Long Periods Of Rainfall Research Articles

Influence of hydraulic properties to residual soil

Tropical country such as Malaysia experienced high intensity and long period of rainfall, which is the main factor of slope failure. The increasing of seepage subjected by rainfall not only distress suction distribution, but also affects hydraulic properties of soil lead to the decreasing of soil strength. This also leads to soil slope failure. The main hydraulic properties for soils are Soil-water characteristic curve (SWCC) and hydraulic conductivity, k. The relationship of these parameters is highly influenced by tropical soil, thus contributes to soil instability phenomenon. The main objective of this paper is to study the relationship between soils' hydraulic properties and particle size distribution (PSD). Four types of soils investigated in this research include one sample taken from Universiti Kebangsaan Malaysia (UKM)'s reserved forest, and three samples were commercially obtained. Other than soil basic properties, pressure plate extractor and permeability tests were conducted for SWCC and permeability, respectively. Tests show that different types of soils demonstrate different characteristic of SWCC and hydraulic conductivity. Result also shows that PSD has the influence and affect the result of hydraulic properties of soils. This study is expected to enhance the understanding of complex phenomenon of residual soil instability.

Flood risks factors and their prevalence in some selected local government areas of Jigawa State, Nigeria

Flood in Auyo and Miga local government areas is worrisome. The location of large parts of the study area is lying on the northern bank of Hadejia River, and many communities are at risk of flood hazard. This study is aimed at assessing flood risk factors in the vulnerable communities of Auyo and Miga LGAs, Jigawa State of Nigeria. A sample size of 666 respondents were drawn for self-administered questionnaire, 601 were fully completed. Data collected were analyzed descriptively for Relative importance index (RII). Findings revealed that, the current trend in the frequency of flood was on the increase, and the year 2012 (59%) and 2018 (61%) marked the worst with floods occurring four times. The major causes of flood were heavy rains (with RII of 4.890), overflow of river/stream with RII of 4.866, rainstorm, (with RII of 4.890), long period of rainfall (with RII of 4.805), steep side channels (4.785 of RII) and mystical beliefs (RII of 3.86). Man-made major factors were discovered to include; deforestation (with RII of 4.389) and lack of flood embankment, (RII of 4.316). Others were: poor waste disposal (RII of 3.915), lack of drainage network (with RII of 3.840), and development and infrastructure in flood-prone areas with RII of 3.733. It is recommended that, proper embankment protection and water regulatory outlets should be made available. Delineate flood risk zones before carrying out construction activities, or rather impose resettlement outside the flood prone areas.

Characteristics and Cause Analysis of the 1954 Yangtze Precipitation Anomalies

In 1954, the Yangtze River valley was hit by heavy precipitation anomalies, which caused large casualties and economic losses; however, systematic analyses of the causes are lacking. Adopting the latest national historical precipitation data collected by the China Meteorological Administration (CMA) and global sea surface temperature (SST) records, this retrospective study determined the spatial–temporal distribution characteristics of the precipitation in 1954 in Wuhan, a city situated in the Yangtze River valley. The results confirmed that the 1954 precipitation anomalies were characterized by a high volume and a long period of rainfall, plus numerous cloudbursts, with most of the precipitation concentrated during June and July at the mid- and low-Yangtze areas along the Yangtze. An El Niño event caused the West Pacific subtropical highs to continually move southward during the summer, creating a long-term rainband in the drainage basin. Moreover, the continued low SSTs in the Sea of Okhotsk generated an active blocking high that continuously brought high-latitude cold air into the south, boosting precipitation over the drainage basin. This study proposed a new causal model of summertime precipitation across the Yangtze River valley in 1954, whereby the unusual SST changes initially triggered atmospheric circulation anomalies, which caused the precipitation anomalies of 1954.

