The San Diego County Board of Supervisors voted 4-0 Wednesday to advance a proposed ordinance change that officials say will help make flood insurance more affordable for residents in unincorporated areas. Supervisors heard the proposed ordinance Wednesday as part of a first reading. A second reading, set for Oct. 9, is needed for formal approval. According to the county Land Use and Environment Group, an updated Flood Prevention Ordinance is needed to meet Federal Emergency Management Agency requirements, increase credits the county earns to lower flood insurance costs for those in the unincorporated regions, and streamline the review process for some development projects.