Douglas River starts at the terminus of an unnamed glacier on the northwest flank of Fourpeaked Mountain in the Aleutian Range on the Alaska Peninsula, and flows north for 28 miles (45 km) to Kamishak Bay, about 108 miles (174 km) northeast of King Salmon and 89 miles (144 km) southwest of Homer, Alaska. The local name was reported in 1904 by G.C. Martin of the U.S. Geological Survey. It was also locally called Andrews River, and this is probably the same stream shown on Russian charts in 1852 as the “Chuyu River”.

The south coast of Kamishak Bay is characterized by extensive reefs that are exposed at low tides. These wave-cut platforms, in addition to elevated marine beach deposits on shore, indicate that this coast is rising. Material dated from Kamishak Bay suggests that the rate of uplift is about a half meter (1.5 feet) per century. This uplift is partly in response to tectonic activity, and possibly in part to isostatic adjustments following deglaciation. The present-day wave-cut platforms on the south shore of Kamishak Bay are completely exposed at low tide and are composed of sandstone strata of the Naknek Formation. A composite section from a nearby sea cliff suggests a thickness of about 2,000 feet (600 m).

Kamishak Bay also contains extensive deposits of estuarine silts emanating from coastal rivers that are exposed at low tide. The heads of most embayments are completely dry on minus tides and the silt deposited in Kamishak Bay can be exposed for 3-6 miles (5-10 km) offshore. The estuarine silts are mostly an accumulation of rock flour carried into the bays by rivers and streams from melting glaciers that form a veneer on the sandstone platforms. Read more here and here. Explore more of Douglas River Tide Flats here: