ARTICLE XIII. ALLUVIAL FAN AREAS.

SECTION 13.1 DEVELOPMENT IN ALLUVIAL FAN ZONE A

1.  Where alluvial fans have been designated as Zone A’s using the standards contained in the Flood Control District of Maricopa County’s Piedmont Assessment Manual, the following shall apply:

a.  Development within an Alluvial Fan High Hazard area (AFHH), Alluvial Fan Uncertain Flow Distribution Area (AFUFD), and Alluvial Fan Floodway (AAFF) shall be regulated in a manner similar to a floodway. Only major engineering measures as outlined in 44 CFR 65.13 can be used to mitigate the alluvial fan flood hazard in these area.

b.  Development within an Alluvial Fan Zone A (AFZA): shall be regulated in a manner similar to a Zone A riverine floodplain. Development may require an engineered plan.

(1) . Development requirements in these areas shall include:

(a) . Lowest floor elevations;

(b) . Ingress and egress; and

(c) . Non-disruption of the water/sediment system.

(2) . The following shall be consistent with Arizona State Standards:

(a) . Watercourse bank stabilization;

(b) . Lateral Migration and channel degradation; and

(c) . Lateral migration setback allowance may be used for flood damage prevention providing these methods recognize the uncertain distribution of floodwater across the areas.

2.  Where alluvial fans have been designated without use of the Piedmont Assessment Manual, development permitted in other sections of this Regulation is permitted in Alluvial Fan Areas with an A Zone designation as defined in Section 11.2 of this Regulation.

3.  In order to control erosion and preserve the natural and beneficial functions of the floodplain, removal of vegetation shall be the minimum necessary for development.

4.  The applicant shall submit a plan of development prepared by an Arizona Registered Professional Engineer. The plan shall include engineering analysis to mitigate all hazards associated with Alluvial Fan flooding including inundation, ground erosion, scour around structures, debris and sediment flow and accumulation in addition to aggradation and degradation of conveyance systems. The plan shall also include building pad and lowest floor elevations.

5.  Nonresidential buildings are permitted in Alluvial Fan Areas with a Zone A designation provided the lowest floor is either elevated or, together with the building contents and utilities, is floodproofed, using flood resistant materials, up to one (1) foot above the base flood elevation with watertight walls substantially impermeable to the passage of water and structural components and utilities having the capacity of resisting the effects associated with a base flood, or the design shall meet the provisions of Section 10.2.10.

6.  Mobile/manufactured homes and recreation vehicles shall be permitted subject to the provisions of Section 10.2.6.

7.  If fill material is to be used to elevate buildings, such fill material shall meet the requirements of Section 10.2.7.

8.  Fill material for purposes other than solid waste landfills shall meet the requirements of Section 10.2.8.

9.  All new construction and substantial improvements that fully enclose areas below the lowest floor that are usable solely for parking of vehicles, building access or storage in an area other than a basement and which are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. The applicant shall provide an Elevation/Floodproofing Certificate by an Arizona Registered Professional Engineer certifying that the flood proofing requirement has been met, or the design shall meet the provisions of Section 10.2.10.10. Whenever an elevation or floodproofing certificate is required, a separate certificate shall be furnished for each building.

SECTION 13.2 DEVELOPMENT IN ALLUVIAL FAN ZONE AO.

1.  In Alluvial Fan Areas with an Zone AO designation, new or substantially improved residential buildings shall have the lowest floor elevated at least one foot above the flood depth at the high point of the natural building pad.

2.  The applicant shall make adequate provisions to maintain all natural and improved drainage or flood conveyance systems.

3.  The applicant shall submit a plan of development acceptable to the Floodplain Administrator. The plan may include engineering analysis to mitigate all hazards associated with Alluvial Fan flooding including inundation, ground erosion, scour around structures, debris and sediment flow and accumulation in addition to aggradation and degradation of conveyance systems. The plan shall also include building pad and lowest floor elevations.

4.  New or substantially improved nonresidential buildings in Alluvial Fan Areas with an Zone AO designation, shall have the lowest floor either elevated or, together with the building contents and utilities, floodproofed, using flood resistant materials, at least one foot above the flood depth with watertight walls substantially impermeable to the passage of water and structural components and utilities having the capacity of resisting the effects associated with a base flood or the design shall meet the provisions of Section 10.2.11.

5.  Mobile/manufactured homes and recreation vehicles shall be permitted subject to the provisions of Section 10.2.5.

6.  All new construction and substantial improvements that fully enclose areas below the lowest floor that are usable solely for parking of vehicles, building access or storage in an area other than a basement and which are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. The applicant shall provide a Floodproofing Certificate by an Arizona Registered Professional Engineer certifying that the floodproofing requirement has been met, or the design shall meet the provisions of Section 10.2.10.

7.  If fill material is to be used to elevate buildings, such fill material shall meet the requirements of Section 10.2.7.

8.  Fill material for purposes other than solid waste landfills shall meet the requirements of Section 10.2.9.

9.  All new residential buildings and substantial improvements to residential buildings shall have an elevation certificate which may be completed by District staff as approved by the Floodplain Administrator.

10. Whenever an elevation or floodproofing certificate is required, a separate certificate shall be furnished for each building.