The requirements outlined in subsections (a) through (i) below apply to all improved or unimproved land areas or lands divided for the purpose of financing, sale or lease, whether immediate or future, the boundaries of which have been fixed by or proposed to be fixed by a recorded plat and which are located in flood hazard areas. These regulations shall also apply in instances where development plans are required by chapter 23B, Tucson Unified Development Code.
(a) Suitability of Land:
(1) Land physically unsuitable for subdivision or development because of severe flooding, drainage or erosion problems endangering life or property shall not be subdivided or developed unless it can be developed in such a way so as to alleviate those problems.
(2) Additionally, if a subdivision proposal or other proposed new development is in a floodprone area, any such proposals shall be reviewed, designed and constructed to assure that:
a. All such proposals are consistent with the need to minimize flood and erosion damage within the floodprone area;
b. All public utilities and facilities such as sewer, gas, electrical and water systems are located and constructed to minimize or eliminate flood and erosion damage. Septic systems, whether public or privately owned, shall not be located in such a way as to avoid impairment to them or contamination from them during flooding. Unprotected excavations shall not be permitted so close to any floodplain crossings, utility structures or facilities as to cause or have the potential to cause an adverse effect on such crossings, utilities or similar facilities.
c. Adequate drainage is provided to reduce exposure to flood and erosion hazards.
(3) When planning and designing developments adjacent to, surrounding or affected by watercourses, the owner/developer should conform to policies set forth in the adopted general plan of the city, existing basin management plans, and this chapter. For all basin management areas, the first consideration in approaching alternative drainage design concepts shall be to maintain natural configurations or existing drainage patterns to reduce exposure to flood and erosion hazards as well as promote groundwater recharge. Where natural washes cannot be maintained, a mitigation plan shall be established with emphasis being placed on earthen or naturally appearing channels with landscaping and texture/color added to bank protection materials. The design of earthen channels will be encouraged in order to allow for a more permeable surface which permits reintroduction of the water into the groundwater system, allowing for the reintroduction of native plant species which promotes a natural, partially soil-stabilized system.
(b) Delineation of Areas Subject to Flooding on Plats and Development Plans:
(1) All tentative plats and development plans submitted shall show the location, by survey or photographic methods, of streams, watercourses, canals, irrigation laterals, private ditches, culverts, lakes and other water features, including those areas subject to flooding and/or erosion. The location shall also include the direction and magnitude of any flow, water surface elevations, and the limits of inundation from the base flood.
(2) Identify on the final plans the elevation(s) of the proposed structure(s) and pads. If the site is filled above the BFE, the final lowest floor and grade elevations shall be certified by a registered professional engineer or surveyor and provided to the floodplain administrator.
(3) All tentative plats and development projects in floodprone areas shall be accompanied by conceptual grading plans and conceptual drainage improvement plans included in a drainage statement or a drainage report prepared by a state-registered professional civil engineer, for approval by the city engineer, unless exempted by the city engineer. These reports or statements should include the following:
a. The methods for mitigation of increased urban peak and/or volumetric flood-water runoff or discharge created by the development on-site and to upstream and downstream properties, up to a reasonable location as determined by the approved hydrologic and hydraulic study.
b. The demonstration that the improvements are compatible with the existing upstream and downstream drainage conditions and that any proposed grading and/or grade change will not have an adverse impact on adjacent property.
c. The methods for adequate erosion and sediment control, as approved by the city engineer.
d. The proposed floodplain management methods for floodproofing (existing nonresidential structure only) drainage control, detention, retention, and/or delineating and setting aside floodprone areas which result in mitigating a flood or erosion hazard on the proposed finished pads (elevations determined) and drainage slopes constructed to protect building foundations from runoff waters.
(4) All tentative plats and development plans in floodprone areas shall show proposed grading and improvement for areas which are subject to flooding or erosion or which have poor drainage. Also included will be a description and location of all facilities proposed to be used to alleviate flooding, erosion or other drainage problems, both in the proposed subdivision or development, and downstream and upstream of any watercourse affected by the subdivision or development, whether they are within or outside the project boundaries.
Prior to commencement of any site improvements or grading, a grading plan shall be submitted to the city engineer for review and approval. Detailed improvement plans of storm drains or channel improvements shall also be submitted to the city engineer for review and approval.
(5) All final plats and development plans in floodprone areas shall show limits of the regulatory floodplains, erosion hazard boundaries, and the floodways and floodplains delineated in a surveyable manner and certified by a state-registered land surveyor.
(6) All tentative plats and development plans in floodprone areas of all developments, including manufactured home parks and subdivisions, submitted shall include base flood elevation data. Also included as a general note shall be the drainage area(s) and their respective base flood peak discharges.
(c) Street Design Criteria: Streets required for permanent access shall be designed and paved/constructed so that the flow depths over them do not exceed one (1) foot in depth except at drainage crossings during the base flood peak discharge. At least one (1) paved permanent access shall be provided to each lot over terrain which can be traversed by conventional motor vehicles in times of flooding. Where the streets are also used for flow of stormwater additional safety features may be required by the city engineer. Fill may be used for streets in areas subject to flooding provided such fill does not unduly increase flood heights. Developers may be required to provide profiles and elevation of streets in areas subject to flooding.
(d) Building Sites: Land which contains area within a floodplain shall not be divided or platted for residential occupancy or building sites unless each lot contains a building site, either natural or manmade, which is not subject to flood-related erosion or to flooding by the base flood, provides all weather access to the building pad, and is certified for compaction of fill for pad by an engineer.
(1) In areas subject to flooding where no fill is proposed to be used, the building line shall be located no closer to the floodplain than the edge of the area subject to flooding by the base flood.
(2) In areas where fill is to be used to raise the elevation of the building site, the building line shall be located not less than twenty-five (25) feet landward from any edge of the fill, unless a study prepared by a state-registered professional civil engineer and approved by the city engineer shows that a lesser distance is acceptable.
(3) No fill shall be placed in any floodway; nor shall any fill be placed where it diverts, retards or obstructs the flow of water to such an extent that it creates a danger or hazard to life or property in the area.
(e) Setbacks From Channels: Setbacks shall be established in accordance with the Drainage Standards Manual or city engineer approved studies prepared by a state-registered professional civil engineer. Also see section 26-7 of this chapter.
(f) Rights-of-way for Drainage; Easement Dedication: Whenever a subdivision plat or development plan contains a watercourse which is regulated by this chapter, all right-of-way associated with the watercourses shall be provided and designated "drainageway" or "drainage easement" as determined by the city engineer.
At the discretion of the city engineer, structural solutions to drainage problems will be required.
When structural solutions are necessary, preference shall be given to landscaped natural appearing channels. While improvements to watercouses should be responsive to the environment, existing conditions may prevent or inhibit the desired approach. Examples of such existing conditions include insufficient right-of-way, insufficient runoff carrying capacity in the channel, large erosion potential, existing residences or businesses exposed to flooding during runoff events, and inadequate street conveyance capacity.
The additional land area required for the purpose of widening, deepening, aligning, improving, stabilizing, constructing and allowing for natural meanders so the watercourse will safety convey the base flood peak discharge shall also be included in the drainageway or drainage easement.
(1) If the watercourse is an improved regional watercourse, the drainageway shall include the channel, the channel improvements, and a fifty-foot-wide area measured outward from the front face of the top of the bank protection, for the city or for county flood control district uses.
(2) If the watercourse is an improved major or minor watercourse, the drainageway or the easement shall include the channel, the channel improvements, and necessary maintenance access.
(3) If the watercourse is to remain natural, the drainageway shall contain the boundaries of the regulatory floodplain and necessary maintenance access.
(4) Along regional watercourses and major watercourses where the peak discharge during the base flood is ten thousand (10,000) cubic feet per second or greater, the drainageway shall be dedicated in fee simple to the city.
(5) Along other watercourses, the city engineer shall determine whether it is necessary for the city to have control of the drainageway. If the city engineer determines that public control is necessary, the owner shall dedicate the drainageway in a fee simple or grant an easement.
(h) Utilities: All public and private utilities are to be constructed so as to minimize or eliminate flood damage and shall comply with the provisions of section 26-6.2.
(i) Arizona Revised Statutes (A.R.S.) Section 48-3610 Compliance: The city engineer upon receipt of an application for any development in a floodplain shall advise the Pima County Regional Flood Control District ("district") in writing and provide a copy of the application and any development plan, tentative plat, or a floodplain use permit application within one (1) mile of the corporate limits of the city. The district shall also provide similar development applications to the city which are located within one (1) mile outside of the city. Written notice and a copy of the development plan and/or tentative plat shall be sent to the district no later than three (3) working days after the receipt by the city engineer.
(j) Construction Conformance: All construction including the detention/retention systems (see section 26-10) shall conform to the city engineer approved plans and specifications. Any deviation shall occur only upon prior approval by the city engineer.
(Ord. No. 7407, § 5, 6-25-90; Ord. No. 11396, § 1, 8-9-16; Ord. No. 11801, § 1, 12-8-20)