Susceptibility assessment of shallow landslides in Hulu Kelang area, Kuala Lumpur, Malaysia using analytical hierarchy process and frequency ratio

Hulu Kelang is known as one of the most landslide susceptible areas in Malaysia. From 1990 to 2011, a total of 28 landslide events had been reported in this area. This paper compares two models as Analytical Hierarchy Process (AHP) and probability–frequency ratio (FR) methods for recognizing landslide susceptibility regions in the Hulu Kelang area. Eleven landslide influencing factors were considered to form the probability–FR and AHP matrix, i.e. lithology-weathering, land cover, curvature, slope inclination, slope aspect, drainage density, elevation, distance to lake and stream, distance to road and trenches, the Stream Power Index and the Topographic Wetness Index. The accuracy of the maps produced from the two models were verified using a receiver operating characteristics. The verification results indicated that the probability–FR model based on probabilistic analysis of spatial distribution of historical landslide events was capable of producing a more reliable landslide susceptibility map in this study area compared to AHP model. About 89 % of the landslide locations have been predicted accurately by using the FR map

Formation of box canyons by mass failure in limestone : a modelling study of the role of groundwater seepage

Groundwater seepage has been shown to unambiguously lead to channel formation inunconsolidated sand to gravel sized sediments. However, its role in the evolution of bedrocklandscapes remains controversial. In this study, we use the coastline of the Maltese Islands as a case study to establish if and how groundwater seepage can form box canyons in limestones.peer-reviewe

Spatiotemporal regional modeling of rainfall-induced slope failure in Hulu Kelang, Malaysia

This study demonstrated the use of transient rainfall infiltration and grid-based regional slope stability analysis model incorporated with spatial rainfall distribution model for regional mapping of rainfall-induced slope failures in a slope failure-prone area in Malaysia, namely Hulu Kelang. Infinite slope analysis was incorporated into the improved model to compute the pore water pressure and slope stability of the region. Digital terrain maps, spatial rainfall distributions, soil profiles, groundwater table, and soil properties were input into the model. The results showed that the slope failures in the study area can be grouped into shallow failures (<4 m) and sub-shallow failures (4–8 m). Most of the shallow slope failures (<4 m) were triggered by the northeast monsoon while the NE monsoon that characterized by more prolonged and intense rainfalls. Spatial temporal distributions of shallow and sub shallow slope failures predicted using the improved model showed reasonably good comparison with the historical slope failure regions. Monsoon events have affected slope stability by reduction in matric suction, complete loss of matric suction, and development of positive pore water pressure (PWP). Computation for the effects of rainfall infiltration on PWP response and consequent effects on slope stability is enhanced by the spatial rainfall distribution model. The pore water pressure response to monsoon rainfall is a function of rainfall duration, the rate of infiltration, groundwater depth, soil thickness, and slope inclination. The amount of the local daily rainfall is not the only factor affecting slope stability. The prolonged antecedent rainfall could have a role to play in building up the slope failure mechanism

Groundwater erosion of coastal gullies along the Canterbury coast (New Zealand): a rapid and episodic process controlled by rainfall intensity and substrate variability

Gully formation has been associated to groundwater seepage in unconsolidated sand- to gravel-sizedsediments. Our understanding of gully evolution by groundwater seepage mostly relies on experiments and nu-merical simulations, and these rarely take into consideration contrasts in lithology and permeability. In addition,process-based observations and detailed instrumental analyses are rare. As a result, we have a poor understandingof the temporal scale of gully formation by groundwater seepage and the influence of geological heterogeneityon their formation. This is particularly the case for coastal gullies, where the role of groundwater in their for-mation and evolution has rarely been assessed. We address these knowledge gaps along the Canterbury coastof the South Island (New Zealand) by integrating field observations, luminescence dating, multi-temporal un-occupied aerial vehicle and satellite data, time domain electromagnetic data and slope stability modelling. Weshow that gully formation is a key process shaping the sandy gravel cliffs of the Canterbury coastline. It is anepisodic process associated to groundwater flow that occurs once every 227 d on average, when rainfall intensi-ties exceed 40 mm d−1. The majority of the gullies in a study area southeast (SE) of Ashburton have undergoneerosion, predominantly by elongation, during the last 11 years, with the most recent episode occurring 3 yearsago. Gullies longer than 200 m are relict features formed by higher groundwater flow and surface erosion>2 kaago. Gullies can form at rates of up to 30 m d−1via two processes, namely the formation of alcoves and tunnelsby groundwater seepage, followed by retrogressive slope failure due to undermining and a decrease in shearstrength driven by excess pore pressure development. The location of gullies is determined by the occurrenceof hydraulically conductive zones, such as relict braided river channels and possibly tunnels, and of sand lensesexposed across sandy gravel cliffs. We also show that the gully planform shape is generally geometrically similarat consecutive stages of evolution. These outcomes will facilitate the reconstruction and prediction of a prevalenterosive process and overlooked geohazard along the Canterbury coastline

