scholarly journals Lion Mountain Landslide in Non-urbanized Terrain: Changing the Myth of Landslide Occurrence in Western Sierra Leone

2020 ◽  
Vol 3 (2) ◽  
pp. p61
Author(s):  
Yusuf A. Lahai ◽  
Dauda M. Kamara ◽  
Chernoh M. Jalloh
Keyword(s):  
Human Factors ◽  
Slip Surface ◽  
Causative Factor ◽  
Geotechnical Properties ◽  
Clear Understanding ◽  
Residual Soil ◽  
Landslide Occurrence ◽  
Rock Types ◽  
Landslide Event ◽  
Thin Section Analysis

Freetown has documented one of the most devastating landslides in the world in 2017. Many debates in the media, few scientific papers and technical documents, have argued with eloquence ascertaining human factors, particularly deforestation and urbanization, as the dominant causative factor. This notion seems to be widely accepted for all other slides by the communities, government agencies and departments. Therefore, this work attempts to expand on existing public knowledge by demonstrating the less influential or insignificant human factors which can have impacts on certain landslide occurrences in the Freetown Layered-Complex. The representative landslide considered for this study occurred beyond the vicinity of urbanized zone. Therefore, to establish a clear understanding of the actual causative factors, fieldwork and laboratory investigations were undertaken. During the field survey, we assessed the rock type, discontinuities, geomorphology and hydrological influence of the landslide. The specific rock series underlying the landslide was confirmed through thin section analysis at the National Minerals Agency (NMA). DCP tests and laboratory analyses enhanced the derivation of geotechnical properties of the residual soil/regolith.This work systematically presented how natural conditions, such as: geology (rock types and tectonic signatures), geomorphology, hydrology and the geotechnical properties of the slope soil, have interplayed in the occurrence of the landslide event. In addition, the slip surface of the landslide occurred at a depth below the reach of plant activities (2.6 m). This information may help modify public messages by institutions and can be a source of useful information for the country’s Landslide Disaster Management Department (LDMD).

Effective Use of the World Wide Web (WWW) for HF/E Consultants

1998 ◽  
Vol 42 (10) ◽  
pp. 714-718 ◽  
Author(s):  
Anthony D. Andre
Keyword(s):  
World Wide Web ◽  
Human Factors ◽  
World Wide ◽  
Clear Understanding ◽  
Human Factors And Ergonomics ◽  
The World ◽  
Effective Use ◽  
The Web

This paper provides an overview of the various human factors and ergonomics (HF/E) resources on the World Wide Web (WWW). A list of the most popular and useful HF/E sites will be provided, along with several critical guidelines relevant to using the WWW. The reader will gain a clear understanding of how to find HF/E information on the Web and how to successfully use the Web towards various HF/E professional consulting activities. Finally, we consider the ergonomic implications of surfing the Web.

scholarly journals Dendrochronological dating as the basis for developing a landslide hazard map – An example from the Western Carpathians, Poland

2018 ◽  
Vol 45 (1) ◽  
pp. 173-184 ◽  
Author(s):  
Katarzyna Łuszczyńska ◽  
Małgorzata Wistuba ◽  
Ireneusz Malik ◽  
Marek Krąpiec ◽  
Bartłomiej Szypuła
Keyword(s):  
Low Cost ◽  
Sampling Site ◽  
Ring Width ◽  
Landslide Hazard ◽  
Hazard Map ◽  
Large Area ◽  
Landslide Occurrence ◽  
Landslide Activity ◽  
Landslide Event ◽  
Landslide Hazard Map

Abstract Most landslide hazard maps are developed on the basis of an area’s susceptibility to a landslide occurrence, but dendrochronological techniques allows one to develop maps based on past landslide activity. The aim of the study was to use dendrochronological techniques to develop a landslide hazard map for a large area, covering 3.75 km2. We collected cores from 131 trees growing on 46 sampling sites, measured tree-ring width, and dated growth eccentricity events (which occur when tree rings of different widths are formed on opposite sides of a trunk), recording the landslide events which had occurred over the previous several dozen years. Then, the number of landslide events per decade was calculated at every sampling site. We interpolated the values obtained, added layers with houses and roads, and developed a landslide hazard map. The map highlights areas which are potentially safe for existing buildings, roads and future development. The main advantage of a landslide hazard map developed on the basis of dendrochronological data is the possibility of acquiring long series of data on landslide activity over large areas at a relatively low cost. The main disadvantage is that the results obtained relate to the measurement of anatomical changes and the macroscopic characteristics of the ring structure occurring in the wood of tilted trees, and these factors merely provide indirect information about the time of the landslide event occurrence.

