Each block of subdivision or part thereof which has access to a storm sewer shall be planned and graded so that the surface water of each lot will not be discharged onto adjoining lots and will drain into a storm sewer system. Where necessary, grading may be extended into lot areas to provide suitable house sites. Tree lawns, turf gutters and other graded areas shall be fertilized, seeded and mulched to assure proper growth of turf. Newly graded areas shall be otherwise protected against erosion and siltation by artificial means where necessary.