Randolph Kinney
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- Joined
- Apr 7, 2005
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- North Carolina
USGS says South Carolina flooding not caused by climate change
Dr. Robert Holmes, USGS National Flood Hazard Coordinator, takes some time to discuss and answer some hot issues related to the flooding in South Carolina.
Is this flooding in South Carolina truly a 1000-year flood?
While this certainly was a catastrophic flood with lots of damage and tragic loss of life, USGS provisional data and preliminary analysis show NO indication that a 1000-year flood discharge occurred at any USGS streamgages. However, based on that analysis, it does appear that the USGS streamgage on the Black River at Kingstree, SC and the one on theSmith Branch at Columbia, SC both measured peak floods in the neighborhood of a 500-year flood. Currently, there appear to be a few more streamgages experiencing a 25-year to 50-year flood, but the majority of USGS streamgages had flood peaks that were less than 10-year floods. USGS will have more accurate estimates of the flood probabilities out in the coming months, as the engineers and scientists in South Carolina take time to do more careful analysis of the statistics.
Why do you think people have been calling it a 1000-year flood?
When USGS uses terminology like “1000-year flood,” it means that, statistically speaking, a flood of that magnitude (or greater) has a 1 in 1000 chance in any given year. In terms of probability, the 1000-year flood has a 0.1% chance of happening in any given year. One must keep in mind a 1000-year flood value is a statistical value based on observed data.
Although the USGS streamgage data in South Carolina does not seem to indicate a 1000 year flood, the amount of rainfall that fell over a 2 to 3 day period (greater than 16 to 20 inches in some locations) had, according to the National Oceanic and Atmospheric Administration (NOAA), a statistical probability of occurrence of 0.1% or 1 in 1000 chance. So, rather than someone saying this was a 1000-year flood, it is more accurate to say that “statistically speaking”, the rainfall that fell was a 1000-year rain storm, although it did not result in a 1000-year flood.
How can we have a 1000-year rain that does not result in a 1000-year flood?
It comes down to a number of factors, including the pattern of movement of the rain storm in each particular watershed, the conditions of the soil and plant matter on the ground in the watershed, and the timing of rain storm in one watershed versus other watersheds, among other things. An example would be that ground that is saturated before 1 inch of rain fell would result in more water going into the stream that if the ground was dry and could soak up more of the rain. Also, less water will runoff into streams from 1 inch of rain falling in the summer with the trees full of leaves versus the winter when there are no leaves to intercept the rain. This is all the science of hydrology, which is the study of the movement and distribution of water on the earth. Of course, in South Carolina, many of the watersheds have streams that are regulated by dams.
Is this flood due to climate change?
USGS research has shown no linkage between flooding (either increases or decreases) and the increase in greenhouse gases. Essentially, from USGS long-term streamgage data for sites across the country with no regulation or other changes to the watershed that could influence the streamflow, the data shows no systematic increases in flooding through time.
A much bigger impact on flooding, though, is land use change. Without proper mitigation, urbanization of watersheds increases flooding. Moreover, encroachment into the floodplain by homes and businesses leads to greater economic losses and potential loss of life, with more encroachment leading to greater losses.
http://water.usgs.gov/floods/events/2015/Joaquin/HolmesQA.html
Hey Pete, it is official, it is from the government - global warming aka climate change did not cause flooding to occur in South Carolina.
But all those global warming truthers are claiming global warming caused the flooding. Claiming it so does not make it so. It does make those who claim it so wackos that will believe anything because it fits the politics. Would that be you, Pete?
Dr. Robert Holmes, USGS National Flood Hazard Coordinator, takes some time to discuss and answer some hot issues related to the flooding in South Carolina.
Is this flooding in South Carolina truly a 1000-year flood?
While this certainly was a catastrophic flood with lots of damage and tragic loss of life, USGS provisional data and preliminary analysis show NO indication that a 1000-year flood discharge occurred at any USGS streamgages. However, based on that analysis, it does appear that the USGS streamgage on the Black River at Kingstree, SC and the one on theSmith Branch at Columbia, SC both measured peak floods in the neighborhood of a 500-year flood. Currently, there appear to be a few more streamgages experiencing a 25-year to 50-year flood, but the majority of USGS streamgages had flood peaks that were less than 10-year floods. USGS will have more accurate estimates of the flood probabilities out in the coming months, as the engineers and scientists in South Carolina take time to do more careful analysis of the statistics.
Why do you think people have been calling it a 1000-year flood?
When USGS uses terminology like “1000-year flood,” it means that, statistically speaking, a flood of that magnitude (or greater) has a 1 in 1000 chance in any given year. In terms of probability, the 1000-year flood has a 0.1% chance of happening in any given year. One must keep in mind a 1000-year flood value is a statistical value based on observed data.
Although the USGS streamgage data in South Carolina does not seem to indicate a 1000 year flood, the amount of rainfall that fell over a 2 to 3 day period (greater than 16 to 20 inches in some locations) had, according to the National Oceanic and Atmospheric Administration (NOAA), a statistical probability of occurrence of 0.1% or 1 in 1000 chance. So, rather than someone saying this was a 1000-year flood, it is more accurate to say that “statistically speaking”, the rainfall that fell was a 1000-year rain storm, although it did not result in a 1000-year flood.
How can we have a 1000-year rain that does not result in a 1000-year flood?
It comes down to a number of factors, including the pattern of movement of the rain storm in each particular watershed, the conditions of the soil and plant matter on the ground in the watershed, and the timing of rain storm in one watershed versus other watersheds, among other things. An example would be that ground that is saturated before 1 inch of rain fell would result in more water going into the stream that if the ground was dry and could soak up more of the rain. Also, less water will runoff into streams from 1 inch of rain falling in the summer with the trees full of leaves versus the winter when there are no leaves to intercept the rain. This is all the science of hydrology, which is the study of the movement and distribution of water on the earth. Of course, in South Carolina, many of the watersheds have streams that are regulated by dams.
Is this flood due to climate change?
USGS research has shown no linkage between flooding (either increases or decreases) and the increase in greenhouse gases. Essentially, from USGS long-term streamgage data for sites across the country with no regulation or other changes to the watershed that could influence the streamflow, the data shows no systematic increases in flooding through time.
A much bigger impact on flooding, though, is land use change. Without proper mitigation, urbanization of watersheds increases flooding. Moreover, encroachment into the floodplain by homes and businesses leads to greater economic losses and potential loss of life, with more encroachment leading to greater losses.
http://water.usgs.gov/floods/events/2015/Joaquin/HolmesQA.html
Hey Pete, it is official, it is from the government - global warming aka climate change did not cause flooding to occur in South Carolina.
But all those global warming truthers are claiming global warming caused the flooding. Claiming it so does not make it so. It does make those who claim it so wackos that will believe anything because it fits the politics. Would that be you, Pete?