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It will likely be eight years
before better maps of the mountains in the Hiwassee River
basin are made by a NC geological team
By Tom Bennett
Special to Hiwassee River Watershed Coalition, Inc.
Murphy, N.C., August 7, 2007 – Cherokee and Clay
counties in the Hiwassee River watershed are NOT among 19
counties scheduled to be mapped by a 2014 target date set by
the scientists of the North Carolina Geological Survey.
Therefore, according to a work schedule envisioned by
that organization, it could be eight years or more before
the science is in place to guide legislators who hopefully
will be willing to write greater statutory protection for
the Cherokee and Clay County mountains.
It’s a critical environmental issue, since soil erosion
and sedimentation moves down the slopes and into the rivers,
such as the Hiwassee, Nottely and Valley here in this
watershed.
Rick Wooten of the NCGS is one of the scientists given
the task of following up on the Hurricane Recovery Act of
2005 and making new maps. The WATR Column sent him
questions by e-mail. Wooten has graciously provided answers
giving greater detail about the math of the mountains. Here
is our interview:
INTERVIEW WITH RICK WOOTEN
1. Will you put in layman's language the math formula that
was in House Bill 1756, the Safe Artificial Slopes Act of
2007, and envisioned an affected area having slopes of 25
percent or more?
Rick Wooten: “The terms 1:1 and 1.5:1 are expressions for
the slope ratios (steepness) measured in terms of slope run
(horizontal distance) over slope rise (vertical distance).
Typically an "H" and "V" are included in the expression like
1H:1V to avoid confusion. For example for a slope of 1H:1V,
the rise is equal to the run; this being equivalent to a 45
degree slope. A slope of 1.5H:1V is equivalent to a slope
of 34 degrees.”
2. An Asheville Citizen-Times article referred to a 2014
target for completion of mapping of the mountains of western
North Carolina. Is that correct?
Rick Wooten: “The Hurricane Recovery Act of 2005
authorized the North Carolina Geological Survey to prepare
landslide hazard maps for the 19 counties declared in the
act. Although there are steep slopes in Cherokee County, it
was not a declared disaster county (nor were Graham and Clay
counties) as a result of the hurricanes of 2004. Presumably
this was because these counties did not experience the
damage from these storms like other counties. The 2014 time
frame is our (NCGS) estimate of the time it will take us to
complete the 19 counties assuming that the funding for the
mapping continues, and the data we need to do the mapping is
available… If funding becomes available to map more than the
original 19 counties we would plan to map Cherokee County;
however, it would be after 2014 unless the N.C. General
Assembly changes the mapping priorities.”
3. In the mapping you are doing, are GPS and aerial photos
used? Describe this in a layman's paragraph, please.
Rick Wooten: “We use a variety of tools in our mapping to
identify areas of past landslides, and areas prone to future
landslides. We use various vintages of aerial photography,
geologic and soil survey maps, and LiDAR integrated into a
computerized geographic information system (GIS).
“LiDAR, an acronym for Li_ght D_etecting A_nd R_anging,
is a form of airborne laser altimetry where high resolution
topographic data (latitude, longitude, and elevation) are
collected by an aircraft with laser equipment. Data from
this method results in a topographic map, or digital
elevation model, which has a much higher resolution, and is
more accurate, than earlier topographic maps made prior to
this technology.
“The LiDAR data was collected for all of North Carolina,
initially to prepare up-to-date flood plain maps for all
N.C. counties. Our review of the maps and aerial
photographs helps us target specific areas for field
verification that appear to have had past landslide activity
and prehistoric landslide deposits.
“Our field verification process includes identifying and
classifying the types of landslides and the different types
of soil and rock involved. Future landslides tend to occur
in the general areas where landslides have occurred in the
past. We also use GPS (global positioning satellite) surveys
extensively to help accurately locate features in the
field.”
4. What is your job title, please?
Rick Wooten: “Senior Geologist for Geohazards and
Engineering Geology, North Carolina Geological Survey.
“We have additional information on landslide hazards in
North Carolina on our website at:
http://www.geology.enr.state.nc.us/Landslide_Info/Landslides_main.htm"
* * *
Tom Bennett of the Martins Creek Community west
of Murphy is a Hiwassee River Watershed Coalition member and volunteer.
E-mail him at
farblumtn@gmail.com
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