Chapter 18.85 OVERLAY ZONE – NATURAL AREAS, PARKS AND FLOODPLAINS (OFPG) This chapter is included in your selections. Sections: 18.85.010 Purpose. 18.85.020 Floodplain – Parks – Greenway overlay zone (OFPG). 18.85.030 Safe harbor protection of wetland and riparian areas. 18.85.040 Compensation for area losses due to setback requirements.