Incentives. Notwithstanding any contrary provision of this chapter that limits or restricts the maximum unit density of a proposed subdivision, for the permanent preservation in its undeveloped state of not less than 50% of the gross land area of a proposed subdivision, including, but not limited to, active agricultural lands and areas having prime soils or statewide important soils, a thirty-percent increase in the maximum unit density for the zoning district may be approved. The calculation of the incentive is based on the maximum density for a proposed subdivision as determined by the Planning Board pursuant to § 205-7B(10).