Two people were killed yesterday and hundreds were stranded or evacuated as Arizona suffered its fourth 100-year flood in 23 months.

Officials said they were concerned about pressure on Stewart Mountain Dam, about 20 miles northeast of Phoenix and the effect of water releases on bridges over the normally dry Salt River, which splits the metropolitan Phoenix area.

Earlier yesterday Gov. Bruce Babbitt declared a state of emergency for Maricopa, Gila and Yavapai counties, permitting the release of $100,000 in state funds to help battle the flooding.

Two bodies were found in Granite Creek at Prescott, about 90 miles northwest of Phoenix, after witness said the driver of a car with two occupants disregarded a barricade and plunged off a bridge.

A 100-year-flood is one so severe that statisticians predict it will occur only once every 100 years. Similar floods occured in Arizona in March and December 1978 and in January 1979.

Meanwhile, a Pacific storm driven by high winds battered southern California with heavy rain for a third day, triggering flash floods and mudslides.

Witnesses said a woman was swept away by a wall of water that also carried off cars and debris in the Hollywood Hills area of the city. The woman, who was not identified, was later found bruised, but apparently not seriously injured, fire officials said.

The nearby coastal city of Santa Monica was hit by heavy flooding, and freeways and intersections throughout the area were blocked.