The Watershed Approach - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 7

The urban sprawl shown in Figure 1.3 completely engulfs the Rouge watershed by the
1970s. This land use boom, in concert with unregulated industrial discharges, had det-
rimental consequences for the water quality of the river. By 1968, the Rouge was flowing
orange from pickling liquor waste and was one of the rivers in the Great Lakes Basin to
catch on fire. In 1985, the Rouge River was identified as one of 42 Areas of Concern in the
Great Lakes Basin. Today, the elimination of some of the Combined Sewer Overflows
and the reduction of industrial discharges have improved the water quality within some
reaches of the river. Yet, a major challenge remains in this watershed related to the amount
of developed land cover and its relationship to surface runoff. Most watershed surface
areas in the United States consist of over 90% land (as does the Rouge's), so taking good care
of the land and reducing its inputs of pollution are therefore required to ensure adequate
water quality. Recent trends, however, indicate that each house being built in southeast
Michigan is consuming more land. For example, between 1990 and 2000, the amount of
land used for homes increased by 19%, while the number of households only grew by 9%.
Prior to 1990, there were 1.14 housing units per ha (2.84 per ac), but this has decreased to an
average of 0.5 per ha (1.26 per ac) after 1990 (SEMCOG 2003). This increase in the amount
of land used for each house is significant because it accounts for 43% more land developed
than would have been with the higher-density construction before 1990. In most instances,
more runoff is produced when more land is developed, and much of this runoff contains
contaminants that threaten surface water and groundwater.
1.4 Major Themes of the Watershed Approach Used in This Topic
A watershed approach is consistent with a geoscience perspective for the solving of envi-
ronmental problems. Watersheds consist of surface water and their drainage systems, the
groundwater that supplies the surface water in gaining streams, the surface and subsur-
face geology including landforms and soil, the flora and fauna, the air, the social and land
use history of the region, and the current political decision making processes within them.
Within this context, we identify five major themes, each having the common denominators
of geology, contamination, and sustainable urban development.
1.4.1 Theme #1: Near-Surface Geology, Hydrogeology, and Surface Hydrology
An accurate physical characterization of a watershed, including its geology, hydrogeology,
and surface hydrology, is a key prerequisite for a successful watershed restoration effort.
This assertion is corroborated by the successful watershed management and restoration
efforts that have been accomplished in North America. Consider the Don River, a stream
flowing through the urbanized area of Toronto, Canada. This watershed is now in the pro-
cess of a major restoration effort, which has been largely successful. Here, the watershed
restoration effort began with a scientific foundation that accounted for the glacial origins
of the topography. This science was translated into the need to preserve certain natural
features so as to maintain natural drainage patterns and minimize investment in new
infrastructure.
The following annotated outline summarizes some of the essential elements for char-
acterizing the geology, hydrogeology, and surface hydrology of a watershed in order to
perform contamination analysis and sustainable remediation: