up to 20% at the annual level and up to 10% at the storm event level compared to the situation without improvements. In terms of surface runoff, the use of porous ground surfaces was identified as the best solution, with relatively small differences between the selected measures. From a financial point of view, tree planting was identified as the best solution, as trees can provide similar surface runoff reduction as green roofs and porous surfaces, with lower construction and maintenance costs.

Modelling Rain Water Ingress in Hygrothermal Simulations

The hygrothermal response of building envelope components is often studied by means of numerical Heat-Air-Moisture (HAM) simulation models. There models aim to capture the most important physics that affect the transport and storage of heat and moisture due to climatic excitations. For a lot of climates and components the wind driven rain load is the main driver for moisture uptake in the construction, and as well, the trigger of important degradation phenomena e.g., freeze-thaw damage, mold growth, wood decay, corrosion, salt transport, algae growth. When building components are subjected to wind driven rain loads and driving rain wind pressures, capillary uptake in porous materials is typically considered in models, but rain water often infiltrates directly into different layers of the construction and these infiltrations may have a significant impact on the hygrothermal behavior. This paper offers a straightforward methodology to take the rain water management of building envelope components into account in hygrothermal simulations. For different types of façade systems a categorical approach is presented to simulate rain water ingress into the different layers. Next to that, also the drainage and retention is discussed in detail. Finally, this methodological approach is embedded in the SAMiRA-framework, which comprises 3 performance levels for each input parameter of the simulations: (i) Superior, (ii) Advanced, (iii) Minimum Requirement Approach. Hence, 3 different levels are offered to implement rainwater infiltration in hygrothermal simulations.

STUDIES OF THE AREA AROUND SINGRAULI COAL FIELD & ENERGY BELT, DISTRICT SIGRAULI, MADHYA PRADESH INDIA

STUDIES OF THE AREA AROUND SINGRAULI COAL FIELD & ENERGY BELT, DISTRICT SIGRAULI, MADHYA PRADESH INDIA

Long-term hydrological monitoring of soils in the terraced environment of Cinque Terre (north-western Italy)

Terraced landscapes represent one of the most widespread human-induced/man-made transformations of hilly-mountainous environments. Slope terracing produces peculiar morphologies along with unusual soil textures and stratigraphic features, which in turn strongly influence slope hydrology. The investigation of the hydrological features of terraced soils is of fundamental importance for understanding the hydrological dynamics occurring in these anthropogenic landscapes, especially during rainfall events. To this purpose, the availability of extensive field monitoring data series and of information on subsoil properties and structure is essential. In this study, multi-sensor hydrological data were acquired over a period longer than 2 years in the experimental site of Monterosso al Mare, in the Cinque Terre National Park (Liguria region, Italy), one of the most famous examples of terraced landscape worldwide. Monitoring data were coupled with accurate engineering-geological investigations to achieve the hydro-mechanical characterization of backfill soils and to investigate their hydrological response at both the seasonal and the single rainstorm scale. The results indicated that the coarse-grained, and anthropically remolded texture of the soils favors the rapid infiltration of rainwater, producing sharp changes in both soil volumetric water content and pore water pressure. Furthermore, the pattern of hydrological parameters showed seasonal trends outlined by alternating phases of slow drying and fast wetting. The study outcomes provide useful insights on the short and long-term evolution of hydrological factors operating in agricultural terraces. These findings represent a useful basis for a better understanding of the time-dependent processes that guide water circulation in terraced systems, which have a key role in controlling the occurrence of erosion and landslide processes.

Deformation Behavior and Reactivation Mechanism of the Dandu Ancient Landslide Triggered by Seasonal Rainfall: A Case Study from the East Tibetan Plateau, China

In recent years, numerous ancient landslides initially triggered by historic earthquakes on the eastern Tibetan Plateau have been reactivated by fault activity and heavy rainfall, causing severe human and economic losses. Previous studies have indicated that short-term heavy rainfall plays a crucial role in the reactivation of ancient landslides. However, the deformation behavior and reactivation mechanisms of seasonal rainfall-induced ancient landslides remain poorly understood. In this paper, taking the Dandu ancient landslide as an example, field investigations, ring shear experiments, and interferometric synthetic aperture radar (InSAR) deformation monitoring were performed. The cracks in the landslide, formed by fault creeping and seismic activity, provide pathways for rainwater infiltration, ultimately reducing the shear resistance of the slip zone and causing reactivation and deformation of the Dandu landslide. The deformation behavior of landslides is very responsive to seasonal rainfall, with sliding movements beginning to accelerate sharply during the rainy season and decelerating during the dry season. However, this response generally lags by several weeks, indicating that rainfall takes time to infiltrate into the slip zone. These research results could help us better understand the reactivation mechanism of ancient landslides triggered by seasonal rainfall. Furthermore, these findings explain why many slope failures take place in the dry season, which typically occurs approximately a month after the rainy season, rather than in the rainy season itself.

