The regulation of development along watercourse is based upon the delegation of regulatory authority from the State to the City for the purpose of managing flooding and floodplain areas under A.R.S. Section 48-3609 and 48-3610. This statutory authority focuses on the hydrological and public safety aspects of floodplain management. State authority is separately delegated to the City under A.R.S. Section 9-462, which authorizes the regulation of land uses and structures under the City's zoning codes. This statutory authority provides for broader regulation of floodplain areas to achieve community aesthetic, cultural and resource preservation goals.
The initial City direction for regulation of watercourses was the adoption of the Interim Watercourse Improvement Policy (IWIP) by the Mayor and Council on June 27, 1988. The IWIP contains specific policies that encourage the preservation of natural watercourses and the design of landscaped, natural-appearing channels. The IWIP also contains policies restricting the use of concrete for bank protection and channelization. The IWIP continues to apply to watercourses that are not otherwise subject to WASH or ERZ regulations.
The fundamental policy direction of the City was restated in Resolution 15269, adopted on April 2, 1990:
"The Mayor and Council find that protection and preservation of natural drainage systems should be the primary emphasis of City stormwater management efforts. Nonstructural solutions to flooding hazards shall be the preferred strategy over structural solutions."
The implementation of this fundamental policy direction in the management of watercourses and floodplains has been established by ordinances, resolutions, administrative interpretations, and development standards including: Chapter 26 of the Tucson Code, the Floodplain and Erosion Hazard Management regulations; the adoption of the Environmental Resource Zone (ERZ) by Ordinance 7450 on July 3, 1990 as an overlay zone, LUC § 2.8.6; adoption of the Watercourse Amenities, Safety and Habitat (WASH) regulations by Ordinance 7579 on March 25, 1991, Tucson Code, Chapter 29, Article VIII, approval of further phases of the Tucson Stormwater Management Study (TSMS) and by adoption of the Floodplain, WASH, and environmental Resource Zone (ERZ) Standard (Development Standard 9-06) by Resolution 20505 on November 6, 2006.