. The ecology of Tijuana Estuary, California : a national estuarine research reserve . DUNE STABILIZATION < — U 3 < EXPERIMENTAL marsh Figure The 495-acre restoration plan to return tidal flows to the southern arm of Tijuana Estuary. Excavation to create channels and marsh would avoid ecologically sensitive areas (Figure ). A single river-training levee (or berm) would divert sediments from future floods. River training levee or berm. The original plan (Figure , Williams and Swanson 1987) called for two large river training berms, the larger being km ( mi) long and 18 m
. The ecology of Tijuana Estuary, California : a national estuarine research reserve . DUNE STABILIZATION < — U 3 < EXPERIMENTAL marsh Figure The 495-acre restoration plan to return tidal flows to the southern arm of Tijuana Estuary. Excavation to create channels and marsh would avoid ecologically sensitive areas (Figure ). A single river-training levee (or berm) would divert sediments from future floods. River training levee or berm. The original plan (Figure , Williams and Swanson 1987) called for two large river training berms, the larger being km ( mi) long and 18 m (60 ft) high; these berms would consume most of the spoils dredged from the restoration site. Subsequent plans (Florsheim et al. 1991) eliminated the smaller berm and reduced the height of the larger berm to about 8 m (25 ft). It would be about km (~1 mi) long and cover 19 ha (46 ac). This size was estimated as the minimum necessary to protect the estuary through a 100-year flood event. The berm was designed to be vegetated, but expected to erode with the larger floods. A wide berm would have sufficient sediment to accommodate erosion under most flood conditions. The berm has been an ecological concern, because it is not certain if the spoils will support native vegetation. It would also abut native bluffs that support coastal sage scrub and associated rare birds. As an alternative, a levee was designed that would be lower (3 m, 10 ft) and narrower (30 m, 100 ft) and cover much less ground (5 ha, 12 ac; Entrix et al. 1991). The choice between a levee and a berm awaits further environmental review and results of research to be conducted on an experimental berm. • Dredge spoil disposal. Dredging at Tijuana Estuary will generate spoils that differ in quality, depending on their source and presence of contaminants (to be assessed in a detailed sampling program). Sandy spoils may be used to replenish the beach and dunes, but spoils of low quality will be taken off site. Whe
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