The board of supervisors may restrict the use of, or close, any county highway whenever the board considers such closing or restriction of use necessary:
(a)
For the protection of the public.
(b)
For the protection of such county highway from damage during storms.
(c)
During construction, improvement or maintenance operations thereon.
No liability shall attach to the county, or to the board of supervisors, for the restriction of use, or closing, of any county highway for the above public purposes.
This section does not constitute a change in, but is declaratory of, the pre-existing law.