Influence Of Rainfall Intensity Research Articles

Investigation of rainfall intensity on the slope failure process using GPU-accelerated coupled MPM

Rainfall-induced slope failure is a common geo-hazard, which can cause catastrophic damages to human life and properties. In order to prevent the occurrence of catastrophes, understanding the mechanism of rainfall-induced slope failure and estimating its failure process is of significant importance. This paper presents a solid–fluid coupling material point method (MPM) in simulating the rainfall-induced slope failure process, and meanwhile, the influence of rainfall intensities on the slope failure process is explored. The solid–fluid coupling MPM is enhanced with a cubic B-spline shape function, rainfall infiltration boundary condition and GPU-accelerated framework, so that a computationally efficient and numerically stable simulation can be realized. One-dimensional consolidation, infiltration and two-dimensional slumping block tests are firstly simulated to test the effectiveness and capability of the solid–fluid coupling MPM in simulating large deformation hydro-mechanical problems. Thereafter, an in-door rainfall-induced slope failure experiment is simulated, where a consistent failure pattern is reproduced. Finally, the influence of rainfall intensity on the slope failure process is studied. Deep-seated and shallow surface failures are two major failure patterns corresponding to small and large rainfall intensities, respectively. Further analyses prove that different evolutions of pore pressure fields and seepage channels play important roles in forming the different failure patterns.

Stemflow temporal dynamics differ significantly between standing live and dead branches of two xerophytic shrub species

Shrub mortality due to self-thinning and climate change is a natural consequence of the long residence times of standing dead branches in unmanaged shrub plantations. Stemflow (SF) represents a key point source of input water and nutrients into the soil in shrub ecosystems. However, little information is available about how shrub mortality affects SF variables. In this study, we measured the SF volume (SFV), funneling ratio (FR), SF intensity, time lag to rain, and rainfall characteristics for live and standing dead branches of two major shrub species comprising Caragana korshinskii and Salix psammophila during the rainy season in 2022 on the Chinese Loess Plateau. The results demonstrated that the SF variables and temporal dynamic processes differed between standing live and dead branches of the two shrubs. For C. korshinskii, the mean SFV and FR were 1.9 and 1.8 times higher for live branches than dead branches, respectively, whereas for S. psammophila, the mean SFV and FR were 1.3 and 1.6 times higher for dead branches than live branches. These contradictory results can be explained by differences in the canopy structures of the species, such as the surface area that contributes to the generation of SF in the upper canopy, branch angles, and the degree of branch bark decomposition and decay. In addition, the SF variables were significantly temporally dependent on the rainfall characteristics. SFV, SFI, and SFD were positively and linearly correlated with the rainfall amount, intensity, and duration at the inter-event scale (P < 0.001). The influence of rainfall intensity on SF time lag to rain were not significant at the intra-event scale (P > 0.05). Considering the enrichment ratio due to canopy dry deposition and bark decomposition, the periodic flattening of dead S. psammophila branches to restore their growth is less significant than allowing them to die and renew naturally. These findings may serve as a reference for developing management practices for shrub species in areas with soil water and nutrient deficiencies.

Influence of Rainfall Intensity and Slope on the Slope Erosion of Longling Completely Weathered Granite

Serious slope erosion occurs in the distribution areas of fully weathered granites, and rainfall intensity and slope gradient are important factors affecting slope erosion. In this study, we investigate the erosion characteristics of Longling completely weather granites with a focus on the effects of rainfall intensity and slope gradient. Based on an indoor 60-min simulated rainfall test, we selected four slope gradients (10°, 20°, 30°, and 40°) and three rainfall intensities (50, 80, and 110 mm/h) for evaluation. A total of 12 groups of tests were conducted to analyze the erosion and surface hydrodynamic characteristics of the completely weathered granite slope. The results indicate a significant positive correlation between rainfall intensity and slope gradient, and the correlation between rainfall intensity and flow velocity became stronger as the slope gradient increased. The peak sediment yield rate represents the moment at which the change in slope shape is maximized. After the peak appears, the slope will no longer undergo great deformation, and the sediment yield rate will decrease and then become stable. Finally, rainfall intensity and slope gradient, which are the two key factors that determine slope flow velocity, are described using a binary function. The findings provide a reference for the study of slope erosion in completely weathered granites.

