Attaining Sustainable Urban Watersheds - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 507

land contamination and degradation, (2) preserve those land areas that are undamaged
or minimally damaged, and (3) remediate and rehabilitate degraded brownfields to the
fullest extent possible. These three tasks can be thought of as principles forming the basic
framework for the first step of urban watershed management. Based on the definitions of
sustainability and sustainable development, attainment of these tasks represents sustain-
able development activity.
Our definition of watershed management also views individual watersheds as sites and
recognizes that impacts occur within and between multiple watersheds (Chapter 15). This
reality means there are processes operating at geographic scales beyond those of a single
watershed that may influence its ability to achieve sustainability. The framework devel-
oped here is upwardly compatible with the comprehensive watershed management effort
required at the geographic scales of the watershed and beyond.
16.3.1 Prevent Further Land Contamination and Degradation
A sustainable outcome in urbanized watersheds is not possible without significantly pre-
venting further land contamination and land degradation. Source control is the most effec-
tive strategy of pollution prevention in terms of cost and it has the highest environmental
efficiency (Rogers et al. 2006). Source control strategies should take advantage of opportu-
nities to integrate point and nonpoint source control measures. The identification of these
locations is assisted by geology and the products of geological investigations.
Some of the integrated source control opportunities provided by the outcomes of geo-
logical investigations include
• Geological maps . These maps show the location of surface water, groundwater, and
their flow paths. They can be used to identify areas in the watershed where poten-
tial point source releases and nonpoint source transport mechanisms (overland
water flow and wind) overlap. These locations can then be prioritized for source
control measures based on the contaminant risk factors (CRF) scores of the con-
taminants and the relative abilities of the geological environmental and the non-
point transport mechanism to disperse them.
Three-dimensional geologic maps show the relationships between groundwater and
surface water. The locations of discharge points between groundwater and surface water
can help with the design of a contamination monitoring network. This information pro-
vides feedback on the efficacy of source control efforts, which is necessary for their opti-
mization. These maps also identify locations where contamination may migrate outside
of the watershed. For example, in the Rouge River watershed, the presence of a lower clay
layer effectively routes groundwater horizontally into the Great Lakes (Figure 5.11).
• Geologic vulnerability maps . These maps indicate where stormwater flows may
intersect groundwater recharge zones. As a source control measure, groundwater
vulnerability assessment should be incorporated into every site planning process.
• Stratigraphic columns and cross-sectional maps . These outputs characterize the depo-
sitional history of the watershed and the resulting landforms. Of particular impor-
tance to source control efforts is the ability to evaluate the natural landscape's
capability to store water and minimize stormwater runoff. This information also
provides important parts of the science necessary to perform the sequence of steps