Table 5. Ice thickness measurements.
heavy snow year, the other events listed
had total snowfall amounts well below
Ice
Total depth
average. As stated previously, however,
thickness (top ice to bed)
Location
(in.)
(in.)
it is really snow on the ice before break-
up that is significant. For the 1991 flood,
a. St. John River
while the total snowfall before breakup
8 Jan 92
Nine Mile
2024
6084
was 18 in. below average, there was still
6 holes
6 to 12 in. of snow on the ground at Cari-
21 Jan 92
bou, Maine. This amount of snow is suf-
N.W. Branch at confluence with Daaquam River
33, 27
42, 36
Daaquam River at confluence
19, 19
36, 33
ficient to prevent decay from solar radia-
0.6 mile downstream of confluence
13
36
tion and to insulate the ice from high
4.5 miles downstream of confluence
16
22
daytime air temperatures.
Confluence of S.W. and N.W. branches
22
30
Perhaps the most indicative of the
Confluence of S.W. and Baker branches
28
30
Cascade Road bridge
19, 17
30, 36
terms in Tables 2 and 3 are those in col-
umns 9 and 10 dealing with the interval
22 Jan 92
Moody bridge
24
26
between the onset of warm weather and
2 miles downstream of Moody bridge
21
48
significant increases in discharge. As de-
6 miles downstream of Moody bridge
22
56
scribed previously, large values of these
10 miles downstream of Moody bridge
27
--
terms generally indicate a slow warming,
22 Jan 92
with adequate time for melting and de-
0.6 mile upstream of 7 Islands
28, 24
72, 36
cay of the ice cover prior to breakup.
7 Islands
17
57
Priestly Islands
24
26
Conversely, the value of 2 for the 1991
flood indicates that water discharge in-
23 Jan 92
Base of Poplar Rapids
30
48
creased beyond the 10,000-ft3/s thresh-
Base of Big Rapids
23
36
old, while mean daily temperatures were
23 Jan 92
still below freezing. Such low values for
Left channel at St. Clair Island
28
48
these two terms would indicate that the
Dickey bridge
20
36
ice cover deteriorated less and was near
1 mile downstream of Dickey
29
56
its late-winter thickness and strength.
1.6 miles downstream of Dickey
23
84
2 miles downstream of Dickey
30
60
Values listed for the specific events in
Table 3 are on the order of one standard
b. Aroostook River
23 Jan 92
deviation or more below the average val-
Boat launch off of Gardner Brook Road--Wade
ues for 197091. Of the two terms, DQ10
2 miles upstream of boat launch
24
48
Dmax and DQmax Dmax, it would
3.8 miles upstream of boat launch
23
48
appear that the first is the more reliable
7.5 miles upstream of boat launch
23
90
14 miles upstream of boat launch in Ashland at
indicator. Warm weather, capable of
brook entering under Wrightville Road
22
96
generating flows in excess of 10,000 ft3/s
25 Mar 92
within about 8 days or fewer following
Fort Fairfield adjacent to N.B. border
31
--
0.3 mile downstream Route 1A bridge in
the onset of mean daily temperatures
business district
29
--
above freezing, would appear to be
0.3 mile upstream of Route 1A bridge
32
--
prime cause for severe flooding in Fort
Across from Strickland Road
28
--
Fairfield.
Presque Isle, downstream of Route 1 bridge
18
--
1.2 miles upstream Route 1 bridge
16
--
Washburn--right channel at Stratton Island
24
grounded
FIELD OBSERVATIONS IN THE
Masardis at USGS gage
30
--
Oxbow check point
33
--
ST. JOHN RIVER BASIN, 199192
SEASON
The field observations consisted of visual
Field observations were made from early
observations, video recordings and ice thickness
December 1991 to April 1992. They covered more
than 200 miles of river and necessitated the use
measurements at selected locations (Table 5).
of aircraft and snowmobiles, since the upper riv-
They were complemented by near-real-time data
er reaches were only marginally accessible by
on river stage, precipitation and air tempera-
truck from the major logging roads that were
tures provided by the USGS network of stream
winter maintained. The field trips are listed in
gaging stations equipped with telemetry and
Table 4.
located throughout the St. John River basin. In
7
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