A succession of storms that swept across the region in the past week left hundreds of homes without power and parts of major roads obstructed by fallen trees and branches as emergency crews and volunteer firefighters rushed to clear roads and barricade homes during the first major storm system of the winter season.

The final two storms, part of a three-part system that grew in strength between Wednesday and Sunday, dumped an average of eight and a half inches on parts of the county over the weekend.

“It was pretty much nonstop,” said Tim Thompson, battalion chief of the county’s fire department, referring to reports of downed trees that led to closures on a handful of roads across the county, including sections of Point Reyes-Petaluma Road near Point Reyes Station, Ridgecrest Boulevard on Mount Tamalpais and Highway One near Tomales. 

Part of Vision Road in Inverness remained closed as of Wednesday afternoon, and officials with the Department of Public Works are working to remove a five-foot-wide redwood tree from Fairfax-Bolinas Road, near Alpine Dam. The road will remain closed until the weekend, according to the county dispatch center.

The “pineapple express” of rain and wind that toppled trees and downed power lines was part of what weather specialists call an “atmospheric river,” a storm system driven by southern air currents that occasionally unleashes downpours on the Bay Area and other parts of the West Coast.

In Muir Woods, a National Park Service warehouse sustained flood damage after a three-and-a-half-foot-wide tree collapsed a portion of its roof and punctured a water line, Yvette Ruan, chief of fire and emergency management with the Golden Gate National Recreation Area, said.

Minor flooding was reported in some low-lying areas—including in Lucas, Ross and San Geronimo Valleys—where emergency officials used sandbags to protect homes from water rushing from storm drains, Mr. Thompson said.

In Woodacre, some properties along Hill Avenue and Castro Street were submerged in water spilling over from the Papermill Creek. The Nicasio Reservoir also overflowed over the weekend, according to reports.

The storm cut power to hundreds of homes across West Marin, though the highest concentration of outages was reported in Sonoma and Napa Valleys, according to Pacific Gas and Electric Co. In Inverness, utility workers and groups of contractors restored power early Sunday to more than 750 homes. 

Power outages also affected more than 350 homes early Sunday in Point Reyes Station and Marshall, according to the utility, which saw more than 315,000 customers across the Bay Area lose power between Thursday and Sunday.

Still, despite the reach of a five-day system that engulfed the Bay Area and outlying counties, “this really wasn’t much of a storm,” said Mr. Thompson, whose 30-plus years with the county’s fire department has seen crippling winter weather. “In the grand scheme of things,” he said, “all it was, was a decent rain—we didn’t have the wind.”

Officials with the Marin Municipal Water District measured its level after the storm at more than 15 feet below capacity. Alpine Lake had risen to slightly less than four feet from capacity. Bon Tempe Lake and Nicasio Reservoir were at capacity as of Sunday.

The storm also brought into question the condition of a portion of Olema Hill where part of a lane collapsed nearly two years ago and is still not repaired, with stop signs bringing traffic to a halt along a steep stretch of the road. County officials believe a continued lag in the construction process—attributed in part to a thorough environmental review by the state’s Department of Transportation—could result in further erosion, Liza Crosse, an aide to Supervisor Steve Kinsey, said.

“It’s extremely frustrating for all of us,” she said, adding that pending approval of environmental studies from the state’s Office of Historic Preservation may further slow the process, which qualified for federal funding.