Multiseasonal probabilistic slope stability analysis of a large area of unsaturated pyroclastic soils

The analysis of slope stability over large areas is a demanding task for several reasons, such as the need for extensive datasets, the uncertainty of collected data, the difficulty of accounting for site-specific factors, and the considerable computation time required due to the size of investigated areas, which can pose major barriers, particularly in civil protection contexts where rapid analysis and forecasts are essential. However, as the identification of zones of higher failure probability is very useful for stakeholders and decision-makers, the scientific community has attempted to improve capabilities to provide physically based assessments. This study combined a transient seepage analysis of an unsaturated-saturated condition with an infinite slope stability model and probabilistic analysis through the use of a high-computing capacity parallelized platform. Both short- and long-term analyses were performed for a study area, and roles of evapotranspiration, vegetation interception, and the root increment of soil strength were considered. A model was first calibrated based on hourly rainfall data recorded over a 4-day event (December 14–17, 1999) causing destructive landslides to compare the results of model simulations to actual landslide events. Then, the calibrated model was applied for a long-term simulation where daily rainfall data recorded over a 4-year period (January 1, 2005–December 31, 2008) were considered to study the behavior of the area in response to a long period of rainfall. The calibration shows that the model can correctly identify higher failure probability within the time range of the observed landslides as well as the extents and locations of zones computed as the most prone ones. The long-term analysis allowed for the identification of a number of days (9) when the slope factor of safety was lower than 1.2 over a significant number of cells. In all of these cases, zones approaching slope instability were concentrated in specific sectors and catchments of the study area. In addition, some subbasins were found to be the most recurrently prone to possible slope instability. Interestingly, the application of the adopted methodology provided clear indications of both weekly and seasonal fluctuations of overall slope stability conditions. Limitations of the present study and future developments are finally discussed.

Identification of major loci for seed dormancy at different post-ripening stages after harvest and validation of a novel locus on chromosome 2AL in common wheat

A long-period duration of seed dormancy helps to reduce pre-harvest sprouting (PHS) damage in common wheat when a long period of rainfall or high humidity occurs. Identification of genes or loci underlying seed dormancy duration is of high importance for investigating genetic mechanism of PHS tolerance of wheat. In the present study, the germination index (GI) of different mapping populations at 5 days (GI5), 15 days (GI15), and 30 days (GI30) after harvest (DAH) was recorded during the 2011–2012, 2012–2013, 2013–2014, and 2014–2015 cropping seasons. Field sprouting (FS) values were also determined in 2012–2013 and 2014–2015 cropping seasons. Association analysis was performed in 260 wheat varieties and advanced lines differing in seed dormancy (SD) using 557 SSR and 14 gene-specific markers for PHS/SD-related genes. The result indicated that a total of 47 loci were significantly (P < 0.01) associated with SD using both the general linear model (GLM) and mixed linear model (MLM). Five major loci were consistently detected at different post-ripening stages after harvest, including four for GI5 and GI15 on chromosomes 3AS, 3BL, 5AL, and 5BL responsible for middle-duration SD, and one for GI5, GI15, and GI30 on 2AL associated with longer-duration SD. The major locus on 2AL (designated Qsd.ahau-2AL) is likely to be a novel QTL, which was linked to Xwmc658 by mapping analysis in 165 recombinant inbred lines (RILs) derived from the Jing 411 × Wanxianbaimaizi cross and 728 F2 plants from Jimai 20 × Suiningtuotuomai. Furthermore, a CAPS marker CAPS-2AL was developed for Qsd.ahau-2AL locus and was validated using the 728 F2 plants and 201 accessions of the Chinese mini-core collection. Our results also revealed that the TaMFT-like gene on 3AS had a more significant association with dormancy duration than the other six genes underlying SD/PHS resistance in Chinese wheat germplasm. This study provides useful information for marker-assisted selection in wheat breeding and enhances our understanding of molecular genetics of SD in wheat.

Vertical hydraulic gradient research in hyporheic zone of Beberibe river in Pernambuco State (Brazil)

ABSTRACT The interaction between groundwater and surface water occurs naturally and is dependent on the dynamics in the hyporheic zone. The hyporheic zone is the interface between the surface water source and the phreatic aquifer and it’s a system that also influences the water quality. An important feature is the ability to flux in this zone. This work aimed to evaluate the vertical hydraulic gradient in the hyporheic zone at two points in Beberibe river, Olinda-PE, to understand the hyporheic environment characteristics and water flow dynamics in experimental area, in addition to identify the existence of hydraulic connection between surface water and groundwater. The experimental phase consisted of infiltration tests in riverbed with cylinder infiltrometer and vertical hydraulic gradients readings with differential piezometer, complemented with grain size information, for an assessment of the water budget between the river and the aquifer. Analyzing the behavior of the interaction over the period of 10 months, it was observed that the Beberibe river (middle course) contributes to the groundwater recharge in most of the time. The average infiltration rate was 1.02 mm/min in point 1 and 0.85 mm/min in point 2. It was concluded that there is a variability in flow direction, which often is top-down, but may undergo change in the stream showing upstream after long periods of rainfall. Another conclusion is that grain size distribution of bed sediment, that is predominantly sandy, influences hydraulic conductivity of hyporheic zone and influences consequently the vertical flow rates.

