By Abby Kuranz, Fall 2013 Intern, CFWE
On September 9th, 2013, a low-pressure system settled over Boulder, Colorado for 5 days straight and dropped over 14 inches of precipitation, breaking daily and monthly rainfall records in Boulder County. The University of Colorado-Boulder is situated in the foothills-plains interface of the Flatirons, where Boulder Creek flows through the city center. Boulder Creek, which typically runs at about 300 cubic feet per second, maxed out at 5,000 cfs during the 5-day deluge.
Several parts of the CU-Boulder community were severely impacted by the floods: entire families were displaced, dorm rooms flooded, and campus infrastructure suffered major damage. However, students, faculty and local families have responded in-kind through a concerted effort of volunteering, fundraising, organizing high school service projects, and offering a slew of resources to aid students and faculty.
As cleanup in Boulder continues, roads are re-opened, and hiking and biking trails are rebuilt. CU-Boulder researchers are also picking up the pieces. While many researchers will need to adjust and redesign long- and short-term projects, others are using the rare opportunity to gather data for unique comparisons in an effort to accurately characterize the hydrologic event.
Picking Up the Pieces
Many researchers face setbacks with the effects of high waters on their research cites:
The Boulder Creek Critical Zone Observatory captured the entire flood event, and subsequent damage of their research cite, in a time-lapse video. The camera captures the influx of the water and a stream gauge washing away at Gordon Gulch, a small basin located above Boulder, CO.
Others used the flood as a opportunity to conduct a “natural experiment” to either further their current research or begin new projects:
Rachel Gabor, and helpful INSTAAR (Institute of Arctic and Alpine Research) staff, Aneliya Sakaeva and Chris Jaros, collected large samples of floodwater from Boulder Creek at two sites – 30th St. and Eben G. Fine Park. Some of the water is being tested for various water quality parameters (e.g., metals, DOM quality, etc.) to help guide decisions on further sampling. They collected a large volume (five 15-20 L carboys at 30th St. and six at Eben G. Fine Park) so they could isolate the humic material from the DOM. They have a similar sample collected during snowmelt in May 2013 which will allow them to compare the two high flow events. Their work is also part of the Boulder Creek Critical Zone Observatory.
Figuring Out What Happened and Why
One week after the flooding, John Pitlick, co-director of the Graduate Program in Hydrologic Sciences at CU-Boulder, changed the topic of his scheduled Hydrology and Water Resource Seminar to address the recent flood and the surrounding speculation.
“The hazards associated with rare but intense rainfall are well known in Colorado, and many communities along the Front Range have taken action over the years to mitigate potential damage and loss of life from rare floods. Last week we had the opportunity to observe first-hand what it is like to get half a years-worth of precipitation in one or two days, and we can begin to appreciate how the actions taken to reduce flood risks in Boulder benefited the community as a whole. Nonetheless, throughout Boulder, streets and alleys become torrents, carrying mud and rocks indiscriminately into homes and businesses. Residents in mountain towns and outlying areas have been isolated by road washouts and bridge failures. Certainly many questions will arise in the aftermath of the 2013 flood. For example, newspapers are reporting that this was a 100-yr flood. What is the basis for that estimate? How do published maps of inundation for floods with different return periods compare with the extent of flooding in 2013? Did burned areas contribute disproportionately to the floods? I don’t have complete answers to these questions, but I am happy to share results from past work (my own plus others) that helps put the 2013 Boulder Creek flood in perspective.”
The seminar, which typically hosts 20-30 graduate students and faculty each week changed venues to accommodate expected numbers for the highly anticipated talk. With standing room only, Pitlick explained that by his analysis, the flood registered somewhere between a 20-year to 50-year event.
When media told use the event was a “biblical,” “100-year,” or “1000-year” flood, CU-Boulder and the Cooperative Institute for Research in Environmental Sciences (CIRES) responded by assembling a panel of science experts to discuss if and how weather and climate played a role in the flood event. Western Water Assessment, an applied research program that addresses societal vulnerabilities related to climate, also put together a preliminary assessment to address whether or not the flood was human-induced or if it was on track with Colorado’s historical hydrologic cycle:
“If we query the NOAA 20th-century reanalysis dataset—which blends historic surface and upper observations in a numerical weather model to create detailed and consistent images of past atmospheric circulation—we can do a quick comparison of the setup for the 1938 event with that for 2013. What we find is that the patterns were remarkably similar: a low pressure area to the west that drew moisture from the south and east, and blocking highs that kept the moisture flow pinned in place for several days.
While research is ongoing at CIRES to investigate how the 2013 flood may have been influenced by human-caused climate change, the 1938 flood tells us that the climate system was capable of producing that type of flood event—in September, no less—under more “natural” atmospheric conditions.”
While the flooding in Boulder is sobering reminder of the power of water and its intricate connection to land-use, it is also an opportunity to learn, evaluate, and adapt.
- CU-Boulder Students Help Residents Clean Up After The Colorado Floods (huffingtonpost.com)