STUDI NILAI KUAT GESER TANAH HAMBALANG BERDASARKAN KADAR AIR

Soft soils have low strength and easy to compress when they are loaded. A soil compaction test is performed to measure maximum soil density at the optimum water content to evaluate the strength of soft soil. To maintain these circumstances, however, efforts are necessary to preserve the water content at optimal levels, which is not easy. In actual condition the compacted soil can still be penetrated by water through soil cracks occurred especially on the slopes. The shear strength of the soil will decrease if rainwater infiltration is excessive. In a laboratory investigation, direct shear testing (ASTM D3080 - SNI 3420:2016) was used to determine how changes in the value of the Hambalang clay soil shear strength as reflected by the cohesion value (c) and the soil shear angle (f). Creating soil samples with a fixed density and variations in water content (w). The test results at w = 14.47% obtained c = 0.047 kg/cm2, f = 45.75⁰; at w = 21.75% obtained c = 0.203 kg/cm2, f = 33.39⁰, at w = 26.62% obtained c = 0.186 kg/cm2, f = 24.10⁰, at w= 31.59% obtained c = 0.086 kg/cm2, f = 21.90⁰ and at w = 33.70% obtained c = 0.082 kg/cm2, f = 21.21⁰. From these results it can be concluded that the largest of cohesion and angle of internal friction or strength parameter values will reach at optimum moisture content.

Experimental and numerical investigation on failure mechanism of expansive soil subgrade slope

AbstractShallow landslides of expensive soil slopes occur from time to time, and most engineering geological problems are directly or indirectly caused by soil structure cracks. The existence of tensile cracks can significantly affect the hydro-mechanical properties of soils. In this paper, the mechanism of expansive soil landslide formation is explored, and swelling pressures, and drying and wetting cycles are introduced into the discrete element method (DEM), and the landslide process of expansive soils is studied by the numerical simulation mothed. The relationship between the crack development and the instability of expansive soil slopes was investigated. The results show that under the condition of seasonal dry and wet alternation, the cracks of the expansive soil slope gradually develop, the rainwater infiltrates rapidly, the mechanical properties gradually deteriorate, and under the effect of such adverse cycle, the soil gradually softens and the stability decreases. Under the influence of human activities, vehicle loads and other factors, the slope body slides. These findings are helpful for the design and construction of expansive soil slopes and foundations.

Multi-objective optimization of rainwater infiltration infrastructures along an urban–rural gradient

Many cities are developing infiltration infrastructures aimed at restoring natural hydrological processes. Among those, Nature-Based Solutions (NBS) can generate co-benefits, which contribute to cities’ adaptation to climate change. However, choosing optimal locations for infiltration infrastructures within limited available urban space is a complex spatial problem. It requires taking into account spatial patterns of infiltration potential as well as urban-rural gradients of costs and benefits. To address this, we apply a multi-objective optimization on a simple monocentric model city designed to give generic insights into location choices. We test a series of hypotheses: in comparison with a reference situation, we test the impact of the impossibility to infiltrate rainwater in city centers, the impact of substitution effects due to the presence of urban parks, and the possibility to mix NBS with grey infrastructures. The solutions reveal two polar strategies: locating infrastructures in the city center with higher co-benefits despite higher opportunity costs, or selecting suburban locations with the highest infiltration potential and lower opportunity costs - and a diversity of hybrid solutions. Substitution effects lead to discarding locations near urban parks, especially in centric locations. Finally, mixing NBS and grey infrastructures leads to a specialization of solutions by area and the potential to reach higher benefits at less opportunity costs.

Transient infiltration tests in pyroclastic soils with double porosity

Fallout volcanic deposits of Somma- Vesuvius (Campania, southern Italy), characterized by the presence of layers with contrasting textural and hydraulic properties, are frequently affected by shallow landslides during rainwater infiltration. The soils of the stratigraphic sequence present intra- particle pores, originated by the gases escaped during magma decompression in the volcanic conduit, thus are characterized by double porosity (i.e., intraparticle and interparticle pores), which is expected to affect their hydraulic behaviour, and to play a key role in rainwater infiltration through layered deposits. To understand the effect of double porosity on the hydraulic behaviour of the involved soils, controlled experiments have been carried out in an infiltration column. The experimental apparatus is provided with newly designed non-invasive Time Domain Reflectometry (TDR) probes, not buried in the investigated soil layers so as to minimize disturbance to the flow, allowing water content measurement during vertical flow processes. Specifically, transient flow experiments are carried out through reconstituted specimens of black scoriae and grey pumices, both loose pyroclastic granular soils from fallout deposits of Somma-Vesuvius, featuring double porosity with different pore size distributions, that were estimated by X-ray tomography and Mercury Intrusion Porosimetry. The experimental results highlight the effects of the double porosity and clearly indicate the different behaviour of the two soils during wetting and drying processes, mainly related to the different dimensions of intraparticle pores.

Analysis of the Recharge Area of the Perrot Spring (Aosta Valley) Using a Hydrochemical and Isotopic Approach

The Perrot Spring (1300 m a.s.l.), located to the right of the Chalamy valley in the Monte Avic Natural Park (Valle d’Aosta, Italy), is an important source of drinking water for the municipality of Champdepraz. This spring is located on a large slope characterised by the presence of a Quaternary cover of various origins (glacial, glaciolacustrine, and landslide) above the bedrock (essentially serpentinite referred to the Zermatt–Saas Zone, Penninic Domain). Water emerges at the contact between the landslide bodies and impermeable or semi-permeable glaciolacustrine deposits. The aim of this study is to define the processes and recharge zones of this spring. The analysis of the data revealed the presence of two contributions to the Perrot Spring input: a spring thaw contribution defined by a small increase in flow and an autumn contribution from rainwater infiltration. The low average temperature and low variation of the annual temperature (4.8–6.5 °C) suggest a sufficiently deep flow circuit. Chemical analyses showed a groundwater chemistry consistent with the regional geology: the hydrochemical facies is calcium–magnesium bicarbonate and isotopic analyses (δ2H and δ18O) of rainfall and spring water suggested a recharge altitude of about 2100 m a.s.l. In conclusion, this study makes it possible to recognize the water inputs to the spring discharge and to delineate its recharge area, which can be proposed to implement strategies to protect the resource.

Experimental Study on the Stability of Shallow Landslides in Residual Soil

Landslide disasters are one of the most severe geological hazards in China. Soil slopes are prone to triggering landslides under the influence of main factors such as rainfall, resulting in economic losses, casualties, and ecological damage. Taking a residual soil landslide in Xingguo County as an example, this study investigated the influencing factors and mechanical properties of soil slope stability under rainfall infiltration through physical model experiments. The main conclusions were as follows: with the increase in rainfall intensity, the amount of rainwater infiltration and the weight of the soil mass increased, which led to greater changes in soil pressure. The maximum amplitude of the experimental process was 5.51 kPa. The response time of pore water pressure under a rainfall intensity of 45 mm/h was 20–30 min earlier than that under a rainfall intensity of 21 mm/h, with a larger fluctuation range. The maximum amplitude of the experimental process was 6.66 kPa. Under the condition of rainfall intensity of 21 mm/h, the slope undergone local shallow sliding failure, while under the condition of rainfall intensity of 45 mm/h, the slope undergone overall shallow sliding failure. The physical model experimental results were consistent with the historical deformation of the landslide and the actual situation on site. The conclusions of the experiment can provide a reference for the research on the failure mechanism of similar landslides.

A Study on the Change in Rainwater Infiltration Functions of Green Spaces Affected by Urbanization

A Study on the Change in Rainwater Infiltration Functions of Green Spaces Affected by Urbanization

Imaging hydrological dynamics in karst unsaturated zones by time-lapse electrical resistivity tomography

The hydrodynamics of karst terrain are highly complex due to the diverse fractures and reservoirs within limestone formations. The time delay between rainfall events and subsequent flow into reservoirs exhibits significant variability. However, these hydrological processes are not easily visualized in karst topography. Subsurface geophysics, specifically 2D time-lapse electrical resistivity tomography (ERT), provides an effective method for studying the relationships between hydrological and geophysical features. In our research, we adopted ERT in the Karst Critical Zone (KCZ) to visualize specific karstic zones, including cave galleries, water storage reservoirs, wetting fronts, soil layers, and potential preferential flow paths down to a depth of 20 m. To capture spatial and seasonal variations in resistivity, we presented a comprehensive approach by combining sixteen inversion models obtained between February 2020 and September 2022 above the Villars Cave in SW-France—a well-known prehistoric cave. We used a multi-dimensional statistical technique called Hierarchical Agglomerative Clustering (HAC) to create a composite model that divided the synthetic ERT image into eight clusters representing different karst critical zones. The ERT image clearly visualized the cave gallery with high resistivity values that remained consistent throughout the seasons. Our analysis revealed a close seasonal relationship between water excess and resistivity variations in most infiltration zones, with time delays increasing with depth. The karst reservoirs, located at significant depths compared to other clusters, displayed sensitivity to changes in water excess but were primarily affected by fluctuations in water conductivity, particularly during summer or dry periods. These findings have significant implications for predicting rainwater infiltration pathways into caves, thereby assisting in the conservation and preservation of prehistoric caves and their cultural heritage.

