Flooding Forces Thousands From Homes in Northern California (PHOTOS, VIDEO)

At a news conference Wednesday morning San Jose Mayor Sam Liccardo called on those who have been evacuated to remain in safe zones, saying that the water in the affected area is not safe. As the flow ran through neighborhoods, it collected sewage, rubbish, household detergents and engine fuel.

"We are urging people not to return to their homes in those mandatory evacuation areas," the mayor said. "The water is not safe. There is contamination in this water and the contamination runs the gamut."

Before being transferred by bus to shelters, hundreds of rescued residents were taken to a decontamination area where they were rinsed off to avoid illness from contaminated water.

The flooding was caused by a series of large storms that resulted in the overflow of the Anderson Reservoir which feeds Coyote Creek, the longest creek in Santa Clara County. The reservoir became full Saturday morning, but it was not until another heavy rainfall Sunday night and Monday morning that it began pouring thousands of gallons of water an hour into Coyote Creek.

​According to assistant city manager Dave Sykes, the flooding from the overflow of the Anderson Reservoir is "a 100-year event."

​City officials were not prepared for the first major flooding that came into the Rock Springs area, as water in Coyote Creek was flowing below the capacity of the channel where the creek burst its banks.

"We weren't expecting to have issues at Rock Springs for many, many hours, and we certainly weren't expecting Rock Springs to be the first place we had issues." Sykes told reporters.

​Many residents were shocked that they were not informed in advance about the potential of severe flooding, and the possible scope of the devastation.

"If the first time a resident is aware that they need to get out of a home is when they see a firefighter in a boat, clearly something went wrong," the mayor said.

​San Jose firefighters, chest-deep in water, rescued residents trapped in homes and in trees, including homeless people at an encampment near Coyote Creek.

​"This is the worst flooding and water-rescue situation that I personally have participated in," San Jose Fire Department Capt. Mitch Matlow told reporters.

​Temporary shelters were set up at two community centers and two high schools, where hundreds of residents stayed overnight.

​Residents in 14,000 households were forced to flee their homes, and another 36,000 were put under a voluntary evacuation order late Tuesday night, as the flooding shut down the Route 101 freeway, a key commuter artery into Silicon Valley, in both directions at about 10:45 p.m.

​By 1 a.m. Wednesday, the water district had repaired the canal that caused the freeway flooding, by creating a temporary dam.

​Route 101 and other major roads closed overnight were reopened by 11 a.m. on Wednesday, according to the California Highway Patrol.

​Liccardo announced a relief fund set up through his office and the Silicon Valley Community Foundation, saying that cash would be more helpful than donations of items.