Physical Model Experiments on Failure Mechanism on Slopes of Weathered Basalt Soils during Heavy Rainfall Events.

Basalt platforms are widely distributed in many areas of China, where landslides occur frequently. It is well recognized that landslide hazards seriously threaten engineering constructions and property safety. It is, therefore, of great significance to understand deformation and failure behaviors and their mechanisms in basalt slopes to reduce the loss caused by landslides. In this work, the Pengshan Landslide in Zhejiang Province is taken as a prototype and slope model tests are carried out. During the tests, real-time monitoring of pore pressure, earth pressure and slope deformation is conducted. Based on the experimental data, the influence of rainfall intensity and the thickness of a weak interlayer on the slope stability are obtained. It is demonstrated that the rainfall and weak interlayer are the most important factors causing the slope instability of a basalt platform. Furthermore, damage from a basalt platform slope usually starts from local failure, and the slope foot is the most likely sliding part. Moreover, when the rainfall intensity is doubled, the initial deformation time of the slope is reduced by about half and the final failure time is advanced by one-third. In addition, when the thickness of the weak interlayer is doubled, the initial deformation time of slope is shortened by about half and the final failure time is advanced by one-quarter.

Instability of High Liquid Limit Soil Slope for the Expressway Induced by Rainfall

The instability of high liquid limit soil slope is a common engineering problem in highway construction. This study focused on the slope at section K79 + 880 of the Guang-Le Expressway in Guangdong Province, China. In order to reduce the landslide and learn the mechanism of the high liquid limited soil slope, the effects of different rainfall intensities and rainfall time on the high liquid limit soil slope were studied by in-site monitoring and numerical simulation. According to the characteristics of the slope deformation and the monitoring data, the slope landslide is divided into three grades. Numerical simulation results show that the influence of rainfall intensity on the safety factor of high liquid limit soil slope is greater than that of rainfall time. At the slope top, the cumulative changes of Mises stress in Group B and Group C were −2.19 kPa and −2.91 kPa, respectively, and the cumulative decreases were −7.22% and −9.60%, respectively. At the slope bottom, the cumulative changes of Mises stress in Group B and Group C were −2.05 kPa and −4.32 kPa, respectively, and the cumulative decreases were −4.50% and −9.48%, respectively. With the increase of rainfall for 24 h, the safety factor of Group C decreased by an average of 0.0408, and with the increase of rainfall time, the safety factor increased, and the safety factor of 96 h of rainfall in Group C was 0.1249 lower than that of 24 h of rainfall. The greater the rainfall intensity, the greater the change of matrix suction at the top of the slope, and the more prone the top of the slope to shallow landslides. For the high liquid limit soil slope, slope instability phenomena such as surface flow collapse occur easily and have little impact on the deep sliding surface. The dimensionless displacement coefficient K is proposed to quantify the landslide displacement under different rainfall. A general method is proposed to measure the cumulative displacement of the K79 + 880 slope where the sensor is not placed.

