Kodiak Island Detailed Geography

The Kodiak Island Archipelago is located in the Gulf of Alaska about 30 miles across Shelikof Strait, and 252 air miles southwest of Anchorage. The island group is approximately 177 miles long and 67 miles across, extending from the Barren Islands on the north, to Chirikof Island and the Semidi Islands group on the south. The Archipelago encompasses roughly 5,000 square miles of land, no point of which is more than 15 miles from the sea. Kodiak Island's 3,588 square miles make it the second largest island in the United States (only the island of Hawaii is larger).

 The second largest island of the archipelago is Afognak, located north of Kodiak Island. The Kodiak Island Borough includes the entire archipelago and the Shelikof Strait shore-side lands of Katmai National Park. Kodiak Island consists primarily of mountainous terrain, with the ridge of the mountains running northeast-southwest. Although several peaks are greater than 4,000 feet, most range between 3,000 and 4,000 feet. About 40 small cirque glaciers (none greater than 2 miles) are evident along the main divide. Numerous hanging valleys feed into the main canyons radiating from the central divide. The uplands are drained by relatively short, swift, clear mountain streams.

The Barren Islands to the north of Shuyak Island are primarily rocky landscapes. Tugidak Island on the south is relatively flat and supports extensive areas of wet and moist tundra. The outlying islands south of the Trinity Islands are lower in elevation than Kodiak Island and support more limited vegetation growth.

From Shuyak Island to northeastern Kodiak Island, stands of Sitka spruce dominate land from shore to the tree line. These stands extend south to a general northwest-southeast dividing line running from Kupreanof Peninsula to Cape Chiniak. Southwest Kodiak Island is relatively flat and supports extensive areas of wet and moist tundra.

Exposed bedrock and shallow soils prevail along the 2500-mile rugged coastline. Northwest Kodiak shows effects of glaciation, with long, narrow fjords and U-shaped valleys. These lie perpendicular to the mountains and the geologic fault lines. Rivers typically enter at the heads of the fjords and are backed by extensive flat lands. The east and southeast coasts of the Archipelago are characterized by shorter, wider estuarine embayments. Southwest Kodiak Island and the Trinity Islands tend toward long, continuous shorelines with few bays. Most of the sandy beaches occur on the west coast of Kodiak Island and the Trinity Islands. Specific geographic features within the Kodiak Island Borough include: offshore areas; estuaries; lagoons; wetlands and tidelands; rocky islands and sea-cliffs; exposed high-energy coasts; rivers, streams, and lakes; and important upland areas.

Offshore Areas

Offshore areas include submerged lands and waters beyond mean lower low water to the limit of Kodiak Island Borough. Because of the extensive estuarine system of the Borough, offshore areas are those outside the headlands of the estuaries. Living resources are abundant in the Borough's offshore area. Dominant fauna include shellfish, finfish, marine mammals, and marine birds. Kelp and other macro algal beds provide habitat for sea otters, spawning herring, and juvenile fish. They are important feeding areas for waterfowl and marine birds, and provide valuable primary production exported as algal drift, which is assimilated elsewhere in the marine ecosystem.


In the borough, most near shore marine waters are designated as estuarine because of their extensive dilution by fresh water. Estuarine areas are considered to extend from headland to headland of bays, inlets, and fjords. Well-developed delta systems, apparently dominated by tidal action, lie at the head of most Kodiak fjords. Kodiak estuarine areas are highly productive. The complexity of the submarine topography and sediments and good algae growth, including extensive kelp beds, provide basic nutrients and diverse habitat to support herbivore and carnivore populations. In addition, many marine finfish and shellfish utilize the estuarine areas during larval and juvenile stages of development.


Lagoons are most prevalent in the south and southwestern portions of the Archipelago. Unlike other estuarine systems of the Islands, lagoons included in this habitat are shallow and tend to have sandy or flat shorelines.

Wetlands and Tide flats

The presence of coastal tidelands surrounding the Kodiak Archipelago is relatively low; however, the actual amount of habitat varies by region. Kodiak and Afognak Islands have very limited tide flat wetland complexes. Extensive tide flat-wetland complexes usually occur only at the heads of bays or around lagoons on these islands. In addition to these saltwater habitats, large inland wetlands occur in the Karluk River and Ayakulik River drainages in southwestern Kodiak. In sharp contrast to the availability of these habitat types on Kodiak and Afognak Islands, shorelines around the Trinity Islands contain extensive tide flats, and most of the Tugidak Island mainland is wetland habitat. Tide flat-wetland complexes provide valuable habitat for birds and marine mammals, particularly when used in combination with adjacent waters. In addition, the tide flat areas, especially those that are composed of sandy beaches, provide habitat for abundant clam and polychaete populations.

