Geographic Basics- Location Location Location

Claudette Reichel  |  6/25/2008 9:38:05 PM

Figure 1, Climate Regions

Figure 2, Wind Speed Zones

Figure 3, Formosean Subterranean Termite Nest in Wall

Climate

Most of Louisiana, all of Florida and much of the gulf coastal region are in the hot - humid climate region. (Figure 1, Climate Regions)  1

A hot-humid climate is defined as a region that receives more than 20 inches of annual rainfall and where one or both of the following occur:

  • A 67 degrees F or higher temperature for 3,000 or more hours during the warmest six consecutive months of the year, or
  • A 73 degrees F or higher temperature for 1,500 or more hours during the warmest six consecutive months of the year.

This zone corresponds to the U.S. Dept. of Energy Climate Zones 1A + 2A + 3A, as indicated below the warm-humid line. (“A” represents the “moist” portion of the Department of Energy temperature zones.) South Louisiana is in DOE climate zone 2A; the northern half of Louisiana is in zone 3A.

Southeast Louisiana and coastal Mississippi are in an extreme annual rainfall region (more than 60 inches). The remainder of the Gulf Region is in a high annual rainfall region (40-60 inches).

New Orleans has 2,655 cooling degree days (a measure of how hot a climate is), 1,513 heating degree days (a measure of how cold a climate is) and 62 inches average annual rainfall. Shreveport has 2,368 cooling degree days, 2,264 heating degree days and 46 inches average annual rainfall.

Northeast Louisiana and most southeastern states are in the mixed- humid climate region.[1]

A mixed-humid climate is defined as a region that receives more than 20 inches of annual precipitation, has less than 5,400 heating degree days (65 F basis)6 and where the average monthly outdoor temperature drops below 45 F (7 C) during the winter months.

This zone corresponds with DOE Climate Zones 4A and the portion of 3A located above the warm-humid line. The northeast corner of La. is and a large portion of most southern region states, except Florida, are in the mixed-humid zone.

Lake Providence in NE La. has 2,518 heating degree days, 2,250 cooling degree days and 55 inches average annual rainfall.

Wind Hazard

The wind hazard zones for Louisiana and the Gulf Region are shown in the diagrams. (Figure 2, Wind Speed Zones)  [2]

  • South Louisiana, all of Florida and part of all southern and eastern coastal states are in a hurricane zone. The closer to the coast, the higher the wind speed risk.
  • Tornadoes are common in the northern belt of Gulf States and along the edge of hurricanes in the coastal areas.
  • High winds can put great forces on a building, including shear loads (racking), lateral loads (push, pull) on wall connections, and uplift on the roof.
    • A house in an unobstructed open clearing or within 1,500 feet of open water is susceptible to higher wind forces from unobstructed winds.
    • Structural reinforcements can help enable homes to withstand hurricane force winds
    • Rather than fortify the entire structure against tornadic winds, a specially reinforced “safe room” can more economically provide a shelter that can remain standing even when a house is destroyed.
  • Minimum design standards for wind loading have been developed by the American Society of Civil Engineers and are referenced in the International Building Code and International Residential Code (IRC). (Louisiana enacted statewide enforcement of the latest version of the IRC beginning January 1, 2007.)

Flood Hazard

Much of the gulf region’s land area lies in Special Flood Hazards Areas (SFHAs). Flood patterns change, and areas not in a designated SFHA have flooded.

·Flood Insurance Rate Maps (FIRMs) are used by insurance agents to rate flood insurance and by parish and local governments in regulating development. Contact the local building or permit official for flood maps for your community.

  • “A” floodzones are typically static or slow-moving floodwater; water may move faster in some areas.
  • “V” zones are more hazardous because they are subject to surge and wave action. “V” zones are typically along the coast and around large lakes.
  • Flood damage prevention ordinances and building codes apply to new construction, repair and remodeling, even for buildings that have never flooded.
  • Homes are required to be protected from a “100-year flood” by building so that the lowest floor is at or above that level, called the Base Flood Elevation (BFE).
  • Non-residential buildings can meet flood protection requirements by dry floodproofing (sealing the walls and openings to keep water out of the building).

·Elevating homes to a flood level higher than the minimum required BFE is highly recommended.

  • Homes built at BFE have a 1 percent chance of flooding in any year, or a 26 percent chance of flooding during the 30-year life of a mortgage. This is roughly five times the normally accepted fire risk.
  • Homes built above BFE qualify for lower flood insurance premiums. The higher above BFE, the lower the owner’s flood insurance cost. Building at least 2 feet above BFE creates a substantial drop in annual insurance premiums.
  • Elevating or making your home flood-damage resistant in levee protected areas is wise, even where not required by ordinances or the BFE. If the levee fails, flood levels may far exceed the BFE, as so tragically occurred after Hurricane Katrina.

Termites

·Subterranean termites (native and Formosan) usually make their nests in the ground and create passageways to sources of food (cellulose) and moisture (leaks and condensation). They break into houses through construction elements and gaps as small as 1/32 of an inch.

·The Formosan subterranean termite is the most destructive insect in the United States. It can cause major structural damage to a home in six months and almost complete destruction in two years.  (Figure 3, Formosean Subterranean Termite Nest in Wall)

  • This species is a serious threat in South Louisiana, spreading through the gulf coast, and has been found in isolated cases in northern areas of Gulf States.
  • To reach cellulose (wood, paper) or a water source, the termites can chew through and destroy many noncellulose materials, such as electric lines, plastics, mortar, plaster, rubber insulation, stucco, thin sheets of soft metal, neoprene and seals on water lines. Unprotected foam insulation can become a hidden superhighway for termites.


[1] Based upon hygro-thermal regions as defined in Builder’s Guide to Hot-Humid Climates by Joseph Lstiburek, 2005 edition.

[2] Based upon the 3-second gust design wind speed map in the 2006 International Residential Code. Some states adopt different codes or maps.

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