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Open Access Publications from the University of California

Understanding Nutrient Loading to the Coastal Zone from Urban Watersheds


Nutrient loading from urban development and intensive agriculture can have a significant adverse impact on coastal environments. The focus of this research proposal is to (1) measure and characterize nutrient loading by landuse on a watershed scale to the near-shore coastal environment using representative watersheds in southern California; and (2) develop a model to predict future nutrient export from these watersheds resulting from projected changes in landuse. The model will be based on an integrated modular framework and should prove a useful tool in watershed planning and management. The selected study watersheds drained by Carpinteria and Franklin creeks are distinctive but regionally characteristic catchments. Santa Monica Creek, draining an adjacent catchment, will be used to test the portability of the model. Both Franklin and Santa Monica Creeks carry a high nutrient load from urbanization and intensive agriculture to one of southern California's few remaining wetlands, the Carpinteria Salt Marsh (Ferren et al, 2000).

With an intensive sampling program throughout the wet and dry seasons, I will characterize nutrient loading by landuse type. Existing information on landuse, soils, geology, vegetation and basin hydrology will be gathered and structured in a geographical information system (GIS) database. This will guide the sampling strategy and provide basic data for determining export coefficients for various landuses. A nutrient export coefficient model (NEC-M) will be constructed and integrated with an existing urban growth model for the Santa Barbara area of California (SLEUTH/UCIME). The combined model will be used to predict nutrient export for various growth scenarios, which can be used to evaluate zoning and "best management practice" pollution control alternatives. In addition, the project results will provide important watershed discharge data for the Santa Barbara Coastal Long Term Ecological Research (SBC-LTER) project in a collaborative effort to understand the dynamics of near-shore oceanic water quality.

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