Hydraulic and Physical Properties Affecting Ice Jams
KATHLEEN D. WHITE
that do exist for some ice jam processes are not
INTRODUCTION
sufficiently well known or described.
River ice jams can form suddenly, bringing
Beltaos (1995) and Ashton (1986) provide thor-
about rapid fluctuations in stage. Ice jams can
ough discussions of the various processes impor-
cause flooding upstream and decrease down-
tant in ice cover initiation, growth, breakup, trans-
stream discharge. Damage to riverine structures
port, and jamming. The purpose of the present
such as bridges, locks, dams, dikes, groins, levees,
study is to review available information on the
and riprap installations is also possible. Ice jams
properties of ice covers and ice jams that are im-
affect navigation through delays, stoppages, or
portant in modeling river ice jam hydraulics. An
damage to tows, barges, and mooring/fleeting
overview of ice jam hydraulics identifies specific
areas. Ice can block hydropower and water sup-
ice properties of interest, which are discussed in
ply intakes. Ice-induced scour may cause the ero-
detail in the following section. Information is also
sion of river beds and banks, with adverse impacts
presented about miscellaneous ice properties ad-
on fish and wildlife habitat, as well as the expo-
dressed in the literature but not explicitly included
sure of utilities buried beneath the streambed.
in hydraulic models of ice jams.
Emergency and medical relief to flooded areas
may be limited by flooding or ice-related scour and
erosion of roads resulting in road closures, or by
OVERVIEW OF ICE JAM HYDRAULICS
the closure of bridges weakened or destroyed by
ice. The potential exists for death or serious injury
Formation processes of river ice covers range
during ice-related flooding, evacuations, and other
from the purely static to the purely dynamic. Static
ice mitigation operations.
ice cover formation is a largely thermal process in
Ice-related damages can be minimized or
that the initiation and growth of ice crystals result
avoided through the use of hydraulic modeling
from heat transfer between the water and the at-
to predict jam location, upstream and downstream
mosphere. Statically initiated ice covers in rivers
stages, jam thickness, and other jam characteris-
are found in quiescent areas and along the banks
tics. While knowledge about ice jam formation,
(border ice). Dynamic ice cover formation results
progression, and failure has increased in recent
from the mechanical processes associated with floe
years, to date no deterministic model of these ice
interactions. These may range from relatively low-
jam processes has been developed. In part, these
energy processes such as the juxtaposition of ice
complex physical processes are poorly understood
floes into a single layer of ice that then freezes in
because field observations of ice processes and
place, or higher-energy processes such as the ac-
properties are spatially and temporally limited and
cumulation of floes into an ice jam by shoving and
can be dangerous to acquire. Data are often scat-
internal collapse. Temperature plays an important
tered, and although earlier literature reviews (e.g.,
role in ice cover formation. Andres (1999) states
Bolsenga 1968) contain a great deal of historical
that for large, moderately sloping rivers, colder
information regarding river ice covers, they do not
temperatures will result in juxtaposition, while
include the tremendous amount of information
higher temperatures will result in ice covers
gathered over the past few decades. As a result,
formed by shoving and internal collapse (or "con-
many of the variables and parameters included in
solidation"). However, he finds that for very mild
the empirical, analytical, and numerical models
slopes and very steep slopes, the process is rela-
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