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Conclusions:Within a watershed, about 10% of development is not subject to drainage regulations resulting in cumulative effects from urbanization that significantly degrade watersheds. Instead of regulatory thresholds (e.g. 10% EIA), process controls are required to mitigate the impacts of urbanization on aquatic systems. Without these controls, strict development limits are the only way to limit watershed degradation.Thresholds/Learnings:The study cautions against the use of discrete “thresholds” to predict specific physical and biological effects, but does suggest that thresholds are appropriate indicators for when the perception and tolerance of watershed impacts triggers a regulatory response.
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Conclusions: The amount of upstream impervious area affects downstream fish habitat quality, channel stability, and water quality. The use of riparian buffers can reduce the magnitude of urban impacts, however, they cannot fully mitigate the impacts of upstream development in the watershed. Threshold percentages of impervious areas , as well as the percentage of forest cover in a watershed appear to be the most effective indicators of watershed health. Thresholds/Learnings: Impervious areas should be kept at or below 10% of a watershed, and forest cover should be maintained at a minimum of 65% in order to effectively mitigate the impacts of urbanization and development on watersheds. Synopsis: This paper articulates...
Categories: Publication;
Types: Citation,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: Cedar River-Lake Washington, Green-Duwamish River, White River,
Central Puget Sound Watershed,
King County, Washington,
Land use configuration,
Natural cover amount, All tags...
Sammamish Watershed, Snoqualmie-Skykomish River,
Strait of Georgia/Puget Lowland, and North Cascades,
Washington,
fish habitat,
forest cover,
impervious surface,
riparian systems/watershed,
stream stability,
sub-regional,
thresholds,
water quality, Fewer tags
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