Urbanization and the Disruption of Matter and Energy Flows within Watersheds - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 422

FIGURE 12.4
Nested watersheds. (From Marsh, W.M., Landscape Planning:
Environmental Applications , 5th edn., New York, John Wiley &
Sons, 2010.)

1

1

1

1

1

1

2 1

2

1

2

3

1

2

1

3

1 4

3

1

1

2

1

2

1

1

4

1

Mouth

FIGURE 12.5
Stream orders (the dashed line demarcates the headwater region). (From Federal Interagency Stream Restoration
Working Group (FISRWG), Stream corridor restoration—principles, processes and practices, adopted as Part
653 of the National Engineering Handbook, USDA Natural Resources Conservation Service, http://www.nrcs.
usda.gov/technical/stream.restoration (accessed May 29, 2010), 2001.)

Stream orders are important for watershed sustainability, because they indicate loca-
tions where there is a potential mismatch between the naturally evolved stream capacity
and the higher runoff volumes created by urban development. Lower-order streams are
also more vulnerable, because they are unable to dilute contaminants.

12.3 Watershed Function
Watersheds exist at the crossroads of Earth's great environmental spheres: the atmo-
sphere, biosphere, hydrosphere, and lithosphere. Many of the interactions between the