It is the intent of this chapter to enable any county to adopt such a retirement, disability and death benefit plan as may be determined upon by the board of supervisors or qualified electors thereof for those officers and employees in the public service whose duties expose them to more than ordinary risks, and in recognition of a public obligation to such officers and employees and to provide a means whereby such officers and employees who become incapacitated in the performance of their duties by injury, sickness, or age, may, without hardship or prejudice, be replaced by more capable officers and employees to the betterment of the public service, and whereby the surviving spouse, or minor children, or dependent parents of any such officer or employee may be provided for upon his death.