Rocky Islands and Sea Cliffs

Rocky islands generally have rock or cliff-lined shorelines. Occasionally rocky islands have tundra-vegetated interiors or areas along their coasts that are fairly level. This habitat category applies to most of the offshore islands. Along the coast of the major islands, however, this habitat type is limited to those shores with vertical cliffs. Offshore rocky islands and sea cliffs are particularly important to marine mammals and marine birds as haul out and nesting sites. Many of these sites are along the east coast of Kodiak Island in the vicinity of Chiniak and Ugak Bays. The remaining sites are distributed around the archipelago and along the shoreline on the west side of Shelikof Strait.

Exposed High-Energy Coasts

Exposed bedrock shores comprise approximately 50 percent of Kodiak and Afognak Islands, and a large percentage of the Alaska Peninsula coastline on the west side of Shelikof Strait. Almost 90 percent of the Barren Islands are exposed bedrock. Exposed bedrock shores usually have moderate to steep gradients. Exposed high-energy coasts provide habitat for a variety of marine littoral-zone flora and fauna, which in turn are used by important fish and wildlife resources. In addition, high-energy coasts provide feeding and nesting habitat for bird species and a food source and resting habitat for marine mammals.

Rivers, Streams and Lakes

The largest lakes and longest rivers within the Borough are located in southwest Kodiak Island. Major southwest lakes include Karluk, Frazer, Red, Akalura, and South Olga lakes. Other important lake systems on Kodiak Island, such as Spiridon, Little River, Uganik, Terror, Buskin, and Lake Rose Tead, are significantly smaller. Small pothole and high mountain lakes are also prevalent. Pothole lakes are generally found along the Upper Ayakulik River, between Olga Bay and the ocean, at the mid-reach of the Karluk River, on the Lower Aluilik Peninsula, and throughout Tugidak Island. Pothole lakes are also prevalent in the north and northeast sections of Afognak Island and on Shuyak Island. Major lakes on Afognak Island include: Selief Lake, Afognak Lake, Big and Little Kitoi Lakes, Pauls, Laura, and Gretchen Lakes, Portage Lake, Little Waterfall Lake, Hidden Lake, and Upper and Lower Melina Lakes. Due to the steep topography of the Aleutian Range mountains on the west side of Shelikof Strait, there are few lakes located in that area of the Kodiak Island Borough. With the exception of the Ayakulik and Karluk rivers in southwest Kodiak Island, rivers in the archipelago tend to be short and steep, often originating in small mountain lakes or small glaciers. Rivers, streams, and lakes provide critical aquatic habitat for resident and anadromous fish populations. In addition, they support summer and winter activities of bird and mammal populations, particularly waterfowl, bear, beaver, and land otters. Rivers and streams are the conduit for the freshwater component of estuarine systems, and serve as a valuable link between upland and marine environments.


The archipelago uplands can be subdivided into four general areas based primarily on vegetative and terrain features. These areas are; (1) north of Kodiak Island, (2) the major portion of Kodiak Island, (3) southwest of Kodiak Island, lower Aliulik Peninsula, and the Trinity Islands, and (4) the Alaska Peninsula coastline west of Shelikof Strait. The first category, characterized by well-developed stands of mature Sitka spruce, includes Shuyak, Afognak, Raspberry, Whale, Spruce, and Marmot Islands.

The major portion of Kodiak Island forms the second category of uplands. Upland habitat distributions are closely related to differences in elevation. At very high elevations, unconsolidated material is generally absent. Below the peaks, mountainous areas have typical alpine vegetation. Steep mountains below 3,000 feet have dense shrub and ground cover. Lower slopes and valley floors are covered by sand and gravel of glacial origin, valley alluvium, alluvial fans, talus deposits, and ash from the 1912 eruption of Mt. Katmai. Cottonwood and occasionally Kenai birch are common stands along the lower reaches of major drainages. The third region includes southwest Kodiak Island and the Trinity Islands. This region escaped glaciation and is different in vegetation and topography from the rest of the Kodiak Archipelago. Plants are uniquely similar to species found in the Alaskan Arctic and unlike those found elsewhere in the Archipelago. The area is characterized by extensive moist and wet tundra surrounded by rounded low hills. The upland terrain along the west side of Shelikof Strait is dominated by the northeast-southwest trending mountains of the Aleutian Range. The short, steep-gradient drainages to the Gulf of Alaska are generally situated in steep valleys with cottonwood stands along the stream courses. At higher elevations, the vegetation is characteristic alpine tundra and bare rock and soil.