El Nifio events, the rate of sea level rise has 

 been even higher. The highest sea level on 

 record occurred in January 1983, when 

 predicted sea levels were exceeded by 26 cm 

 due to the coincidence of El Nifio, high spring 

 tides, and a major sea storm. Still, the water 

 levels might have been even higher if these 

 three events had also coincided with the 

 highest point in the 19-year tidal cycle 

 (Cayan and Flick 1985). The future location 

 and configuration of the shoreline will depend 

 on both the chronic and catastrophic increases 

 in sea level. While the former will shift 

 estuarine habitats inland, the latter will lap 

 away at the marine margins. 



The 1904 map of Tijuana Estuary (Figure 

 2.3) provides the earliest indication of 

 historic conditions. Three features that are 



clearly mapped are not evident in later 

 photographs. First, there is an isolated, land- 

 locked lagoon in the northeastern part of the 

 estuary. Without a natural connection 

 between the lagoon and the rest of the estuary, 

 this habitat must have been a highly variable 

 wetland that filled in the rainy season and 

 dried out in summer. Second, the mouth of the 

 Tijuana River is represented as a minor bay, 

 rather than a narrow channel. If this map 

 does not represent an unusually high tide, 

 then there was a much larger subtidal area 

 than exists at present, and major 

 sedimentation occurred after 1904. Third, 

 there are two river courses, one entering the 

 center of the estuary and one toward the 

 southern end. The latter no longer connects 

 with the river. 





/ 



^—7— 



X 



j-0 T A Y 



V A L L 





 







"mv.xk" 



R 2 * 



Figure 2.3. The 1904 map of Tijuana Estuary (from U.S. Coast and Geodetic Survey). 



1 1 



