Tag Archives: erosion

Rivers flood, seas rise – and land faces erosion

Polar melting cannot be separated from farmland soil erosion and estuarine flooding. All are part of climate change.

LONDON, 7 September, 2020 – Climate heating often ensures that calamities don’t come singly: so don’t forget what erosion can do.

In a warmer world the glaciers will melt ever faster to raise global sea levels ever higher. In a wetter world, more and more topsoil will be swept off the farmlands and downriver into the ever-rising seas.

And the pay-off of silt-laden rivers and rising sea levels could be catastrophic floods, as swollen rivers suddenly change course. Since many of the world’s greatest cities are built on river estuaries, lives and economies will be at risk.

Three new studies in two journals deliver a sharp reminder that the consequences of global heating are not straightforward: the world responds to change in unpredictable ways.

First: the melting of the ice sheets and the mountain glaciers. Researchers warn in the journal Nature Climate Change that if the loss of ice from Antarctica, Greenland and the frozen rivers continues, then climate forecasters and government agencies will have to think again: sea levels could rise to at least 17cms higher than the worst predictions so far.

“Avulsions are the earthquakes of rivers. They are sudden and sometimes catastrophic. We are trying to understand where and when the next avulsions will occur”

That means an additional 16 million people at hazard from estuarine floods and storm surges.

In the last 30 years, the flow from the Antarctic ice cap has raised sea levels by 7.2mm, and from Greenland by 10.6mm. Every year, the world’s oceans are 4mm higher than they were the year before.

“Although we anticipated the ice sheets would lose increasing amounts of ice in response to the warming of the oceans and the atmosphere, the rate at which they are melting has accelerated faster than we could have imagined,” said Tom Slater of the University of Leeds, in the UK, who led the research.

“The melting is overtaking the climate models we use to guide us, and we are in danger of being unprepared for the risks posed by sea level rise.”

Dr Slater and his colleagues are the third team to warn in the last month that observations of climate already match the worst-case scenarios dreamed up by forecasters preparing for a range of possible climate outcomes.

Erosion risk rises

The latest reading of glacial melt rates suggests that the risk of storm surges for many of the world’s greatest cities will double by the close of the century. But coastal cities – and the farmers who already work 38% of the terrestrial surface to feed almost 8bn people – have another more immediate problem.

In a warmer world, more water evaporates. In a warmer atmosphere, the capacity of the air to hold moisture also increases, so along with more intense droughts, heavier rainfall is on the way for much of the world. And the heavier the rain, or the more prolonged the drought, the higher the risk of soil erosion.

In 2015 the world’s farmers and foresters watched 43 billion tonnes of topsoil wash away from hillsides or blow away from tilled land and into the sea. By 2070, this burden of silt swept away by water or blown by wind will have risen by between 30% and 66%: probably more than 28 bn tons of additional loss.

This could only impoverish the farmland, according to a study by Swiss scientists in the Proceedings of the National Academy of Sciences. It could also impoverish people, communities and countries. The worst hit could be in the less developed nations of the tropics and subtropics.

But the flow of ever-higher silt levels into ever-rising seas also raises a new hazard: hydrologists call it river avulsion. It’s a simple and natural process. As conditions change, so rivers will naturally change their flow to spill over new floodplains and extend coastal lands.

Survival in question

But river avulsions can also be helped along by rising sea levels. Since 10% of humanity is crowded into rich, fertile delta lands, and since some of the deadliest floods in human history – two in China in 1887 and 1931 claimed six million lives – have been caused by river avulsions, the question becomes a matter of life and death.

US scientists report, also in the Proceedings of the National Academy of Sciences, that rising sea levels alone could make abrupt river avulsion more probable, especially as delta lands could be subsiding, because of groundwater and other extraction.

The dangers of avulsion are affected by the rate of sediment deposit in the river channels, and this is likely to rise with sea levels. This in turn raises the level of the river and eventually a breach of a levee or other flood defence will force the river to find a swifter, steeper path to the sea.

