§ 7-347 — SPECIFIC STANDARDS

§ 7-347 SPECIFIC STANDARDS.

In all areas of special flood hazards where base flood elevation data have been provided, the following provisions are required. (a) Residential construction. New construction and substantial improvement of any residential structure shall have the lowest floor (including basement, finished garage, and machinery or equipment servicing the building), elevated at least two feet above the fully developed base flood elevation or the FEMA regulatory base flood elevation, whichever is greater. A registered public land surveyor or professional engineer shall submit a certification to the floodplain administrator that the standards of this subsection (a) and § 7-333(a)(3) are satisfied. (b) Nonresidential construction. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall have either: (1) The lowest floor (including basement, finished garage, and machinery or equipment servicing the building), elevated two feet above the fully developed base flood elevation or the FEMA regulatory base flood elevations, whichever is greater; or (2) The lowest floor (including basement, finished garage, and machinery or equipment servicing the building) together with attendant utility and sanitary facilities, be floodproofed and shall: a. Be designed so that below the level of two feet above the fully developed base flood elevation or the FEMA regulatory base flood elevation, whichever is greater, the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; b. Have a registered professional engineer or architect develop and/or review structural design, specifications and plans for the construction, and certify that the design and methods of construction are in accordance with accepted standards of practice as outlined in this subsection (b) and adhere to FEMA standards; and c. Provide a record of such certification which includes the specific elevation (in relation to mean sea level) to which such structures are floodproofed. The record shall be maintained by the floodplain administrator. (c) Enclosures. New construction and substantial improvements, with fully enclosed 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. Designs for meeting this requirement must either be certified by a registered professional engineer or architect and meet or exceed the following minimum criteria: (1) A minimum of two openings on separate walls having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided; (2) The bottom of all openings shall be no higher than one foot above grade; and (3) Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwaters. (d) Manufactured homes. For new or existing manufactured home parks or subdivisions located within areas of special flood hazard the following shall apply. (1) All new and replacement manufactured homes to be placed or substantially improved within an area of special flood hazard must be elevated on a permanent foundation such that the bottom of the frame of the manufactured home is elevated two feet above the fully developed base flood elevation or the FEMA regulatory base flood elevation, whichever is higher. (2) All new and replacement manufactured homes to be placed or substantially improved within areas of special flood hazard, shall be installed using methods and practices which minimize flood damage. The manufactured home must be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement with certification by a registered professional engineer that the improvements will not increase flood flows, heights, or damages. Methods of anchoring may include, but are not limited to, use of over-the-top or frame ties to ground anchors. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces. (3) All manufactured homes shall be in compliance with subsection (a) of this section. (4) Fully enclosed areas below elevated manufactured homes shall comply with the requirements of subsection (c) of this section. (5) Mechanical equipment and outside appliances shall be elevated two feet above the fully developed base flood elevation or the FEMA regulatory base flood elevation, whichever is higher. (6) No manufactured home will be allowed to be placed within a floodway. (e) Recreational vehicles. (1) All recreational vehicles to be placed on sites within areas of special flood hazard must either: a. Be on the site for fewer than 180 consecutive days; b. Be fully licensed and ready for highway use; or c. Meet the permit requirements of § 7-333, and the elevation and anchoring requirements for "manufactured homes" in subsection (d) of this section. (2) A recreational vehicle is ready for highway use if it is on wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions. (f) Temporary structures and temporary storage. (1) Temporary structures placed in areas of special flood hazard. Temporary structures shall be erected for a period of less than 180 days. Temporary structures shall be anchored to prevent flotation, collapse or lateral movement resulting from hydrostatic loads, including the effects of buoyancy, during conditions of the base flood. Fully enclosed temporary structures shall have flood openings that are in accordance with subsection (c) of this section to allow for the automatic entry and exit of flood waters. (2) Temporary storage in areas of special flood hazard. Temporary storage includes storage of goods and materials for a period of less than 180 days. Stored materials shall not include hazardous materials. (3) Floodway encroachment. Temporary structures and temporary storage in floodways shall meet the requirements of § 7-350 of this article. (h) Critical facilities. Construction of new critical facilities shall be, to the extent possible, located outside of the limits of the area of special flood hazard. Construction of new critical facilities shall be permissible within the area of special flood hazard area if no feasible alternative site is available. Access routes elevated to or above the base flood elevation shall be provided to all critical facilities to the maximum extent