scholarly journals Landslide susceptibility on selected slopes in Dzanani, Limpopo Province, South Africa

2014 ◽  
Vol 6 (1) ◽  
Author(s):  
Makia L. Diko ◽  
Shallati C. Banyini ◽  
Batobeleng F. Monareng
Keyword(s):  
Landslide Susceptibility ◽  
Critical State ◽  
Anthropogenic Activities ◽  
Limpopo Province ◽  
Silty Clay ◽  
Clay Loam ◽  
Landslide Occurrence ◽  
Landslide Event ◽  
Physical Attributes

Inherent soil properties and anthropogenic activities on slope faces are considered potential recipes for landslide occurrence. The objectives of this study were to physically characterise unconsolidated soils and identify on-going anthropogenic activities on selected slopes in Dzanani in order to appraise their role as contributory factors in enhancing landslide susceptibility. Methods employed for this study comprised mapping, description of soil profile, identification of anthropogenic activities, as well as experimental determination of soil colour, particle size distribution and Atterberg limits. Geologically, the study area comprised rocks of the Fundudzi, Sibasa and Tshifhefhe Formations, ascribed to the Soutpansberg Group. Digging of foundations for construction purposes and subsistence agriculture were identified as the main anthropogenic activities. The soils were predominantly reddish-yellow in colour, texturally variable (silty clay – clayey – silty clay loam and clay loam) and of medium plasticity. Compared to soils from other parts of the world developed on volcanic cones or associated with a landslide event, those from Dzanani were qualified as generally inactive and not prone to landslides. Although the physical attributes suggested the soils were not at a critical state, on-going anthropogenic activities may enhance deep weathering and ultimately alter current soil physical characteristics to a critical state.

scholarly journals Regional rainfall thresholds for landslide occurrence using a centenary database

2017 ◽  
Author(s):  
Teresa Vaz ◽  
José Luís Zêzere ◽  
Susana Pereira ◽  
Sérgio C. Oliveira ◽  
Ricardo A. C. Garcia ◽  
...  
Keyword(s):  
Daily Rainfall ◽  
Early Warning Systems ◽  
Rain Gauge ◽  
Warning Systems ◽  
Rainfall Thresholds ◽  
Period Analysis ◽  
Landslide Occurrence ◽  
Landslide Event ◽  
Landslide Early Warning ◽  
Regional Rainfall

Abstract. This work proposes a comprehensive methodology to assess rainfall thresholds for landslide initiation, using a centenary landslide database associated with a single centenary daily rainfall dataset. The methodology is applied to the Lisbon region and include the rainfall return period analysis that was used to identify the critical rainfall combination (quantity-duration) related to each landslide event. The spatial representativeness of the reference rain gauge is evaluated and the rainfall thresholds is assessed and validated using the receiver operating characteristic (ROC) metrics. Results show that landslide events located up to 10 km from the rain gauge can be used to calculate the rainfall thresholds in the study area; however, such thresholds may be used with acceptable confidence up to 50 km distance from the rain gauge. The obtained rainfall thresholds using linear and potential regression have a good performance in ROC metrics. However, the intermediate thresholds based on the probability of landslide events, established in the zone between the lower limit threshold and the upper limit threshold are much more informative as they indicate the probability of landslide event occurrence given rainfall exceeding the threshold. This information can be easily included in landslide early warning systems, especially when combined with the probability of rainfall above each threshold.

scholarly journals Landslide susceptibility map using certainty factor for hazard mitigation in mountainous areas of Ujung-loe watershed in South Sulawesi