Cities such as New Orleans and the coastal communities of the Mississippi delta are already vulnerable. “Avulsions are the earthquakes of rivers,” said Michael Lamb, of California Institute of Technology, one of the authors.

“They are sudden and sometimes catastrophic natural events that occur with statistical regularity, shifting the direction of major rivers. We are trying to understand where and when the next avulsions will occur.” – Climate News Network

Polar melting cannot be separated from farmland soil erosion and estuarine flooding. All are part of climate change.

LONDON, 7 September, 2020 – Climate heating often ensures that calamities don’t come singly: so don’t forget what erosion can do.

In a warmer world the glaciers will melt ever faster to raise global sea levels ever higher. In a wetter world, more and more topsoil will be swept off the farmlands and downriver into the ever-rising seas.

And the pay-off of silt-laden rivers and rising sea levels could be catastrophic floods, as swollen rivers suddenly change course. Since many of the world’s greatest cities are built on river estuaries, lives and economies will be at risk.

Three new studies in two journals deliver a sharp reminder that the consequences of global heating are not straightforward: the world responds to change in unpredictable ways.

First: the melting of the ice sheets and the mountain glaciers. Researchers warn in the journal Nature Climate Change that if the loss of ice from Antarctica, Greenland and the frozen rivers continues, then climate forecasters and government agencies will have to think again: sea levels could rise to at least 17cms higher than the worst predictions so far.

“Avulsions are the earthquakes of rivers. They are sudden and sometimes catastrophic. We are trying to understand where and when the next avulsions will occur”

That means an additional 16 million people at hazard from estuarine floods and storm surges.

In the last 30 years, the flow from the Antarctic ice cap has raised sea levels by 7.2mm, and from Greenland by 10.6mm. Every year, the world’s oceans are 4mm higher than they were the year before.

“Although we anticipated the ice sheets would lose increasing amounts of ice in response to the warming of the oceans and the atmosphere, the rate at which they are melting has accelerated faster than we could have imagined,” said Tom Slater of the University of Leeds, in the UK, who led the research.

“The melting is overtaking the climate models we use to guide us, and we are in danger of being unprepared for the risks posed by sea level rise.”

Dr Slater and his colleagues are the third team to warn in the last month that observations of climate already match the worst-case scenarios dreamed up by forecasters preparing for a range of possible climate outcomes.

Erosion risk rises

The latest reading of glacial melt rates suggests that the risk of storm surges for many of the world’s greatest cities will double by the close of the century. But coastal cities – and the farmers who already work 38% of the terrestrial surface to feed almost 8bn people – have another more immediate problem.

In a warmer world, more water evaporates. In a warmer atmosphere, the capacity of the air to hold moisture also increases, so along with more intense droughts, heavier rainfall is on the way for much of the world. And the heavier the rain, or the more prolonged the drought, the higher the risk of soil erosion.

In 2015 the world’s farmers and foresters watched 43 billion tonnes of topsoil wash away from hillsides or blow away from tilled land and into the sea. By 2070, this burden of silt swept away by water or blown by wind will have risen by between 30% and 66%: probably more than 28 bn tons of additional loss.

This could only impoverish the farmland, according to a study by Swiss scientists in the Proceedings of the National Academy of Sciences. It could also impoverish people, communities and countries. The worst hit could be in the less developed nations of the tropics and subtropics.

But the flow of ever-higher silt levels into ever-rising seas also raises a new hazard: hydrologists call it river avulsion. It’s a simple and natural process. As conditions change, so rivers will naturally change their flow to spill over new floodplains and extend coastal lands.

Survival in question

But river avulsions can also be helped along by rising sea levels. Since 10% of humanity is crowded into rich, fertile delta lands, and since some of the deadliest floods in human history – two in China in 1887 and 1931 claimed six million lives – have been caused by river avulsions, the question becomes a matter of life and death.

