Ice Jam Flood Assessment for the St. John River Basin,
Aroostook County, Maine
JAMES L. WUEBBEN, DAVID S. DECK, JON E. ZUFELT AND JEAN-CLAUDE TATINCLAUX
(19731992) (Table 1). Most recently, in the
INTRODUCTION
spring of 1991, devastating ice jam floods on the
An ice jam is a stationary accumulation of
St. John River caused damage estimated at
fragmented ice or frazil ice that restricts flow
,000,000. On 9 and 10 April 1991, the two
(IAHR 1986). These accumulations include
bridges in the village of Dickey, located in the
freezeup jams as well as breakup jams. Freezeup
town of Allagash, 1000 ft of state highway and
jams are created by pieces of floating ice collect-
11 houses were destroyed (Fig. 1) and an addi-
ing during periods of relatively steady flow
tional 22 houses were damaged. On 1314 April,
when the ice cover initially forms early in the
ice jam floods on the Aroostook River caused
winter season. Breakup jams, on the other hand,
damage to shoreline, roads, 16 houses in the
form during the often highly unsteady flow con-
town of Fort Fairfield and properties in the vil-
ditions when the ice cover breaks up because of
lage of Crouseville located in the town of Wash-
significant rainfall, snowmelt or other increase
burn.
in runoff.
Except for the 1991 jam event, ice jam flood-
In contrast to open water flooding, where
ing at Fort Fairfield was previously reported on
high water levels directly result from excessive
by the U.S. Army Engineer Division, New Eng-
water discharge, ice-affected flooding results
land (USACE 1987). On 15 May 1991, the U.S.
from added resistance to flow and blockage of
Senate Committee on Environment and Public
flow caused by accumulations of ice. The forma-
Works adopted a resolution requesting the
tion of an ice cover or ice jam on a river roughly
Corps of Engineers to study the entire St. John
doubles the wetted perimeter of a wide channel.
River basin within the United States (Fig. 2) "in
The added resistance to flow caused by the ice
the interest of flood damage reduction particu-
cover, along with the reduction in flow area
larly relating to ice jam flooding, recreation, wa-
caused by the ice, results in higher stages than a
ter quality, irrigation, and related purposes to
comparable open water discharge would pro-
serve the needs of the State of Maine." The New
duce. This is particularly true for the case of ice
England Division (NED) then contacted CRREL
jams, which can cause flood stages comparable
for help in assessing ice jam flooding. Personnel
to rare open water events, despite discharge re-
of CRREL's Ice Engineering Research Division
currence intervals on the order of 2 years or less
(IERD) conducted a field study to determine the
(exceedence probabilities on the order of 0.5 or
ice processes particular to the upper St. John
greater).
River and to the Aroostook River, to identify the
Ice jams occur almost every year both on the
ice jam flooding problem areas of these rivers,
Aroostook River and the St. John River. While
and to determine where available means of alle-
many of these ice jams result in minor or no
viating ice jam flood damages may be applicable
flooding, there has been severe flooding and
and should be further evaluated.
damage directly attributable to ice jams or made
During the course of the study, contacts were
greater by ice six times over the past 20 years
made with representatives of local, State, and
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