`the Main Impacts Arising From Mass Movement Events Are Environmental Rather Than Social.` How Far Do You Agree?

Mass movements, the downhill movement of surface material under the influence of gravity, occur when the gravitational force acting on a slope exceeds the slopes resisting force or more simply, when the shear stress put on a slope exceeds its shear strength. Mass movements can take place from the time period of a few seconds to years, but it is the extremely fast and large mass movements that pose threats to vulnerable populations that result in the most devastating impacts, both social and environmental, which tend to vary with spatial and temporal change. Therefore, it makes most sense to focus on slides (rock, mud, land and rotational) and falls in comparing the main impacts from slope failure events, and it transpires through the study of the Vaiont Dam disaster (north-east Italy), the Nevado del Ruiz lahar (Andes) and the Hunza Valley landslide (northern Pakistan) that these main impacts tend to be social rather than environmental, in strong disagreement with the title statement, but this can vary depending on location and time.

Firstly, mass movement events are more destructive socially in the minutes and hours directly following the event than environmentally, most notably in the form of lost life and injury. On 9 October 1963, a massive landslide in the middle of the night that fell into the reservoir created by the Vaiont Dam caused a man-made megatsunami in which 50 million cubic metres of water overtopped the dam in a 250 metre high wave which caused complete destruction in the several villages occupying the Piave valley below. Estimates of the death toll range from 1,900 to 2,200 people in the village of Longarone with hundreds more killed downstream in the villages of San Martino and Villanova, and about 350 families lost all members. It is also interesting that Mario Pancini, the engineer of the Vaiont Dam, was summoned to court to discuss the known geology of the Vaiont gorge, but he killed himself before the appearance. Furthermore, the Armero tragedy, where the eruption of the Nevado del Ruiz volcano resulted in four lahars being sent down its slopes, engulfing the town of Armero and killing 20,000 inhabitants, is a further example where the social impacts outweigh the environmental. Given, 3400 ha land was lost, 15,000 farm and endangered animals were killed and 35 million tonnes of material was released, but this does not compare to the huge loss of human life caused by the mass movement event. In Longarone, land below the dam was forced into into a flat plain of mud with an impact crater 60 metres deep and 80 metres wide. But, again, this does not weigh up to the monumental loss of life and trauma.

However, it must be noted that the impacts of mass movements are not definitive and vary with spatial and temporal changes. Mass movement events in more sparsely populated areas should clearly have less social effects than in an urban area, however, the development of a country significantly alters this balance between social and environmental effects. On the 4th January 2010 in the Hunza valley, northern Pakistan, a rock avalanche of approximately 23 x 106 cubic meters in volume was sent towards Attabad village. 19 people were killed, minimal social effects in comparison to the Vaiont Dam or Nevado del Ruiz disasters, but, the failure to properly manage the aftermath resulted in long lasting social effects that ultimately outweigh the environmental. From an environmental perspective, the Hunza River was blocked for 5 months, creating a massive lake called Lake Gojal. Another environmental impact of the landslide was that there was a loss of topsoil and hence several floras were not able to grow due to the lack of soil and stability in the ground. Also, there was a great loss of vegetation and trees. Due to this, habitats of several different species of fauna were damaged and most were entirely demolished. But, moreover, the creation of Lake Gojal displaced 6,000 people from upstream villages, stranded a further 25,000, and inundated over 12 miles of the Karakorum highway. Therefore, despite the significant changes in the topography of the area, it appears that any significant environmental impacts only lead to even greater social impacts on the local populations.

In addition to this, when looking at the aftermath of the Nevado del Ruiz lahars, it becomes clear that the social impacts are longer lasting and more severe than the environmental impacts due to the LEDC nature of Colombia. The government s poor ability to cope with the management of the displaced people, the overpopulation of Armero, inadequate housing and poor land planning only added to the loss of infrastructure and death toll. Furthermore, the long-term social impacts were exacerbated by Colombia allowing Armero to become derelict and failing to recognise the psychological impact on families who had lost their homes, livelihoods and loved ones. Indeed, many hectares of farmland and rivers were contaminated but more significantly this contamination greatly affected local fishing industries and economic activity for years to come. In stark contrast, the response to the flooding of the Piave valley caused by the mass movement in the Vaiont gorge was quick and efficient, with 10,000 aid workers sent in, along with machinery to clear the rubble and ambulances with sanitation workers. Survivors were also entitled to business start up loans, public subsidies and tax exemptions to help them recover and Longarone was completely re-built with modern housing. It is clear that the social effects of the Nevado del Ruiz lahars persist today due to the LEDC nature of the country, whereas the Piave valley in a more developed Italy has completely recovered. However, despite these differences it still follows through that the social impacts are the main effects of mass movement events, rather than environmental.

In conclusion, I disagree with the title statement as the case studies of the Vaiont Dam, Nevado del Ruiz and Hunza Valley all demonstrate that the main impacts arising from mass movement events are social rather than environmental. However, it s evident that the extent to which social impacts outweigh environmental depends on the time and location of the mass movement, essentially the development of the country and the size of the vulnerable population at risk. Ultimately, the immense risk posed to human life by mass movement events is undeniably the main reason as to why social impacts are more important than environmental.