Union student center; and the Mayflower residence hall,
which houses nearly 1,100 students. University staff raced
to save $500 million worth of art from the severely damaged
Museum of Art. The water plant was narrowly spared from
total loss.
The disaster struck during summer, a quieter period on
campus. Still, maintenance and technical staff hurried to get
everything back on track before classes started in fall.
The Federal Emergency Management Agency (FEMA)
declared it the greatest damage ever to a single entity
nationwide. Engineers considered it worse than a 500-year
event – defined as a flood so severe that there is only a
0.2 percent chance of its occurrence in any given year.
(The 1993 flood was considered a 100-year flood.) When
all building repairs, replacements, and flood mitigation
measures are completed, the university expects the bills to
total between $900 million and $1 billion.
Ayres Associates was hired in fall 2008 to develop a
flood mitigation plan that included a study of the river’s
behavior during a flood. Since then Ayres Associates has
worked with other project consultants to design effective yet
unobtrusive ways to control the effects of future flooding.
“One of the initial challenges was the public perception
that a floating barge and cofferdam in the river at the time
of the flood caused the flooding upstream,” said Ayres
Associates project manager Andrea Faucett, who conducted
the study. Hydraulic models, however, showed they had
minimal effects on the flooding.
Study results also revealed that FEMA’s floodway
mapping of the river through campus was incorrect. FEMA’s
floodway boundaries extended beyond the river banks, yet
modeling showed them within the banks. A floodway is the
channel of a river or other watercourse and adjacent land
areas that must be reserved for discharging a base flood
without cumulatively increasing the water surface elevation
more than a designated height, Faucett explained.
Because FEMA doesn’t allow building or filling
areas within the floodway, the university couldn’t raise
its sidewalks or install other flood mitigation alternatives
within it. Ayres Associates received FEMA permission to
correct the floodway boundaries, allowing the university to
move forward with mitigation plans along the river bank.
The new hydraulic model covered a 27-mile area around
the river in detail, including aerial mapping and modeling of
the river bottom, and was used to calculate the university’s
risk when the river rises. Groundwater impact – river water
coming through storm sewers and other utility penetrations
into building basement drains – was a secondary focus
because it accounted for how much of the 2008 damage
occurred. Based on modeling results from both surface water
and groundwater, Ayres Associates prepared a new flood
emergency response plan for the university that detailed
what the university needed to do to prepare for and defend
TRENDS
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