HomeMy WebLinkAboutReview of Channel Migration Zone - PLN General - 10/20/2003 DRAFT
October 20, 2003
MEMORANDUM
TO: Jerry H. Johnson and Laurie Cox, Resource Protection Foresters
FROM: Laura Vaugeois, Engineering Geologist #514, Forest Practices Division
SUBJECT: Review of Channel Migration Zone potential on the Tahuya River in
Mason County, T22RO3W, section 12.
At your request, I have reviewed the photographic history of the Tahuya River in the
area of interest. Stereopairs of historic aerial photos were reviewed to determine
whether the channel of the Tahuya River has actively migrated during the photo record.
Four sets of photos at 1-12,000 scale were reviewed, one set of photos at 1-60,000
(high altitude) were reviewed. The length of photo history went back to 1965. The
photographic history clearly shows that this stretch of the Tahuya has migrated, typically
in response to late winter storm events (Figure 1).
The position of the river and associated active channels was mapped from the photo
onto mylar acetate. The information from these photos and their overlays were
transferred onto the basemap using a zoom transfer stereoscope. This method ensures
that slight scale differences between photo years can be removed.
Page 1 of 2
DRAFT
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Figure 1 . A map of the Tahuya River in the area of interest. The position of the stream and channels is mapped in
different colors for different photo years.
Page 2 of 2
Map Output Page 1 of 1
FOREST PRACTICE ACTIVITY MAP
TOWNSHIP 22 NORTH HALF 0, RANGE 3 WEST (W.M.) HALF 0, SECTION 12
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Please use the legend from the FPA Instruction or provide a list of symbols used.
Friday,September 26,2003 1:37:44 PM
NAD 83
Contour Interval:40 Feet
http://www3.wadnr.gov/dnrapp5//servlet/com.esri.esrimap.Esrimap?ServiceName=fparsact... 9/26/2003