Gov. George Deukmejian has proclaimed a state of emergency for storm-battered Santa Barbara County and the City of Ventura to allow residents of the area to qualify for state disaster relief. Deukmejian last Thursday made the declaration for Los Angeles, Orange and San Diego counties. He said Southern California has suffered an estimated $49.4 million damage from the storm. The governor also asked President Reagan to make a similar federal declaration for the areas. Deukmejian's declaration is the necessary legal requirement for the state to authorize mutual aid and paves the way for property tax relief for victims of the storms. It is also a requirement before a federal declaration.