Tropical cyclones don’t only destroy houses and trees; they also bring heavy rains and cause major flooding. Dr. Guus Stelling was one of people working on a warning system for the Indian sub-state, Andhra Pradesh.
It helps the Indians keep their feet dry.
Indians have pretty much gotten used to it: every few years a cyclone destroys a large costal area and claims thousands of victims. The sea penetrates the land up to several kilometers and torrential rains cause little streams to swell into huge rivers that wipe whole villages off the map.
Many Indians accept their fate, but with the right information they could avoid the violence of nature. If only they knew where the water would go and where they could go to keep their feet dry.
Dr. Guus Stelling is trying to find an answer to this question for Andhra Pradesh, the sub-state on the east coast of India, an area with about four million inhabitants. Stelling, who is a professor of numerical fluid mechanics at the TU, joined together with researchers from the ‘Waterloopkundig Laboratorium’ (WL) and the UK Meterological Office to develop an information system that gives a precise view as to which areas might flood when a cyclone is heading for the coast. They say that: ”Tropical cyclones are the greatest natural killers in South-East Asia. We can save a lot of lives with this new warning system.”
Supercyclone
The model builder can see it happening: whenever a cyclone approaches, Andhra Pradesh’s weather bureau sends a detailed chart to all coastal provinces, allowing people in the risk areas to evacuate on time. ”It’s not like in America, where everyone is ready to leave with their cars. Still, many people in India will be able to find a safer place because of the extra information.”
It’s Stelling’s opinion that it will be several years before the warning system truly saves lives. The Indian government needs to provide detailed height data. ”They aren’t supplying the data now because it might be a military secret, but the data is necessary to determine accurately the location of floods.”
Once all the necessary data is available, the warning system has a lot to offer, Stelling says. So far Indian weather stations only give information about the strength of cyclones and the estimated time the cyclone will hit the coast. They can’t chart the flooding risks. ”In October 1999 a cyclone hit the sub-state Orissa, just north of Andhra Pradesh. It was accurately predicted, but people just didn’t act on it. Nobody realized the magnitude of the flooding that it would result. Thousands of people drowned.”
Mess
Every year, tens of tropical storms develop in the Bengal Sea off the East Coast of India, and some of them grow to become storms that stretch for hundreds of kilometers. Thunderstorms and powerfulwind characterize these depressions. They’re just like giant tornadoes. The only difference is that they come into existence above tropical waters. They get their energy from the warm ocean water.
The super cyclone that hit Orissa in 1999 had wind velocities of over 200 kilometers per hour. An estimated nine thousand people were killed, most of them drowned. About eight hundred houses were destroyed, and eighteen million acres of farmland flooded. Cyclones with an equivalent strength hit India in 1977, 1989 and 1990. And it can be worse. In 1970, a cyclone hit neighboring Bangladesh, killing an estimated three hundred thousand people.
”The force of a cyclone is gigantic,” says Stelling. In twenty-four hours seventy centimeters of rain can fall from a cyclone, which is about the average annual precipitation in Holland. ”You can imagine that it becomes one big mess. All the rain gets concentrated in the valleys and there is major flooding there. Little rivers swell to something gigantic in a day, about the size of the Maas or Rhine.”
Satellites
The prediction of where a cyclone will cause floods isn%t a simple matter. Cyclones move in an unpredictable way, like a feather in the wind. You can see what direction they are headed via satellites though. If a cyclone is a day away from the coast, a strip of a hundred kilometers along the coast can be identified that is pretty much certain to be hit first.
Stelling: ”You have to realize that a cyclone moves at the speed of a bicyclist % about 15 to 25 kilometers per hour. Thanks to this we have some time to prepare ourselves for it. This is impossible with, for instance, a tidal wave, that has about the same speed as a Boeing plane. The cyclone route is, however, the weakest link in our predictions of floods. Small variations in the water surface can change the course of the cyclone.”
The warning system that Stelling%s team developed is based on a rain model, a storm-flooding model, and a wind and river model. One of the inputs to the models is the route of the cyclone in question. The Indian weather station estimates the route based on satellite images. A geographical information system finally charts the expected floods and the wind damage.
”If the cyclone doesn’t deviate too much from the predicted route, you can predict pretty accurately where floods will be,” says Stelling. As long as there is also detailed data of the terrain altitudes and the water system. It’s his opinion that the warning system is at best ninety percent accurate. Of course, everything depends on the quality of the data that is put into the system. The models themselves are good enough, he says. The water motion model, for instance, was extensively tested in Holland. It could simulate historical floods in the Dutch river area very well.
Cholera
Applying the models to the situation in Andhra Pradesh shows how vulnerable deltas and some river valleys are. ”The water level indeltas can rise about seven meters due to storm flooding at sea and the water supply from the rivers. The valleys, especially those of the West- and East-Godavari River, are very dangerous areas to be in. The river overflows it’s banks quickly here and can easily flood expanses of rice fields and villages,” Stelling tells us. Also, cholera outbreaks often occur after a heavy storm and the surface water is full of germs. The team is also currently working on a warning system for Vietnam. This country also gets its fair share of cyclones from the Bay of Bengal. Many other countries could benefit from a good warning system for the effects of heavy storms. Stelling sees it in a larger context. ”Wherever dikes or other engineering works aren’t enough to protect us we have to rely on computer models, so that we can anticipate the natural violence. It’s happening all over the world: information technology is getting to be more and more important for our safety.”