Simulation of a persistent medium-term precipitation event over the western Iberian Peninsula

Abstract. This study evaluated the performance of the WRF-ARW (Weather Research and Forecasting with Advanced Research) weather prediction model in simulating the spatial and temporal patterns of an extreme rainfall period over a complex orographic region in north-central Portugal. The analysis was performed during the rainy season and, more specifically, the month of December 2009. In this period, the region of interest was under the influence of a sequential passage of low-pressure systems associated with frontal surfaces. These synoptic weather patterns were responsible for long periods of rainfall, resulting in a high monthly precipitation. The WRF model results during the study period were furthermore evaluated with the specific objective to complement gaps in the precipitation recordings of a reference meteorological station (located in Pousadas), the data of which are fundamental for hydrological studies in nearby experimental catchments. Three distinct WRF model runs were forced with initial fields and boundary conditions obtained from a global domain model: (1) a reference experiment with no nudging (RunRef); (2) observational nudging for a specific location, i.e. the above-mentioned Pousadas reference station (RunObsN); and (3) nudging to the analysed field (RunGridN). Model performance was evaluated, using several statistical parameters, against a dataset of 27 rainfall stations that were grouped by elevation. The three model runs had similar performances, even though RunGridN resulted in a slight improvement. Regarding the other two experiments, this improvement justifies its use for complementing the surface measurements at the Pousadas reference station. Overall model accuracy, expressed in root mean square error (RMSE), of the three runs was comparable for the stations of the different elevations classes. Even so, it was slightly better for stations in the lowlands than the highlands. Furthermore, model predictions tended to be less accurate for stations located in rough terrain and deep valleys.

Performance of nonwoven geotextile-reinforced walls under wetting conditions: laboratory and field investigations

ABSTRACT: The first geosynthetic retaining wall in Brazil was constructed in 1984 as an instrumented 10 m high geotextile-reinforced soil wall with a poorly draining backfill. This structure has been showing excellent performance throughout its service life, even after long periods of rainfall. In the past, the excellent performance of the wall had been attributed to the influence of soil confinement on the geotextile strength properties as well as the comparatively high interface shear strength between the fine soil and the nonwoven geotextile. Now there is also evidence of the beneficial effect of the internal drainage capacity when using nonwoven geotextiles as reinforcements. In order to clarify the understanding of the performance of the pioneer history case wall (SP-123 wall) and the effect of nonwoven geotextiles as reinforcements of fine-grained soils, full-scale laboratory models of geotextile reinforced walls were tested under wetting conditions. Results from the instrumentation have shown no significant positive water pressures and relatively small displacements even after intense periods of precipitation. The consistency between field and laboratory investigations provides strong evidence in support of the use of nonwoven geotextiles to reinforce poorly draining soils.

Study on Stability of Dayantang Landslide under the Engineering Disturbance and Rainfall

Dayantang slope was stable before Shuibuya project construction. Based on the long-term safety monitoring, it has appeared the obvious deformation during the project construction. According the monitoring datas, the stability of the landslide before and after the construction was discussed and analyzed. Considering the rainfall effect on landslide after it has been strongly anthropogenic disturbance, the numerical results show that it is in critical steady state without rainfall, while get worse and even unstable failure under the influence of the intensive rain and the long period of rainfall.

Relevance of tectonic and structural parameters in Triassic bedrock formations to landslide susceptibility in Quaternary hillslope sediments

