Waters have begun to recede after historic flooding in Northern California left towns along the Russian River land-locked.
Floods isolated the towns of Rio Nido, Guerneville, Monte Rio and Cazadero, inundating roads around those communities, according to the Sonoma County emergency operations centre.
Evacuation orders and "shelter-in-place" advisories remained in effect for thousands of residents on Thursday as floodwaters were receding more slowly than anticipated because of high tides.
Officials said they hoped to allow displaced residents to return home on Friday, once inspectors had a chance to check the safety of bridges and remove hazards such as downed power lines.
County officials had ordered some 3,600 people evacuated on Tuesday as the Russian River overran its banks, sending floodwaters to the rooftops of homes and submerging cars in and around the town of Guerneville, about 70 miles (112 km) north of San Francisco.
The river was expected to drop below flood level by 3am local time on Friday.
About 3,000 properties were damaged by flooding, according to local officials.
An estimated 3,000 to 4,000 residents were left stranded in communities isolated by high water, county officials said.
In a Facebook post on Wednesday morning, the Sheriff's Office said: "Good morning. Guerneville is officially an island. Due to flooding all roads leading to the community are impassable. You will not be able to get into or out of town without a boat today."
The Russian River had risen to over 13 metres by Wednesday afternoon, and was set to peak at 14 metres, its highest level in more than 20 years, according to the weather service.
Brian Gipson, director of marketing at the Farmhouse Inn hotel near Guerneville, said: “I've been here 30 years. I've never seen it rain so hard.”
The nearby city of Santa Rosa got 4.64 inches of rain, smashing its previous record of 1.56 inches in a single storm, according to National Weather Service data.
Sonoma County Sheriff Mark Essick said on Twitter: “Guerneville is land-locked. You cannot get into or out of town. All roads leading to the community are flooded."
The Sonoma County Sheriff's Office posted a video on the department's Facebook page of brown, muddy water rising above a road and flooding homes.
The evacuation orders affect about two dozen communities stretching dozens of miles along the river, with a population of more than 4,500.
Residents got around flooded towns in kayaks.
A California Highway Patrol helicopter landed on a dry section of street in Guerneville to evacuate a woman with a serious medical issue, the sheriff's office reported.
About 200 miles (320 km) north, a man drowned in a separate flood on Wednesday in the Northern California town of Ferndale, the Humboldt County Sheriff's Office said in a statement.
California Governor Gavin Newsom issued an emergency declaration on Thursday for five Northern California counties to help them recover from the flooding. The state is experiencing one of its wettest winters in decades.