Groundwater seepage is a key driver of theater-headed valley formation in limestone

Groundwater seepage leads to the formation of theater-headed valleys (THVs) in unconsolidated sediments. In bedrock, the role of groundwater in THV development remains disputed. Here, we integrate field and remote-sensing observations from Gnejna Valley (Maltese Islands) with numerical modeling to demonstrate that groundwater seepage can be the main driver of THV formation in jointed limestone overlying clays. The inferred erosion mechanisms entail (1) widening of joints and fractures by fluid pressure and dissolution and (2) creeping of an underlying clay layer, which lead to slope failure at the valley head and its upslope retreat. The latter is slower than the removal of the talus by creep and sliding on the valley bed. The location and width of THVs are controlled by the location of the master fault and the extent of the damage zone, respectively. The variability of seepage across the fault zone determines the shape of the valley head, with an exponential decrease in seepage away from the fault giving rise to a theater-shaped head that best matches that of Gnejna Valley. Our model may explain the formation of THVs by groundwater in jointed, strong-over-weak chemical sedimentary lithologies, particularly in arid terrestrial settings

Qualitative and quantitative landslide susceptibility assessments in Hulu Kelang area, Malaysia

Hulu Kelang is an area in Malaysia that is very susceptible to landslides. From 1990 to 2011, a total of 28 major landslide events had been reported in this area. This paper compares and evaluates the analytical hierarchy process (AHP), probability-frequency ratio (FR), statistical index (Wi), and weighting factor (Wf), used for assessing landslide susceptibility in the Hulu Kelang area. Eleven landslide influencing factors were considered in the analyses. These factors included two indices (the stream power index (SPI) and the topographic wetness index (TWI)) and several other factor including lithology, land cover, curvature, slope inclination, slope aspect, drainage density, elevation, distance to lake and stream, distance to road and trenches found in the area. The accuracy of the maps produced from the four models were verified using a receiver operating characteristics (ROC), and relative distributions of susceptibility level and active landslide zone. All the verification results indicated that the probability-frequency ratio (FR) model which was developed quantitatively based on probabilistic analysis of spatial distribution of historical landslide events was capable of producing a more reliable landslide susceptibility map in this study area compared to its other counterparts. About 89% of the landslide locations have been predicted accurately by using the FR map. On the contrary, the analytical hierarchy process (AHP) model that relies mainly on qualitative judgment yielded the least accuracy in landslide prediction

Effect of weathered surface crust layer on stability of Muar trial embankment

This paper attempts to evaluate the effect of surface crust layer on the stability and deformation behavior of embankment. A full-scale case history trial embankment constructed on Muar flat in the valley of the Muar River in Malaysia was modeled and analyzed. The Muar trial embankment was simulated in two- and three-dimension (2-D and 3-D) utilizing finite element programs PLAXIS 2-D AND PLAXIS 3-D FOUNDATION, using staged-construction procedure. Sensitivity analysis was performed by varying the thickness of weathered crust layer beneath the embankment fill, i.e., three models of embankment with no surface crust, 1 m surface crust and 2 m surface crust layer. Predictions were made for the vertical and the horizontal displacements of the embankment. Factor of safety for each meter increase in the embankment height was defined until the failure is reached. It is concluded that the bearing capacity of the ground and the deformation behavior of the embankment were sensitive to the thickness of the weathered crust layer. The surface crust layer has a positive effect on the stability of the embankment and consequently reduces the settlement and increases the failure height of the embankment fill up to 37%

