The trimming or removal of natural vegetation in a strip paralleling the shoreline and extending 35 feet inland at all points along the normal high-water mark of any shoreline shall be limited in accordance with the following provisions: natural vegetation may be replaced by artificial planting that is equally effective in controlling erosion and the flow of effluent but is not to exceed 30% of the length of the strip as measured along the normal high-water mark. These provisions shall not apply to the removal of dead, diseased or damaged vegetation.