Bolinas Lagoon inlet is a natural laboratory in which a large amount of data has been 

 collected over the years— perhaps more than for any other lagoon in existence. Even then, 

 the data are insufficient to define adequately the importance of the variables involved in the 

 relationships discussed above. However, the source, nature, and availability of data on the 

 Bolinas Lagoon inlet are summarized here as a guide to possible future desirable studies at 

 Bolinas and at other inlets. 



II. NATURE AND SOURCES OF BASIC DATA 

 1. General. Bolinas Lagoon, 1,100 acres in area and located in Marin County about 15 

 miles northwest of San Francisco, is separated from the ocean (Bolinas Bay) by a long sand 

 spit. (See Figures 1 and 4.) In 1956, the Bolinas Harbor District was formed to investigate 

 the possibility of establishing a harbor of refuge in Bolinas Lagoon. In 1966, 

 Norman T. Gilroy and Associates were engaged to coordinate, implement, and report on a 

 multidisciplinary program of study and research into the natural environmental systems of 

 the lagoon and its watershed, designed as the first step for planning the long-term 

 conservation and use of the region and the lagoon. The natural environment of Bolinas 

 Lagoon was analyzed in three fundamental segments— the watershed, the system of natural 

 dynamics of Bolinas Lagoon and Bolinas Bay, and the ecosystem. The scope of these various 

 studies has been published by Gilroy (1970a, 1970b). 



For the watershed studies, the U.S. Geological Survey (USGS), in cooperation with the 

 Bolinas Harbor District, began an investigation of the hydraulic and sedimentation 

 characteristics of the lagoon to provide information on: the freshwater inflow into the 

 lagoon, the quantity of fluvial sediment transported into the lagoon, the quantity of 

 sediment transported into and out of the lagoon through the tidal inlet, the direction of 

 littoral transport near the inlet, the circulation of water within the lagoon, the bottom 

 topography, and the sediment movement within the lagoon. Some of the data from these 

 studies have been published by Ritter (1969). Not all of these data, however, relate to the 

 inlet itself, but where the data are pertinent to this report a summary is presented at the 

 appropriate place below. 



Of particular importance to the sedimentation problem in Bolinas Lagoon is the 

 following comment by Ritter (1969): 



"Lagoons are temporary features along a coast. A generalized history of a 

 lagoon may begin with a river mouth drowned by a rising sea level. Littoral drift 

 creates a spit or barrier bar across the mouth so that its access to the ocean is 

 restricted to a narrow inlet. The lagoon begins to fill with sediment and becomes a 

 tidal flat with channels carrying much of the tidal water. The filling continues 

 until the lagoon becomes a salt marsh as vegetation grows on the rising tidal flats. 

 Eventually, the lagoon becomes a flat plain that may be eroded by waves lapping 

 against its seaward edge. The life of a lagoon depends on the rate at which 

 sediment is entrapped in the lagoon. 



Bolinas Lagoon, the seaward end of a rift valley created by the San Andreas 

 Fault, is now probably in the stage of a tidal flat that is becoming a salt marsh." 



