Humpy Creek, Kachemak Bay

Humpy Creek, Kachemak Bay

by | May 1, 2022

Humpy Creek drains a watershed of 6,912 acres (2,797 ha) and flows generally northwest for about 4.5 miles (7 km) from Emerald Lake at an elevation of 1,138 feet (347 m) in the Kenai Mountains to the southeastern shore of Kachemak Bay, about 67 miles (108 km) southwest of Seward and 14 miles (22.5 km) east-northeast of Homer, Alaska. The local name was first published by U.S. Geological Survey in 1950 and is likely for the pink or ‘humpback’ salmon that spawn in this river. Emerald Lake is fed by several smaller streams that drain alpine cirque basins. The Kenai Mountains are a range of the Chugach Mountains and reach an elevation of 6,612 feet (2,015 m). The range is formed by an accretionary prism with underlying structural geology primarily comprised of metamorphic and igneous rock. This area is an active subduction zone that is the boundary between the North American plate and the Pacific plate, which are converging at a rate of about 2-3 inches (6 cm) per year. Subduction is ultimately responsible for the main features of the local and regional bedrock geology, as well as the many earthquakes and frequent eruptions of Cook Inlet volcanoes. The accreted ocean-floor rocks that form the Kenai Mountains are part of the Chugach terrane, which is comprised of several different rock formations. The rocks forming the Humpy Creek watershed are part of the McHugh Complex which consists of intensely deformed sedimentary and volcanic rocks scraped off the deep-sea floor at the subduction zone. The main rock types are, from base to top, basalt, chert, argillite, greywacke, and limestone. Chert and the basalt on which it rests range in age from Middle Triassic to mid-Cretaceous on the geological time scale. The greywacke is known to be as old as Early Jurassic at the one location, but mid-Cretaceous in other places. The Permian limestone blocks are inferred to represent the tops of seamounts that were clipped off a now-subducted piece of Paleozoic ocean floor.

Humpy Creek and other streams in this area drain short steep and recently deglaciated watersheds resulting in relatively low concentrations of primary nutrients that flow directly into Kachemak Bay. Deglaciation of the Cook Inlet Basin was underway by 15,000 years ago and the ice that had filled Kachemak Bay was gone and revegetation began well before 12,000 years ago on the north shore and at least 10,000 years ago on the south shore when habitable land first became available for human settlement. Archaeological excavations in Aurora Lagoon, about 3 miles (5 km) north-northeast of Humpy Creek, suggest the occupation of the maritime Ocean Bay people about 4500 years ago. Excavations from Chugachik Island, about 7 miles (11 km) north-northeast of Humpy Creek, indicate the occupation of a more advanced culture about 4,000 years ago. The longest-lived, most widely distributed, and best-known prehistoric cultural entity in Kachemak Bay is the Kachemak tradition that occupied the bay from about 3,000 to 1500 years ago. Major excava­tions on Yukon Island, at Cottonwood Creek, near Halibut Cove, and on Chugachik Island revealed over 6000 artifacts that characterize this tradition, including evidence that they developed methods to catch large numbers of salmon with weighted nets. The Kachemak tradition peoples abandoned the bay about 1500 years ago.  The causes for this displacement are not clearly understood but may be related to glacial advancement, or a population increase estimated at 200-400 people that placed a strain on food resources, especially considering the difficulties of storing food such as salmon when caught in large quantities. There is some evidence that the Dena’ina Athabascans arrived in Kachemak Bay about 1000 to 1500 years ago, migrating from the Mulchatna and Stony River areas where they had lived for thousands of years prior. Humpy Creek was likely an important area for gathering food, catching salmon, and hunting.

Humpy Creek is within Kachemak Bay State Park that was designated in June 1970 and was Alaska’s first state park. Today, there are nearly 400,000 acres (161,874 ha) of land within the park and the adjoining state wilderness area. Kachemak Bay is considered a critical habitat area due to its biodiversity. Kachemak Bay also exhibits a biological produc­tivity reputedly three times higher than elsewhere in lower Cook Inlet. Major sea mammals include harbor seals, two species of porpoises, sea otters, sea lions, beluga, orcas, and humpback and minke whales. Sea otters have only recently reestab­lished themselves in Kachemak Bay after being eliminated from the area in the early 1900s. Humpy Creek is between Grewingk Creek to the south and Portlock River to the north and may easily be confused with Grewingk Creek which is only 1 mile (1.6 km) to the southwest and is larger but does not have a salmon run. Kachemak Bay lacks major salmon streams; however, 25 streams have anadromous fish runs with some recently artificially created or enhanced. Humpy Creek receives a small run of chum salmon that spawn in early August and a sizeable run of pink salmon that spawn during mid to late August. The average annual pink salmon escapement to Humpy Creek is 47,300 based on ground surveys between 1960 and 2006. For context, an aver­age of 4 to 10 million salmon enter Cook Inlet each year but relatively few of them stop in Kachemak Bay. The Emerald Lake Loop Trail is a popular hike of 12.6 miles (20 km) that starts at the mouth of Humpy Creek and follows the edge of the high tide line through the grass, then climbs into the woods and soon provides views of the Humpy Creek drainage and the glacial flats of Grewingk Creek. The trail intersects with the Emerald Lake Trail which leads to beautiful Emerald Lake and its alpine surroundings. The trail then climbs to Portlock Plateau for dramatic views of Kachemak Bay. Read more here and here. Explore more of Humpy Creek here:

About the background graphic

This ‘warming stripe’ graphic is a visual representation of the change in global temperature from 1850 (top) to 2021 (bottom). Each stripe represents the average global temperature for one year. The average temperature from 1971-2000 is set as the boundary between blue and red. The color scale goes from -0.7°C to +0.7°C. The data are from the UK Met Office HadCRUT4.6 dataset. 

Credit: Professor Ed Hawkins (University of Reading). Click here for more information about the #warmingstripes.

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