2018 ◽  
Vol 2 (1) ◽  
pp. 79 ◽  
Author(s):  
Andang Suryana Soma ◽  
Tetsuya Kubota
Keyword(s):  
Landslide Susceptibility ◽  
Causative Factor ◽  
Susceptibility Map ◽  
Landslide Susceptibility Map ◽  
Landslide Occurrence ◽  
Sparse Vegetation ◽  
Dense Vegetation ◽  
South Sulawesi ◽  
Landslide Hazards ◽  
Causative Factors

This study aims to build a landslide susceptibility map (LSM) by using certainty factor (CF) models for mitigation of landslide hazards and mitigation for people who live near to the forest. In the study area, the mountainous area of the Ujung-loe watersheds of South Sulawesi, Indonesia, information on landslides were derived from aerial photography using time series data images from Google Earth Pro© from 2012 to 2016 and field surveys. The LSM was built by using a CF model with eleven causative factors. The results indicated that the causative factor with the highest impact on the probability of landslide occurrence is the class of change from dense vegetation to sparse vegetation (4-1), with CF value 0.95. The CF method proved to be an excellent method for producing a landslide susceptibility map for mitigation with an area under curve (AUC) success rate of 0.831, and AUC predictive rate 0.830 and 85.28% of landslides validation fell into the high to very high class. In conclusion, correlations between landslide occurrence with causative factors shows an overall highest LUC causative factor related to the class of change from dense vegetation to sparse vegetation, resulting in the highest probability of landslide occurrence. Thus, forest areas uses at these locations should prioritize maintaining dense vegetation and involving the community in protection measures to reduce the occurrence of landslide risk. LSM models that apply certainty factors can serve as guidelines for mitigation of people living in this area to pay attention to landslide hazards with high and very high landslide vulnerability and to be careful to avoid productive activities at those locations.

scholarly journals Storm-triggered landslides in the Peruvian Andes and implications for topography, carbon cycles, and biodiversity

2015 ◽  
Vol 3 (3) ◽  
pp. 631-688 ◽  
Author(s):  
K. E. Clark ◽  
A. J. West ◽  
R. G. Hilton ◽  
G. P. Asner ◽  
C. A. Quesada ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Amazon Basin ◽  
Low Frequency ◽  
Mountain Forest ◽  
Ecological Disturbance ◽  
Peruvian Andes ◽  
Landslide Occurrence ◽  
Carbon Cycles ◽  
Landslide Event ◽  
Frequency Relationship

Abstract. In this study, we assess the geomorphic role of a rare, large-magnitude landslide event and consider the effect of this event on mountain forest ecosystems and the erosion of organic carbon in an Andean river catchment. Proximal triggers such as large rain storms are known to cause large numbers of landslides, but the relative effects of such low-frequency, high-magnitude events are not well known in the context of more regular, smaller events. We develop a 25 year duration, annual-resolution landslide inventory by mapping landslide occurrence in the Kosñipata Valley, Peru, from 1988 to 2012 using Landsat, Quickbird and Worldview satellite images. Catchment-wide landslide rates were high, at 0.076 % yr−1 by area, indicating landslides may completely turn over hillslopes every ~ 1320 years and strip 28 tC km−2 yr−1 of soil (73 %) and vegetation (27 %). A single rain storm in March 2010 accounted for 27 % of all landslide area observed during the 25 year study and removed 26 % of the organic carbon that was stripped from hillslopes by all landslides during the study. An approximately linear magnitude–frequency relationship for annual landslide areas suggests that large storms contribute an equivalent landslide failure area to the sum of smaller frequency landslides events occurring over the same period. However, the spatial distribution of landslides associated with the 2010 storm is distinct. On the basis of precipitation statistics and landscape morphology, we hypothesize that spatial focusing of storm-triggered landslide erosion at lower elevations in the Kosñipata catchment may be characteristic of longer-term patterns. These patterns may have implications for the source and composition of sediments and organic material supplied to river systems of the Amazon basin, and, through focusing of regular ecological disturbance, for the species composition of forested ecosystems in the region.

scholarly journals Evaluation of potential meteorological triggers of large landslides in sensitive glaciomarine clay, eastern Canada

