In the preparation of the State or local forest conservation programs, the State and local authorities shall provide for the granting of variances to the requirements of this subtitle, where owing to special features of a site or other circumstances, implementation of this subtitle would result in unwarranted hardship to an applicant. Variance procedures adopted under this section shall: Be designed in a manner consistent with the spirit and intent of this subtitle; and Assure that the granting of a variance will not adversely affect water quality.