Important controlling factors of mass movements are generally soil water and geometric-topographic terrain factors such as inclination, curvature type and degree, and the relative position of unstable slopes and embankments. In addition, various geologic parameters that have a direct or indirect connection to soil-mechanical properties of slide masses are also of importance. Some studies also emphasise tectonic parameters in the context of susceptibility to mass movements. This study considers the relevance of tectonic and structural parameters in bedrock formations for landslides in periglacial hillslope sediments on top of the bedrock. The research area is part of the southern Solling anticline, a saddle structure in the Middle Bunter Sandstone formation in northern Hesse and southern Lower Saxony (Germany). In this geologic formation, sandstone, siltstone, and mudstone are interbedded with impermeable strata. Uplift of the Solling anticline, in particular during the Quaternary, resulted in a partially intensive dissection of the Bunter Sandstone plateau into separate blocks with disrupted, tilted, and partially rotated layers. The structural conditions have an indirect impact upon landslides in the superposed hillslope sediments. Water flow along strata and joints above water impermeable strata cause water infiltration and moistening of the periglacial hillslope sediments on top of the bedrock. Mass movements are frequently linked to sites of outcrop springs and occur after long periods of rainfall. A GIS-based analysis was used to statistically evaluate possible factors controlling landslides. Factors were weighted and included in an empiric-statistical model that allows spatial description of hazard potentials due to mass movements. In addition to morphologic parameters, the structural parameters of the bedrock are of utmost importance for the occurrence of landslides.

IN SITU MEASUREMENT OF THE SOIL MOISTURE CONTENT PROFILE AT A DECOMPOSED GRANITE CUT-SLOPE

Two selected sites at a decomposed granite cut-slope were instrumented with a rain gauge and a series of ThetaProbes installed at depths up to 90 cm from the slope surface. The objective of this study was to evaluate the significance of antecedent soil moisture conditions in controlling the hydrologic responses of the soils at each site. The antecedent moisture content of the soil in Site #1, in general, increases with depth. The response of the soil to saturation process is more or less confined to the shallow depth. On the other hand, the measurement data of the soil in Site #2 showed that the near surface soil exhibits higher antecedent moisture condition than the deeper soil. The ingress of the wetting front could reach more than 90 cm depth during long period of rainfall. Thus, these results suggest that the hydrological response of the soils is spatially variable and is influenced by the antecedent soil moisture conditions within the soil profile. The presence of soil layers, the distribution of macro cracks within the soil profile, and additional lateral source of moisture may also have significant influences on soil response to saturation process.

A distribution‐free test to detect gradual changes in watershed behavior

This paper presents a distribution‐free statistical test aimed at detecting gradual changes in the hydrological behavior of watersheds. The proposed test uses a rainfall‐runoff model to identify watershed behavior over successive time periods and a resampling approach to quantify the significance of trends. The method can be applied with any model deemed suitable for the studied watershed. To assess test efficiency, we used three different case studies: An afforested agricultural watershed, a burnt‐over forested watershed, and a watershed covered by old‐growth forest. All three watersheds had a long period of rainfall and runoff records (60, 35, and 40 years, respectively), on which stationarity could be tested. The test was shown to adequately detect gradual changes, and it can therefore be useful to identify hydrological trends, wherever rainfall and streamflow time series are available.

First report of leaf spot of Paederia scandens caused by Pseudocercospora paederiae in Korea

