US ARMY CORPS OF ENGINEERS LOS ANGELES DISTRICT Morro Bay Estuary City of Morro Bay, San Luis Obispo County, CA Ecosystem Restoration Feasibility Study F3 Conference Report Without-Project Conditions Analysis July 2003 Draft - F3 Conference Report Syllabus This report presents an analysis of existing conditions and projected future without project conditions that examines ecosystem needs and opportunities at the Morro Bay Estuary in Morro Bay, San Luis Obispo County, California. The goal of the analysis is to identify restoration alternatives that will restore significant ecosystem function, structure, and dynamic processes that have been degraded. Restoration recommendations will be formulated to support the goals and objectives of ongoing USEPA/NEP, regional, and local watershed planning and management efforts. Morro Bay is a transitional freshwater-to-marine aquatic environment whose channels and eelgrass beds provide valuable foraging and juvenile rearing habitat for marine fishes, as well as potential migration corridors for steelhead. The Bay supports rich invertebrate populations, including commercially and recreationally important bivalves. The open waters, eelgrass beds, and tidal flats of the Bay provide a critical stopover area for migratory and wintering shorebirds and waterfowl, and provide habitat for a number of threatened, endangered, and otherwise sensitive species of plants, fish and wildlife. The salt and brackish marshes of the Bay, upstream riparian corridors, and surrounding dune scrub and other upland habitats, both natural and manmade, also provide critical habitat for a number of threatened, endangered, and otherwise sensitive species of plants, fish and wildlife. The relative proportion and location of habitats are expected to change under the without project condition due to anthropogenic influences in the watershed. The analysis of without project conditions indicates that if historic sedimentation trends and reduction of tidal prism continue, subtidal habitat and shallow to low-intertidal mudflats that support eelgrass beds in the Morro Bay Ecosystem will continue to diminish. Eelgrass supporting mudflats are likely to shrink as marsh-building continues at the mouths of the creeks, while increased elevation of upper tidal marshes will further isolate them from tidal influence. Overall, the existing balance of habitats within the bay would become less marine-estuarine and more wetland-like and freshwater riparian. The scope of this report includes physical, economic, and environmental baseline data, and projections of future habitat conditions throughout the 50-year study period. Ecosystem problems and restoration opportunities identified in the analysis are used in the preliminary screening of alternative improvement measures. This report identifies and presents a preliminary evaluation of potential structural and non-structural ecosystem restoration and aquatic habitat protection measures. The analysis supports the decision to proceed with the feasibility study as presented in the concluding section of the report, based upon the projected significant anthropogenic, sediment-induced change in estuary habitats. Morro Bay Estuary Ecosystem Restoration Feasibility Study i Draft - F3 Conference Report Table of Contents 1 Introduction............................................................................................................................. 1 1.1 Study Authority............................................................................................................... 1 1.2 Study Purpose and Scope................................................................................................ 1 1.3 Study Participation and Coordination............................................................................. 2 1.4 Prior Studies and Corps Projects..................................................................................... 2 1.4.1 Prior Studies by the Corps ...................................................................................... 2 1.4.2 Prior Studies by Others ........................................................................................... 3 1.4.3 Existing Corps Projects........................................................................................... 4 2 Study Area .............................................................................................................................. 4 2.1 Location and Description................................................................................................ 4 2.2 Geology........................................................................................................................... 8 2.3 Topography..................................................................................................................... 8 2.4 Climate............................................................................................................................ 9 2.5 Hydrology ....................................................................................................................... 9 2.6 Coastal Processes.......................................................................................................... 10 2.7 Land Use ....................................................................................................................... 11 2.7.1 Urban Lands.......................................................................................................... 11 2.7.2 Parklands............................................................................................................... 12 2.7.3 Morro Harbor........................................................................................................ 14 2.7.4 Agriculture ............................................................................................................ 14 2.8 Socio-Economic Profile................................................................................................ 14 2.8.1 Population ............................................................................................................. 14 Morro Bay Estuary Ecosystem Restoration Feasibility Study ii Draft - F3 Conference Report 3 Environmental Resources ..................................................................................................... 16 3.1 Water Quality................................................................................................................ 16 3.2 Sediment Characteristics............................................................................................... 18 3.2.1 Physical Characteristics ........................................................................................ 18 3.2.2 Preliminary Hazardous, Toxic, and Radioactive Waste Database Search............ 19 3.3 Biological Resources .................................................................................................... 19 3.3.1 Open-water and Sub-tidal Habitats....................................................................... 23 3.3.2 Eelgrass Beds and Related Habitat ....................................................................... 24 3.3.3 Mudflat Habitat..................................................................................................... 25 3.3.4 Salt Marsh Habitat ................................................................................................ 26 3.3.5 Fringing Wetland Habitat ..................................................................................... 27 3.3.6 Riparian Habitats .................................................................................................. 28 3.3.7 Upland Habitats .................................................................................................... 29 3.3.8 Special Status Species........................................................................................... 31 4 Sedimentation Analysis ........................................................................................................ 31 4.1 Historical Sedimentation............................................................................................... 32 4.2 Littoral Transport.......................................................................................................... 34 4.3 Fluvial Transport........................................................................................................... 34 4.4 Aeolian Transport ......................................................................................................... 34 4.5 Sediment Budget........................................................................................................... 35 5 Future Without Project Conditions ....................................................................................... 35 5.1 Projected Sediment Delivery and Deposition............................................................... 36 5.2 Projected Change in Morro Bay Habitats ..................................................................... 38 5.2.1 Habitat Change Modeling..................................................................................... 38 5.2.2 Summary Future Habitat Acreage – Average Yield Scenario.............................. 45 Morro Bay Estuary Ecosystem Restoration Feasibility Study iii Draft - F3 Conference Report 5.3 Projected Habitat Values............................................................................................... 47 5.3.1 Habitat Evaluation Method..................................................................................