11. Tidal Currents. Data on currents resulting from tidal action within Bolinas Bay are 

 relatively sparse. Known data follow: 



1. Measurement of water and sediment flow through a section of the entrance to Bolinas 

 Lagoon was made over a tidal day by the USGS on three occasions, 22 June, 24-25 

 October 1967, and 16-17 May 1968. (Ritter, 1969.) 



2. A limited number of current measurements by the use of current drogues, dye, and 

 bottle caps were made in Bobnas Bay and vicinity in connection with a sewerage study for 

 Marin County. (Brown and Caldwell, 1967.) 



12. Sediment Transport in Bolinas Lagoon Inlet. Suspended-sediment discharge in or near 

 the inlet was measured during the tidal current measurements mentioned above. (Ritter, 

 1969 and 1972.) 



13. The Ecosystem. Although not of primary importance in relation to the inlet to Bolinas 

 Lagoon, an extensive series of studies of the ecosystem of the lagoon was completed by a 

 team led by Joel Gustafson of Resources and Ecology Projects, Inc. Reports on this phase of 

 the total investigation of Bolinas Lagoon are included in the report by Gilroy (1970a, 

 App. No. 6). 



ffl. SUMMARY OF DATA RELEVANT TO THE INLET 



The investigations pertaining to various natural processes occurring in the Bolinas Bay- 

 Bolinas Lagoon-system were briefly described in Section II. Data for those aspects of the 

 system which specifically influence the dynamics of the Bolinas Lagoon inlet are 

 summarized as follows: 



1. Wave Data. The most reliable data on wave climate and severe storm conditions for the 

 central California coast are those compiled by National Marine Consultants (1960a, 1960b) 

 for Station 3 at Lat. 37.6°N, Long. 123.5°W. (See Figure 1.) Figure 2 presents the average 

 annual sea and swell data for Station 3. These data are for deep water, and to project such 

 information to the vicinity of the Bolinas Lagoon inlet requires the use of wave refraction 

 diagrams for a large range of wave periods and directions. An illustration of wave refraction 

 into Bolinas Bay is shown in Figure 3 for a 12-second wave from the west. 



As previously mentioned in Section II, some visual observations of wave conditions were 

 made in 1968-69 at Stinson Beach State Park and at Bolinas. Also, a wave gage was operated 

 offshore between the two beach stations. The locations of these observation sites are shown 

 in Figure 4. It is of interest to note that the wave direction observed at the Bobnas station 

 by a special sighting device showed that for the entire period of observation waves 

 approached the Bobnas Lagoon inlet within a narrow sector between 10° and 20° east of 

 south. (Gilroy, 1970a, App. No. 3.) Summaries of data on wave power and littoral currents 

 derived from observed and hindcast wave data are presented below. 



2. Wave Power. As mentioned in Section II, computations of wave power (both sea and 

 swell) were made for Station 3 offshore from the Golden Gate. (Johnson et al., 1971.) A 

 plot of the monthly wave power (H^T) for all directions of both sea and swell is shown in 

 Figure 5. The power in swell is relatively small in this region during June, July, and August. 



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