The Zoning Board of Appeals statement may include recommendations as to desirable revisions to be incorporated in the final site plan, of which conformance with shall be considered a condition of approval. If the preliminary site plan is disapproved, the Zoning Board of Appeals' statement shall contain the reasons for such findings. In such a case, the Zoning Board of Appeals may recommend further study of the site plan and resubmission of the preliminary site plan to the Zoning Board of Appeals after it has been revised or redesigned. No modification of existing stream channels, filling of lands with a moderate to high susceptibility to flooding, grading or removal of vegetation in areas with moderate to high susceptibility to erosion, or excavation for and construction of site improvements, shall begin until the developer has received preliminary site plan approval. Failure to comply shall be construed as a violation of this Zoning Law and, where necessary, final site plan approval may require the modification or removal of unapproved site improvements.