(1) A comprehensive plan may include additional elements, items, or studies dealing with other subjects relating to the physical development within its jurisdiction, including, but not limited to:

(a) Conservation;

(b) Solar energy.

(2) A comprehensive plan may include, where appropriate, subarea plans. Subarea plans must be consistent with the comprehensive plan.

(3) The department recommends that counties and cities give strong consideration to including elements on the following within comprehensive plans:

(a) Environmental protection (including critical areas);

(b) Natural resource lands (where applicable);

(c) Design;

(d) Historic preservation;

(e) Natural hazard reduction.