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When the banks are stabilized to the level of the base flood (plus an appropriate freeboard) the setback to structures shall be a minimum of twenty (20) feet for access and maintenance. When access and maintenance easements are not required by the city engineer, the minimum setback may be reduced to ten (10) feet at the discretion of the city engineer. When banks are not stabilized, the setback to structures shall be as calculated from guidelines in the Standards Manual.
(Ord. No. 7407, § 5, 6-25-90)
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)
All new and replacement manufactured homes, additions to existing manufactured homes or additions to existing manufactured home parks or subdivisions, and recreational vehicles which are left on a site for longer than one hundred eighty (180) days and are not licensed and ready for highway use shall be securely anchored to an adequately anchored foundation system to resist flotation, collapse or lateral movement. Methods of anchoring may include but are not to be limited to use of over-the-top or frame ties to ground anchors. The provisions of this paragraph and subsection (a)(1) do not apply to recreational vehicles which are on a site for fewer than one hundred eighty (180) days and which are fully licensed and ready for highway use. A recreational vehicle is ready for highway use if it is on its wheels or jacking system and is attached to the site only by quick disconnect type utilities and security devices and has no permanently attached additions.
(a) General Provisions:
(1) All newly placed, repaired or replacement manufactured homes, additions to existing manufactured homes and recreational vehicles, where applicable, shall be placed and elevated so that the bottom of the structural frame or the lowest point of any attached appliances, whichever is lower, is at or above the regulatory flood elevation.
(2) A manufactured home which has incurred substantial damage by a flood may be repaired or may be replaced by another manufactured home. If the damage is less than fifty (50) percent of its value before the flood, it may be repaired or may be replaced by another manufactured home.
(3) All public and private utilities shall be located and constructed so as to minimize or eliminate flood damage.
(4) A plan for evacuating residents of all manufactured home parks or subdivisions located within floodprone areas shall be developed and filed with and approved by the county department of emergency services, disaster planning and preparedness. A copy of the approved plan shall be submitted to the city engineer's office for record.
(b) Certification: Certification by a state-registered professional civil engineer that the installation of a manufactured home meets all of the requirements of this section is required. Such certification shall be provided by the person installing the manufactured home, the owner, the developer of the manufactured home park or subdivision, or an agency regulating manufactured home placement, whichever is deemed appropriate by the city engineer. Certification of elevations listed on the floodplain use permit shall be prepared by a state-registered land surveyor and provided to the city engineer prior to habitation of the structure in the form of an Elevation Certificate prepared by FEMA for Building Under Construction stage or at Final Construction.
(Ord. No. 7407, § 5, 6-25-90; Ord. No. 11396, § 1, 8-9-16)
(a) When deemed necessary by the city engineer, flood detention/retention systems shall be employed in lieu of or in combination with structural flood control measures to reduce flooding potential or restrict it to a level no greater than pre-platting and/or pre-development conditions. The amount of reduction is stipulated within the Stormwater Detention/Retention Manual, and subsequent amendments, which was approved for use by the city engineer as development standard in the Technical Standards Manual section 4-03.0.
All proposed residential net densities of three (3) or more units per acre and all proposed commercial and industrial developments greater than one (1) acre in size shall provide some method of peak and volumetric runoff reduction. The amount of reduction is stipulated within the Stormwater Detention/Retention Manual, and subsequent amendments, which was approved for use by the city engineer as development standard in the Technical Standards Manual section 4-03.0.
(b) Basins which have been identified by the city engineer as unsuitable for additional development because of the high probability of increased flooding, or flooding of existing improvements or properties not previously studied, may be developed further only upon the incorporation of adequate detention/retention systems as reviewed and approved by the city engineer. The following criteria shall be considered:
(1) If a drainage basin is determined to be a balanced basin, detention or retention systems shall be employed. These systems shall maintain the existing balance within the basin by limiting the flood peak discharges from the site to values no greater than pre-developed conditions.
(2) If a drainage basin is determined to be a critical basin where potential flood problems currently exist, detention or retention systems shall be employed. The purpose of such systems in a critical basin shall be to reduce the potential flood hazard through the detention or retention of storm runoff in fair and equitably apportioned increments.
(c) The design of a detention or retention system, as reviewed and approved by the city engineer, shall include consideration of the degree of existing development within the basin and the capacity of the downstream drainage facilities. The systems will be designed with strict conformance to the public's health, safety and welfare. The effects of recharging storm runoff and possible pollution of the groundwater shall be evaluated for all systems employing infiltration systems, such as dry wells, in order to prevent contamination of the groundwater aquifer.
(d) Structural flood control measures may be utilized in conjunction with or in place of a detention/retention system if it can be clearly demonstrated that such measures shall accomplish, with an equal or greater degree of success, the function of such system, which includes preservation of the water and sediment equilibrium in the affected watercourse and mitigation of the environmental impacts. Appropriate structural flood control measures, such as channelization to a logical conclusion downstream of the proposed development and/or improvements to existing off- site flood control systems within the affected drainage or stream reach, shall be completed in accordance with plans reviewed and approved by the city engineer.
(e) A fee may be utilized in place of a detention/retention system, at the request of affected persons, when it can be clearly demonstrated that detention at the site does not provide off- site flood relief due to the parcel size, location within the drainage basin, or other factors. The fees collected will be used to construct public flood control improvements which will be designed to mitigate the potential damage of floodwaters associated with the property from which the fees are contributed. In balanced and critical basins, and where development is less than three (3) units to the acre, use of a fee system may be considered appropriate in lieu of a detention system in order to preserve the natural drainage patterns. The amount of the fee shall be proportional to the cost of the otherwise required detention/retention system.
(f) The city engineer shall prepare and retain for public inspection and use an official map designating critical and balanced basins within the city.
(g) All repairs and maintenance of detention/retention systems shall conform to the city engineer approved design drawings and specifications. Any deviation shall occur only if approved 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)
(a) Except as otherwise provided in these regulations, it shall be unlawful for any person to establish, erect, alter or relocate a use or structure in the regulatory floodplain or an erosion-prone area as described in section 26-11.1(2) without first obtaining a floodplain use permit from the city engineer.
(b) It shall be unlawful for any person to perform any grading operation in or alteration of any watercourse in violation of this chapter. Without written authorization from the city engineer, any such act, including excavation of any kind, is a public nuisance per se and may be abated, prevented or restrained by action of the city.
(c) No license, permit or other similar approval for any development which would be in conflict with the provisions of this chapter shall be issued by any department, official or employee of the city; and any such license, permit or approval, if issued in conflict with the provisions of this chapter, shall be considered null and void.
(Ord. No. 7407, § 5, 6-25-90)
The city engineer shall review all of the following applications for compliance with these regulations:
(1) Applications for development within a regulatory floodplain and erosion hazard areas.
(2) Applications for development requiring building permits within an area five hundred (500) feet on either side of delineated floodway boundaries in floodplains having watersheds larger than thirty (30) square miles, or two hundred fifty (250) feet on either side of watercourses having watersheds between ten (10) and thirty (30) square miles, and one hundred (100) feet on either side of watercourses having watersheds less than ten (10) square miles shall be reviewed. If, within twenty (20) working days, the city engineer determines that the location is subject to flood or erosion hazards, an application for a floodplain use permit pursuant to section 26-11.2 is required. Property owners may request a preliminary determination from the city engineer for property in such areas prior to any application for actual development.
(3) Applications for subdivision plat approval.
(Ord. No. 7407, § 5, 6-25-90; Ord. No. 11396, § 1, 8-9-16)
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