Paederia scandens (P. foetida), a fast-growing, perennial, deciduous climbing plant in the Rubiaceae, is a native of eastern and southern Asia. The plant is widely distributed in grassland on the seashore of the subtropical island Cheju, as well as in the foothills of the middle and southern districts of Korea. Paederia scandens has traditionally been used as a medicinal herb in Asia. In Florida, where it is known as skunk vine weed, it creates dense canopies leading to injury, structural alteration, or death of native vegetation (Walker et al., 2001). In France and Germany it has been cultivated as an ornamental and used to produce a sweet juice. In July 2000 a brown leaf spot was observed on P. scandens for the first time in Keryong Mountains in Chungnam district, South Korea. Further surveys for Paederia leaf spot in the southern districts, Chonnam, Kyeongnam, and Cheju island revealed that the disease was widespread under moist and warm conditions. Typical disease symptoms were generally observed in late July and August due to a long rainy period. In addition, the long period of rainfall during late June and July 2000 favoured more development and spread of the disease than in 2001. The initial symptoms generally observed in early July consisted of small, brown leaf spots that expanded and coalesced, resulting in discoloration, blight, necrosis and defoliation. Leaf spots were amphigenous, circular, irregular, distinct, orbicular, blackish or bright brown, sometimes reddish brown, often bordered with a raised, dark linear margin on both leaf surfaces, and with grey to brown centres, commonly 1–5 mm (up to 20 mm) in diameter. The leaf spots were more severe on leaves near the ground and progressed to the upper leaves. Small blackish brown leaf spots were also observed until late October. Conidiomata were densely fasciculate to synnematous and the scars of the conidiogenous cells, which are rather inconspicuous, unthickened and not darkened, were the only definitive diagnostic signs observed. The morphological characteristics of conidiomata and scars matched previously reported descriptions of Pseudocercospora paederiae (Cercospora paederiae) (Hsieh & Goh, 1990; Guo & Liu, 1991), although the morphology resembled Phaeoisariopsis, whose conidiomata were generally synnematous. Conidiophores were chiefly hypophyllous, but sometimes epiphyllous with globular or subglobular stromata, about 10–30 in dense synnemata, 119–210 μm long and 3–5 μm wide, arising from stromata, multiseptate, generally straight but often curved at the apices. They were caespitose, slightly wider at the apex than base, and sometimes forming rather loose synnemata at the apex. Synnemata were black-brown, often branched, 102–153 μm long and 14–41 μm wide. Conidia were hyaline to brown, single, obclavate, generally slightly curved, with a rounded apex and an obconic truncate base, mostly 2–7 (up to 10) septate, 31–120 μm long, 2–6 μm wide at the apex and scar, respectively. Pathogenicity of the fungus was determined on 4-weekold leaves of P. scandens. For inoculation, a conidial suspension (approximately 10 spores mL) containing fungal mass such as synnematous conidiophores and mycelia was prepared from cultures grown on Paederia leaf extract-potato dextrose agar for 3 weeks. Slightly wounded (done by softly scratching the leaf surface with a needle) and nonwounded leaves of two plants were inoculated using a hand sprayer, and placed in a moist chamber at 25°C for 5 days, then moved into a growth chamber at about 25°C, or moved into a greenhouse. Symptoms similar to those originally observed began to appear on the leaves 2–3 weeks after inoculation. Non-inoculated control leaves exposed to the same environmental conditions remained healthy. Pseudocercospora paederiae was consistently reisolated from inoculated plants. This is the first report of P. paederiae on P. scandens in Korea.

Failures of Moraines and a Debris Flow due to Intense Rainstorm in July 1995 in the Shirouma-Daisekkei Valley, the northern Japanese Alps

A number of collapses, landslides, and debris flows occurred in the Himekawa river basin, in the northeastern part of the Japanese Alps, caused by an intense rainstorm (814 mm/2 days) on 11 and 12 July 1995 after the long periods of rainfall. A debris flow induced by failures of late glacial moraines at thresholds of two cirques traveled down into the Shirouma-daisekkei valley, a tributary of the Himekawa river in the midst of the rainstorm. The debris flow deposits (2, 200 m in length, 80 m100 m in width, 2.5×104 m3 in volume), covered the large snowpatch remaining on the valley bottom, and a longitudinal trench was formed at the center of the snow patch by debris flow. The moraines had been saturated with a large quantity of precipitation during the rainy season and snow meltwater in early summer, followed by the large volume of water of the rainstorm. Consequently, a voluminous discharge concentrated on the cirque floors, and rushed out to the moraines of the cirques, causing their collpse. The frequency of such an intense rainstorm in the area is considered to be once in two hundred years, therefore, the volume of moraine failures induced by intense rainstorms can be estimated to be more than 1×106 m3 during the Post Glacial period. This kind of moraine failure plays an important role in the degrading processes of Pleistocene glacial landforms located in the upstream of the glaciated valleys in Japan, because of its rainy and snowy climatic characteristics.

Phosphorus Removal at Low Sludge Loadings

Pilot plant studies for phosphorus removal with settled domestic waste water at low loadings resulted in 40–50 % P-removal. Addition of 100 mg acetic-acid-COD per liter waste water at low sludge loadings showed a P-removal of more than 97,5 %, even at long periods of rainfall. Instead of dosing acetic acid, experiments were carried out by prolongation of the sludge retention time in the anaerobic zone to promote production of low fatty acids. Half an hour stirring followed by three hours non-stirring of the anaerobic zone improved the P-uptake to 79 %. Seeing that the last-mentioned method did not lead to P-effluent values of less than 1 mg/1 biological P-removal experiments were carried out supported by partly P-stripping of the sludge. The P-effluent content dropped to a constant value of 0,4 mg P/l or more than 97,5 % P-removal. Also during long periods of rainfall the P-effluent value remained 0,4 mg P/l. The investigation is in full progress and focused on studying parameters to shorten the sludge retention time in the stripper tank.