1. neighbourhood and towns. Steepening of slopes

1. IntroductionLandslides are a high-risk natural phenomenon that occurs all around the world. Globally landside has caused approximately 1000 deaths per year (Lee and Pradhan 2007). In addition to these causalities, these landslides poses serious threat to structures that supports transportation, settlements and tourism. Basically, a landslide is a downward movement of soil, rock or debris occurring either in a curved or planar surface of rupture as a coherent mass with little or no internal deformation. Landslides can effect a man-made structure when they are in direct or indirect path of a landslide. Landslide damage to a lifelines such as sewer line, water line or electric line can cause disruption of services to an entire region as a whole. Commercial structures if affected can cause damage to the building itself and also to the whole community due to interruption of business. One of the largest consequences due to landslides can be to the transportation infrastructures. Landslides commonly occurs on cut slopes or embankments alongside roads and railways disrupting the commute. In addition to the potential fatalities, delays in the travel time can bring about monetary losses as well. Various factors contribute to the occurrence of landslides. It can be a). Natural & b). Man-Made. Natural category of causes include three main triggering factors i). Water, ii). Seismic Activity and iii). Volcanic Activity. These three can occur singly or either in combination. Effects of all these causes can widely vary based on the slope geometry, soil type, whether there are people or structures on the affected area etc. Man-Made causes are majorly due to population expanding onto new land and creating new neighbourhood and towns. Steepening of slopes for development, changes in loading patters, disturbing drainage patters, removing vegetation etc. are some of the reasons that can act as a triggering factor for landslides. Saturation by water is a primary cause of landslides. It can occur in the form of precipitation, snow melt, change in ground water levels etc. Chiefly variation in precipitation due to climate change control or influence the occurrence of majority of landslides (Ciabatta, Camici et al. 2016). A study focused on finding the major causes for landslides (Kazmi, Qasim et al. 2017) suggests that rainfall contributes majority (62%) as the triggering factor for landslides. Effect of rainfall is even more pronounced in tropical and sub-tropical countries. Storm induced landslides are common in many tropical or sub-tropical countries like Singapore, Malaysia, Taiwan, Japan, Hong Kong etc. (Zhang, Zhang et al. 2011). Climate change due to global warming is expected to lead to a greater frequency and magnitude of heavy precipitation. For example, Dore (2005) infers that due to climate change, northern hemisphere will receive a larger amount of precipitation while in the equatorial regions frequency is likely to be effected. Considering the fact that precipitation is most common trigger to the landslide activity, it’s not very surprising that there is a strong theoretical basis for increased landslide activity as a result of climate-change.Earthworks slopes (embankments and cutting) forms a major portion of any transportation networks. As described above, a landslide that occurs on cut slopes or embankments alongside roads and railways can bring about major delays and disruption to network operation. In an engineering perspective of sustainability, when considering the effects of climate change in the slope stability there can be potential social and economic risks which need to be addressed. Assessing this risk and adapting the infrastructure to a changing climate scenario requires knowledge about resilience of these structures to projected climate change. 1.1 Landslide risk analysisQuantifying the increased landslide activity and risk associated with it due to climate change warrants a methodical approach to be implemented. Quantitative Risk Assessment (QRA) for engineered slopes and landslides is a framework described in terms of 4 main analysis steps (Fig. 1). This is achieved by breaking up the whole process into smaller process of different disciplines. Process are formulated such that they all are independent and sequential in nature so that each of the process can be handled by the experts in each field more clearly and rigorously. Four Major process in QRA are Hazard Analysis, Risk Analysis, Risk Evaluation and Risk Mitigation. Hazard analysis includes landslide characterization and calculating frequency associated with it. Risk analysis includes both hazard analysis and consequence analysis. Risk is defined as defined as measure of the probability of an adverse effect to life, health and environment (Fell, Ho et al. 2005). Quantitatively, Risk = Hazard x Consequence.Consequence can also be termed as potential worth of loss. Loss can be either in terms of property or persons. Consequence analysis involves identifying these elements of potential loss and quantifying its probability or vulnerability. Hazard is the probability that a particular danger occurs within a given period of time (Fell, Ho et al. 2005). Occurrence of a landslide due to failure of slope can be considered as hazard event and probability of that particular slope to fail in a given period of time (e.g. a year) is the hazard associated with that event. Hazard analysis forms the basis of risk analysis using the QRA framework.  Figure 1 Schematic representation of Quantitative Risk Assessment Process (adapted from Fell, Ho et al. (2005))1.1.1 Hazard AnalysisHazard analysis includes the process of identification and characterisation of the potential landslides to evaluate their corresponding frequency of occurrence. The frequency of landslides can be expressed in terms of probability of a particular slope experiencing land sliding in a given period.