(a) In a subdivision, retainer walls or bulkheads on all property abutting on canals or waterways shall not be required, except at the option of the subdivider, but, if constructed, they shall be designed and planned to meet the approval of the city. When retainer walls are not constructed, the subdivider shall slope all lots or parcels abutting on canals, rivers or waterways at a grade not to exceed eight degrees. All slopes shall be grassed from the high-water level to the crown of the slope.

(b) If retainer walls or bulkheads are constructed, the applicant shall provide written verification of compliance with, or waiver from, any and all requirements of the state department of environmental protection or its successor departments/agencies and, where applicable, the U.S. Army Corps of Engineers. Written verification shall consist of either the appropriate construction permit or correspondence waiving all permitting requirements.