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Landscape Characterization / Impervious Surfaces / What is an Impervious Surface?
What is an Impervious Surface?
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Impervious surfaces are mainly constructed surfaces
- rooftops, sidewalks, roads, and parking lots - covered by impenetrable
materials such as asphalt, concrete, brick, and stone. These materials
seal surfaces, repel water and prevent precipitation and meltwater
from infiltrating soils. Soils compacted by urban development are
also highly impervious.
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Materials like cement, asphalt, roofing,
and compacted soil prevent percolation of runoff into the ground.
The amount of impervious surface grows with increasing urbanization.
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Source: Johnson, Baltimore County
DEPRM. |
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Impervious urban surfaces are "desert-like"
in terms of hydrology and micro-climate.
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AN OVERVIEW OF IMPERVIOUS SURFACES.
- Storm water washes over paved, sparsely vegetated surfaces in much the same
manner as it runs over a desert landscape.
- Intense storms quickly generate large volumes of runoff, followed by dry
conditions a short time later.
- Rapid runoff and the paucity of vegetation reduces evapotranspiration; therefore
insolation (incoming solar radiation) is used for heating rather than evaporation.
- Impervious surfaces have higher thermal conductivities than do vegetated,
pervious surfaces.
- Impervious surfaces cause nonpoint water pollution problems.
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