After Acadia’s Record Storm: Repairing Historic Carriage Roads and Trails

More than 5 inches of rain fell on parts of Acadia National Park in under 3 hours on June 9, 2021, and the historic carriage roads that had shed rain for decades lost hundreds of tons of their surface. A National Park Service article follows what staff found and what they weighed afterward.

Damage from the June 9 storm stripped many layers of material from the carriage road and left only the base. NPS photo.

The storm

A park stream gage showed flow rising from 0.61 cubic feet per second to 527 cubic feet per second. Acadia’s 45-mile carriage road system, its trails and its paved roads were damaged, and as the water ran off the roads, upwards of 300 to 400 tons of road surface material was swept into the woods along with decades of soil from the surrounding forest. Just over a month later, initial assessments counted more than $1.5 million in damage and repair costs.

To most visitors the carriage roads are a place for car-free recreation. For managers they are also an infrastructure network and a nationally registered historic resource, set in celebrated natural ecosystems.

Assessing the damage

Maintenance, resource management and emergency management staff fanned out across the network, reporting by radio. Damage was severe enough to close 10 miles of carriage roads, along with Schoodic Peninsula bicycle paths and other roads and trails. Safety was the first concern: cyclists traveling up to 20 mph could be badly hurt on washed-out sections. The park announced the closures in press releases and on social media and put out signs and cones.

A park maintenance vehicle stops above a deep washout on a curve. Such washouts were dangerous and needed quick repair in case of more rain. NPS photo.

The carriage roads were built from 1913 to 1940 to withstand heavy rain, with stone culverts, drainage systems, a pronounced crown and roadbeds of rock layers graded from large stones to fine ones. Since the 1990s the Friends of Acadia have supported their maintenance. John D. Rockefeller Jr. designed the culverts and drainage, and they were built by skilled craftsmen, yet they were no match for what the article calls the monsoon-like rain.

Damage beyond the roads

Carriage road surface material washed into the woods. NPS photo.

Hundreds of tons of gravel in the woods meant unprecedented harm to natural resources. Dense tree cover normally shields the forest floor and protects its soil, but on June 9 the rush of water stripped soil from tree roots and washed away vegetation, leaving trees more open to disease and drought.

The Maple Springs Trail

The Maple Springs Trail, which historic documentation dates possibly to the late 1800s, runs through a gorge and gave access to Hemlock Bridge, the Giant Slide Trail and the Sargent Mountain South Ridge Trail. Storm water washed out sections once lined with fine stonework such as steps and walls. By November 2021 it was the last storm-damaged carriage road or trail still closed. Staff, volunteers and Friends of Acadia partners visited to assess it and discuss strategy.

Park staff discuss the trail damage from an intact section. NPS photo.

Because climate change is bringing heavier and more frequent rain, managers considered three options:

• relocate the trail out of the gorge, avoiding costly replacement of features that future storms might wash out;
• rebuild it as it was and keep up with future storm damage, preserving the hike through the gorge;
• abandon the trail and send visitors to nearby trails that reach the same places without the gorge.

A rough estimate put the cost of simply stabilizing the trail with a passable replacement at approximately $750,000, with deeper assessments to come.

Getting back to use

The first goal was to repair the carriage roads for recreation, since 2021 brought record visitation after the pandemic and demand from hikers, bikers and horse riders was high. The Eagle Lake loop was already closed that day for a planned construction project. Crews spread what material stockpiles they had, and when those ran low the park sought emergency relief funding and hired contractors for more material and help.

Red areas on the map show significant damage from the June 9 storm. NPS image.

What next

The carriage roads have largely reopened, but how to protect them and the surrounding forest in future is unsettled. The park is adapting cloud-based GIS technology normally used for wildland fire to document damage and is consulting science and engineering partners. Its original drainage handles typical rain safely, but a warming climate is making storms like June 9 more frequent and intense, so the team is weighing larger drainage. It is also considering temporary fencing, which may be unsightly, to prevent more damage until restoration is done, and long-term forest monitoring plots to track the effect of soil loss.

Sources

• National Park Service, Acadia National Park, “Road to Recovery? Park Staff Assess and Repair Storm Damaged Historic Carriage Roads and Trails”: https://www.nps.gov/articles/000/storm-damage-to-roads-and-trails.htm; rewritten in hubnx's own words.