US scientists report, also in the Proceedings of the National Academy of Sciences, that rising sea levels alone could make abrupt river avulsion more probable, especially as delta lands could be subsiding, because of groundwater and other extraction.

The dangers of avulsion are affected by the rate of sediment deposit in the river channels, and this is likely to rise with sea levels. This in turn raises the level of the river and eventually a breach of a levee or other flood defence will force the river to find a swifter, steeper path to the sea.

Cities such as New Orleans and the coastal communities of the Mississippi delta are already vulnerable. “Avulsions are the earthquakes of rivers,” said Michael Lamb, of California Institute of Technology, one of the authors.

“They are sudden and sometimes catastrophic natural events that occur with statistical regularity, shifting the direction of major rivers. We are trying to understand where and when the next avulsions will occur.” – Climate News Network

India's dam building bonanza

FOR IMMEDIATE RELEASE
India is in the midst of a massive hydro electric dam building programme, necessary, it says, to fuel the energy needs of its fast growing economy. Kieran Cooke, one of the editors of the Climate News Network, has been in India and reports on the country’s energy plans.

Assam, northeastern India, March 16 – This region, east of Bangladesh and bordering China to the north, is an area described by politicians as India’s ‘future powerhouse’ and is a key focus point of the country’s dam building programme.

The ambition of planners in New Delhi is not in doubt. So far plans for more than 160 dams – both big and small – have been announced in the northeast, the majority of them to be built in the remote, mountainous state of Arunachal Pradesh and harnessing the waters of the mighty Brahmaputra river and its tributaries.

It’s planned that in total more than 60,000 MW of electricity will be generated from the planned dams. More projects are likely to follow.

Not to be outdone, China, which borders Arunachal Pradesh, is involved in a major dam building programme on its side of the border, also using the waters of the Brahmaputra – which it calls the Yarlung Tsangpo.

Controversy

The dam building programme is highly controversial: critics say it not only ignores geological and ecological factors – it also fails to take into account the impact of climate change in the region.

The Brahmaputra, 10 kilometres wide in places, is one of the world’s major rivers, winding for nearly 3,000 kilometres from the Tibetan Plateau through China, India and Bangladesh before joining with the Ganges and flowing out into the Bay of Bengal.

It is an extremely volatile, tempestuous river system: the Brahmaputra’s waters rise dramatically during monsoon season, causing widespread flooding, erosion  and misery for many thousands of mostly subsistence farmers.

Ashwini Saikia is a farmer on the banks of the Brahmaputra river, in the small settlement of Rohomoria in northern Assam. Even now, in pre monsoon season when the river is low, there is the “plop, plop” sound of land falling into the waters.

Erosion fears

“Each year the river has eaten away more and more of my land. Then in 2010 the waters rose so much I lost my house for the fifth time in the last 15 years” says Ashwini.

Ashwini has given up farming and is now being forced to move with his family and livestock – to where he’s not entirely sure.

Dr Partha Das is an Assamese academic who has been studying the Brahmaputra for several years. He also runs Aaranyak, a locally based environmental NGO.

“The dam building programme has many question marks hanging over it including the fact that the northeast is a highly seismic region, with an earthquake in 1950 completely altering the geological structure of the Brahmaputra river basin.

Climate change impacts

“Then there is the whole question of climate change, which has scarcely been mentioned by the planners. Already we’re seeing an increase in intense rainfall events that are accelerating the high rate of soil erosion and landslides in mountainous regions. And as temperatures rise and glaciers melt on the Tibetan Plateau and in the Himalayas, river flow levels – at least in the short term – are likely to increase.”

The Indian government defends its dam building programme, saying the power generated will mean that the country will be able to wean itself off its dependence on coal for energy, most of it low quality and extremely polluting.

But many in the northeast, who have long felt cut off from the rest of India and neglected by central government, are unconvinced by New Delhi’s arguments.

There are accusations that the mostly privately backed dam building projects are money making exercises for the wealthy: most of the power produced will be exported to other parts of India and not used to build up local industries.

Tribal concerns

The northeast is a tribal area: indigenous peoples say the influx of labourers from elsewhere in India is threatening local culture. They say the dams will also lead to more deforestation – and threaten some of India’s most important wildlife habitats.

Opponents of the dam building say no proper overall plan has been put in place: though India and China recently reached agreement on sharing various river resources, there is no specific deal on managing the Brahmaputra’s waters.

Protests about the dams has been growing, with work on what is India’s biggest dam construction project to date – the 2,000MW Lower Subansiri dam on one of the Brahmaputra’s tributaries – repeatedly held up. – Climate News Network

FOR IMMEDIATE RELEASE
India is in the midst of a massive hydro electric dam building programme, necessary, it says, to fuel the energy needs of its fast growing economy. Kieran Cooke, one of the editors of the Climate News Network, has been in India and reports on the country’s energy plans.

Assam, northeastern India, March 16 – This region, east of Bangladesh and bordering China to the north, is an area described by politicians as India’s ‘future powerhouse’ and is a key focus point of the country’s dam building programme.

The ambition of planners in New Delhi is not in doubt. So far plans for more than 160 dams – both big and small – have been announced in the northeast, the majority of them to be built in the remote, mountainous state of Arunachal Pradesh and harnessing the waters of the mighty Brahmaputra river and its tributaries.

It’s planned that in total more than 60,000 MW of electricity will be generated from the planned dams. More projects are likely to follow.

Not to be outdone, China, which borders Arunachal Pradesh, is involved in a major dam building programme on its side of the border, also using the waters of the Brahmaputra – which it calls the Yarlung Tsangpo.

Controversy

The dam building programme is highly controversial: critics say it not only ignores geological and ecological factors – it also fails to take into account the impact of climate change in the region.

The Brahmaputra, 10 kilometres wide in places, is one of the world’s major rivers, winding for nearly 3,000 kilometres from the Tibetan Plateau through China, India and Bangladesh before joining with the Ganges and flowing out into the Bay of Bengal.

It is an extremely volatile, tempestuous river system: the Brahmaputra’s waters rise dramatically during monsoon season, causing widespread flooding, erosion  and misery for many thousands of mostly subsistence farmers.

Ashwini Saikia is a farmer on the banks of the Brahmaputra river, in the small settlement of Rohomoria in northern Assam. Even now, in pre monsoon season when the river is low, there is the “plop, plop” sound of land falling into the waters.

Erosion fears

“Each year the river has eaten away more and more of my land. Then in 2010 the waters rose so much I lost my house for the fifth time in the last 15 years” says Ashwini.

Ashwini has given up farming and is now being forced to move with his family and livestock – to where he’s not entirely sure.

Dr Partha Das is an Assamese academic who has been studying the Brahmaputra for several years. He also runs Aaranyak, a locally based environmental NGO.

“The dam building programme has many question marks hanging over it including the fact that the northeast is a highly seismic region, with an earthquake in 1950 completely altering the geological structure of the Brahmaputra river basin.

Climate change impacts

“Then there is the whole question of climate change, which has scarcely been mentioned by the planners. Already we’re seeing an increase in intense rainfall events that are accelerating the high rate of soil erosion and landslides in mountainous regions. And as temperatures rise and glaciers melt on the Tibetan Plateau and in the Himalayas, river flow levels – at least in the short term – are likely to increase.”

The Indian government defends its dam building programme, saying the power generated will mean that the country will be able to wean itself off its dependence on coal for energy, most of it low quality and extremely polluting.

But many in the northeast, who have long felt cut off from the rest of India and neglected by central government, are unconvinced by New Delhi’s arguments.

There are accusations that the mostly privately backed dam building projects are money making exercises for the wealthy: most of the power produced will be exported to other parts of India and not used to build up local industries.

Tribal concerns

The northeast is a tribal area: indigenous peoples say the influx of labourers from elsewhere in India is threatening local culture. They say the dams will also lead to more deforestation – and threaten some of India’s most important wildlife habitats.

Opponents of the dam building say no proper overall plan has been put in place: though India and China recently reached agreement on sharing various river resources, there is no specific deal on managing the Brahmaputra’s waters.

Protests about the dams has been growing, with work on what is India’s biggest dam construction project to date – the 2,000MW Lower Subansiri dam on one of the Brahmaputra’s tributaries – repeatedly held up. – Climate News Network

India’s dam building bonanza

FOR IMMEDIATE RELEASE India is in the midst of a massive hydro electric dam building programme, necessary, it says, to fuel the energy needs of its fast growing economy. Kieran Cooke, one of the editors of the Climate News Network, has been in India and reports on the country’s energy plans. Assam, northeastern India, March 16 – This region, east of Bangladesh and bordering China to the north, is an area described by politicians as India’s ‘future powerhouse’ and is a key focus point of the country’s dam building programme. The ambition of planners in New Delhi is not in doubt. So far plans for more than 160 dams – both big and small – have been announced in the northeast, the majority of them to be built in the remote, mountainous state of Arunachal Pradesh and harnessing the waters of the mighty Brahmaputra river and its tributaries. It’s planned that in total more than 60,000 MW of electricity will be generated from the planned dams. More projects are likely to follow. Not to be outdone, China, which borders Arunachal Pradesh, is involved in a major dam building programme on its side of the border, also using the waters of the Brahmaputra – which it calls the Yarlung Tsangpo.

Controversy

The dam building programme is highly controversial: critics say it not only ignores geological and ecological factors – it also fails to take into account the impact of climate change in the region. The Brahmaputra, 10 kilometres wide in places, is one of the world’s major rivers, winding for nearly 3,000 kilometres from the Tibetan Plateau through China, India and Bangladesh before joining with the Ganges and flowing out into the Bay of Bengal. It is an extremely volatile, tempestuous river system: the Brahmaputra’s waters rise dramatically during monsoon season, causing widespread flooding, erosion  and misery for many thousands of mostly subsistence farmers. Ashwini Saikia is a farmer on the banks of the Brahmaputra river, in the small settlement of Rohomoria in northern Assam. Even now, in pre monsoon season when the river is low, there is the “plop, plop” sound of land falling into the waters.

Erosion fears

“Each year the river has eaten away more and more of my land. Then in 2010 the waters rose so much I lost my house for the fifth time in the last 15 years” says Ashwini. Ashwini has given up farming and is now being forced to move with his family and livestock – to where he’s not entirely sure. Dr Partha Das is an Assamese academic who has been studying the Brahmaputra for several years. He also runs Aaranyak, a locally based environmental NGO. “The dam building programme has many question marks hanging over it including the fact that the northeast is a highly seismic region, with an earthquake in 1950 completely altering the geological structure of the Brahmaputra river basin.

Climate change impacts

“Then there is the whole question of climate change, which has scarcely been mentioned by the planners. Already we’re seeing an increase in intense rainfall events that are accelerating the high rate of soil erosion and landslides in mountainous regions. And as temperatures rise and glaciers melt on the Tibetan Plateau and in the Himalayas, river flow levels – at least in the short term – are likely to increase.” The Indian government defends its dam building programme, saying the power generated will mean that the country will be able to wean itself off its dependence on coal for energy, most of it low quality and extremely polluting. But many in the northeast, who have long felt cut off from the rest of India and neglected by central government, are unconvinced by New Delhi’s arguments. There are accusations that the mostly privately backed dam building projects are money making exercises for the wealthy: most of the power produced will be exported to other parts of India and not used to build up local industries.

Tribal concerns

The northeast is a tribal area: indigenous peoples say the influx of labourers from elsewhere in India is threatening local culture. They say the dams will also lead to more deforestation – and threaten some of India’s most important wildlife habitats. Opponents of the dam building say no proper overall plan has been put in place: though India and China recently reached agreement on sharing various river resources, there is no specific deal on managing the Brahmaputra’s waters. Protests about the dams has been growing, with work on what is India’s biggest dam construction project to date – the 2,000MW Lower Subansiri dam on one of the Brahmaputra’s tributaries – repeatedly held up. – Climate News Network

FOR IMMEDIATE RELEASE India is in the midst of a massive hydro electric dam building programme, necessary, it says, to fuel the energy needs of its fast growing economy. Kieran Cooke, one of the editors of the Climate News Network, has been in India and reports on the country’s energy plans. Assam, northeastern India, March 16 – This region, east of Bangladesh and bordering China to the north, is an area described by politicians as India’s ‘future powerhouse’ and is a key focus point of the country’s dam building programme. The ambition of planners in New Delhi is not in doubt. So far plans for more than 160 dams – both big and small – have been announced in the northeast, the majority of them to be built in the remote, mountainous state of Arunachal Pradesh and harnessing the waters of the mighty Brahmaputra river and its tributaries. It’s planned that in total more than 60,000 MW of electricity will be generated from the planned dams. More projects are likely to follow. Not to be outdone, China, which borders Arunachal Pradesh, is involved in a major dam building programme on its side of the border, also using the waters of the Brahmaputra – which it calls the Yarlung Tsangpo.

Controversy

The dam building programme is highly controversial: critics say it not only ignores geological and ecological factors – it also fails to take into account the impact of climate change in the region. The Brahmaputra, 10 kilometres wide in places, is one of the world’s major rivers, winding for nearly 3,000 kilometres from the Tibetan Plateau through China, India and Bangladesh before joining with the Ganges and flowing out into the Bay of Bengal. It is an extremely volatile, tempestuous river system: the Brahmaputra’s waters rise dramatically during monsoon season, causing widespread flooding, erosion  and misery for many thousands of mostly subsistence farmers. Ashwini Saikia is a farmer on the banks of the Brahmaputra river, in the small settlement of Rohomoria in northern Assam. Even now, in pre monsoon season when the river is low, there is the “plop, plop” sound of land falling into the waters.

Erosion fears

“Each year the river has eaten away more and more of my land. Then in 2010 the waters rose so much I lost my house for the fifth time in the last 15 years” says Ashwini. Ashwini has given up farming and is now being forced to move with his family and livestock – to where he’s not entirely sure. Dr Partha Das is an Assamese academic who has been studying the Brahmaputra for several years. He also runs Aaranyak, a locally based environmental NGO. “The dam building programme has many question marks hanging over it including the fact that the northeast is a highly seismic region, with an earthquake in 1950 completely altering the geological structure of the Brahmaputra river basin.

Climate change impacts

“Then there is the whole question of climate change, which has scarcely been mentioned by the planners. Already we’re seeing an increase in intense rainfall events that are accelerating the high rate of soil erosion and landslides in mountainous regions. And as temperatures rise and glaciers melt on the Tibetan Plateau and in the Himalayas, river flow levels – at least in the short term – are likely to increase.” The Indian government defends its dam building programme, saying the power generated will mean that the country will be able to wean itself off its dependence on coal for energy, most of it low quality and extremely polluting. But many in the northeast, who have long felt cut off from the rest of India and neglected by central government, are unconvinced by New Delhi’s arguments. There are accusations that the mostly privately backed dam building projects are money making exercises for the wealthy: most of the power produced will be exported to other parts of India and not used to build up local industries.

Tribal concerns

The northeast is a tribal area: indigenous peoples say the influx of labourers from elsewhere in India is threatening local culture. They say the dams will also lead to more deforestation – and threaten some of India’s most important wildlife habitats. Opponents of the dam building say no proper overall plan has been put in place: though India and China recently reached agreement on sharing various river resources, there is no specific deal on managing the Brahmaputra’s waters. Protests about the dams has been growing, with work on what is India’s biggest dam construction project to date – the 2,000MW Lower Subansiri dam on one of the Brahmaputra’s tributaries – repeatedly held up. – Climate News Network