Dusting River Ice with Leaf Mulch to
Aid in Ice Deterioration
ROBERT B. HAEHNEL, CHARLES H. CLARK AND SUSAN TAYLOR
Corps of Engineers 1979, 1994a). During the first
INTRODUCTION
few years that the Yukon River was dusted, a
The decay of river ice depends not only on the
modified B-25 aircraft was used to spread river
ambient air and water temperature, but also the
sand on the ice. More recently crop-dusting air-
absorption of solar radiation into the ice. Ashton
craft have been used to spread the river sand on
(1985, 1986) shows that once the ambient air tem-
the ice. The dusting operations that have been car-
perature reaches freezing, the rate of deterioration
ried out on the Platte River use crop dusting air-
of the ice cover (i.e., structural weakening of the
craft as well; however, on the Platte coal slag was
cover) depends greatly on the absorption of the
used as the dusting material.
solar radiation by the ice cover. Thus reduction of
Although aircraft are well suited for dusting
the albedo (reflected solar radiation/solar radia-
large rivers, such as the Platte, many rivers, such
tion incident to the surface) of the ice surface can
as those found in New England, cannot be dusted
contribute to accelerated decay of an ice cover.
using aircraft because they are narrow and are
This, in turn, can reduce the potential for ice jam
lined by trees and dwellings. We found it neces-
formation on a given river reach during ice
sary to develop a new way to apply dusting ma-
breakup.
terials on these small rivers. Also, coal dust and
Dusting (application of a dark material to a
slag are considered a threat to the riverine aquatic
snow/ice surface) can be used to hasten ice cover
life due to the contaminants they contain. Further-
deterioration by reducing the albedo of the snow/
more, small particles such as sand, coal dust, and
ice surface (for a review of dusting applications,
slag can also be a problem in many New England
see Slaughter 1969). Typical albedo values for
rivers since they tend to clog the spaces between
"black" or clear ice are about 20% (Perovich 1992),
rocks where the fish like to lay their eggs and
while "white" ice--which contains air bubbles,
thereby inhibit reproduction. The above environ-
snow ice or frazil--can have albedo values as high
mental concerns led us to explore the use of bio-
as 60 to 80% (Prowse and Demuth 1992). Albedo
degradable dusting materials that might be more
values for fresh snow can be as high as 90%. How-
environmentally friendly.
ever, as snow ages the albedo decreases. A typical
This report details the use of leaf mulch, which
value for this old snow is around 50% (Colbeck
was spread on two rivers in Vermont using a
1988). Depending on the type of "dust" used and
hydroseeder. We describe the performance of the
the amount applied, dusting can reduce the albedo
leaves as a dusting material, and the usefulness of
of a snow or ice surface to 15 to 20% (Williams
a hydroseeder in applying the leaves.
1967). Thus, dusting can be used to increase ab-
sorption of solar radiation in all but black ice.
However, if snow is on top of this black ice, dust-
EVALUATION OF DUSTING MATERIALS
ing can be used to accelerate the ablation of the
overlying snow, allowing the sunlight to get to and
During the winters of 1993 and 1994, several
melt the ice faster than would occur naturally.
dusting tests were conducted on an ice covered
The dusting material is frequently put on the
pond at CRREL in Hanover, New Hampshire. Fig-
ice using an aircraft. Examples of this include dust-
ure 1 shows a typical test plot setup on the pond.
ing operations on Yukon River in Galena, Alaska
The purpose of these tests was to evaluate the ef-
(U.S. Army Corps of Engineers 1968) and on the
fectiveness of several organic dusting materials at
Platte River near Omaha, Nebraska (U. S. Army
melting snow and ice. During these tests the snow
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