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- Info
Land use change and impacts on the San Francisco estuary: A regional assessment with national policy implications
| Author: |
McCreary, Scott; Twiss, Robert; Warren, Bonita [and others] |
| Date: |
1992 |
| Periodical: |
Coastal Management |
| Abstract: |
The nation's estuaries are at risk of further deterioration from land use change and intensification. These risks include direct impacts on wetland habitats and stream environments and indirect impacts from nonpoint source pollutant loading. This article reports on the methods, findings, and policy implications of a major study, "The Effects of Land Use Change and Intensification on the San Francisco Estuary." By using a geographic information system (GIS), future growth scenarios were played out and the impacts on wetlands, streams, and water quality were estimated on a region wide basis. The land use scenario developed from the General Plans of the Bay-Delta Region's 12 counties shows that the total area planned as urban use outside existing incorporated cities is 331,530 acres, an increase of 37%. This land use change and intensification associated with increased growth will continue to stress an overtaxed estuarine system. Results are expressed according to 14 receiving water segments and the associated 34 watersheds. Direct impacts on wetlands and stream environment zones occur in every watershed containing these resources. We estimate that over 39,500 acres of wetlands may be potentially impacted. Of 377,000 acres of stream environment in the 12 county study area, 28,000 acres are also subject to impacts of urbanization. Our analysis suggests that protection of farmed wetlands in the Delta and North Bay and the enhancement of biodiversity in the South Bay deserve special attention. The construction of land use scenarios for the estuary region has presented, for the first time, an opportunity to examine the cumulative contribution of nonpoint source urban runoff to the levels of pollutants in the bay and delta. To date, more modest studies in smaller urban watersheds have provided only a glimpse of the overall effect that urbanization has in a region the size of the estuary. We found that these impacts can be expected to decrease the overall water quality of the estuary. The existing system of land use planning delegates responsibility to local governments. However, of 111 jurisdictions -within the estuary study region, only 18 have specific ordinances to protect streams and wetlands. We recommend that the existing system regulation and management be strengthened to protect, enhance, and restore the environmental well-being of the estuary. The results of our study suggest that improvements are needed in the goals, management strategies, and institutional arrangements now in place for the San Francisco estuary. We advance several specific management options to help frame the debate over strengthening |
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