Task 6: Flat End Buffer Type Fix
If the outputs of task 5 result in missing
buffer segments along the NHD flowline as shown below, follow the below process
to fill in these missing segments. Perform this task two times. Once for the
30m buffer and once for the 100m buffer.
Missing buffer segments from 30m buffer (flat end type)
Step 1: Create a
second 30m buffer but this time create a round end type buffer. In your table
of contents, place this layer below the flat end type buffer to get an idea
where you are no longer missing segments.
Buffer segments from 30m buffer shown in blue
(round end type)
Step 2: Run the Erase
tool using the round end type buffer as the input feature and the flat end type
buffer as the erase feature. Name the output feature class NHD_30m_buffer_filler.
Segments created using erase tool. Note: these are the segments
the flat end type buffer did not have
Step 3: To dissolve
the semi-circles from the round end type buffer to their respective segment,
run the Dissolve tool. The input feature will be the NHD_30m_buffer_filler. Name the output feature class NHD_30m_buffer_filler_dissolve. Uncheck “Create multipart features.”
Step 4: Open the
attribute of the NHD_30m_buffer_filler_dissolve
and create a new field and label it “Area”. Make the type “Double” and
precision 6 and scale 2. Right-click on the field and “Calculate Geometry.” Use
meters as your units.
Step 5: To get rid of
all the small semi-circles that exist at the upper reaches of the NHD line, we
need to start and editing session. First, use the “Select by Attribute” command
and set up a query that looks like the following. The values will not be the
same. You need to assess what the area is of the majority of the semi-circles
and use this value within the query. Once the segments are satisfied, right
click on one segment and hit Delete. When satisfied with the edits, save edits
and stop the editing session.
Selecting by attribute to remove unwanted semi-circles
Step 6: Run the Merge
tool. The input datasets will be the edited NHD_30m_buffer_filler_dissolve
and the original flat buffer end type layer. Name the output dataset NHD_30m_buffer_final. This will create a
more accurate buffer that will not alter the zonal statistics that will be used
in the next task.
Final 30m buffer with missing segments