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Missouri River Flooding. Enhanced podcast 8/10/2011
Host: Rachael Hoagland
Interviewee: Richard Wilson, NEWSC Associate Director
RH: Welcome to Nebraskast where we talk to real USGS scientists about the important water-resources
work they are doing all over Nebraska. My name is Rachael Hoagland. Iím here with Rick Wilson. He is
the associate director for the USGS Nebraska Water Science Center. And weíre here to talk a little bit about
flooding thatís been going on here this summer. The images that youíre seeing are of our hydrologists and
our hydrologic technicians working on the river. Rick, what can you tell me about the flood thatís going on
on the Missouri (River)?
RW: This is a historic event in many ways, and the Missouri is a complicated system, and Iíll describe
that in a little bit, but the flood goes from the confluence at St. Louis up to Montana. Thatís over 2,000
miles. So it started primarily in snow melt. This has been going on primarily in June and July of 2011. Now
itís actually extending into August. The Missouri River is a complicated river and the reason is there are a
series of reservoirs on the mainstem channel, and that complicates the flow, that regulates the flow, and in a
lot of ways it protects downstream. What happened was the reservoirs filled up. There was so much runoff
and rainfall in the upper basin that filled the reservoirs and so that caused releases from the dams to go on
for months on end to evacuate the extra water.
Because of the high quantity, high volume of water, releases have been high. Itís flooded agricultural areas,
along the way. Fortunately, in that stretch of the river, there are levees that have protected much of the
infrastructure, but throughout the season we had breaks in levees. We had large areas inundated from
flooding because of that. We talk about the duration and magnitude of this flood. In historic terms, we donít
really know what this event is compared to prior to dam construction. We think that itís probably a 500-
year event, which is a very extreme event. Releases out of Gavins Point Dam, the most downstream
reservoir in the system, peaked at 160,000 cfs (cubic feet per second).
Typically in the winter releases from Gavins Point Dam can be about 20,000 cfs and in the summer
months, itís approximately 40,000 cfs. So you can see we were four times the volume of water, and this
was a long duration, over 10 weeks in length. A normal flood occurs quickly, the water rises, it floods the
area. In this flood event, itís as I just said, itís over a 10-week period of time.
RH: What can you tell us about the USGS work thatís going on on the river in past weeks and coming into September?
RW: Well we want to know the volume of water because 1) with that information we can estimate how
high it is, and the stage, because that is how we predict flooding and how we respond to the flood event,
and 2) the velocity of the water. Velocity is critical because it causes scour. Scour is a phenomenon that
with high-velocity water, high-volume of water, it erodes critical structures, it erodes the bed of the river,
but also it can undermine bridges, water-intake structures, levees, and cause very serious problems. We
responded with a series of sonar device (surveys). One was called a multibeam echosounder that would
actually allow us to determine scour holes in critical infrastructure, including pipelines and transmission
Also, we used a tool called electromagnetic geophysics to do surveys of levees. Levees were a major
concern because they protected key infrastructure. We used this tool to determine the geologic properties,
the soil properties, and the underlying geology of levees that protected a coal power plant. We were able to
use this tool to survey almost 3 Ĺ miles of levee to determine areas of potential seepage, where seepage
could undermine the levee, or flow through the structure itself.
RH: As this water is moving, itís also changing the bed of the river, is it not? Are you collecting data that
looks at how the bed of the river is changing as the water is moving through over such a long period of time?
RW: The Missouri River is a unique river. Itís a sand-bed river. This is not like a mountain stream which is
a hard rock surface which is stable. The Missouri changes, and the more water, the more scour we observe
or bed degradation. We used the sonar devices to make measurements to determine how the bed evolution
has occurred. So with that device, that will allow us to determine change. Also we used a technology where
we would take samples not only of the suspended sediment in the water itself Ė the amount of sediment in
the water column -- but also we were measuring bed load and thatís the amount of material that movies
along the bottom of the river bed. In these extreme events, in these high-flow events, that typically is a lot
of material that is being moved by the river.
RH: So flooding is probably going to continue for a handful more weeks so thereís still more data to be
RW: Correct. I think weíve dodged the bullet. As of Aug. 1, flow rates are now being reduced out of
Gavins Point Dam. By the end of September, they will be down to normal levels, 30,000 cfs. So as the flow
declines, additional surveys will be needed, additional monitoring will be needed, but the major concern
and the major problems, it looks like they have passed.
RH: Well, Rick, Iíd like to thank you for taking the time to talk with me today.
RW: Thank you.
Title: USGS Activities During Missouri River Flooding 2011
USGS Nebraska Water Science Center Associate Director Richard "Rick" Wilson describes the reasons for and extent of the flooding on the Missouri River in 2011, the risks associated with the flooding, and the work the USGS is doing on the river to characterize the amount of scour and other potential damage resulting from the flood waters.
Location: NE, Missouri River, USA
Date Taken: 8/1/2011
Video Producer: Rachael Hoagland , USGS Nebraska Water Science Center
Note: This video has been released into the public domain by the U.S. Geological Survey for use in its entirety. Some videos may contain pieces of copyrighted material. If you wish to use a portion of the video for any purpose, other than for resharing/reposting the video in its entirety, please contact the Video Producer/Videographer listed with this video. Please refer to the USGS Copyright section for how to credit this video.
Additional Video Credits:
Brenda Woodward, Ben Dietsch, Kirk Harvey, Rick Wilson, Ryan Thompkins and Brian Imig
For more information see: Nebraskast Podcasts
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