1. In a county whose population is less than 700,000, the provisions of this chapter do not apply to the retention or detention of developed stormwater flow for the purpose of flood control or stormwater management if:
(a) The governing body of the county or city requires such retention or detention as a condition of the approval of a development pursuant to NRS 278.010 to 278.630, inclusive; and
(b) Such retention or detention does not impair the predevelopment recharge of the relevant sources of groundwater or the offsite predevelopment flow of the relevant sources of surface water.
2. As used in this section, “developed stormwater flow” means the increase of surface stormwater runoff created by or attributable to the construction of man-made impervious surfaces as part of the development of land.