(a)   General. Subdivisions shall be planned to take advantage of the topography in order to utilize the natural surface drainage, to economize in the construction of sewers, to reduce the amount of grading, and to minimize destruction of trees and top soil. The natural features and other distinctive characteristics of the site shall be integrated into the plan to create functional variations in the neighborhood and more attractive building sites.
   (b)   Topography and Streets. The subdivision shall be planned so that as many lots as possible will be above the street grade. On irregular topography, streets shall be designed to avoid extensive cuts and fills and to comply with grading standards hereinafter established for private driveways and yards as well as for the streets. Streets approximately parallel to contour lines shall be adjusted so that the lots on one side of the street will not be excessively below the street grade.
   (c)   Drainage. The subdivision shall be designed, particularly land of very gentle slopes, to take every advantage of natural grades so that all the land can be satisfactorily drained without excessive grading. Unless water courses or drainage ways are enclosed, the design shall be adjusted so that rear lot lines are approximately parallel to the natural or straightened course, and only where such a design is not possible, may side lot lines be arranged parallel to an open drainage course. Easements for drainage ways and low-lying areas which are subject to flooding may be included as part of a lot but shall not be used as a building site or included in calculating the required lot area or width.
   (d)   Natural Features. Natural features, brooks, lakes, hilltops, and other focal points within, and distant views outside the subdivision shall be integrated in the design to obtain natural variations and interest in each neighborhood. Trees, top soil and other natural resources shall be preserved and utilized in the development of the subdivision.