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Adam Migliore Meyer
GEOG 591
January 27, 2012
Exercise 1: NHD Plus
Question 1: Describe areas in New Hope area that fall into the stream classes.
All Streams
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Urban Stream
Urban streams occur in catchments
classified as greater than 20 percent
urban according to the NCLD values.
Specifically, the NCLD values of 21
(developed, open space), 22 (developed,
low intensity), and 23 (developed,
medium density) are summed to
determine how urban the catchment is.
These areas are concentrated north of
Jordan Lake around the City of Durham
and Towns of Chapel Hill, Carrboro,
and Hillsborough. Generally these areas
tend to have more impervious surfaces,
which are reflected in the higher NCLD
values.
Cumulative Urban
Cumulative Urban Streams are those
streams that drain urban catchments, but
are not necessarily located in an urban
catchment themselves. A good example
is the section of New Hope Creek
flowing into Jordan Lake.
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New Hope Creek drains catchments that are urban, but the catchments immediately north of the
lake are not urban. These streams are still significant to nutrient loading because they carry with
them the nutrients contributed by impervious surfaces found in the urban catchments upstream.
Cumulative Urban / Local non-Urban
This classification of stream is a subset of
the Cumulative Urban Stream. The subset is
a “clipping” of cumulative urban stream
from catchments that are not urban.
Following from the New Hope Creek
example, the section of New Hope
immediately north of Jordan Lake is featured
in this class because it runs through
catchments that are not urban.
By definition these streams are not found
inside urban catchments, but adjacent to
them. These sections of stream are
significant because while they may not be
draining as many nutrients from their own
catchments, they are still carrying nutrients
from urban catchments upstream.
Cumurban_nourban_stream is connected to
Jordan Lake. In conclusion, New Hope area,
one of the main drainage areas of Jordan
Lake can be characterized as urbanized area
when considering the whole upstream area
of New Hope creek.
Question 2: Compare urban areas to sections of stream with high discharge (>30 cfs).
Using the figure on page 1 featuring all stream classes, streams with high discharge tend to drain
the urban areas north of Jordan Lake. New Hope Creek and Morgan Creek are among these
streams. In terms of the significance for water quality, more nutrients are able to make their way
into Jordan Lake because the greater capacity of these streams enables them to deliver a larger
quantity of the nutrients originating in the urban catchments. This degrades water quality. High
stream discharge areas are overlapped mostly with urban and cum_urban stream. Since runoff
from urban is characterized by surface runoff, which is direct, fast and wash-off the
contaminants in impervious area, it threatens water quality problem to Jordan Lake (-0.5).
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The higher capacity streams also increase the quantity of water flowing into the lake by their
very definition of high discharge. These streams naturally have high discharges given their
morphology and topography. However the increased impervious surfaces in the urban areas
amplify the stream discharge, as more water runs off into these streams instead of being absorbed
into the ground.
(24.5/25)
Next time, please use your ONYEN for naming your report.
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