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- Info
Fragmented watersheds: A special problem for urbanizing wildlands
| Author: |
Wells, W.G., II |
| Date: |
1990 |
| Periodical: |
In: Devries, J.J.; Conrad, S.G., eds. California Watersheds at the Urban Interface: Third Biennial Watershed Conference; 1990 October 30-31; Ontario, Canada. |
| Abstract: |
As California's population continues to increase, the pressures at the interface between urban and wildlands will not only increase but will also take a variety of forms. One form of change has been the creation of so-called fragmented watersheds. This hybrid of natural and urbanized watersheds is essentially a natural watershed containing widely spaced islands of urbanized land. The traditional view of urbanization assumes that a given area is urbanized more-or-less uniformly and that the hydrologic characteristics of the landscape are affected in a similarly uniform and homogenous way. In calculating the changes in a watershed’s hydrography as it becomes urbanized, local changes are averaged together and a new hydrograph representing the entire watershed is produced. Questions raised about the applicability of this approach to wildland watersheds that have recreational developments and other insular pockets of urbanization become more important as the rate of fragmentation accelerates. A fragmented watershed is much more complex because of numerous transitions between wild and urbanized land. This may dictate a different approach to predicting the impacts of urbanization. Instead of calculating one “average’ hydrograph for a given watershed, it may be necessary to develop a hydrograph for each urbanized fragment, then, using routing techniques, sum these hydrographs and the natural hydrograph together over a time scale and produce what is essentially a composite hydrograph. |
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