By 1900, families who had taken up residence in South Slough had
substantially altered the landscape to accommodate agricultural,
transportation, and logging needs. Marshes were separated from
the tides with earthen dikes and drained by ditches. Tide gates
kept out salt water and provided drainage of fresh water. The
dikes also served as roadways and, with culverts, as bridges
across small streams or marshy areas. Almost all (90%) of the
former tidelands around the edges of the Coos estuary have been
diked or filled to accommodate transportation routes and to
create flat land for building and agriculture. By the 1960s,
many tide gates along South Slough began to fail and have been
allowed to deteriorate, while the earthen dikes are gradually
eroding and have breached in some spots. As a result, former
pasture lands are in various stages of reversion from uplands
and freshwater wetlands to estuarine habitats. Creeks in the
shallower parts of the South Slough watershed were dredged
during the early to mid-1900s