Spatial patterns of precipitation, altitude and monsoon directions in Hulu Kelang area, Malaysia

Malaysia is characterized by a humid tropical climate with heavy rainfall. The annual temperature varies from 26 to 28°C while Malaysia is being one of the wet climate countries with as annual rainfall is approximately 2250 mm/year. Malaysia monsoon is arranged into two rainfall terms: the primary one coincident with the northeast monthly precipitation (December-March) and the other one with the southwest monthly rainfall in conjunction with inter-monsoon periods (April-November). The rainfall events are gauged at points of precipitation measurement networks in Malaysia. But, there is not full mapping of precipitation in relation with elevation all locations especially in mountains. This paper provides the relationship between monthly precipitation and elevation in the Hulu Kelang area based on Geographically Weighted Regression (GWR) method. Three periods of precipitation" the average monthly rainfall and two monsoons" has been studied in this area. The results of regression analyses performed between three conditions of monthly precipitation in the year and altitude. The mean absolute error (MAE) and the root-mean-square error (RMSE) verification results indicated that the whole year rainfall regression model works quite better than other results for interpreting the spatial variability of precipitation. The relation between original normal precipitation (1990-2010) and topography variables showed that study area precipitation is strongly controlled by elevation in the west region. The final map was represented that precipitation in the west region is generally higher than in east region of Hulu Kelang all around the year

Landslide susceptibility zoning in a catchment of Zagros Mountains using fuzzy logic and GIS

Landslide is one of the dangerous types of natural hazards. This phenomenon causes damages in many countries every year. A detailed landslide hazard assessment is necessary to reduce these damages. This research aims to map the landslide susceptibility zoning (LSZ) using the fuzzy logic method and GIS in the Sorkhab basin as a part of the Zagros fold and thrust belt (FTB), northwestern Iran. All slide types were recorded in fieldwork as landslide inventory. Based on the results, four types, i.e., debris slide, earth slide, and rock fall and complex of landslides, was identified in the region. Then, the effect of each landslide contributing factor including topographical elevation heights, slope classes, aspect classes, geological units, proximity to faults, land covers, rainfall classes, and proximity to streams was constructed in GIS and subsequently normalized using fuzzy membership functions. Finally, by combining all standardized layers using the fuzzy gamma operator, a final map of LSZ was produced. The results showed that a 0.9 fuzzy gamma operator has a high accuracy for the LSZ map in the study area. Besides, the accuracy of the LSZ map revealed a strong relationship (R2) between susceptibility classes, and landslide inventory was calculated using a scatter plot equal to 0.79. Hence, the method represented an appropriate accuracy in predicting the landslide susceptibility in the study area

Hulu Kelang, Malaysia regional mapping of rainfall-induced landslides using TRIGRS model

Rainfall-induced slope failure is one of the most destructive natural disasters that occur frequently in natural or engineered residual soil slopes. Rainfall-induced slope failures often occur as a shallow slope failure, with slip surfaces orientated parallel to the slope surface, especially in Hulu Kelang areas where a residual soil profile has formed over a bedrock interface. The possibility of using the transient rainfall infiltration and grid-based regional slope stability analysis method (TRIGRS) is applied to unstable slopes and three rainfall threshold chart conditions that result in landslides in the study area. We compare the intensity–duration of 3-day rainfall threshold charts (I–D)3, cumulative 30-day rainfall–number of rainy day (API30–N), and cumulative 3-day rainfall–30-day antecedent precipitation index threshold chart (E3–API30) conditions capable of producing slope instability in the study area predicted by TRIGRS, with empirical rainfall I–D thresholds for possible landslide occurrence in the northeast part of Kuala Lumpur. The results showed that TRIGRS is capable of reproducing the frequency of the size of the patches of terrain predicted as unstable by the model, which match the frequency size statistics of landslides in the study area, and the rainfall threshold based on the E3–API30 threshold chart could give a better prediction to a landslide than other conditions in Hulu Kelang area. Our results are a step towards understanding the mechanisms that give rise to landslide regional modelin