Translation by Katy Gerstner
Tropical cyclones don’t only destroy houses and trees; they also bring heavy rains and cause major flooding. Dr. Guus Stelling was one of people working on a warning system for the Indian sub-state, Andhra Pradesh. It helps the Indians keep their feet dry.
Indians have pretty much gotten used to it: every few years a cyclone destroys a large costal area and claims thousands of victims. The sea penetrates the land up to several kilometers and torrential rains cause little streams to swell into huge rivers that wipe whole villages off the map.
Many Indians accept their fate, but with the right information they could avoid the violence of nature. If only they knew where the water would go and where they could go to keep their feet dry.
Dr. Guus Stelling is trying to find an answer to this question for Andhra Pradesh, the sub-state on the east coast of India, an area with about four million inhabitants. Stelling, who is a professor of numerical fluid mechanics at the TU, joined together with researchers from the ‘Waterloopkundig Laboratorium’ (WL) and the UK Meterological Office to develop an information system that gives a precise view as to which areas might flood when a cyclone is heading for the coast. They say that: ”Tropical cyclones are the greatest natural killers in South-East Asia. We can save a lot of lives with this new warning system.”
Supercyclone
The model builder can see it happening: whenever a cyclone approaches, Andhra Pradesh’s weather bureau sends a detailed chart to all coastal provinces, allowing people in the risk areas to evacuate on time. ”It’s not like in America, where everyone is ready to leave with their cars. Still, many people in India will be able to find a safer place because of the extra information.”
It’s Stelling’s opinion that it will be several years before the warning system truly saves lives. The Indian government needs to provide detailed height data. ”They aren’t supplying the data now because it might be a military secret, but the data is necessary to determine accurately the location of floods.”
Once all the necessary data is available, the warning system has a lot to offer, Stelling says. So far Indian weather stations only give information about the strength of cyclones and the estimated time the cyclone will hit the coast. They can’t chart the flooding risks. ”In October 1999 a cyclone hit the sub-state Orissa, just north of Andhra Pradesh. It was accurately predicted, but people just didn’t act on it. Nobody realized the magnitude of the flooding that it would result. Thousands of people drowned.”
Mess
Every year, tens of tropical storms develop in the Bengal Sea off the East Coast of India, and some of them grow to become storms that stretch for hundreds of kilometers. Thunderstorms and powerfulwind characterize these depressions. They’re just like giant tornadoes. The only difference is that they come into existence above tropical waters. They get their energy from the warm ocean water.
The super cyclone that hit Orissa in 1999 had wind velocities of over 200 kilometers per hour. An estimated nine thousand people were killed, most of them drowned. About eight hundred houses were destroyed, and eighteen million acres of farmland flooded. Cyclones with an equivalent strength hit India in 1977, 1989 and 1990. And it can be worse. In 1970, a cyclone hit neighboring Bangladesh, killing an estimated three hundred thousand people.
”The force of a cyclone is gigantic,” says Stelling. In twenty-four hours seventy centimeters of rain can fall from a cyclone, which is about the average annual precipitation in Holland. ”You can imagine that it becomes one big mess. All the rain gets concentrated in the valleys and there is major flooding there. Little rivers swell to something gigantic in a day, about the size of the Maas or Rhine.”
Satellites
The prediction of where a cyclone will cause floods isn%t a simple matter. Cyclones move in an unpredictable way, like a feather in the wind. You can see what direction they are headed via satellites though. If a cyclone is a day away from the coast, a strip of a hundred kilometers along the coast can be identified that is pretty much certain to be hit first.
Stelling: ”You have to realize that a cyclone moves at the speed of a bicyclist % about 15 to 25 kilometers per hour. Thanks to this we have some time to prepare ourselves for it. This is impossible with, for instance, a tidal wave, that has about the same speed as a Boeing plane. The cyclone route is, however, the weakest link in our predictions of floods. Small variations in the water surface can change the course of the cyclone.”
The warning system that Stelling%s team developed is based on a rain model, a storm-flooding model, and a wind and river model. One of the inputs to the models is the route of the cyclone in question. The Indian weather station estimates the route based on satellite images. A geographical information system finally charts the expected floods and the wind damage.
”If the cyclone doesn’t deviate too much from the predicted route, you can predict pretty accurately where floods will be,” says Stelling. As long as there is also detailed data of the terrain altitudes and the water system. It’s his opinion that the warning system is at best ninety percent accurate. Of course, everything depends on the quality of the data that is put into the system. The models themselves are good enough, he says. The water motion model, for instance, was extensively tested in Holland. It could simulate historical floods in the Dutch river area very well.
Cholera
Applying the models to the situation in Andhra Pradesh shows how vulnerable deltas and some river valleys are. ”The water level indeltas can rise about seven meters due to storm flooding at sea and the water supply from the rivers. The valleys, especially those of the West- and East-Godavari River, are very dangerous areas to be in. The river overflows it’s banks quickly here and can easily flood expanses of rice fields and villages,” Stelling tells us. Also, cholera outbreaks often occur after a heavy storm and the surface water is full of germs. The team is also currently working on a warning system for Vietnam. This country also gets its fair share of cyclones from the Bay of Bengal. Many other countries could benefit from a good warning system for the effects of heavy storms. Stelling sees it in a larger context. ”Wherever dikes or other engineering works aren’t enough to protect us we have to rely on computer models, so that we can anticipate the natural violence. It’s happening all over the world: information technology is getting to be more and more important for our safety.”
Translation by Katy Gerstner
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