Lake Forest Municipal Code Art. IV Provisions for Flood Hazard Reduction

In all areas of special flood hazards, the following standards are required:

A. Anchoring.

1. All new construction and substantial improvements shall be anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.

2. All manufactured homes shall meet the anchoring standards of Section 8.70.325.

B. Construction Materials and Methods.

1. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage, as specified in FEMA Technical Bulletin ("TB") 2 ("Flood Damage—Resistant Materials Requirements").

2. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.

3. All new construction and substantial improvements shall be constructed with electrical, heating, ventilation, plumbing and air conditioning equipment and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding.

4. All new construction and substantial improvements within Zones AH or AO shall be constructed so that there are adequate drainage paths around structures on slopes to guide flood waters around and away from proposed structures.

C. Elevation and Floodproofing.

1. In an AO zone, new construction for residential and nonresidential and substantial improvement of a structure shall be elevated at least one foot above the highest adjacent grade to a height equal to or exceeding the depth number specified in feet on the FIRM, or elevated at least two feet above the highest adjacent grade if no depth number is specified. Nonresidential structures may also meet the standards in subsection (C)(2) of this section. In all other SFHA zones, including zone A, new construction and substantial improvement of any structure shall have the lowest floor, including basement, elevated to at least one foot above the base flood elevation. Upon the completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered professional engineer or surveyor, or verified by the community building inspection to be properly elevated. Such certification or verification shall be provided to the Floodplain Administrator.

2. Nonresidential construction shall either be elevated in conformance with subsection (C)(1) of this section or together with attendant utility and sanitary facilities:

a. Be floodproofed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water;

b. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and

c. Be certified by a registered professional engineer or architect that the standards of this subsection are satisfied. Such certifications shall be provided to the Floodplain Administrator.

3. Require, for all new construction and substantial improvements, that fully enclosed areas below the lowest flood that are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or meet or exceed the following minimum criteria:

a. Either a minimum of two openings 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. The bottom of all openings shall be no higher than one foot above grade. Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters; or

b. Be certified to comply with a local flood proofing standard approved by the Federal Insurance Administration.

4. Manufactured homes shall also meet the standards in Section 8.70.325.

D. Flood Openings.

1. All new construction and substantial improvements of structures with fully enclosed areas below the lowest floor (excluding basements) that are usable solely for parking of vehicles, building access or storage, 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 floodwater. Designs for meeting this requirement must meet the following minimum criteria:

a. For non-engineered openings:

i. Have a minimum of two openings on different sides having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding;

ii. The bottom of all openings shall be no higher than one foot above grade;

iii. Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwater; and

iv. Buildings with more than one enclosed area must have openings on exterior walls for each area to allow flood water to directly enter; or

b. Be certified by a registered civil engineer or architect.

(Ord. 41 § 1, 1993; Ord. 325 § 3, 2019; Ord. 374, 2/4/2025)

A. All new and replacement water supply and sanitary sewage system shall be designed to minimize or eliminate infiltration of flood waters into the system and discharge from systems into flood waters.

B. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.

(Ord. 41 § 1, 1993; Ord. 325 § 3, 2019; Ord. 374, 2/4/2025)

A. All preliminary subdivision proposals, and other developments greater than 50 lots or five acres, whichever is the lesser, shall identify the flood hazard area and the base flood elevation.

B. All final subdivision plans will provide the elevation of proposed structure(s) and pads. If the site is filled above the base flood, the final pad elevation shall be certified by a registered professional engineer or surveyor and provided to the Floodplain Administrator.

C. All subdivision proposals shall be consistent with the need to minimize flood damage.

D. All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize flood damage.

E. All subdivisions shall provide adequate drainage to reduce exposure to flood hazards.

(Ord. 41 § 1, 1993; Ord. 325 § 3, 2019; Ord. 374, 2/4/2025)

All manufactured homes that are placed or substantially improved, on sites located: (1) outside of a manufactured home park or subdivision; (2) in a new manufactured home park or subdivision; (3) in an expansion to an existing manufactured home park or subdivision; or (4) in an existing manufactured home park or subdivision upon which a manufactured home has incurred "substantial damage" as the result of a flood shall:

A. Be elevated so that the lowest floor is at or above the base flood elevation; and

B. Be securely anchored to a permanent foundation system to resist flotation, collapse or lateral movement.

(Ord. 41 § 1, 1993; Ord. 325 § 3, 2019; Ord. 374, 2/4/2025)

A. All recreational vehicles placed in Zones A1-30, AH, and AE will either:

1. Be on the site for fewer than 180 consecutive days; or

2. Be fully licensed and ready for highway use. A recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions; or

3. Meet the permit requirements of Section 8.70.210 of this chapter and the elevation and anchoring requirements for manufactured homes in Sections 8.70.310 and 8.70.325.

(Ord. 325 § 3, 2019; Ord. 374, 2/4/2025)

Located within areas of special flood hazard established in Section 8.70.115 are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles, and erosion potential, the following provisions apply:

A. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge;

B. If subsection A of this section is satisfied, all new construction and substantial improvements shall comply with all other applicable flood hazard reduction provisions of this article.

(Ord. 41 § 1, 1993; Ord. 325 § 3, 2019; Ord. 374, 2/4/2025)