AUSABLE WATER WISE: Streams and sediment: The big picture

The confluence of the West Branch of the AuSable River with its tributary the Chubb River, top left, shows signs of increased levels of fine sediment that are challenging the branch, its fishery, homes and public infrastructure. (Provided drone photo — Larry Master, piloted by Ed McNeil)

The Lake Placid area is a paradise of lakes, rivers and streams. Nestled in a valley surrounded by wilderness mountain ranges, it’s home to Lake Placid and Mirror Lake, and the meeting point of the Chubb River and the headwaters of the West Branch of the AuSable River.

Despite their beauty and recreational opportunity, these waterways face challenges, as we know. It’s essential to reduce road salt use to protect Mirror Lake, to ask questions about the consequences of the increased recreational use of Lake Placid, to minimize septic and stormwater effects, and to halt the encroachment of invasive species. But these are human-induced problems and, as a community that cares, we can and do work together toward solutions.

There’s another challenge, however. The increase in sediment — cobble, gravel and sand — in the West Branch running through the town of North Elba. What’s tricky about this challenge is that, unlike road salt or invasive species, the right amount of sediment is good. Sediment is endemic to streams; it’s part of what makes them work. Some bank erosion is natural and beneficial. And streams are machines for moving that eroding sediment. Cobble, boulders, gravel, fine sand and wood are elements that, powered by water, build, and rebuild riffles, pools, banks and floodplains — habitat for aquatic wildlife, birds and native plants.

But it’s a delicate balance.

Stand on the iron bridge along River Road. Look down. You’ll see sand covering the river’s bed, not the cobbles and boulders that once nurtured a healthy population of native and stocked trophy trout. Driving along River Road, it’s easy to spot bank loss at a scale that is disturbing. The river is out of balance. Layers of excess sediment have choked pools and smothered riffles, reducing water quality, stream health, habitat for fish and other species, and angling opportunities. Excess sediment builds up, creating mid-stream islands that force water against banks, increasing erosion, bank collapse and threatening roads and homes. And the problem is moving gradually downstream.

Studies conducted by the Ausable River Association’s staff over the past 20 years have identified sites along River Road as priorities for restoration. But these sites display symptoms — fixing them without addressing the cause would be inefficient, and ineffective in the long-term. The cause of the imbalance lies upstream, in the headwaters above Lake Placid’s iconic ski jumps.

Over 100 years ago, this area was one hub of a massive timbering industry and a network of dams and altered streams running logs to mills downstream. Have these industrial scars not healed? Are they challenged by a shifting climate with increasingly intense storms? How have recent large mountain slides contributed to sedimentation of headwater streams below them? And what of the release of decades of sediment held behind Marcy Dam in the high headwaters, damaged in Tropical Storm Irene and subsequently dismantled by the New York State Department of Environmental Conservation? Are there impacts from existing land uses — roads, culverts, other small dams?

Fortunately, the Ausable River Association’s staff and our stream restoration partners can answer these questions and help define restoration and management solutions. It’s not a matter of scooping out excess cobble. That’s a costly and ultimately fruitless endeavor. It’s about science. Surveying the entire system, understanding what’s in balance and what isn’t, modeling the former to rebuild — perhaps in a new form — damaged sections of the river, to restore the balance and make the river self-sustaining once again. That’s our goal. We have the capacity to achieve it, and we hope to raise the funds this year to answer the questions above and find solutions.

If you’d like to learn more, or contribute to making this work possible, send your inquiry to contactus@ausableriver.org.

(Kelley Tucker is the executive director of the Ausable River Association.)

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