Flat Islands are in southern Cook Inlet at the entrance to Kachemak Bay, 0.9 miles (1.4 km) offshore from the Kenai Peninsula, about 13 miles (21 km) southwest of Seldovia and 6 miles (10 km) west-southwest of Port Graham, Alaska. The presumably descriptive name was given by William H. Dall of the U.S. Coast and Geodetic Survey in 1880. The Flat Islands are treeless, grass-covered, and composed of two closely connected islands joined by bare reefs and surrounded by bull kelp.
The first salmon trap was built in Cook Inlet in about 1885. It was patterned after the pound nets used in the Great Lakes fisheries but was modified considerably to withstand strong tidal currents and waves. This type of salmon trap became known as a pile trap because whole log piles were driven into the sandy bottoms to support the trap and the webbing and wire netting were fastened to piles to form the walls. The first trap was so successful that they soon more were built in other areas including Kachemak Bay which had 4 traps; one on the north shore between Travers Creek and Diamond Creek, and three on the south shore at McDonald Spit, Point Naskowhak, and adjacent to Flat Island on the mainland. By the 1930s, the fish traps were owned by the Fidalgo Island Packing Company, which also operated the cannery at Port Graham.
The Flat Islands form a good radar target that provides an important transit turn point used by large vessels. The Flat Island Light is on a skeleton tower, 70 feet (21 m) above the water, with a red and white diamond-shaped daymark on the northwest point of the northernmost island. Flat Island is also the location of a Coastal-Marine Automated Network (C-MAN) weather station. C-MAN weather stations are part of a meteorological observation network along the U.S. coast. The network consists of about 60 stations installed on lighthouses, at capes and beaches, on nearshore islands, and on offshore platforms. The stations record atmospheric pressure, wind direction, speed and gust, and air temperature. Some are designed to also measure sea surface temperature, water level, waves, relative humidity, precipitation, and visibility. The network is maintained by the National Data Buoy Center of the National Weather Service, which is part of the National Oceanic and Atmospheric Administration. Data from the C-MAN stations are telemetered and ingested into numerical weather prediction computer models. Read more here and here. Explore more of the Flat Islands here: