For major watercourses with base flood peak discharges of two thousand cfs or greater, the following building setbacks shall be required where approved bank protection is not provided:
A. Along the following major natural watercourses, where no unusual conditions exist, a minimum (default) building setback shall be provided at the time of the development, unless an alternative setback is determined by an engineering analysis, prepared by an Arizona registered civil engineer, based on ADWR standards or other applicable engineering methods, which establishes acceptable safe limits for the development and is approved by the chief engineer.
B. Along natural channels where no unusual conditions exist (such as a pronounced channel curvature), the default building setback for erosion hazard protection shall be:
1. A distance of five hundred feet along the Santa Cruz River, Rillito Creek, Pantano Wash, Tanque Verde Creek, San Pedro River, and the Canada del Oro Wash;
2. A distance of two hundred fifty feet along major watercourses with base flood peak discharges greater than ten thousand cfs;
3. A distance of one hundred feet along all major watercourses with base flood peak discharges of ten thousand cfs or less, but more than five thousand cfs; and
4. A distance of seventy-five feet along all other major watercourses with base flood peak discharges of five thousand cfs or less, but more than or equal to two thousand cfs.
C. Along major natural watercourses where unusual conditions do exist that may increase or decrease the required erosion hazard setback, building setbacks shall be established on a case-by-case basis by the chief engineer using the standard adopted by the ADWR or other applicable engineering methods which establish safe limits for the development. Unusual conditions include but are not limited to historical meandering of the watercourse, large excavation pits, poorly defined or poorly consolidated banks, natural channel armoring, proximity to stabilized structures such as bridges or rock outcrops, and changes in the direction, amount and velocity of the flow of waters within the watercourse.
D. When determining building setback requirements, the chief engineer shall consider the danger to life and property due to existing flood heights or velocities and historical channel meandering.
E. For constructed channels, structural bank protection to prevent erosion is required for major watercourses with base flood peak discharges of more than two thousand cfs unless a written waiver of the requirement is granted by the chief engineer. A waiver of the requirement for structural bank protection may be granted based on an acceptable engineering study, which has been prepared and sealed by an Arizona registered civil engineer, demonstrating an appropriate building setback for an earthen channel, based on soil and natural flow conditions.
(Ord. 2010-FC5 § 1 (part), 2010; Ord. 2005 FC-2 § 2 (part), 2005; Ord. 1999 FC-1 § 1 (part), 1999; Ord. 1988 FC-2 Art. 12 (A), 1988).