DEPARTMENT OF THE ARMY
ETL 1110-2-363
U.S. Army Corps of Engineers
CECW-EH
Washington, DC 20314-1000
Technical Letter
No. 1110-2-363
31 January 1994
Engineering and Design
DATA COLLECTION FOR RIVER ICE FORECASTING
1. Purpose
a. Introduction. The formation, extent, and
thickness of stable river ice covers result from the
The purpose of this engineer technical letter (ETL) is
interaction among the river hydraulics, the heat trans-
to describe the data collection program necessary to
fer to the atmosphere, and the mechanics of how a
install and support an operational river ice forecasting
river ice cover forms. To produce accurate forecasts,
system. This ETL should be used to evaluate exist-
the models that simulate these processes must be
ing data collection programs for suitability and
based on actual field data, fully calibrated over a
completeness and to identify unmet data collection
wide range of conditions, and operated using accurate
needs. With a completed data collection program in
information from the field.
place, a river ice forecasting system can be estab-
lished quickly, efficiently, and at a minimum cost.
b. Development of the hydraulic model.
Because of the dynamic interaction between the river
ice formation and the river ice hydraulics, a dynamic
2. Applicability
unsteady flow model is required to model the ice-
covered river. Hydraulic modeling of an ice-covered
This ETL applies to all HQUSACE elements, major
river is similar to applying and calibrating a one-
subordinate commands, districts, laboratories, and
dimensional unsteady flow model for open water
field operating activities having civil works responsi-
conditions. If such a model exists or can be devel-
bilities for planning, design, and operation and main-
oped for the river reaches of interest, it can be incor-
tenance of civil works projects.
porated (with modification) into the ice forecasting
system. The following field data are required to
develop such a model:
3. Discussion
(1) An overall hydraulic and geometric descrip-
A river ice forecasting system is a collection of exist-
tion of the river system for which forecasts are made.
ing software procedures that process forecasts of
Generally, the river system will have a mainstem and
relevant hydrologic and meteorologic parameters to
perhaps several major tributaries. The tributaries
produce forecasts of the production and transport of
should be modeled as far upstream from the main-
river ice. River ice forecasts will provide the result-
stem as necessary to cover the reaches where naviga-
ing extent, thickness, and duration of any stable ice
tion or other factors, such as ice jam flooding, are a
covers along the river reaches of interest. The system
concern. If a tributary is not included in the model,
(Figure 1) is composed of three main numerical
the discharge contributed by that tributary to the
models, plus supporting procedures and pre- and post-
mainstem can be included as a lateral inflow. The
processors. The three main models are a hydraulic
upstream ends of the modeled mainstem and of tribu-
model, a thermal model, and an ice distribution
tary reaches should be locations where discharges are
model. The supporting procedures include initial
known. This is called the upstream hydraulic bound-
condition and boundary condition generators. The
ary. The downstream end of the mainstem should be
pre- and post-processors are procedures designed to
at a location where the stage is measured and a rating
allow the models to interface with existing databases.
curve is available.
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