Form Approved
REPORT DOCUMENTATION PAGE
OMB No. 0704-0188
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1. AGENCY USE ONLY (Leave blank)
2. REPORT DATE
3. REPORT TYPE AND DATES COVERED
December 1997
4. TITLE AND SUBTITLE
5. FUNDING NUMBERS
Factors Influencing Ice Conveyance at River Confluences
CWIS
WU: 33024
6. AUTHORS
Robert Ettema, Marian Muste, Anton Kruger, and Jon Zufelt
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
8. PERFORMING ORGANIZATION
REPORT NUMBER
Special Report 97-34
Iowa Institute of Hydraulic Research
U.S. Army Cold Regions Research and
The University of Iowa
Engineering Laboratory
Iowa City, Iowa 52242-1585
72 Lyme Road
Hanover, New Hampshire 03755
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
Office of the Chief of Engineers
Washington, D.C. 20314-1000
11. SUPPLEMENTARY NOTES
For conversion of SI units to non-SI units of measurement, consult ASTM Standard E380-93, Standard Practice for Use of the International
System of Units, published by the American Society for Testing and Materials, 1916 Race St., Philadelphia, Pa. 19103.
12a. DISTRIBUTION/AVAILABILITY STATEMENT
12b. DISTRIBUTION CODE
Approved for public release; distribution is unlimited.
Available from NTIS, Springfield, Virginia 22161
13. ABSTRACT (Maximum 200 words)
This report documents preliminary findings concerning ice jam conditions in river confluences, using two labo-
ratory approaches. First is categorizing the different conditions of ice discharge into a confluence based on two
general classifications: free drift of ice and movement of contiguous ice accumulations. The variables defining ice
discharge for the two categories are assembled via dimensional analysis into two consistent sets of nondimensional
parameters. The categorization, together with the nondimensional parameters, is used to evaluate ice jam prob-
lems at confluences--the two most common causes of jams seem to be sluggish water velocities in the outflow
channel and local bathymetric features. The second approach examines how confluence geometry and flow pro-
cesses affect ice discharge--for example, the influence on ice discharge of bathymetric features. The approach uses
a large hydraulic model of a two-channel confluence, which is adaptable to a variety of channels, and particle
image velocimetry (PIV) for determining and mapping whole fields of water and ice velocities in a confluence.
PIV, which is becoming extensively used, lends itself very well here. This study is the first demonstration of the
PIV method for ice movement through a two-river confluence. It shows promise. The hydraulic model and PIV
method are used in a case study of ice discharge through the confluence of the Missouri and Mississippi rivers, a
confluence prone to severe ice jams.
14. SUBJECT TERMS
15. NUMBER OF PAGES
Confluence
Hydraulic model
PIV
38
Dimensional analysis
Ice jam
16. PRICE CODE
17. SECURITY CLASSIFICATION
18. SECURITY CLASSIFICATION
19. SECURITY CLASSIFICATION
20. LIMITATION OF ABSTRACT
OF REPORT
OF THIS PAGE
OF ABSTRACT
UNCLASSIFIED
UNCLASSIFIED
UNCLASSIFIED
UL
Standard Form 298 (Rev. 2-89)
NSN 7540-01-280-5500
Prescribed by ANSI Std. Z39-18
298-102
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