How can human activity affect slopes?

        Another human action that influences slopes is the construction of buildings and establishments and often has a notable effect on the soil beneath. The sheer weight of the building foundations as well as the machinery needed to fabricate the buildings condenses the soil, making it more compact and denser. This in turn prevents infiltration and percolation through the soil, increasing overland flow and therefore, flooding of bodies of water.

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The vibrations produced from the machinery can also trigger slope movements, however large or small. Also, different forms of constructions such as road cuttings and embankments can create hazardous slopes. The appropriate precautions need to be taken in order to maintain them safely. The action of gravity, precipitation and climate can cause soil creep, even on the seemingly gentlest of slopes, making them unstable. Rotational slip can be occurring, such as in the Isle of Wight where retirement bungalows are thought to be slipping and to cause a landslide eventually.

        Generally, the land in certain areas are only suitable for particular uses, in farming, slope angles in conjunction with other factors can be crucial for determining the aptitude of the land in question. While steep slopes at low altitudes have a greater potential, there are limits that need to be considered, for instance, the ability for operation of heavy machinery. An example of skilful slope management is the Champagne region in France, where the slopes are assessed for their carrying capacity and the suitable number of vines are planted. This has proved very successful in combining slopes for human uses and not provoking natural disasters. However, the erosion of soil is still an ongoing problem, especially on agricultural land when the land is not taken into consideration. Once initiated, soil erosion reinforces itself and continues and can only be stopped with human intervention.

        Another case of poor management of slopes is in Hong Kong, where the vast majority of the natural terrain is hilly and mountainous and slope safety is a priority. However, in the past 50 years, landslides on man-made slopes have killed more than 470 people. Poor maintenance of slopes is a major contributory factor in many landslides in Hong Kong and prevention schemes are constantly in motion. The removal of natural vegetation on a site also contributes to hazards and disasters. The roots of plants and trees often serve as a binding agent in the soil and soft sedimentary rocks. Material is ‘anchored’ to the soil that would otherwise be easily removed, occasionally causing landslides. Trees usually benefit the slopes, increasing coil cohesion and friction. Humans also aim to control the flow of water, and change the balance of infiltration and runoff both intentionally and unintentionally with surface paving, water channelling and other activities.

        However, having identified some possible human causes to disasters associated with slopes, it is rarely one action that induces accidents, it is often the accumulation of activities that cause disasters. It is found that urban areas are more susceptible to mass movement disasters and having occurred, the repair of various articles is expensive. It is also not natural slopes alone that require management, industries producing masses of waste heaps need careful stabilisation. These artificial slopes require the necessary knowledge to prevent potentially serious hazards. In Aberfan, Wales, 147 people died, most of them children, due to the instability of a coal mine spoil heap. Since then,

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spoil heaps have been reduced in gradient to stop the occurrence of similar events.

        The frequency of human-induced disasters seem to outweigh the naturally occurring accidents and therefore, better consideration of the uses and effects of slopes need to be contemplated in order to address this and end such events. But, with current successes in managing slopes, the revaluation of certain schemes and ideas are required in order to increase the number of successes. The hazards often cause a loss of lives, property damage and countless problems and the awareness and knowledge of the danger of disasters, natural or caused by human activity, can be the best prevention of them. Hill slopes and vegetation play a critical role in defining slope stability and the removal of vegetation needs to be considered to an appropriate extent. The importance of planning in terms of human activities needs to be emphasised in order to minimise hazards.