Sensitivity of Traffic Speed to Rainfall

Abstract Hazardous weather conditions can pose a threat to the functioning of transportation systems. While the impacts of extreme weather events (e.g., hurricanes/tornadoes and flooding) on transportation disruptions have received significant attention, minor transient disturbances in traffic and transport systems due to rainfall events have remained understudied. Given that a road network experiences rainfall events on a regular basis, which in turn likely reduces its efficiency through short-term disruptions, it is imperative to assess the influence of variations in rainfall intensity on the traffic speed. By synergistically using crowdsourced probe vehicle speed data and spatially explicit meteorological data, this study quantifies the sensitivity of traffic speed to rainfall events of different intensities over 1151 road sections within Alabama. It is observed that instead of variations in the rainfall intensity, traffic speed sensitivity is primarily influenced by a road section’s free-flow speed (uninterrupted speed during dry pavement conditions) and antecedent traffic volume. Relative sensitivity of road sections exhibits high consistency over different rainfall intensities across all road sections, thus underscoring the possibility of assessing sensitivities based only on speed data collected during rainfall intensities that are much more frequent. These results may be used to identify road sections and time periods with high sensitivity to rainfall, thus helping in prioritization of mitigation measures. Significance Statement To safeguard against hazardous driving conditions during rainfall events, from either compromised visibility or reduced friction between tires and pavement, drivers often reduce vehicle speed. However, the influence of rainfall intensity on traffic speed reduction remains unclear. This study analyzes the sensitivity of traffic speed to rainfall intensity. Our results indicate that, while rainfall indeed leads to traffic speed reductions, the extent of reduction is predominantly influenced by free-flow speed (uninterrupted vehicle speed) of the road section and the traffic volume on it instead of the rainfall intensity. These results may be used to identify high-sensitivity time periods and locations and guide prioritization of mitigation measures.

Influence of Rainfall Intensity and Slope on Runoff and Sediment Reduction Benefits of Fine Mesh Net on Construction Spoil Deposits

Fine mesh nets (FMNs) are commonly used as a mulch material to control soil erosion in construction spoil deposits. Here, three rainfall intensities (60–120 mm·h−1) and seven slope gradients (5–35°) were considered in relation to an FMN’s function of reducing soil erosion on spoil deposits. Soil surfaces covered with an FMN (NS) were prepared in 2 m × 0.5 m soil boxes, with a smooth surface (SS) as the control. Runoff and sediment reduction benefits (RRB and SRB, respectively) were used to quantify the role of the FMN in soil erosion reduction. The FMN performed better in controlling the total sediment yield (mean SRB: 35.9%) compared with total runoff (mean RRB: 5.3%). There was a difference in runoff between SS and NS under a low rainfall intensity (60 mm·h−1; p &lt; 0.05). SS and NS on different slopes generated similar runoff, with significantly different sediment yields (p &lt; 0.05). The benefits of the FMN basically decreased with increases in the rainfall intensity and slope, although the RRB fluctuated on different slopes. The results demonstrate that the soil and water conservation benefits of the FMN on spoil deposits were influenced by the rainfall intensity and slope. The effectiveness of FMNs in soil erosion control needs further investigation in the context of local climates.

Seasonal factors affecting sea turtle nesting in the Southeastern Caribbean Sea (Gulf of Paria, Venezuela)

The nesting characteristics (number of nests and eggs, time of year, nesting initiation, and nesting length) of leatherback (Dermochelys coriacea) and hawksbill (Eretmochelys imbricata) sea turtles of the southern Caribbean Sea (specifically in the Gulf of Paria in Venezuela), were examined in association with weekly precipitation averages and number of rainy days per week during the period between 2009 and 2018. We hypothesized about the influence of rainfall intensity and patterns as the main abiotic factor for sea turtle nesting. On average, leatherbacks preferred nesting during the drier season of each year (March, April, and May), while hawksbills nested during the rainy season (June to September). For both species, we found few significant correlations between the number of nests or clutch size (number of eggs per nest) and weekly averages of seasonal precipitation rates in the region. Average hawksbill clutch sizes were not correlated with average precipitation rates but were positively correlated with the number of rainy days per week (r=0.66, P≤0.05). Average hawksbill clutch sizes decreased each year on average (-3.3 eggs/year, r=-0.88, P≤0.001), which coincided with a negative long-term trend in the number of rainy days (-0.11 rainy days/week, r=-0.69, P≤0.05). During the study period, nesting activities for both leatherback and hawksbills started progressively later (0.9 and 0.6 weeks/year, respectively p≤0.05) and were shorter (-0.9 and -0.8 weeks /year, P≤0.1 and P≤0.05, respectively).

Removal Effect of Basic Oxygen Furnace Slag Porous Asphalt Concrete on Copper and Zinc in Road Runoff.

