Reading the river: Field surveys on the Ausable

In his hands-on exploration of the Ausable River, Gary Henry maps strategies for effective stream restoration amid changing environments.

By Zachary Matson

Gary Henry’s job as stream restoration manager for the Ausable Freshwater Center (previously named the Ausable River Association) sometimes brings back memories of jumping from rock to rock in streams near his rural Ohio hometown. Now equipped with pricey surveying equipment and fishing waders, Henry spends nearly half of his time in the field, crisscrossing the Ausable, tracing its meandering channel and picking his way across slippery rocks.

“It’s a good job. I get to hop around on rocks in rivers,” Henry said during a field survey earlier this month.

Hired in 2021 as the Ausable River Association’s stream restoration specialist, Henry collects data on the geomorphology, or physical structure, of rivers and streams. That data helps to monitor changes over time, identify areas in need of restoration and provide the level of detail necessary to plan out projects that essentially reconstruct entire sections of river.

Earlier this month, Henry visited a monitoring site on the East Branch of the Ausable River just upstream of Ausable Forks. The 2,000-foot-long section of river is considered a reference reach, an example of a portion of river functioning as it should. By studying reference sites, the freshwater center can see how their restoration projects perform and create a baseline for future projects.

“We didn’t do anything here, yet the river at this site is doing its job efficiently and effectively,” Henry said. “[Reference sites] are very hard to find.” 

The site, reached thanks to private landowners the nonprofit works with, is marked by a pink disk still bearing the group’s former name. The markers are necessary to calibrate and position survey equipment that triangulate between a base, Henry’s field device and satellites to measure streambed elevations and point locations to within a centimeter.

Henry’s survey work serves numerous purposes and enables analysis of the river at varying resolution. This summer, for instance, Henry completed a longitudinal profile of the river over nearly 14 miles from St. Huberts to Jay. He traced the river’s thalweg, the line of the river channel’s deepest point, and documented every eroding bank along the way, snapping over 400 pictures. The pace of work was about four hours per mile. On his longest day, he traversed 2.3 miles of river in 10 hours. “You go very slow,” he said. 

That broad overview of the East Branch’s higher reaches will serve as the foundation of a study to identify future restoration project sites on that section of river, similar to a study of potential restoration sites in Upper Jay and Jay conducted in the aftermath of Hurricane Irene. That study resulted in a handful of restoration projects aimed at mitigating flood risk and improving fish habitat.

The new East Branch study will enable Henry and others to dig into the river’s problem spots and prioritize areas for restoration. They already have a project estimated to cost around $3 million fully designed and awaiting funding slightly downstream of the confluence of the river’s east and west branches. At that site, which in recent years has seen bad ice jam flooding, cobble islands are a telltale sign of unwanted sediment buildup.

The freshwater center won’t know where to target its restoration work without the plodding, in-stream work to map river cross sections.

“It helps us quantify the problems we are seeing,” Henry said.

The surveys can go much deeper when they begin to detail how best to restore a section of river. While Henry measured elevation and distance data for a handful of river cross sections as part of monitoring the reference site, he would document many more cross sections and other measurements like stream velocity and cobble types for a restoration project.

When not wading through a stream, Henry can be found crunching numbers on his desktop. He plots the data in mapping software and constructs detailed diagrams of the river’s shape, both from bank to bank and down its watercourse. He calculated that the reference site had a 0.2% slope.

“You want to be able to build this accurately in your model,” Henry said.

Those models help determine how wide culverts and bridges need to be to safely pass 50-year or 100-year floods and help determine how to design restoration projects to minimize flooding and protect infrastructure. Henry will work with environmental engineers from SLR Consulting to establish a full model of the Ausable River as part of a state-funded flood study. That model will help pinpoint flood-prone areas and give restoration experts a tool to evaluate different project design approaches in the future.

Henry spent time this summer on a project with the Hamilton County Soil and Water Conservation District on Elbow Creek near Wells. The 12-square-mile watershed has persistent sedimentation problems.

As the organization renames and shifts its focus beyond the Ausable watershed, Henry is working more in the Boquet, Hudson and other river systems throughout the park. Kelley Tucker, executive director of the Ausable Freshwater Center, said that as the organization expands across the region and contracts more work in communities, she hopes to hire more specialists to examine river and stream systems for potential restoration.

The freshwater center is also planning to conduct a study focused on heavy sediment loads on the West Branch of the Ausable River. For that study, Henry plans to explore higher in the river’s headwaters to find feeder streams contributing the bulk of the river’s sediment loads. That heavy sedimentation can bury larger cobbles and suffocate fish habitat. When visiting the reference site, Henry was interested to see how floods last December – the fifth biggest in 100 years on the East Branch of the Ausable – altered the river channel.

Sometimes restoration isn’t needed. Henry pointed out a collection of boulders on the river’s right bank, where heavy flows scoured away dirt and vegetation. Boulders “add a lot of complexity to the channel,” he said. As water rushes over the boulders, the constant scouring creates calm pools nestled on their downstream side, which provide important fish habitat. 

Over time, and subsequent high flows, the soil will rebuild and the vegetation will again flourish.

“The river will fix this,” he said.