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Figure 6.3. Initial design for hydrologic 

 enhancement at Tijuana Estuary (from 

 Williams and Swanson 1987). In this 

 concept, a new tidal channel would provide 

 flows to the inland lagoons and maintain flows 

 to Oneonta Slough. In the southern arm, two 

 tidal channel systems would be constructed 

 (as two phases); each would be protected by a 

 berm that would divert flood flows away from 

 the excavation sites. 



Figure 6.4. Constraints map showing 

 sensitive areas at Tijuana Estuary. White 

 areas were judged most suitable for 

 restoration work. Symbols mark areas with 

 critical and valued habitat for both plants and 

 animals, e.g., occurrence of numerous 

 endangered Belding's Savannah sparrows in 

 the southwesternmost corner of the estuary. 

 Mapping was done in 1988, using 1986 aerial 

 photos. 



6.4.2 The Model Project 



The Model Project has three features: 

 First, an experimental marsh (Figure 6.5, at 

 least 20 acres) would be constructed to 

 determine how much detailed tidal creek 

 excavation would be needed to accelerate 

 ecosystem development (i.e., rapid increase in 

 nutrient pools, plant growth, invertebrate 

 populations, and bird use). The marsh would 

 be subdivided into six areas, three with and 

 three without tidal creek networks. The 

 comparison of ecosystem development rates 



under these two treatments would determine 

 the need for tidal creek construction, which 

 would add to the cost of marsh construction 

 throughout the 495-acre restoration 

 program. 



The second feature is a new channel to 

 connect the northern end of Oneonta Slough to 

 the northern tidal pond. In addition to 

 improving tidal flows, it will enhance nature 

 interpretation and increase habitat acreage. 

 The channel will be excavated along the toe of 

 the fill on which the Visitor Center is located 



134 