In order to improve the utilization efficiency of road runoff and the remove effects of heavy metals, porous asphalt pavements have been used as an effective measure to deal with heavy metals in road runoff. However, the removal effect on dissolved heavy metal is weak. In this paper, basic oxygen furnace (BOF) slag was used as aggregate in porous asphalt concrete to improve the removal capacity of heavy metal. Road runoff solution with a copper concentration of 0.533 mg/L and a zinc concentration of 0.865 mg/L was artificially synthesized. The removal effect of BOF slag porous asphalt concrete on cooper and zinc in runoff was evaluated by removal tests. The influence of rainfall intensity and time on the removal effect was discussed. The results obtained indicated that BOF slag porous asphalt concrete has a better removal effect on copper. The removal rate of copper is 57–79% at the rainfall intensity of 5–40 mm/h. The removal rate of zinc is more susceptible to the changes of rainfall intensity than copper. The removal rate of zinc in heavy rain conditions (40 mm/h) is only 25%. But in light rain conditions (5 mm/h), BOF slag porous asphalt concrete maintains favorable removal rates of both copper and zinc, which are more than 60%. The heavy metal content of runoff infiltrating through the BOF slag porous asphalt concrete meets the requirements for irrigation water and wastewater discharge. The results of this study provide evidence for the environmentally friendly reuse of BOF slag as a road material and the improvement of the removal of heavy metal by porous asphalt concrete.

Rainfall Erosion Predictions for Artificial High-Filled Embankment with Reinforcement

In recent years, rainstorm disasters caused by global warming have frequently occurred in China. It has caused serious damage to artificial high embankments. In this paper, the influence of rainfall intensity, slope, and reinforced layers on the erosion and destruction of the artificial high embankment is deeply analyzed. Through the model test, the rainfall erosion prediction model is established. The results show that (1) the gully width, depth, and erosion amount increased with the increase in rainfall intensity and slope and decreased with the increase in reinforcement layers; (2) the final ditch shape of the embankment is influenced by steel bars; and (3) according to the model test data, the mathematical model of dike scouring is established. Rainfall intensity and the coupling between slope and reinforced layers are considered in the model. It can be used for predicting erosion during rainfall.

A lattice Boltzmann model for the viscous shallow water equations with source terms

In this paper, a lattice Boltzmann (LB) model is proposed for a class of viscous shallow water equations, in which a second-order moment of the source term is applied to recover the viscosity in the governing equation and eliminate the additional errors generated during the Chapman-Enskog analysis. There are three different schemes based on different treatments of the source term. Through numerical simulations of several classical benchmark problems, we find that the second-order moment of the source term can not only improve the accuracy of the LB model, but also ensure the conservation of the system. In addition, the influence of rainfall intensity on shallow water flow is also taken into account, and the results show that present LB model can also accurately study such problems as overland flows.

Effects of rainfall intensity on runoff and nutrient loss of gently sloping farmland in a karst area of SW China.

Nutrient losses from sloping farmland in karst areas lead to the decline in land productivity and nonpoint source pollution. A specially tailored steel channel with an adjustable slope and underground hole fissures was used to simulate the microenvironment of the "dual structure" of the surface and underground of sloping farmland in a karst area. The artificial rainfall simulation method was used to explore the surface and underground runoff characteristics and nutrient losses from sloping farmland under different rainfall intensities. The effect of rainfall intensity on the nutrient loss of farmland on karst sloping land was clarified. The results showed that the surface was the main route of runoff and nutrient loss during the rainy season on sloping farmland in karst areas. The influence of rainfall intensity on the nutrients in surface runoff was more substantial than that on underground runoff nutrients. Nutrient loss was more likely to occur underground than on the surface. The losses of total nitrogen, total phosphorus, and total potassium in surface and underground runoff initially increased and then gradually stabilized with the extension of rainfall duration and increased with increasing rainfall intensity and the amount of nutrient runoff. The output of nutrients through surface runoff accounted for a high proportion of the total, and underground runoff was responsible for a low proportion. Although the amount of nutrients output by underground runoff was small, it could directly cause groundwater pollution. The research results provide a theoretical reference for controlling land source pollution from sloping farming in karst areas.

