In addition to the definition of terms contained in section 76-5-103, MCA, and unless the context requires otherwise, as used in the Act and in this chapter:

(1) "Act" means Title 76, chapter 5, MCA, as amended.

(2) "Alteration" means any change or addition to an artificial obstruction that either increases the size of the artificial obstruction or increases its potential flood hazard. Maintenance of an artificial obstruction is not an alteration.

(3) "Artificial obstruction" means any obstruction which is not natural and includes any dam, diversion, wall, riprap, embankment, levee, dike, pile, abutment, projection, revetment, excavation, channel rectification, bridge, conduit, culvert, building, refuse, automobile body, fill or other analogous structure or matter in, along, across, or projecting into any 100-year floodplain which may impede, retard, or alter the pattern of flow of water, either in itself or by catching or collecting debris carried by the water, or that is placed where the natural flow of water would carry the same downstream to the damage or detriment of either life or property.

(4) "Base flood" means a flood having a one percent (1%) chance of being equalled or exceeded in any given year. A base flood is the same as a flood of 100-year frequency.

(5) "Base flood elevation" means the elevation above sea level of the base flood in relation to national geodetic vertical datum of 1929, unless otherwise specified.

(6) "Board" means the board of natural RESOURCES AND CONSERVATION.

(7) "Channelization project" means the excavation and construction of an artificial channel for the purpose of diverting the entire flow of a watercourse or drainway from its established course.

(8) "Department" means the department of natural RESOURCES AND CONSERVATION.

(9) "Establish" means to construct, place, insert, or excavate.

(10) "Flood fringe" means that portion of a designated floodplain outside the limits of a designated floodway.

(11) "Floodplain," means the area adjoining the watercourse or drainway which would be covered by the floodwater of a base flood except for sheetflood areas that receive less than 1 foot of water per occurrence and are considered zone b areas by the federal emergency management agency. The floodplain consists of the floodway and flood fringe.

(12) "Flood boundary" the designated floodplain boundary is based on base flood elevations. The mapped floodplain boundary may be used as a guide for determining whether property is within the designated floodplain, but the exact boundary shall be determined according to the base flood elevation.

(13) "Floodway," means the channel of a watercourse or drainway and those portions of the floodplain adjoining the channel which are reasonably required to carry and discharge the floodwater of any watercourse or drainway.

(14) "Lowest floor" means any floor used for living purposes, storage, or recreation. This includes any floor that could be converted to such a use.

(15) "Manufactured home" means a structure that is transportable in one or more sections, built on a permanent chassis, and designed to be used with or without a permanent foundation when connected to the required utilities. For floodplain management purposes it also includes park trailers, travel trailers, and other similar vehicles placed on a site for greater than 180 consecutive days.

(16) "Permit issuing authority" means the responsible political subdivision, if any, or the department if there is no responsible political subdivision.

(17) "Responsible political subdivision" means a political subdivision that has received board approval of its adopted land use regulations and administrative and enforcement procedures in accordance with section 76-5-302, MCA, and ARM 36.15.201 through 36.15.204.

(18) "Riprap" means stone, rock, concrete block, or analogous material that is placed along the banks or bed of a watercourse or drainway for the purpose of alleviating erosion.

(19) "Sheetflooding" means areas subject to 100-year flooding with depths less than one (1) foot. Sheetflood areas are generally removed from the main stream channel and have been identified as zone b by FEMA or as a sheetflood zone by the soil conservation service.

(20) "Start of construction" for purposes of these rules means the commencement of clearing, grading, filling or excavation for the purposes of preparing a site for construction.

(21) "Substantial improvement" means any repair, reconstruction, or improvement of a structure, the cost of which equals or exceeds fifty percent (50%) of the market value of the structure either:

(a) before the improvement or repair is started, or

(b) if the structure has been damaged, and is being restored, before the damage occurred. For the purposes of this definition, substantial improvement is considered to occur when the first construction to any wall, ceiling, floor, or other structural part of the building commences. The term does not include:

(i) any project for improvement of a structure to comply with existing state or local health, sanitary, or safety code specifications which are solely necessary to assure safe living conditions, or

(ii) any alteration of a structure listed on the national register of historic places or state inventory of historic places.

(22) "Suitable fill" means fill material which is stable, compacted, well graded, pervious, not adversely affected by water and frost, devoid of trash or similar foreign matter, tree stumps, or other organic material; and is fitting for the purpose of supporting the intended use and/or permanent structure.

(23) "Variance" means a grant or relief from the requirements of these rules which would permit construction in a manner that would otherwise be prohibited by these rules.

(24) "100 year frequency flood" - See "base flood".