A downhill battle
The stories may be familiar, but that doesn’t lessen the tragedy. In March, a mudslide triggered by heavy rains sweeps through a village in eastern Uganda, killing at least 100 people. In April, an extended period of heavy rainfall over Rio de Janeiro triggers dozens of landslides across the city, primarily in shanty towns built on its periphery. In the worst, some 50 houses in a slum in Niteroi are swept away, killing at least 150 people. Less than a week later, a large irrigation pipe on a hillside near Merano in the Italian Alps bursts, sending a wave of mud and water crashing into a passing commuter train, killing nine passengers.
These disasters are both grimly routine and somewhat unusual – routine in that globally, hundreds of landslides take place every year in built-up areas, killing a total of around 1,000 people; unusual in that they made the news headlines. ‘Quite often, landslides are underreported and not as easy to recognise as, say, a flood because they happen in very discrete locations, and you can get multiple landslide events,’ says Dr Liz Holcombe, a landslide researcher in the University of Bristol’s School of Geographical Sciences. ‘They are effectively masked by the triggers with which they are associated,’ adds her colleague and former PhD tutor Professor Malcolm Anderson.
Hurricane Mitch illustrates Anderson’s point well. In November 1998, this category-five hurricane brought record rainfall to Honduras, Guatemala and Nicaragua, causing catastrophic flooding. It went on to become the second-deadliest Atlantic hurricane in history, with as many as 20,000 people killed. Around 2.7 million were left homeless and the total damage was estimated at more than US$5billion.
‘The damage wasn’t just a result of flooding,’ says Holcombe. ‘It was also caused by hundreds of landslides that affected the whole region, blocking the road networks, preventing trade and [the distribution of] emergency aid, and causing a significant reduction in economic growth. So even though a significant proportion of the damage was actually through landslides triggered by that rain, it’s recorded as a hurricane, rather than, say, 100 landslides and a flood.’
This intertwining of landslides with other natural disasters, and the multi-faceted nature of their effects, renders their impact equally complex. ‘The global scale of the problem depends on how you cut it,’ says Holcombe. ‘In absolute terms, Asia has the most landslides, the Americas and Caribbean region has the deadliest, and Europe has the costliest, because they’re damaging more expensive infrastructure and property. However, in terms of GDP, the landslides turn out to be relatively more expensive to developing economies.’
In developing countries, losses are greatest in cities, where migration and urbanisation link poverty with vulnerability to landslides. Often, only the steep slopes are available to the poor, who live there in densely populated, informal settlements.
Slope stability
About five years ago, Anderson realised that the research that he had been conducting into slope stability for highway construction could be used to mitigate against landslides, particularly in informal, unregulated settlements built on land that was already at high risk of collapse.
‘I suppose my motivation to understand more about landslides was really driven by the realisation that we didn’t know too much about the movement of water through soils,’ says Anderson. ‘When I started my PhD, I wrote some software that was able to model the movement of water through soils, and I started working in the Far East on big road and highway construction projects.
‘We’ve now migrated that software from planning for road projects to looking at slopes in poor housing areas to do essentially the same sort of thing,’ he continues. ‘But the issues there are far more complicated.’
The increasing movement of people from rural to urban areas has fuelled the growth of unregulated and unplanned shanty developments. Typically, in the eastern Caribbean, more than 60 per cent of the housing is of this nature, Anderson says.
‘I guess the vulnerability is enhanced in the areas in which we are working – the Caribbean – because of the migration to urban areas that is taking place,’ says Anderson. ‘Generally speaking, it’s the poorest people who are making that migration, and they can only get access to the worst land.’
The development of shanty areas changes the geometry, strength, loading, vegetation cover and surface- and groundwater regimes of the slopes, which, in turn, increases the risk of landslides. In order to address this, Anderson and Holcombe established a major landslide-risk-reduction programme entitled MoSSaiC (Management for Slope Stability in Communities) that is aimed at reducing the risk of landslides in vulnerable communities through a low-cost, community-based approach.
Giant umbrella
Following an invitation from the authorities in St Lucia, the programme’s pilot project was launched in Skate Town, an area of Castries, the island nation’s capital, that’s highly susceptible to landslides due to a combination of deep soils, steep slopes and high-intensity rainfall events. Working alongside a social intervention fund that was already active in Skate Town, Anderson and Holcombe approached the local community, holding meetings with residents, who helped them draw up detailed maps that identified past landslides, drainage issues and localised indicators of instability.
