A. Uses Allowed Without Permits: The following open-space uses shall be allowed without a permit within the 100-year floodplain provided that: such uses conform to the provisions of Section 4-11-16 of these regulations; are not prohibited by any other ordinance, resolution, or statute; and do not require fill, excavation, permanent storage of materials, or equipment or structures other than portable structures:
1. Agricultural uses;
2. Accessory uses such as loading and parking areas, or emergency landing strips associated with industrial and commercial facilities;
3. Private and public recreational uses such as golf courses, driving ranges, archery ranges, picnic grounds, boat-launching ramps, parks, wildlife management and natural areas, game farms, fish hatcheries, shooting preserves, target ranges, trap and skeet ranges, hunting and fishing areas, and hiking or horseback riding trails;
4. Forestry, including processing of forest products with portable equipment;
5. Residential uses such as lawns, gardens, parking areas, and play areas;
6. Irrigation and livestock supply wells, provided that they are located at least five hundred feet (500') from domestic water supply wells;
7. Fences, except permanent fences crossing channels; and
8. Recreational vehicles provided that they be on the site for fewer than one hundred eighty (180) consecutive days or 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 with wheels intact, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions.
9. Individual- or multiple-family subsurface sewage disposal systems are allowed only when they are reviewed and approved under laws and regulations administered by the Department of Health and Environmental Sciences or the local health board.
B. Uses Requiring Permits: The following artificial obstructions and structures may be permitted in the 100-year floodplain subject to the issuance of a permit by the Floodplain Administrator:
1. Excavation of material from pits and pools provided that:
a. A buffer strip of undisturbed land is left between the edge of the channel and the edge of the excavation. This buffer strip must be of sufficient width to prevent flood flows from channeling into the excavation;
b. The excavation meets all applicable laws and regulations of other local and State agencies; and
c. Excavated material is disposed of or stockpiled outside the floodplain.
2. Railroad, highway, and street stream crossings, provided the crossings are designed to offer minimal obstruction to flood flow. Stream crossings shall not increase the elevation of the 100-year flood more than one-half foot (1/2') nor cause a significant increase in flood velocities.
3. Limited filling for highway, street, and railroad embankments not associated with stream crossings, provided that:
a. Reasonable alternate transportation routes outside the designated floodplain are not available; and
b. Such floodplain encroachment is located as far from the stream channel as possible and shall not result in a cumulative increase in base flood elevations, after allowable encroachments into the floodplain, exceeding one-half foot (1/2').
4. Buried or suspended utility transmission lines, provided that:
a. Suspended utility transmission lines are designed so the lowest point of the suspended line is at least six feet (6') higher than the base flood elevation;
b. Towers and other appurtenant structures are designed and placed to withstand and minimally obstruct flood flows; and
c. Utility transmission lines carrying toxic or flammable materials are buried to a depth of at least twice the calculated maximum depth of scour for a 100-year-flood. The maximum depth of scour shall be determined by hydraulic engineering methods acceptable to the Floodplain Administrator.
5. Storage of materials and equipment, provided that:
a. The material or equipment is not subject to major damage by flooding and is properly anchored to prevent floatation or downstream movement; or
b. The material or equipment is readily movable within the limited time available after flood warning. Storage of flammable, toxic, hazardous, or explosive materials shall not be permitted.
6. Domestic water supply wells, provided that:
a. They are driven or drilled wells located on ground higher than the surrounding ground to assure positive drainage from the well;
b. Well casings are watertight to a distance of at least twenty five feet (25') below the ground surface;
c. Water supply and electrical lines have a watertight seal where the lines enter the casing;
d. All pumps, electrical lines, and equipment are either submersible or adequately floodproofed; and
e. Check valves are installed on main water lines at wells and at all building entry locations.
7. Buried and sealed vaults for sewage disposal in recreational areas, provided they meet applicable laws and standards administered by the Montana Department of Health and Environmental Sciences.
8. Public or private campgrounds, provided that:
a. Access roads require only limited fill and do not obstruct or divert flood waters; and
b. Recreational vehicles and travel trailers are licensed and ready for highway use. They are ready for highway use if on wheels or jacking system with wheels intact, are attached to the site with only quick disconnect type utilities and securing devices, and have no permanently attached additions.
9. Structures accessory to the uses permitted in this Section such as boat docks, marinas, sheds, picnic shelters, tables, and toilets provided that:
a. The structures are not intended for human habitation;
b. The structures will have a low flood damage potential;
c. The structures will, insofar as possible, be located on ground higher than the surrounding ground and as far from the channel as possible;
d. The floodproofing standards of Section 4-11-8 are met; and
e. The structures will be constructed and placed so as to offer minimal obstruction to flood flows and are anchored to prevent floatation.