possible. (i) Tanks. (1) New and replacement tanks in flood hazard areas shall either be elevated above the base flood elevation on a supporting structure designed to prevent flotation, collapse or lateral movement during conditions of the base flood, or be anchored to prevent flotation, collapse or lateral movement resulting from hydrostatic loads, including the effects of 1.5 times the buoyant forces assuming the tank is empty, during conditions of the base flood. (2) New and replacement tank inlets, fill openings, outlets and vents shall be placed a minimum of two feet above the base flood elevation or fitted with covers designed to prevent the inflow of floodwater or outflow of the contents of the tank during conditions of the base flood. (j) Fences and walls. (1) Fences are a form of development and require a floodplain development permit. Evaluation of floodplain development permit applications for proposed fences will be based on the following criteria: a. Fencing that consists of solid walls, creates a barrier impervious to stream flow or fencing that greatly restricts the passage of water will not be allowed. These include masonry walls, retaining walls, chain link fencing, space board-type fencing or similar fencing that creates a solid wall either by design or the accumulation of debris. b. Fencing outside of the floodway but within the special flood hazard area will be restricted to the least flow-restrictive types of open fencing that allows the passage of water. (2) New and replacement fencing shall be designed to collapse under conditions of the base flood or to allow the passage or water and debris. The following provisions shall apply to all fences permitted in the special flood hazard area: a. Fences in the regulatory floodway are prohibited; b. Fences must be setback a minimum of five feet from the top-of-bank; c. Fencing must be built in removable sections; d. Fencing that consists of solid walls, creates a barrier impervious to stream flow or fencing that greatly restricts the flow of water is prohibited; and e. Fences that are significantly damaged or destroyed by a flood shall require a floodplain development permit to ensure that reconstruction methods are consistent with the need to minimize future flood damages. (k) Compensatory Valley Storage. (1) Watercourse. No reduction in Valley Storage (0.0%) is allowed anywhere within a FEMA Special Flood Hazard Area (SFHA) and anywhere the contributing drainage area is 64 acres or greater (where a FEMA SFHA would eventually be mapped) when comparing pre-project (existing) to post-project (proposed) topography using existing land use hydrology. Evaluation of floodplain development permit applications for Valley Storage in Watercourse areas will be based on the following criteria: a. A Valley Storage impact analysis is performed as part of a Drainage and/or Flood Study, in accordance with the Stormwater Criteria Manual, by comparing the pre-project (existing) conditions and post-project (proposed) conditions topography below the 1% annual chance "100- year", 20% annual chance "5-year", and 100% annual chance "1-year" water surface elevations, respectively. For a project that would impact Valley Storage to a SFHA that does not require a new hydrologic analysis, then the 1% annual chance and 10% annual chance "10-year" peak discharges may be used from the effective FEMA Flood Insurance Study (FIS) or best available data as determined by the floodplain administrator or their designee. Compensatory storage and related calculations are not required for projects that do not involve grading within the FEMA areas described in 7-347(k)(1), for any of the design storms specified in this section. b. An equivalent volume of Valley Storage must be provided for each design flood, as described in the Stormwater Criteria Manual, within the same Watercourse reach as the proposed development. The Floodplain Administrator, or their designee, shall determine the proposed reach limits. c. Exceptions. Subsection (k) shall not apply to the following: 1. Construction of new roadways or widening of existing roadways by the city; 2. Watercourses that are proposed to be within a Storm Drain Pipe System at the upstream limit of the SFHA (existing or proposed), as described in § 7-347(k)(1)(a); 3. Outfall and intake structures; 4. Utility Crossings; 5. Bank stabilization activities; and 6. Maintenance, repair, or approved equivalent replacement of existing infrastructure. d. Trinity River. Development within the Trinity River Corridor shall be consistent with Division 6 of this Article. (2) Sump Areas. No reduction in Valley Storage (0.0%) is allowed at sites located within a Sump Area for the 1% annual chance "100-year" design flood. Evaluation of floodplain development permit applications for Valley Storage in Sump Areas will be based on the following criteria: a. The 1% annual chance water surface elevation found in the FEMA FIS shall be used when available. When not available, the Floodplain Administrator, or their designee, shall determine the 1% annual chance water surface elevation. b. The determination of compensatory Valley Storage impacts consists of a flood study comparing pre-project (existing) conditions and post-project conditions topography below the 1% annual chance water surface elevation. c. Exceptions. If a floodplain development permit is requested for one single-family lot, the flood study requirement may be waived by the Floodplain Administrator, or their designee, if the home is constructed using a "pier and beam" or similar construction method to preserve flood storage beneath the lowest floor. d. An equivalent volume of Valley Storage must be provided within the designated Sump Area of the proposed development. (3) Variances. A variance to the compensatory Valley Storage requirements may be granted in conformance with the provisions of § 7-334, (Ord. 11998, § 1, passed 6-13-1995; Ord. 25350-03-2022, § 1, passed 3-8-2022, eff. 3-23-2022; Ord. 28191-12-2025, § 3, passed 12-9-2025, eff. 1-23-2026)