Balancing the Three R's (Regulation, Research, and
Restoration) On the Kenai River, Alaska
The Kenai River is Alaska's most popular salmon sport fishery. By attracting fishermen,
the river contributes about $40 million annually to the local economy. Much of the fishing
effort is in pursuit of the river's chinook salmon, which are among the largest in the
world. Many people benefit from the river through its numerous recreational opportunities
or by making a living providing fishery support services. To preserve the fishery and the
opportunities the river provides, we must find the proper balance of regulation, research,
and restoration in the watershed.
|
|
The Kenai River watershed drains about 2,200 square miles of the Kenai Peninsula in
southcentral Alaska  (map 115 Kb). The Kenai River begins at the
outlet of Kenai Lake, a narrow, 22-mile long lake, and flows for 17 miles before it passes
through 15-mile-long Skilak Lake. From Skilak Lake, the river flows another 50 miles
before entering Cook Inlet near the city of Kenai. Near Skilak Lake, about 16 miles of the
Kenai River flow through the Kenai National Wildlife Refuge, where development is
restricted. Because the Kenai River is within easy driving distance from Anchorage --- the
main population center of Alaska --- development of the non-refuge portion of the river
and use of the river have steadily increased along with the population of Anchorage.
The Kenai River supports all 5 species of North American Pacific salmon and 29 other
species of fish. It provides a source of chinook, coho, pink, and sockeye salmon for
recreational and commercial fisheries. Fishery biologists believe that some of the reasons
why the river may be one of the most productive salmon rivers in the world are linked to
the following unique features:
- The river has sustained high flows for extended periods of time providing salmon
adequate periods to spawn and migrate in the river.
- Two large lakes along the river, Kenai and Skilak Lakes, regulate streamflow variations,
reduce sediment movement, and provide salmon with rearing and overwintering habitat.
- Much of the Kenai River channel is stable, which helps maintain adequate spawning and
rearing sites.
- Historically, development in the river's watershed has been sparse and sources of water
pollution have been few.
Salmon return and harvest numbers have been increasing in recent years. However,
regulations restrict development in the river's flood plain and close other areas to
fishing. Many damaged streamside areas on the river are being restored, yet little
monitoring of the performance of these restoration projects or research towards improving
restoration designs has been accomplished. The role of the U.S. Geological Survey and
other Federal and State agencies is to complete high-quality scientific research to help
develop fair regulations and proper restoration designs for the preservation of the Kenai
River fisheries.
Developed areas of the Kenai River watershed are concentrated near the communities of
Kenai, Soldotna, Sterling, and Cooper Landing and within a narrow corridor along both
banks of the river downstream from the Kenai National Wildlife Refuge. Many aspects of
this development increase erosion and sedimentation along the river. For example,
vegetation is removed from riverbanks to obtain access to the river, structures are built
into the river, and river uses---such as boating---are increasing.
Erosion and sedimentation can have significant effects on salmon populations. Material
eroded from the riverbanks and the river bottom moves downstream and is deposited in other
areas that may be important spawning or rearing habitat. Young salmon have difficulty
developing properly with increases in sediment concentrations and may not emerge from
their spawning beds if fine-grained-sized sediment deposition occurs over them (see graph
below). In the Kenai River, habitat for juvenile salmon is already in short supply;
increased erosion caused by development can further reduce this critical habitat.
Structures such as docks, jetties, and retaining walls modify the channel and alter fish
habitat. Selection of the appropriate streamside structure requires knowledge of the
potential effects on fish habitat.
This graph shows that as the percentage of fine-grained sediment
in the streambed increases, development of salmon eggs into emergent fry decreases. [Data
from USGS]
|
|
Developed areas along the river were significantly affected
by the flood of September 1995. After the flood, the U.S. Geological Survey found that as
much as 25 feet of bank was eroded landward during the flooding in a developed section of
the lower river; only 8 feet of bank eroded in a heavily vegetated undeveloped section of
the upper river. Accelerated erosion of the riverbanks caused by removal of streamside
vegetation and changes in the stream channel may continue until a new post-flood
equilibrium is reached, which may take years. Research is currently being planned to
quantify and understand the potential habitat effects of severe flooding In addition to
the fall 1995 flooding on the Kenai River, below-average snow accumulation in southcentral
Alaska in 1995-96 resulted in low springtime snowmelt flow in the river. U.S. Geological
Survey data show that the Kenai River was as much as 35 percent below mean daily flow
during May and June 1996 (see graph below). This low flow causes potentially dangerous
boating conditions, delays the returns of salmon, dries out spawning grounds, and reduces
food sources for young fish. The numerous potentially detrimental effects of low-flow
conditions on the salmon fishery are cause for concern.
This graph shows the maximum, mean, and minimum flows for the
Kenai River at Soldotna during the period 1965-95 and compares them with the mean daily
flow for May and June of 1996.
Low-flow conditions will likely continue until significant rainfall occurs or
temperatures increase and glacier melting begins. [Data from USGS]
Cooperative efforts currently being undertaken to understand the complex relations
between the river and its fish habitat include:
- Stream-gaging stations at Cooper Landing and Soldotna operated by the U.S. Geological
Survey (see map)
- Regulation of streamside development by the Kenai Peninsula Borough
- Identification and restoration of fish habitat along the river by the Alaska Department
of Fish and Game
- Revision of the "Comprehensive Management Plan for the Kenai River Special
Management Area" by Alaska State Parks
- Investigation of boat-wake-induced streambank erosion by the National Marine Fisheries
Service, the Alaska Department of Fish and Game, and the U.S. Geological Survey
Additional information that would complement these efforts and help to balance the
regulation, research, and restoration of the Kenai River includes:
- Real-time streamflow and water-quality data at Soldotna for flood forecasting and river
management
- Detailed river channel geometry data for flood and fish habitat modeling and for
geomorphic investigations
- Digital watershed land-use information to evaluate changes and trends in the physical,
chemical, and biological characteristics of the river
- Monitoring of restoration project performance to evaluate future designs
- Records of commercial and private boat activity on the river
- Determining historical and present rates of streambank erosion
Joseph M. Dorava and Gary S. Liepitz
For more information contact:
U.S Geological Survey
4230 University Dr. Suite 201
Anchorage, Alaska 99508-4664
phone 907-786-7100
email:jmdorava@usgs.gov
Cooperating Agencies
Alaska Department of Fish and
Game
USGS
July 1996
Fact Sheet FS--160--96 |