Experimental study on anti-eroding effect of slope protected by degradable geocell

In order to study the anti-erosion mechanism of the new degradable geocell which is designed for slope protection and the influence of rainfall intensity and materials on its anti-erosion performance, based on the laboratory simulated rainfall tests, the erosion damage mode and water erosion of slope under the protection of linen fiber and bamboo fiber braided geocell under different rainfall intensities are studied by taking photos of the slope surface and collecting and weighing the erosion material. The results show that the new type of degradable geocell for slope protection can effectively prevent the development of slope gullies, and the slope damage is mainly splash erosion and sheet erosion. The use of linen fiber and bamboo fiber braided geocell can effectively reduce the maximum water erosion by more than 10% and the accumulated water erosion by more than 20%. With the increase of rainfall intensity, the maximum water erosion and accumulated water erosion are increased, but the increase range is 20% ∼ 33% and 35% ∼ 57% lower than that of bare slope, respectively. The results show that the anti-erosion ability of bamboo fiber braided geocell is slightly better than that of linen fiber braided geocell, and the ratio of maximum water erosion and accumulated water erosion reduced is slightly higher than that of linen fiber braided geocell.

Influence of Rainfall Intensity on the Stability of Unsaturated Soil Slope: Case Study of R523 Road in Thulamela Municipality, Limpopo Province, South Africa

The purpose of this paper was to analyze the impact of extreme rainfall on the recurrence of slope instability using the Thulamela Municipality roads (R523) as a case study. To this end, the historical rainfall data of the area of study were analyzed between 1988 and 2018. The results show that a significant increase in rainfall is usually experienced in the summer months of December and January. Following this, the factor of safety (FoS) of slopes of silt clay, clay, and clay loam soils were estimated using the SLIDE simulator (Numerical software “Finite Element Method (FEM)”) under sunny to rainy conditions of the area. A complementary model, FLACSlope (Numerical software “Finite Difference Method (FDM)”), was utilized to simulate FoS and pore water pressure in sunny and rainy conditions of the area. Simulation results show that extreme rainfall has the ability to reduce the shear strength and resistance of the soil slope material. This may explain the recurrent landslides noted in the area. Finally, the water pore pressure has been simulated to increase with the increased water table, which generally pushes the soil particles apart and reduces the stress between the particles resulting in soil slope failure. Extreme rainfall alters the phase of the material solid in a manner that may require further research for a better understanding.

Parameterization of the Collection Efficiency of a Cylindrical Catching-Type Rain Gauge Based on Rainfall Intensity

Despite the numerous contributions available in the literature about the wind-induced bias of rainfall intensity measurements, adjustments based on collection efficiency curves are rarely applied operationally to rain records obtained from catching-type rain gauges. The many influencing variables involved and the variability of the results of field experiments do not facilitate the widespread application of adjustment algorithms. In this paper, a Lagrangian particle tracking model is applied to the results of computational fluid dynamic simulations of the airflow field surrounding a rain gauge to derive a simple formulation of the collection efficiency curves as a function of wind speed. A new parameterization of the influence of rainfall intensity is proposed. The methodology was applied to a cylindrical gauge, which has the typical outer shape of tipping-bucket rain gauges, as a representative specimen of most operational measurement instruments. The wind velocity is the only ancillary variable required to calculate the adjustment, together with the measured rainfall intensity. Since wind is commonly measured by operational weather stations, its use adds no relevant burden to the cost of meteo-hydrological networks.

