The problem is particularly evident in Tranquillity, officials say, where a levee has weakened because of the high flows of the San Joaquin River. Several county agencies and water districts are working to repair the threatened breach and prepare for evacuations if necessary.
County officials say the that high water levels at local reservoirs along with recent storms has prompted the high water releases.
By declaring a local emergency, the county will be able to seek support from the State of California if costs run high.
The Fresno County Board of Supervisors will consider ratification of the action at their meeting next Tuesday.