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The
initial parameters developed by SCIAA served
as the basic guidelines for model
development.
In
order to identify the High Probability Areas
for Level I sites, consisting of low rises
within or immediately adjacent to flood
plains, ESRI-USC created a vector theme that
included the floodplains and a 100 m buffer
layer around the flood plains. From this
theme, only the closed contours (i.e. those
that fell entirely within the buffered flood
plain theme) were selected. The areas within
these closed contours were designated High
Probability Areas for Level I sites.
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From a DEM slope model, assign a value of 1 to those
areas (grids) with a slope of 5% or
less.
All other grid cells were
assigned a value of zero (Layer 1).
-
Create a 200 m buffer around the linear hydrograph and
assign a value of 1 within that area, 0
otherwise (Layer 2).
-
Create a 200 m buffer around the flood plain and
assign a value of 1 within that area, 0
otherwise (Layer 3).
-
By using map algebra on the grid layers created, the
areas with positive nonzero values (1 or
2) were created with the formula:
Layer
4 = Layer 1 * (Layer 2 + Layer 3)
The
grid cells with positive nonzero values were
then converted back to a vector layer and
were designated as High Probability Areas
for Level II sites.
Although
ESRI-USC created the model in conjunction
with SCIAA, the actual locations of known
sites on Willamette property were
intentionally not shared with ESRI-USC.
This strategy allowed model testing
by SCIAA independent of ESRI-USC with
“fresh” data (i.e., data that has not
been used to calibrate the model in the
first place).
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