Field studies on the influence of rainfall intensity, vegetation cover and slope length on soil moisture infiltration on typical watersheds of the Loess Plateau, China

AbstractSoil moisture is a key process in the hydrological cycle. During ecological restoration of the Loess Plateau, soil moisture status has undergone important changes, and infiltration of soil moisture during precipitation events is a key link affecting water distribution. Our study aims to quantify the effects of vegetation cover, rainfall intensity and slope length on total infiltration and the spatial variation of water flow. Infiltration data from the upper, middle and lower slopes of a bare slope, a natural grassland and an artificial shrub grassland were obtained using a simulated rainfall experiment. The angle of the study slope was 15° and rainfall intensity was set at 60, 90, 120, 150, and 180 mm/hr. The effect these factors have on soil moisture infiltration was quantified using main effect analysis. Our results indicate that the average infiltration depth (ID) of a bare slope, a grassland slope and an artificial shrub grassland slope was 46.7–73.3, 60–80, and 60–93.3 cm, respectively, and average soil moisture storage increment was 3.5–5.7, 5.0–9.4, and 5.7–10.2 mm under different rainfall intensities, respectively. Heavy rainfall intensity and vegetation cover reduced the difference of soil infiltration in the 0–40 cm soil layer, and rainfall intensity increased surface infiltration differences on the bare slope, the grassland slope and the artificial shrub grassland slope. Infiltration was dominated by rainfall intensity, accounting for 63.03–88.92%. As rainfall continued, the contribution of rainfall intensity to infiltration gradually decreased, and the contribution of vegetation cover and slope length to infiltration increased. The interactive contribution was: rainfall intensity * vegetation cover &gt; vegetation cover * slope length &gt; rainfall * slope length. In the grass and shrub grass slopes, lateral flow was found at a depth of 23–37 cm when the slope length was 5–10 m, this being related to the difference in soil infiltration capacity between different soil layers formed by the spatial cross‐connection of roots.

Numerical and Experimental Investigation on the Function of Siphons for Tipping-Bucket Rain Gauges

AbstractSiphons can effectively reduce the influence of rainfall intensity on the mechanical bias of tipping-bucket rain gauges (TBRs). To identify the function of siphons for TBRs, this study investigated three types of siphons: a Texas Electronics (TE) siphon, a RIMCO (RIM) siphon, and a Sutron siphon, with both computational fluid dynamics (CFD) simulations and laboratory experiments. To provide better structural designs, further simulations were conducted to adjust two parameters of the siphons: d, the distance from the cap to the outer part, and w, the distance from the main part to the cap part. The simulation results reveal that the most significant advantage of a siphon over a rain gauge collector is to provide stable outflow for the tipping bucket. The stable outflow rates were around 1.5 g s−1 (TE) and 1.55 g s−1 (RIM), while the Sutron siphon increased from 1.75 to 2.45 g s−1. The ratio of stable outflow time to a complete siphon event was 69% (TE), 81% (Sutron), and 83% (RIM). In experiments with rainfall intensity higher than 1 mm min−1, the RIM and TE siphons showed oscillations in the outflow during consecutive siphon events, whereas the Sutron siphon was relatively stable. Further simulations showed that the recommended d and w for the TE siphon are 2.5 and 1.1 mm, respectively, while the recommendations for the RIM siphon are d = 2.5 mm and w = 0.9 mm. The manufacturer’s specifications for d and w are best for the Sutron siphon. These results help to understand the functionality of siphons for TBRs, and benefit the structural design of common siphons.

Influence of Rainfall Intensity on the Nutrient Loading from an Inflowing River in the Plain River Network of the Taihu Catchment