Ligustrum lucidum invasion alters the soil water dynamic in a seasonally multi-specific dry forest

Plant invasion is one of the major global environmental threats with the potential to alter the ecosystem stability and functioning. In water-limited ecosystems, the impacts of non-native invasive trees on the water balance are particularly relevant since they can compromise the use of water by native taxa of the ecosystem and water provision for humans. In this paper, we assessed the hydrological impacts of the Ligustrum lucidum (Chinese glossy privet) invasion on a mountain seasonally dry forest of the Chaco region (Central Argentina). More specifically, we determined volumetric soil water content, runoff, and actual evapotranspiration, and their relations to the size of rainfall events in native forest stands and its adjacent invaded stands. We combined three-years field measurements and remote sensing data. L. lucidum stands showed less water content through the soil profiles than the native forest (0–70 cm depth; 19.6 and 23.1 %, respectively), particularly during the dry conditions. The drier condition in the deeper soil layers compared to the upper ones in the invaded stands indicated less rainwater percolation throughout the soil profile over the year, independently of the magnitude of the rainfall events. Daily variation of deep-water content (60–70 cm depth), only observed in L. lucidum stands, showed nightly increase and day-time decrease in dry conditions. Runoff was similar and almost nil in both native and invaded forests, even after large rainfall events (>30 mm). L. lucidum stands showed ∼ 18% higher annual actual evapotranspiration rates than native stands. Based on our results, relatively higher water consumption for mono-specific L. lucidum stands in periods when photosynthetic activity of multi-specific native dry forest is still low may represent a competitive advantage in terms of plant invasion, and at the same time it generates negative impacts on water resources, reducing soil water content and limiting deep-water recharge in a water-limited ecosystem.

Load bearing capacity analysis of concrete sidewalk system designed to ensure comfort of walking for people with a motor disability

The paper looks at a novel structural solution to sidewalks. The proposed system consists of a box element as a substructure and a concrete slab with openings for rainwater infiltration. Such a design will make the sidewalk comfortable for pedestrians with motor impairments, friendly for urban tree root systems and durable. The article provides stress and strain calculations for the variants of the new design. We used the finite element method for the analysis. The results confirm that the proposed variants meet the assumed strength criteria and can therefore be used in the next research steps, that is, permeability tests, rain-water retention simulations, laboratory testing. Highlights Concrete paving slab with environmental approach. Concrete paving slab for people with motor disabilities. The first study implementing FEM method supported by the Barcelona model to analyse stresses and strains in sidewalk pavement.

Advancing Urban Wastewater Management: Optimizing Sewer Performance through Innovative Material Selection for the Armlet with a Wet Circuit Measurement System

Rainwater infiltration presents substantial challenges for urban wastewater management systems. This article delves into enhancing the quality of wastewater systems by proposing a novel device designed to tackle this issue comprehensively. The focal point of our research revolves around the conceptualization, construction, rigorous testing, and the potential multifaceted applications of this innovative wastewater device. Our study is dedicated to assessing the viability of a cutting-edge apparatus that empowers municipal entities in swiftly identifying rainwater ingress points within channels during precipitation events. Our findings vividly showcase the device’s remarkable capability to directly measure moisture levels along the channel’s path, eliminating the arduous need for manual data input, extensive data collection, and intricate water analysis procedures. To ensure the seamless flow of both sewage and water within the sewer channel, the use of a relatively slender strap is conventionally favored. However, factoring in the requisite structural robustness, we recommend a minimum thickness of 4 mm for 3D printing applications. For instances where maintaining the channel’s cross-sectional area integrity is paramount, opting for an armlet with a wet circuit measurement thickness of up to 7 mm is vital. In the realm of material selection, our investigation advocates for the utilization of PC/ABS (polycarbonate/Acrylonitrile Butadiene Styrene), ABS, ASA (Acrylonitrile Styrene Acrylate), or HIPS (High Impact Polystyrene) for strap housing. For sewer diameters surpassing 315 mm, the application of thin-walled PVC (Poly Vinyl Chloride) emerges as a practical recommendation. Notably, the incorporation of PVC flat bars is discouraged, as their presence might potentially hinder the fluidity of sewage flow, thereby compromising the precision of wet circuit measurements. The pivotal innovation lies in the armlet with a wet circuit measurement system, harboring immense potential for broad-scale integration across municipal facilities. This solution emerges as a streamlined and efficient strategy, offering a comprehensive avenue for continuously monitoring, fine-tuning, and optimizing the structural soundness and operational efficacy of sewer systems.

