(a) Remove the following from “Lowest floor” definition in Chapter 16.08 CMC:

2. For residential structures, all subgrade enclosed areas are prohibited as they are considered to be basements (see “Basement” definition). This prohibition includes below-grade garages and storage areas.

(b) Add the following section into the code at CMC 16.20.010(3):

16.20.010(3){X} Crawlspace Construction.

This sub-section applies to buildings with crawl spaces up to 2 feet below grade. Below-grade crawl space construction in accordance with the requirements listed below will not be considered basements.

a. The building must be designed and adequately anchored to resist flotation, collapse, and lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Crawl space construction is not allowed in areas with flood velocities greater than 5 feet per second unless the design is reviewed by a qualified design professional, such as a registered architect or professional engineer;

b. The crawl space is an enclosed area below the BFE and, as such, must have openings that equalize hydrostatic pressures by allowing for the automatic entry and exit of floodwaters. For guidance on flood openings, see FEMA Technical Bulletin 1-93;

c. Crawl space construction is not permitted in V zones. Open pile or column foundations that withstand storm surge and wave forces are required in V zones;

d. Portions of the building below the BFE must be constructed with materials resistant to flood damage. This includes not only the foundation walls of the crawl space used to elevate the building, but also any joists, insulation, or other materials that extend below the BFE; and

e. Any building utility systems within the crawl space must be elevated above BFE or designed so that floodwaters cannot enter or accumulate within the system components during flood conditions.

f. Requirements for all below-grade crawl space construction, in addition to the above requirements, to include the following:

1. The interior grade of a crawl space below the BFE must not be more than 2 feet below the lowest adjacent exterior grade (LAG), shown as D in figure 3 of Technical Bulletin 11-01;

2. The height of the below-grade crawl space, measured from the interior grade of the crawl space to the top of the crawl space foundation wall must not exceed 4 feet (shown as L in figure 3 of Technical Bulletin 11-01) at any point;

3. There must be an adequate drainage system that removes floodwaters from the interior area of the crawl space within a reasonable period of time after a flood event, not to exceed 72 hours; and

4. The velocity of floodwaters at the site should not exceed 5 feet per second for any crawl space. For velocities in excess of 5 feet per second, other foundation types should be used.

(a) Definitions into Chapter 16.08 CMC:

“Area of special mudslide (i.e., mudflow) hazard” is the area subject to severe mudslides (i.e., mudflows). The area is designated as Zone M on the Flood Insurance Rate Map (FIRM).

“Mudslide” describes a condition where there is a river, flow or inundation of liquid mud down a hillside, usually as a result of a dual condition of loss of brush cover and the subsequent accumulation of water on the ground, preceded by a period of unusually heavy or sustained rain.

“Mudslide (i.e., mudflow) prone area” means an area with land surfaces and slopes of unconsolidated material where the history, geology, and climate indicate a potential for mudflow.

(b) CMC 16.20.{X}, Mudslide (i.e., mudflow) prone areas, into Chapter 16.20 CMC:

16.20.{X}, Mudslide (i.e., Mudflow) Prone Areas.

A. The Floodplain Administrator shall review permits for proposed construction of other development to determine if it is proposed within a mudslide area.

B. Permits shall be reviewed to determine that the proposed site and improvement will be reasonably safe from mudslide hazards. Factors to be considered in making this determination include, but are not limited to:

1. The type and quality of soils;

2. Evidence of ground water or surface water problems;

3. Depth and quality of any fill;

4. Overall slope of the site; and

5. Weight that any proposed development will impose on the slope.

C. Within areas which may have mudslide hazards, the Floodplain Administrator shall require:

1. A site investigation and further review by persons qualified in geology and soils engineering;

2. The proposed grading, excavation, new construction, and substantial improvement be adequately designed and protected against mudslide damages;

3. The proposed grading, excavations, new construction, and substantial improvement not aggravate the existing hazard by creating either on-site or off-site disturbances; and

4. Drainage, planting, watering, and maintenance not endanger slope stability.

(a) Definitions into Chapter 16.08 CMC:

“Area of special flood-related erosion hazard” is the land within a community which is most likely to be subject to severe flood-related erosion losses. The area may be designated as Zone E on the Flood Insurance Rate Map (FIRM).

“Flood-related erosion” means the collapse or subsidence of land along the shore of a lake or other body of water as a result of undermining caused by waves or currents of water exceeding anticipated cyclical level or suddenly caused by an unusually high water level in a natural body of water, accompanied by a severe storm, or by an unanticipated force of nature, such as a flash flood or an abnormal tidal surge, or by some similarly unusual and unforeseeable event which results in flooding.

“Flood-related erosion area” or “Flood-related erosion prone area” means a land area adjoining the shore of a lake or other body of water, which due to the composition of the shoreline or bank and high water levels or wind-driven currents, is likely to suffer flood-related erosion damage.

“Flood-related erosion area management” means the operation of an overall program of corrective and preventive measures for reducing flood-related erosion damage, including but not limited to emergency preparedness plans, flood-related erosion control works, and floodplain management regulations.

(b) CMC 16.20.{X}, Flood-related erosion-prone area, into Chapter 16.20 CMC:

16.20.{X}, Flood-Related Erosion-Prone Area.

A. The Floodplain Administrator shall require permits for proposed construction and other development within all flood-related erosion-prone areas known to the community.

B. Permit applications shall be reviewed to determine whether the proposed site alterations and improvements will be reasonably safe from flood-related erosion, and will not cause flood-related erosion hazards or otherwise aggravate the existing hazard.

C. If a proposed improvement is found to be in the path of flood-related erosion or would increase the erosion hazard, such improvement shall be relocated or adequate protective measures shall be taken to avoid aggravating the existing erosion hazard.

D. Within Zone E on the Flood Insurance Rate Map, a setback is required for all new development from the ocean, lake, bay, riverfront or other body of water to create a safety buffer consisting of a natural vegetative or contour strip. This buffer shall be designated according to the flood-related erosion hazard and erosion rate, in relation to the anticipated useful life of structures, and depending upon the geologic, hydrologic, topographic, and climatic characteristics of the land. The buffer may be used for suitable open space purposes, such as for agricultural, forestry, outdoor recreation and wildlife habitat areas, and for other activities using temporary and portable structures only.