2012 ◽  
Vol 12 (11) ◽  
pp. 3359-3375 ◽  
Author(s):  
D. Gauthier ◽  
D. J. Hutchinson
Keyword(s):  
Causative Factor ◽  
Rain Event ◽  
External Energy ◽  
Eastern Canada ◽  
Antecedent Precipitation ◽  
Landslide Event ◽  
Precipitation Threshold ◽  
Short And Long Term ◽  
Several Intervals

Abstract. Heavy rains spread over some interval preceding large landslides in sensitive glaciomarine clay in eastern Canada are often noted as a triggering or causative factor in case studies or research reports for individual landslides, although the quantity or duration of the triggering rain event has never been characterized adequately. We selected five large landslide events that occurred in the glaciomarine clay in eastern Canada, and calculated cumulative antecedent precipitation for intervals ranging between one and 365 days preceding each event. We also calculated the antecedent precipitation values for every other day in the record, and computed the relative rank of the landslide day within the complete record. Our results show that several intervals for each landslide event are highly ranked – including those preceding a presumably earthquake-triggered landslide – but overall the rankings were highly variable, ranging between 99% and 6%. The set of highest-ranking intervals are unique for each event, including both short and long-term cumulative precipitation. All of the landslides occurred in the spring months, and the release of sequestered surface and ground water during the spring ground thaw may be related to the timing of the large landslides, so that the evolution of ground frost in the early winter may be of interest for landslide prediction. We found no simple precipitation threshold for triggering large landslides in sensitive glaciomarine clay in eastern Canada, suggesting that some complex temporal and spatial combination of pre-conditions, external energy (e.g. earthquakes), precipitation triggers and other factors such as ground frost formation and thaw are required to trigger a landslide.

scholarly journals Adapting sudden landslide identification product (SLIP) and detecting real-time increased precipitation (DRIP) algorithms to map rainfall-triggered landslides in Western Cameroon highlands (Central-Africa)

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Alfred Homère Ngandam Mfondoum ◽  
Pauline Wokwenmendam Nguet ◽  
Jean Valery Mefire Mfondoum ◽  
Mesmin Tchindjang ◽  
Sofia Hakdaoui ◽  
...  
Keyword(s):  
Real Time ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Cox Model ◽  
Daily Rainfall ◽  
Landsat 8 ◽  
Landslide Occurrence ◽  
Starting Point ◽  
Landslide Event ◽  
Recent Landslide

Abstract Background NASA’s developers recently proposed the Sudden Landslide Identification Product (SLIP) and Detecting Real-Time Increased Precipitation (DRIP) algorithms. This double method uses Landsat 8 satellite images and daily rainfall data for a real-time mapping of this geohazard. This study adapts the processing to face the issues of data quality and unavailability/gaps for the mapping of the recent landslide events in west-Cameroon’s highlands. Methods The SLIP algorithm is adapted, by integrating the inverse Normalized Difference Vegetation Index (NDVI) to assess the soil bareness, the Modified Normalized Multi-Band Drought Index (MNMDI) combined with the hydrothermal index to assess soil moisture, and the slope inclination to map the recent landslide. Further, the DRIP algorithm uses the mean daily rainfall to assess the thresholds corresponding to the recent landslide events. Their probability density function (PDF) curves are superimposed and their intersections are used to propose sets of dichotomous variables before (1948–2018) and after the 28 October 2019 landslide event. In addition, a survival analysis is performed to correlate landslide occurrence to rainfall, with the first known event in Cameroon as starting point, and using the Cox model. Results From the SLIP model, the Landslide Hazard Zonation (LHZ) map gives an overall accuracy of 96%. Further, the DRIP model states that 6/9 ranges of probability are rainfall-triggered landslides at 99.99%, between June and October, while 3/9 ranges show only 4.88% of risk for the same interval. Finally, the survival probability for a known site is up to 0.68 for the best value and between 0.38 and 0.1 for the lowest value through time. Conclusions The proposed approach is an alternative based on data (un)availability, completed by the site’s lifetime analysis for a more flexibility in observation and prediction thresholding.

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