Posts tagged results
Boulder says pedestrians and bikers are safe, statistically speaking
Feb 7th
City releases 40-month report on biking and walking in Boulder
Between January 2008 and April 2011, only 7.8 percent of all collisions in Boulder involved a bicycle or pedestrian, according to the recently released Safe Streets Boulder report.
The report analyzes more than 8,000 collisions in Boulder – involving motor vehicles, bicycles and pedestrians – over a 40-month period. The main take-away: walking and biking in Boulder is safe, and these modes represent only a small percentage of all collisions reported on city streets.
The report also identifies the top 15 locations with the most motor vehicle collisions (with bicycles and pedestrians), the most common types of crashes and what the city is doing to help decrease collision rates. It also outlines collision demographics and at what time of day most accidents occur.
“Among many things, the report speaks to the safety of Boulder’s transportation system – specifically for walking and biking,” said Director of Transportation for Public Works Tracy Winfree. “Reports like this are powerful because the numbers help to identify successes and areas for improvement, as well as dispel myths.”
For instance, the safety of flashing crosswalks has been an underlying community conversation, but the results show that collisions in these crosswalks account for less than 1 percent of all collisions.
Mini quakes to shimmy the Rio Grand rift
Jan 11th
SOME EARTHQUAKES EXPECTED ALONG RIO GRANDE RIFT
IN COLORADO AND NEW MEXICO, NEW STUDY SAYS
IN COLORADO AND NEW MEXICO, NEW STUDY SAYS
The Rio Grande Rift, a thinning and stretching of Earth’s surface that extends from Colorado’s central Rocky Mountains to Mexico, is not dead but geologically alive and active, according to a new study involving scientists from the University of Colorado Boulder’s Cooperative Institute for Research in Environmental Sciences.
“We don’t expect to see a lot of earthquakes, or big ones, but we will have some earthquakes,” said CU-Boulder geological sciences Professor Anne Sheehan, also a fellow at CIRES. The study also involved collaborators from the University of New Mexico, New Mexico Tech, Utah State University and the Boulder-headquartered UNAVCO. The Rio Grande Rift follows the path of the Rio Grande River from central Colorado roughly to El Paso before turning southeast toward the Gulf of Mexico.
Sheehan was not too surprised when a 5.3 magnitude earthquake struck about 9 miles west of Trinidad, Colo., in the vicinity of the Rio Grande Rift on Aug. 23, 2011. The quake was the largest in Colorado since 1967 and was felt from Fort Collins to Garden City, Kan.
Along the rift, spreading motion in the crust has led to the rise of magma — the molten rock material under Earth’s crust — to the surface, creating long, fault-bounded basins that are susceptible to earthquakes, said Sheehan, a study co-author and also associate director of the CIRES Solid Earth Sciences Division. The team studied the Rio Grande Rift region to assess the potential earthquake hazards.
Using Global Positioning System instruments at 25 sites in Colorado and New Mexico, the team tracked the rift’s miniscule movements from 2006 to 2011. “Questions we wanted to answer are whether the Rio Grande Rift is alive or dead, how is it deforming and whether it is opening or not,” said Sheehan.
The high-precision instrumentation has provided unprecedented data about the volcanic activity in the region. Previously, geologists had estimated the rift had spread apart by up to 2 inches or 5 millimeters each year, although the errors introduced by the scientific instruments were known to be significant. “The GPS used in this study has reduced the uncertainty dramatically,” Sheehan said.
Using the latest high-tech instrumentation, the scientists found an average strain rate of 1.2 “nanostrain” each year across the experimental area, the equivalent of about one-twentieth of an inch, or 1.2 millimeters, over a length of about 600 miles. “The rate is lower than we thought but it does exist,” Sheehan said.
The researchers also found the extensional deformation, or stretching, is not concentrated in a narrow zone centered on the Rio Grande Rift but is distributed broadly from the western edge of the Colorado Plateau well into the western Great Plains. “The surprising thing to come out of the study was that the strain was so spread out,” Sheehan said.
Results of the study are published in the January edition of the journal Geology.
The team plans to continue monitoring the Rio Grande Rift, probing whether the activity remains constant over time, said lead study author Henry Berglund of UNAVCO, who was a graduate student at CU-Boulder working at CIRES when he completed this portion of the research. Also, the team may attempt to determine vertical as well as horizontal activity in the region to tell whether the Rocky Mountains are still uplifting or not, Berglund said.