To reveal the law of external pollution in the plain river network of the Taihu catchment, we investigated nitrogen, phosphorus, and dissolved organic carbon daily, as well as automatic recording data for flow rate and rainfall in Dapu River from 1st March, 2017 to 28th February, 2018. Dapu River, a typical inflowing river of Lake Taihu, usually has a reciprocating flow. A reciprocating flow is a common condition in the plain river network located in the Yangtze Delta. The response flow rate in the river was relatively slow to different intensities of rainfall. Flow rate significantly increased only when the rainfall intensity reached heavy rain (>25 mm·d-1). The concentrations were statistically non-significant under different rainfall intensities, and the concentrations of total nitrogen averaged 3.00±0.58, 3.34±0.93, 3.55±1.05, and 3.37±1.14 mg·L-1 under heavy rain (>25 mm·d-1), medium rain (10 mm·d-1-25 mm·d-1), light rain (<10 mm·d-1), and no rain. The concentrations of total phosphorus averaged 0.228±0.068, 0.258±0.121, 0.219±0.083, and 0.225±0.121 mg·L-1, respectively. The concentration of dissolved organic carbon and nitrogen in the Dapu River changed little during the 3 typical rainfall processes, but the concentration of phosphorus increased significantly after heavy rain when the duration was 2 days. The concentration of total phosphorus and particulate phosphorus increased significantly after medium rain when the duration was 1 day. The concentration of phosphorus did not show an obvious change after light rain. The concentration of total nitrogen was the highest under light rain, and the concentration of total phosphorus was the highest under medium rain. The daily loadings of total nitrogen from the Dapu River to Lake Taihu were 7.64, 3.19, 3.21, and 2.62 t·d-1 under conditions of heavy rain, medium rain, light rain, and no rain, respectively. The daily loadings of total phosphorus were 0.59, 0.26, 0.22, and 0.20 t·d-1 under conditions of heavy rain, medium rain, light rain, and no rain, respectively. Although the daily loading of nutrients under heavy rain conditions was the highest, the contribution of annual nutrient loading was small during heavy rain days. The reason was that the percentage of heavy rain during the entire year was small. The total nitrogen loading in heavy rain days was 61.11 tons in the observatory year, which was only 5.6% of annual loading. The total phosphorus loading in heavy rain days was 4.72 tons, which was only 5.8% of the annual loading. These low percentages of nutrient loading under heavy rainfall are quite different from situations in mountain catchments. This research showed that the transport processes of nutrients in the plain river network was complicated and its influence on nutrient concentrations and loadings in connected rivers was slow and indirect. The amount of inflow water was an important source of external nutrient loading in the plain river network. These conclusions have reference value for estimating the external loading and deciding non-point control policy of lakes in plain river network of the Taihu catchment.

Stability characteristics of shallow landslide triggered by rainfall

Rainfall-induced shallow landslides are known to be extremely dangerous since the sliding mass can propagate quickly and travel far from the source. Although the sliding mechanism in sloping ground is simple to understand, the problem may be complicated by unsaturated transient water flow. The flow behavior of rainwater in unsaturated sloping ground and the consequent factor of safety must be clearly understood to assess slope stability under rainfall conditions. A series of laboratory experiments was conducted to examine the critical hydrological states so that assessment of slope stability under rainfall condition can be performed. Based on the test results, a unique relationship between critical hydrological states, rainfall intensity, and soil properties was formulated. Sequential stability analysis provided insights into the stability of slopes subjected to variations in soil properties, slope angles and rainfall intensities, and the consequent variation in the depth of the failure plane, vital in landslide risk assessment, was determined through this analysis. The variation of rainfall intensity was found to strongly affect the depth of the failure plane in cohesionless sloping ground. Furthermore, the influence of rainfall intensity on the depth of the failure plane may be alleviated by a small magnitude of cohesive strength. The results of this study will reinforce knowledge of landslide behavior and help to improve mitigation measures in susceptible areas.

The influence of rainfall intensity and duration on sediment pathways and subsequent clogging in permeable pavements

The trapping of sediments within permeable pavements during infiltration is an important process that contributes to their water quality treatment performance. However, this process also leads to clogging, which decreases the infiltration capacity of the pavement. With different rainfall intensities and durations, this study investigates the amount and size of sediment passing through a porous paver, as well as through the gravel-filled gaps that separate adjacent pavers. One of the major challenges in this study was to design an experiment where the characteristics of the sediment particles that are trapped while passing through these two different infiltration pathways are assessed. This was overcome by developing a new type of rainfall application device in combination with a two-tiered sediment capturing system. A better understanding of the infiltration pathways of sediment and the associated clogging processes should help designers improve the effective life of permeable pavements. Overall, it was found that while the porosity of porous pavers serves a useful function in terms of removing excess surface water during and after a rainfall event, it serves little purpose in removing sediment from stormwater.