Evaluation of the Performance of the Horizontal Drain in Drainage of the Infiltrated Water from Slope Soil under Rainfall Conditions

It is known that rainwater infiltration is crucial for rainfall-induced slope failure because the infiltrated water can significantly weaken the shear strength of unsaturated soil. Horizontal drains are commonly used to provide appropriate drainage for the rainwater that percolates out of a slope. However, the effects of the length and location of the subsoil pipe on the performance of horizontal drains have not been extensively investigated. In this paper, a parametric analysis by using a numerical model was adopted to investigate the distribution of pore-water pressure in a slope. The results reveal that an inclination angle of 10–15 degrees and strategic placement at the slope toe and mid-slope provide optimal drainage performance, as compared to the effect of pipe length. Multi-layers of horizontal drain (based on 10 m length) are recommended for slopes with a height of more than 15 m.

Numerical simulation for strip-island freshwater lenses involving a precipitation-fed freshwater table

The freshwater table is the upper boundary of the entire freshwater lens and is very important for understanding the formation of freshwater lenses and for managing fresh groundwater on islands. However, little attention has been given to the position of the freshwater table, as it is difficult to visually distinguish it from the unsaturated zone in physical models. Under the natural conditions, the process of rainfall infiltration into soils involves both pore-water flow and air flow in soil voids, and thus, the airflow induced by infiltration has implications for groundwater recharge and formation of freshwater lenses. Therefore, research on the precipitation-fed freshwater table in an oceanic island should consider the water-air two-phase flow induced by rainwater infiltration. This study focuses on simulating the steady-state position of the freshwater table using TOUGH2/EOS7, a model that considers liquid and gas two-phase flow and brine, water and air three-component in unsaturated-saturated porous media, and verifying it by comparing the numerical results with the analytical solutions. The numerical results delineated the entire geometry of island freshwater lenses that involve a freshwater table replenished by precipitation, which were then compared with the Dupuit-Ghyben-Herzberg (DGH) analytical solutions that ignore the outflow face and with Van der Veer's analytical solutions that consider the outflow face. Reasonable fits between the numerical results and the DGH analytical solutions were obtained, with the exception that the lens obtained by the DGH analytical model is smaller in size than that simulated by the numerical model for various cases; a better agreement was found between the results from the numerical model and Van der Veer's analytical solutions for the homogeneous island case. The agreements between the results from the proposed numerical model and the DGH and Van der Veer's analytical models verified the proposed numerical model. The numerical modeling method investigated here enhanced the numerical simulation techniques for studying groundwater movements and the interaction of freshwater and saltwater on oceanic islands and can provide a reference for modeling more complicated island groundwater patterns.

Modeling vadose zone hydrological processes in naturally occurring piezometric depressions: the Chari-Baguirmi region, southeastern of the Lake Chad Basin, Republic of Chad

The Chari-Baguirmi region, southeastern of the Lake Chad (Africa), has a wide naturally occurring piezometric depression with values deeper than the expected regional groundwater level. To date, the most widely accepted hypotheses to explain its origin and dynamics are based on lack of rainwater infiltration and exfiltration processes. The code HYDRUS-1D is applied to numerically simulate the hydrological flow processes along the unsaturated zone in two soil profiles located in the central part and on the boundary of this piezometric depression under bare and vegetated soil coverage. The simulated time period is 2004–2015 with 715 mm annual rainfall average. The computed recharge with respect to total precipitation accounts for 21% on the boundary and 12% in the central part, which is limited by thick silty low permeability layer on the top surface. Considering modelling uncertainty and limitations under the simulated climatic conditions, the rainfall effect is observed only at upper soil layers, which leads to low aquifer recharge, while the upward water flux causing water table evaporation is very low. Past climate conditions, capable of developing a drying front to reach the water table after thousands of years of drying and geological structural constraints, may explain the current depressed area.