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New Mat-Su Stream Map Uncovers a Surprise

High-Tech Tools Help Forecast Floods and Conserve Fish Habitat


A Nature Conservancy team harnessed new tech tools to map Mat-Su streams with better detail than ever before. The project promises to help conserve salmon habitat and lead to a better understanding of local flooding. This example of the new stream data from the confluence of Willow Creek and the Susitna River shows numerous tributary streams that simply weren’t documented until now.

The Nature Conservancy in Alaska

ANCHORAGE, ALASKA — If you were to add up the total length of each and every stream in the Mat-Su Borough, how many miles would you get? The actual number might surprise you.


A team of scientists led by The Nature Conservancy in Alaska crunched the numbers and came up with a total of more than 50,000 miles – double the previous tallies.


“We’re astonished,” says Jim DePasquale, a Mat-Su-based Nature Conservancy scientist in charge of the digital map project that led to the finding. “It’s a discovery of 28,000 miles of streams – enough to reach around the equator and then some.”


Most importantly, the map offers a helpful tool for protecting public safety and habitat for salmon. For one, it offers a new foundation for understanding floods in the Mat-Su. Also, fish biologists who are working with communities to restore fish passage by fixing improperly placed culverts can now pinpoint the worst offenders. 


“The Mat-Su is the fastest growing area in the state by a large margin. How do you conserve habitat if you don’t know where it is? You have to identify where your streams are and that’s what The Nature Conservancy’s new stream map does for the Mat-Su,” says Larry Engel of Palmer, a retired Alaska Department of Fish and Game biologist and member of the Mat-Su Borough Fish and Wildlife Commission.


Salmon numbers remain strong in most of the Mat-Su, but some declines show the region is not immune to the same pressures that fish have faced elsewhere.


“The improved mapping project recently completed for the Mat-Su Basin sets a new standard for fish habitat conservation efforts to emulate all across Alaska. One significant application I see of this new technology will be to help identify previously unknown salmon streams, which after on-the-ground confirmation, will ensure as much protection of fish habitat as possible,” says Alaska Department of Fish and Game biologist Roger Harding, who coordinates the state’s fish habitat partnerships.


The new maps show an array of smaller streams that a casual observer might easily overlook. But scientists say these waters provide flows and safe nurseries that baby fish need before swimming to the sea.


“These smaller streams are very important to salmon. The new maps now coming online present a great opportunity for the people of Alaska and the Mat-Su to plan a future in which salmon and our communities will co-exist,” says Kacy Krieger, a geospatial scientist at the University of Alaska Anchorage who coordinates the state’s stream map database.


Mat-Su Borough planners recognize the updated maps can help streamline permitting processes.


“The improved detail and accuracy of the new hydrographic maps will help the Mat-Su Borough support permitting processes such as storm water discharge for development projects,” says Alex Strawn, Mat-Su Borough Development Services manager.


Alaska has long been known as the last frontier of the nation’s map library because many of its maps are based on black-and-white aerial photos collected during military over-flights dating back as far as the 1950s. Advances in technology – namely, the use of satellite imagery, laser measurements of the earth’s surface, and new capabilities in analyzing big data – have since revolutionized how cartographers make maps.


Recognizing this, the federal budget released this month specifically calls for investment in similar high-tech updates of Alaska’s topographic maps.


The two-year project covered the entire 25,000-square-mile Mat-Su watershed, or, more precisely, all lands drained by the Matanuska, Susitna and Little Susitna rivers. The new blue streamlines are already incorporated into the official National Hydrography Dataset, part of the USGS National Map – meaning future maps of the region will incorporate the Conservancy’s updated stream data.


Later this year, USGS will release a set of revised 7.5-minute series topographic maps for the Mat-Su that feature the updated stream lines. These popular maps are the go-to source for landowners, hunters, hikers, industry and subdivision developers, as well as fisheries biologists and borough planners.


The Mat-Su stream map project received technical guidance from the Alaska Hydrography Technical Working Group, which oversees the development of a statewide map of Alaska's lakes, rivers and streams. The group includes representatives from Alaska Department of Fish and Game, Alaska Department of Environmental Conservation, Alaska Department of Natural Resources, U.S. Fish and Wildlife Service, U.S. Geological Survey, Bureau of Land Management, National Oceanic and Atmospheric Administration, National Park Service, U.S. Forest Service, and the University of Alaska.


The Association of Fish and Wildlife Agencies Multistate Conservation Grant Program, U.S. Fish and Wildlife Service, Mat-Su Borough, Gordon and Betty Moore Foundation, National Fish Habitat Partnership, The Nature Conservancy, National Fish and Wildlife Foundation, and the U.S. Geological Survey funded the $330,000 Matanuska-Susitna Hydrographic Mapping project.


The Mat-Su approach is inspiring a larger statewide stream map effort – a process to update stream maps for the Kenai Peninsula is already underway. Rather than calling for proposals from sole contractors, a common method of commissioning large infrastructure projects, this program’s collaborative approach built in efficiencies that brought costs down to just one-third of standard projections.


“All of us on the team are proud of our lower-cost methods,” says the Conservancy’s DePasquale. “The cost savings are icing on the cake.”


The Nature Conservancy is a leading conservation organization working around the world to conserve the lands and waters on which all life depends. Visit The Nature Conservancy in Alaska at nature.org/alaska. To keep up with current Conservancy news, follow @nature_AK on Twitter.

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