Then, using Anderson’s risk-prediction software, which had been further developed by Holcombe, they were able to model individual scenarios on a very small scale, in order to predict whether removing water from the soil would make the development safer or not. ‘Once you have that detailed information, you can identify locations in which to build surface drains to capture water and safely remove it from the slope,’ says Holcombe. ‘In conjunction with that, you can capture all of the rain that falls on the roofs of a settlement such as this [via a system of gutters and drains] and drain it away safely. It’s a bit like putting a giant umbrella over the slope to keep all the rainwater off.’
All of the physical work of building drains is tendered out to contractors in the community, encouraging participation in the planning, execution and maintenance of the water-management system and ensuring that more than 80 per cent of funds are spent within the communities themselves.
‘Using our computer model, you can see that by reducing the rainfall, you’re improving stability,’ says Holcombe. ‘That’s effectively what we’ve been doing – mapping the community with the people in the community, identifying potential locations for drains.’ These locations are then passed to the government, which provides the engineers needed to build the drains. ‘We’re just fulfilling an advisory role – it’s up to the government what it does with those ideas and the diagnosis that we provide.’
Changing behaviour
Since establishing the project in Skate Town, MoSSaiC programmes have been launched in other communities on St Lucia, as well as in parts of Dominica, St Vincent, Bequia and the British Virgin Islands. Anderson and Holcombe were also recently invited by the World Bank to join its disaster-risk-reduction team in Washington.
In the future, they hope that their community-level ‘toolkit’ can be fine-tuned so that it can be rolled out across other regions that are at risk from landslides. ‘In the next year or two, I would like us to complete a resource configuration [toolkit] that could be deployed by the different stakeholders – communities, governments and donors – across the world,’ says Holcombe.
They’re also keen to revisit some of the areas in which they first worked to see what progress has been made. ‘I would like to go back to some of those areas to conduct a survey that measures whether the programme has fundamentally changed people’s behaviour and the way in which they deal with the threat from landslides in their communities,’ says Anderson. ‘This is not a case of us just going in there and saying, “We can fix that,” moving on to somewhere else and saying, “We’ll fix that” – bouncing around all over the place. What we want is for communities to take ownership of landslide-risk-reduction strategies as a longer-term approach to the problem – not just in the eastern Caribbean, but in all areas at risk from landslides.’
To learn more about MoSSaiC, visit www.mossaic.org
June 2010
These disasters are both grimly routine and somewhat unusual – routine in that globally, hundreds of landslides take place every year in built-up areas, killing a total of around 1,000 people; unusual in that they made the news headlines. ‘Quite often, landslides are underreported and not as easy to recognise as, say, a flood because they happen in very discrete locations, and you can get multiple landslide events,’ says Dr Liz Holcombe, a landslide researcher in the University of Bristol’s School of Geographical Sciences. ‘They are effectively masked by the triggers with which they are associated,’ adds her colleague and former PhD tutor Professor Malcolm Anderson.
Hurricane Mitch illustrates Anderson’s point well. In November 1998, this category-five hurricane brought record rainfall to Honduras, Guatemala and Nicaragua, causing catastrophic flooding. It went on to become the second-deadliest Atlantic hurricane in history, with as many as 20,000 people killed. Around 2.7 million were left homeless and the total damage was estimated at more than US$5billion.
‘The damage wasn’t just a result of flooding,’ says Holcombe. ‘It was also caused by hundreds of landslides that affected the whole region, blocking the road networks, preventing trade and [the distribution of] emergency aid, and causing a significant reduction in economic growth. So even though a significant proportion of the damage was actually through landslides triggered by that rain, it’s recorded as a hurricane, rather than, say, 100 landslides and a flood.’
This intertwining of landslides with other natural disasters, and the multi-faceted nature of their effects, renders their impact equally complex. ‘The global scale of the problem depends on how you cut it,’ says Holcombe. ‘In absolute terms, Asia has the most landslides, the Americas and Caribbean region has the deadliest, and Europe has the costliest, because they’re damaging more expensive infrastructure and property. However, in terms of GDP, the landslides turn out to be relatively more expensive to developing economies.’
In developing countries, losses are greatest in cities, where migration and urbanisation link poverty with vulnerability to landslides. Often, only the steep slopes are available to the poor, who live there in densely populated, informal settlements.
