SUMMARY OF REPORT
Preparation of this report was authorized by the U.S. Army Corps of
Engineers (COE) under Delivery Order No. 0001 of Contract DACW57-96-D-0011
with Northwest Hydraulic Consultants, Inc.
The purpose of this report is to document the meteorological and
hydrologic conditions associated with the flood of February 1996. It is
intended to provide a reference base for future hazard mitigation
planning, disaster preparedness planning, floodplain delineation studies,
evaluation of project operation effectiveness, and environmental
effects.
The report is a guidebook to observed hydrologic conditions and flood
management efforts during a large northwest flood. It draws upon and
complements a previous postflood report prepared by the Portland District
COE to document the District's last major flood event which occurred in
December 1964. This report differs from the 1964 postflood report in the
following respects:
- Substantially more hydrometric gages (streamflow, water level,
snowpack, meteorological) were in operation in 1996 than in 1964,
providing for a relatively thorough documentation of the 1996 event.
- This report preserves substantially all of the pertinent hydrometric
data in digital form, an option not available in 1964.
- This report was prepared with a budget of only about one tenth of
that spent on the 1964 report. Due to budget limitations, this report's
descriptions of flood damages and flood fighting efforts is based on
data and reports obtained from various agencies including federal,
state, and local government offices, newspapers, and individuals with
anecdotal knowledge of conditions in areas of interest. No work was
done as part of this report to verify or confirm the accuracy of dollar
estimates prepared by others and presented herein to describe flood
damages, flood fight costs, and damages prevented.
The major emphasis of the report is on the hydrologic and meteorologic
aspects of the February 1996 event.
The report is organized into thirteen chapters covering six major subject
areas, followed by Figures, Tables, and Appendices. A sleeve is provided
at the end of the report for a CD-ROM disk containing all of the
hydrometeorological data which were collected during the study, together
with related work products of possible use to others.
The six major subject areas covered by the text of the report are
organized by subject and geographic area so that information of interest
can be readily located from the table of contents. The major subject
areas are:
- Introduction and overview of study area: Chapters 1 and 2.
- Description of hydrometeorologic data obtained: Chapter 3.
- Analysis of storm meteorology: Chapter 4.
- Analysis of project performance and flood hydrology: Chapter 5.
- Basin-by-basin assessments of storm conditions, flooding, and
project operations: Chapters 6 through 12.
- Area-by-area descriptions of flood fight activities and flood
damages: Chapter 13.
All frequency analyses of rainfall and streamflow data, as well as a
summary of project operations (i.e., percent of flood control reservoir
flood storage used) are contained in Chapters 4 and 5, so that all similar
data analyses are summarized in one location. The basin-by-basin
assessments of Chapters 6 through 12 restate the results of those
analyses, provide plots of the rainfall and streamflow data, and identify
relevant sections in Chapter 13 for basin-specific flood damage and flood
fight information.
Files provided on the CD-ROM were prepared with a number of public-domain
and proprietary software programs which are required to make effective use
of the digital data. These programs are not included with the CD-ROM.
Hydrometeorological data are archived using COE Hydrologic Engineering
Center Data Storage System (HECDSS) software. Flood and precipitation
frequency analyses files are in COE Hydrologic Engineering Center Flood
Frequency Analysis (HECFFA) format. Basin mapping is provided in Bentley
Systems (formerly Intergraph) Microstation 95. Figures excluding mapping
were prepared using Golden Software GRAPHER, Version 1.30. Tables and
worksheets for GRAPHER files are in Microsoft Excel, Version 5.0. The
report text is in Microsoft Word for Windows, Version 6.0.
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