10. The new construction, alterations, and substantial improvements of residential structures, including manufactured homes, must be constructed on suitable fill such that the lowest floor elevation (including basement) is two feet (2') or more above the base flood elevation. The suitable fill shall be at an elevation no lower than the base flood elevation and shall extend for at least fifteen feet (15'), at that elevation, beyond the structure(s) in all directions;
11. The new construction, alteration, and substantial improvement of commercial and industrial structures can be constructed on suitable fill as specified in subsection B10 of this Section. If not constructed on fill, commercial and industrial structures must be adequately floodproofed to an elevation no lower than two feet (2') above the base flood elevation. Floodproofing must be certified by a registered professional engineer or architect that the floodproofing methods are adequate to withstand the flood depths, hydrodynamic and hydrostatic pressures, velocities, impact, buoyancy, and uplift forces associated with the 100-year flood.
a. If the structure is designed to allow internal flooding of areas below the lowest floor, use of this space shall be limited to parking, loading areas, building-access, and storage of equipment or materials not appreciably affected by flood waters. The floors and walls shall be designed and constructed of materials resistant to flooding to an elevation no lower than two feet (2') above the base flood elevation. Walls shall be designed to automatically equalize hydrostatic forces by allowing for entry and exit of flood waters. Openings may be equipped with screens, louvers, valves, other coverings, or devices which permit the automatic entry and exit of flood waters.
b. Structures whose lowest floors are used for a purpose other than parking, loading, or storage of materials resistant to flooding shall be floodproofed to an elevation no lower than two feet (2') above the base flood elevation. Floodproofing shall include impermeable membranes or materials for floors and walls and watertight enclosures for all windows, doors, and other openings. These structures shall also be designed to withstand the hydrostatic, hydrodynamic, and buoyancy effects of a 100-year flood.
c. Floodproofing of electrical, heating, and plumbing systems shall be accomplished in accordance with Section 4-11-8 of these regulations.
12. All manufactured homes placed in the 100-year floodplain must have the chassis securely anchored to a foundation system that will resist floatation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, over-the-top or frame ties to ground anchors. The following conditions also apply;
a. When a manufactured home is: 1) altered; 2) replaced because of substantial damage as a result of a flood; or 3) replaced on an individual site, the lowest floor must be elevated two feet (2') above the base flood elevation. The home can be elevated on fill or raised on a permanent foundation of reinforced concrete, reinforced mortared block, reinforced piers, or other foundation elements of at least equivalent strength.
b. Replacement or substantial improvement of manufactured homes in an existing manufactured home park or subdivision must be raised on a permanent foundation. The lowest floor must be two feet (2') above the base flood elevation. The foundation must consist of reinforced concrete, reinforced mortared block, reinforced piers, or other foundation elements of at least equivalent strength.
c. Manufactured homes proposed for use as commercial or industrial structures must be elevated and anchored, rather than floodproofed;
13. Structures or fill must not be prohibited by any other statute, regulation, ordinance, or resolution;
14. Structures or fill must be compatible with the local Comprehensive Plan;
15. Roads, streets, highways, and rail lines shall be designed to minimize increase in flood heights. Where failure or interruption of transportation facilities would result in danger to the public health or safety, the facility shall be located two feet (2') above the base flood elevation;
16. Agricultural structures that have a low damage potential, such as sheds, barns, shelters, and hay or grain storage structures must be adequately anchored to prevent floatation or collapse and all electrical facilities shall be placed above the base flood elevation; and
17. Recreational vehicles, if they are on the site for more than one hundred eighty (180) consecutive days or are not ready for highway use, must meet the elevating requirements of subsection B12 of this Section.
C. Permits for Flood Control Works: Flood control works shall be allowed subject to the issuance of a permit by the Floodplain Administrator with the following conditions:
1. Levees and floodwalls are permitted if:
a. The proposed levee or floodwall is designed and constructed to safely convey a 100-year flood; and
b. The cumulative effect of the levee or floodwall combined with allowable floodplain encroachments does not increase the unobstructed base flood elevation more than one-half foot (1/2'). The Floodplain Administrator may establish either a lower or higher permissible increase in the base flood elevation for individual levee projects only with concurrence from the Montana Department of Natural Resources and Conservation and the Federal Emergency Management Agency based upon consideration of the following criteria:
(1) The estimated cumulative effect of any anticipated future permissible uses; and
(2) The type and amount of existing flood-prone development in the affected area.
c. The proposed levee or floodwall, except those to protect agricultural land, are constructed at least three feet (3') higher than the base flood elevation.
2. Riprap, except that which is hand-placed, if:
a. The riprap is designed to withstand a 100-year flood;
b. The riprap does not increase the base flood elevation; and
c. The riprap will not increase erosion upstream, downstream, or adjacent to the riprap site.
3. Channelization projects if they do not significantly increase the magnitude, velocity, or base flood elevation in the proximity of the project.
4. Dams, provided that:
a. They are designed and constructed in accordance with the Montana Dam Safety Act and applicable safety standards; and
b. They will not increase flood hazards downstream, either through operational procedures or improper hydrologic/hydraulic design.
D. Permits for Water Diversions: Permits for the establishment of a water diversion or change in place of diversion shall not be issued if, in the judgment of the Floodplain Administrator:
1. The proposed diversion will significantly increase the upstream base flood elevation to the detriment of neighboring property;
2. The proposed diversion is not designed and constructed to minimize potential erosion from a 100-year flood; and
3. Any permanent diversion structure crossing the full width of the stream channel is not designed and constructed to safely withstand a 100-year flood.
E. Prohibited Uses: The following artificial obstructions and nonconforming uses are prohibited within the 100-year floodplain:
1. Solid and hazardous waste disposal; and
2. Storage of highly toxic, flammable, hazardous, or explosive materials. Storage of petroleum products may be allowed by permit if stored on compacted fill at least two feet (2') above the base flood elevation and anchored to a permanent foundation to prevent downstream movement. (Ord. 95-1, 2-7-95)