The Ecology of Tijuana Estuary, California: An Estuarine Profile

around the periphery of the wetland. However.
there was only a path and no houses on the barrier
dune adjacent to the salt marsh. Signs of
agriculture in the floodplain are evident upstream
of the estuary and north of what is now Monurnent
Road.
Several physiographic features that changed in
later years are noted in the photos of 1925. 1953,
1964. 1970. 1984. and 1985. In 1928. the dune
had intermittent vegetation extending from what is
now Imperial Beach Slvd. south to the estuary
mouth. This is consistent with Purer's (1936)
description of a rich flora that included shrubs
such as lemonadeberry (Rhus integr~folia).
Channels had major bare mudflats along their
periphery. The inland lagoons clearly contained
marsh vegetation throughout. Only a small area of
channel is visible, and that was dredged to link the
lagoon with the estuary. Two islands were present
in the main north-south channel. The mouth
(Figure 9b) had tidal flushing through an opening
that angled southwest. A relatively large
embayment was located south of the mouth.
although it may have been shallower than indicated
on the 1904 map (Figure 6). What appear to be
large salt pannes were present east of the the
inland lagoon.
Changes that took place in the 1960's and
1970's were described using additional air photos;
for the most part, changes remained visible in the
1978 photo (Figure 11). By 1964. apartment
buildings had been constructed along the beach.
extending south to their present limit. Dune
vegetation remained relatively dense south of the
apartments. Near the mouth were disturbed areas
and areas of bare sand toward the main estuary
channel. A second dike had been built within the
inland lagoon. Sewage was then discharged to two
oxidation ponds before overflowing to the estuary.
By 1953 (Figure lo), many changes had
occurred both in the periphery of the estuary and
within the area of tidal influence. Imperial Beach
was a well-populated community: a military airport
had been built east of the estuary; military activity
was evident along the southernmost portion of the
beach; and agricultural activities had proceeded to
within a few blocks of the beach.
Withln the estuary, several habttats had
changed dramatically The barr~er dune had begun
to be developed for houslng along the northwestern
part of the estuary although dune vegetation was
still present farther south Salt marsh vegetation
had established along the edges of the channels
A sewage-treatment plant had been bu~lt north of
the inland lagoon, and the northernmost depresston
had been diked to create a sewage pond
Presumably the dredged channel carried the
overflow to the ocean A bridge had been built over
the dredged channel, probably to truck gravel from
shallow pits just south of the inland lagoon The
mouth was sttll open to tldal fiushtng through an
opening that had m~grated south of its 1928
location Much of rhe area that was deep-water
habltat appeared to have filled In with beach sand,
and the southern channel had become constrrcted
Salt Dannes were strli ev~denl east of the tnland
iagodn, but a brackish marsh had appeared at the Figure 10, The 1953 aerlaf photograph of Tfjuana
teimlnus of urban drainage from the airport, Estuary (from U.S. Department af Agriculture). Mate
perhaps in a depress~on caused by ex~~~ailon bridge (5) aver the dredged channel, sewage ox~dation
Add~ttonal disturbance caused by gravel extractron pond (S), bracktrrh marsh (BM), mrlrtary instaliations
was evldent just west of the new wetland area fM1), and agricultural use$ IAf.