“Present-day measurements of deformation within continental interiors have been difficult to capture due to the typically slow rates of deformation within them,” Berglund said. “Now with the recent advances in space geodesy we are finding some very surprising results in these previously unresolved areas.”
As far as the potential for future earthquakes in the region, the study’s results are unequivocal, however. “The rift is still active,” Sheehan said.
The new study also is co-authored by CU-Boulder Associate Professor and CIRES Fellow Steven Nerem, Frederick Blume of UNAVCO, Anthony Lowry of Utah State University, Mousumi Roy of the University of New Mexico and Mark Murray of New Mexico Tech.
The National Science Foundation provided the funding for this study and the NSF-funded EarthScope program and UNAVCO provided instruments, equipment and engineering services. The Boulder-headquartered UNAVCO is a nonprofit, university-governed consortium that facilitates geosciences research and education.
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CU study: less hail may increase flooding on Front Range
Jan 9th
STUDY INDICATES HAIL MAY DISAPPEAR
FROM COLORADO’S FRONT RANGE BY 2070
FROM COLORADO’S FRONT RANGE BY 2070
Summertime hail could all but disappear from the eastern flank of Colorado’s Rocky Mountains by 2070, says a new study by the National Oceanic and Atmospheric Administration, the University of Colorado Boulder’s Cooperative Institute for Research in Environmental Sciences and the National Center for Atmospheric Research.
Less hail damage could be good news for gardeners and farmers, said lead author Kelly Mahoney, a research scientist at CIRES, but a shift from hail to rain can also mean more runoff, which could raise the risk of flash floods. “In this region of elevated terrain, hail may lessen the risk of flooding because it takes awhile to melt,” Mahoney said. “Decision makers may not want to count on that in the future.”
For the new study, published this week in the journal Nature Climate Change, Mahoney and her colleagues used “downscaling” techniques to try to understand how climate change might affect hail-producing weather patterns across Colorado.
The research focused on storms involving pea-sized and smaller hailstones on Colorado’s Front Range, a region that stretches from the foothill communities of Colorado Springs, Denver and Fort Collins up to the Continental Divide. Colorado’s most damaging hailstorms tend to occur further east and involve larger hailstones not examined in this study.
In the summer in Colorado’s Front Range above about 7,500 feet, precipitation commonly falls as hail. Decision makers concerned about the safety of mountain dams and flood risk have been interested in how climate change may affect the amount and nature of precipitation in the region.
Mahoney and her colleagues began exploring that question with results from two climate models, which assumed that levels of climate-warming greenhouse gases will continue to increase in the future, from about 390 parts per million in the atmosphere today to about 620 parts per million in 2070.
But the weather processes that form hail, like thunderstorms, occur on much smaller scales than can be reproduced by global climate models. So the team “downscaled” the global model results twice: first to regional-scale models that can take regional topography and other details into account, then again to weather-scale models that can resolve individual storms and even the cloud processes that create hail. The regional-scale topography step was completed as part of NCAR’s North American Regional Climate Change Assessment Program.
Finally, the team compared the hailstorms of the future, from 2041 to 2070, to those of the past, from 1971 to 2000, as captured by the same sets of downscaled models. Results were similar in experiments with both climate models.
“We found a near elimination of hail at the surface,” Mahoney said.
In the future, increasingly intense storms may actually produce more hail inside clouds, the team found. However, because those relatively small hailstones fall through a warmer atmosphere, they melt quickly, falling as rain at the surface or evaporating back into the atmosphere. In some regions, simulated hail fell through an additional 1,500 feet of above-freezing air in the future as compared with the past.
The research team also found evidence that precipitation events over Colorado become more extreme in the future, while changes in hail may depend on the size of the hailstones — results that will be explored in more detail in ongoing work.
Mahoney’s postdoctoral research was supported by the Postdocs Applying Climate Expertise, or PACE, program administered by the University Corporation for Atmospheric Research and funded by CIRES Western Water Assessment, NOAA and the U.S. Bureau of Reclamation. PACE connects young climate scientists with real-world problems such as those faced by water resource managers.
Co-authors of the new paper include James Scott and Joseph Barsugli of CIRES and NOAA, Michael Alexander of the NOAA Earth System Research Laboratory and Gregory Thompson of NCAR.
