control arena. However, five other respondents
a thermistor or thermometer to obtain these mea-
indicated the use of some type of computer or elec-
surements. Some of those individuals are possi-
tronics under "other" (e.g., NWS instruments, elec-
bly getting results from other agencies or did not
tronic instruments through computer). It could be
know how temperatures were being measured,
assumed that some of these five responses were
but it does raise questions about the completeness
referring to DCPs. The reported use of satellite im-
of some survey respondents' replies.
agery is very light, as might be expected given the
On the other hand, 26 respondents indicated
present limitations on its use, but continuing ad-
the use of an ice thickness kit, but an additional
vances in technology may make the use of satel-
six individuals indicated the use of an ice auger
lite imagery more important and commonplace.
or ice auger and tape under the "other" category,
All of the observation methods shown in Table
making the total number of respondents using an
4 are limited by weather and light conditions. The
ice thickness kit or ice auger equal to the number
potential for instrumentation designed to reduce
who actually indicated observing ice thickness.
the reliance on human observers and increase the
Eight responses under the "other" category indi-
span of conditions under which observations can
cated measurements were made visually, but it is
be made is great, but may be limited by budget-
likely, based on the previous question, that many
ary and other concerns.
more people make visual observations but did not
report them under "other."
Instrumentation in use
The final question in the first part of the survey
Ice impacts
explored the instrumentation currently in use to
The second part of the survey deals with the
collect ice data. The respondents were asked to
impact of ice on various structures or operations
select among the following choices: ice thickness
in terms of frequency and timing. The structures
kit, glass-bead thermistor, thermometer, velocity
and operations included for rating were naviga-
meter/probe, still camera, video camera, and
tional locks, navigational structures other than
other. The results (Table 5) indicate that cameras
locks, navigation traffic, hydroelectric power gen-
are used in all of the Divisions that make ice ob-
eration, municipal water supply intakes, power
servations, but that ice thickness kits are used most
plant water intakes, and flood control structures
to obtain data. Glass-bead thermistors are used to
(levees, tainter gates, drainage structures, etc.).
measure air or water temperature in only one Di-
Questions on frequency that were left blank were
vision (Missouri River), and velocity probes are
assigned to the "never" category, and some re-
used in only one Division (as of 1995).
spondents who indicated some frequency of oc-
It should be noted that the number of responses
currence did not indicate timing of occurrence (Fig.
to various types of instruments did not agree well
5 and 6). The closure of some navigation projects
with the number of individuals making observa-
during the ice-affected season may be a factor in
tions that would be expected to rely on those par-
the large number of "no impact" responses. Flood
ticular instruments. For instance, 75 and 66 respon-
control structures are the type of USACE struc-
dents reported the use of air and water tempera-
ture most impacted by ice (Fig. 5).
tures, respectively, but only 24 reported the use of
Ice impacts were reported with equal frequency
Table 5. Survey results on use of various instruments. Survey results on use of various
instruments.
Positive
Observation
responses
instrument
(no.)
MRD
NAD
NCD
NED
NPD
ORD
√
√
√
√
√
Ice thickness kit
26
√
√
√
√
√
Thermometer
23
√
√
√
√
√
Others
19
√
√
√
√
√
√
Camera
17
√
√
√
√
√
Video camera
11
√
√
Velocity meter/probe
2
√
Glass-bead thermistor
1
Note: South Pacific Division did not respond to this question.
8
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