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COLD REGIONS TECHNICAL DIGEST NO. 96-1
tural Ice Control; Review of Existing Methods (Tuthill 1995)
updates Perham (1983). CRREL Special Report 92-21, Salmon
River Experimental Ice Boom (White 1992) provides background
information on ice boom design, focusing on formation booms on
pool-riffle rivers.
Advantages and
Ice booms have many advantages over fixed ice control struc-
tures such as weirs, piers, piles, and man-made islands. Booms
limitations of
ice booms
are generally installed in the fall, just before the onset of the ice
formation season, and removed in the spring, shortly after ice-out.
They therefore do not interfere with open water uses of the river
or lake, such as recreation and commercial navigation. Booms
have a negligible effect on the natural hydraulic conditions of the
river, causing only minor changes in water depth and current
velocity. They typically do not cause scour or the deposition of
sediment, nor do they present a barrier to migrating fish. In addi-
tion, floating structures avoid the foundation settlement problems
typical of fixed structures in rivers and lakes with soft clayey
bottom sediments. Ice booms are designed to submerge under
extreme loading conditions, avoiding structural failure. This fea-
ture allows the structures to survive breakup and impacts from
large floes. Ice booms may be assembled from a wide variety of
commonly available materials and components, reducing costs
and construction time, and booms are readily installed using stan-
dard maritime or land-based construction equipment.
One possible limitation of ice booms is that, although the ini-
tial cost of an ice boom is low relative to a fixed ice control
structure, the ongoing costs of installation, removal, and mainte-
nance may be substantial.
Hydraulic
The main hydraulic constraint to floating ice retention struc-
constraints
tures is that they are effective only at sites with mild slope and
associated low surface water velocity. Surface water velocity and
depth are important, since they strongly affect the total ice force
acting on the boom. Wind stress on the ice cover is also important.
If the water drag and wind stress on the ice are too great, the ice
pieces may underturn and pass under the boom, or the ice may
ride up and submerge the boom unit to pass over the top. A great
deal of research and practical experience gives a range of 0.08 to
0.12 for the maximum Froude number,* and 22.5 ft/s (0.61.4
* Froude number: FR = V gh , where V = average channel velocity upstream of
the ice cover, h = average channel depth upstream of the ice cover, and g =
acceleration of gravity.
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