Slope stability
About five years ago, Anderson realised that the research that he had been conducting into slope stability for highway construction could be used to mitigate against landslides, particularly in informal, unregulated settlements built on land that was already at high risk of collapse.
‘I suppose my motivation to understand more about landslides was really driven by the realisation that we didn’t know too much about the movement of water through soils,’ says Anderson. ‘When I started my PhD, I wrote some software that was able to model the movement of water through soils, and I started working in the Far East on big road and highway construction projects.
‘We’ve now migrated that software from planning for road projects to looking at slopes in poor housing areas to do essentially the same sort of thing,’ he continues. ‘But the issues there are far more complicated.’
The increasing movement of people from rural to urban areas has fuelled the growth of unregulated and unplanned shanty developments. Typically, in the eastern Caribbean, more than 60 per cent of the housing is of this nature, Anderson says.
‘I guess the vulnerability is enhanced in the areas in which we are working – the Caribbean – because of the migration to urban areas that is taking place,’ says Anderson. ‘Generally speaking, it’s the poorest people who are making that migration, and they can only get access to the worst land.’
The development of shanty areas changes the geometry, strength, loading, vegetation cover and surface- and groundwater regimes of the slopes, which, in turn, increases the risk of landslides. In order to address this, Anderson and Holcombe established a major landslide-risk-reduction programme entitled MoSSaiC (Management for Slope Stability in Communities) that is aimed at reducing the risk of landslides in vulnerable communities through a low-cost, community-based approach.
Giant umbrella
Following an invitation from the authorities in St Lucia, the programme’s pilot project was launched in Skate Town, an area of Castries, the island nation’s capital, that’s highly susceptible to landslides due to a combination of deep soils, steep slopes and high-intensity rainfall events. Working alongside a social intervention fund that was already active in Skate Town, Anderson and Holcombe approached the local community, holding meetings with residents, who helped them draw up detailed maps that identified past landslides, drainage issues and localised indicators of instability.
Then, using Anderson’s risk-prediction software, which had been further developed by Holcombe, they were able to model individual scenarios on a very small scale, in order to predict whether removing water from the soil would make the development safer or not. ‘Once you have that detailed information, you can identify locations in which to build surface drains to capture water and safely remove it from the slope,’ says Holcombe. ‘In conjunction with that, you can capture all of the rain that falls on the roofs of a settlement such as this [via a system of gutters and drains] and drain it away safely. It’s a bit like putting a giant umbrella over the slope to keep all the rainwater off.’
All of the physical work of building drains is tendered out to contractors in the community, encouraging participation in the planning, execution and maintenance of the water-management system and ensuring that more than 80 per cent of funds are spent within the communities themselves.
‘Using our computer model, you can see that by reducing the rainfall, you’re improving stability,’ says Holcombe. ‘That’s effectively what we’ve been doing – mapping the community with the people in the community, identifying potential locations for drains.’ These locations are then passed to the government, which provides the engineers needed to build the drains. ‘We’re just fulfilling an advisory role – it’s up to the government what it does with those ideas and the diagnosis that we provide.’
Changing behaviour
Since establishing the project in Skate Town, MoSSaiC programmes have been launched in other communities on St Lucia, as well as in parts of Dominica, St Vincent, Bequia and the British Virgin Islands. Anderson and Holcombe were also recently invited by the World Bank to join its disaster-risk-reduction team in Washington.
In the future, they hope that their community-level ‘toolkit’ can be fine-tuned so that it can be rolled out across other regions that are at risk from landslides. ‘In the next year or two, I would like us to complete a resource configuration [toolkit] that could be deployed by the different stakeholders – communities, governments and donors – across the world,’ says Holcombe.
They’re also keen to revisit some of the areas in which they first worked to see what progress has been made. ‘I would like to go back to some of those areas to conduct a survey that measures whether the programme has fundamentally changed people’s behaviour and the way in which they deal with the threat from landslides in their communities,’ says Anderson. ‘This is not a case of us just going in there and saying, “We can fix that,” moving on to somewhere else and saying, “We’ll fix that” – bouncing around all over the place. What we want is for communities to take ownership of landslide-risk-reduction strategies as a longer-term approach to the problem – not just in the eastern Caribbean, but in all areas at risk from landslides.’
To learn more about MoSSaiC, visit www.mossaic.org
June 2010
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