Coastal
Resource Inventory Tutorial
Learn
More | Metadata | Links | Basin
Legend | Larger Basin Map | Sub-pixel
Legend | Larger Sub-pixel
Map
5.
Learn More About Impervious Surfaces
What
is it?
Two
ways of displaying information on impervious surface (IS) are shown
in the maps below. Both are based on a new technique developed by the
UConn Center for Land use Education and Research (CLEAR)
that evaluates how much area of each 100 foot square land cover pixel
(see tutorial data layer #2)
consists of IS. The resulting image has pixels that represent 20-30%
imperviousness, 30-40% imperviousness, etc.—up to 90-100% imperviousness.
The lower map shows this information directly, using color coding to
show each pixel's percentage of IS. The upper map takes all these individual
values and creates an average for each local watershed (see tutorial
layer #4). Each watershed is shown
as green (0-10% imperviousness), yellow (10-25% imperviousness), or
red (25-100% imperviousness).
Why
is it important?
As
noted, a growing body of national research indicates that there is a
strong correlation between the levels of impervious cover in a watershed,
and the health of the waterway to which that watershed drains. The color-coded
watershed averages depicted on the top map relate to this research:
low (green) levels of IS generally are protective of waterway health,
while medium (yellow) levels usually indicate the onset of water quality
and quantity impacts. High (red) levels indicate a watershed that is
almost surely experiencing impacts. This relationship can be a useful
way to quickly evaluate the impacts, or potential impacts, of development
patterns on downstream coastal resources. Because of this, the IS watershed
map will reappear in the last section (#9)
of this tutorial, as an informative overlay for the coastal resource
data layers.
What
else should I consider?
CLEAR is currently working on at least 3 separate research
tracks on ways to estimate impervious cover. The idea is to create estimation
and prediction methods that are accurate enough to save you the time,
energy and money of going out with a tape measure (or a set of aerial
photos) and measuring this stuff! These methods and more will all be
described in a new "Impervious Surface" site on the NEMO Home
Page, coming soon. ALSO, remember that impervious surfaces are a useful
framework, and should not become the sole focus of any planning effort.
Of equal importance to the amount of impervious surface is what planning,
design, and best management practices are being put into place to minimize,
mitigate or clean the runoff coming from those surfaces.
| Metadata |
Impervious
Surfaces by Watershed Basin |
|
Impervious
Surfaces by Sub-pixel classification |
Click
Here |
CT
DEP data layers
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| Links |
| For
a technical conference proceeding paper detailing the method used
to create the sub-pixel impervious surface map, click
here. |
Back
to Top
| Impervious
Surfaces Basin Legend |
Impervious
Surfaces By Watershed Basin
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Watershed
Basins
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Town
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Water
Features
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Impervious
Surface by Watershed Basin
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| Impervious
Surfaces Basin Larger View |
Back
to Top
| Impervious
Surfaces Sub-pixel Legend |
Impervious
Surfaces by Sub-pixel Classification
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Watershed
Basins
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Town
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Water
Features
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Impervious
Surface by Sub-pixel Classification
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| Impervious
Surfaces Sub-pixel Larger View |
