Colusa County Municipal Code Art. VIII Flood Resistant Development

(Ord. No. 822, Exh. A)

In addition to the subdivision provisions in Appendix G[1], attached to the ordinance codified in this chapter, the following requirements apply:

(a) In zones AH and AO, adequate drainage paths shall be provided to guide floodwater around and away from proposed structures.

(b) When fill will be placed to support buildings, the fill shall be placed in accordance with the building code and approval of the subdivision shall require submission of as-built elevations for each filled pad certified by a licensed land surveyor or registered civil engineer.

[1]

Editor's Note: Ord 822, Appendix G is included as an attachment to this title.

(Ord. No. 822, Exh. A)

In addition to the site improvement provisions in Appendix G, attached to the ordinance codified in this chapter, the requirements of this section shall apply.

(a) Limitations On Placement of Fill. Where the placement of fill is permitted by the building code, Appendix G, or these regulations, fill shall be designed to be stable under conditions of flooding including rapid rise and rapid drawdown of floodwaters, prolonged inundation, and protection against flood-related erosion and scour. In addition to these requirements, when intended to support buildings and structures, fill shall comply with the requirements of the building code. The placement of fill intended to change base flood elevations, change floodway boundaries, or change boundaries of flood hazard areas shown on FIRMs shall be subject to the requirements of Section 104-2 of Appendix G.

(b) Nonstructural Fill or Alteration of Sand Dunes in Coastal High Hazard Areas (Zone V/VE) and Coastal A Zones. Nonstructural fill or alteration of sand dunes in coastal high hazard areas (zone V/VE) and coastal A zones shall be permitted only when authorized by appropriate federal, state or local authorities. Where permitted, such fill or alterations shall comply with the following, as applicable:

(1) Minor grading and the placement of minor quantities of nonstructural fill shall be permitted for landscaping, for drainage purposes under and around buildings, and for support of concrete slabs used for parking, floors of enclosures, landings, decks, walkways, and similar uses.

(2) Nonstructural fill with finished slopes that are steeper than one unit vertical to five units horizontal shall be permitted only when an analysis prepared by a qualified registered design professional demonstrates no harmful diversion of floodwaters or wave runup and wave reflection that would increase damage to adjacent buildings and structures.

(3) Alteration of sand dunes shall be permitted only when an engineering analysis demonstrates that the proposed alteration will not increase the potential for flood damage.

(4) Sand dune construction and restoration of sand dunes under or around elevated buildings are permitted without additional engineering analysis or certification of the diversion of floodwater or wave runup and wave reflection when the scale and location of the dune work is consistent with local beach-dune morphology and the vertical clearance is maintained between the top of the sand dune and the lowest horizontal structural member of the building.

(c) Other Site Improvements in Coastal High Hazard Areas (Zone V/VE) and Coastal A Zones. Development and site improvement activities other than buildings and structures, where located in coastal high hazard areas (zone V/VE) and coastal A zones, shall be permitted only when authorized by appropriate federal, state or local authorities. In addition, development and site improvement activities shall be permitted when located outside the footprint of, and not structurally attached to, buildings and structures and when analyses prepared by qualified registered design professionals demonstrate no harmful diversion of floodwaters or wave runup and wave reflection that would increase damage to adjacent buildings and structures. Such development and site improvement activities include but are not limited to:

(1) Bulkheads, seawalls, retaining walls, revetments, and similar erosion control structures.

(2) Solid fences and privacy walls, and fences prone to trapping debris, unless designed and constructed to fail under flood conditions less than the base flood or otherwise function to avoid obstruction of floodwaters.

(3) On-site sewage treatment and disposal systems, including mound systems.