Friday, July 16, 2010

Map Shows High Landslide Risk for Haywood County Mountain Real Estate


Unpublished Haywood County Stability Index Hazard Map.
Research shows that 49% of Haywood County land is unstable.

Western North Carolina Landslide Hazard Maps

February 2005 marks the month and year that the state acknowledged the fact that Western North Carolina landslide hazard maps were pre-development necessities for 19 high-risk counties. Hazardous-land identification became an acute concern after the September 2004 Western North Carolina landslide disasters.

With the passage of the Hurricane Recovery Act, legislators found:

Further...people could not know the landslide risks associated with their housing location because such maps are not readily available. The state needs to...prepare landslide mapping for the region so that homes may be built in safe areas.
History of Western North Carolina Landslide Mapping Program

The Western North Carolina Landslide Mapping Program is not a state initiative as readers are led to believe. The Federal Emergency Management Agency requires states to identify and mitigate natural hazards or risk losing access to disaster funds. ( Robert T. Stafford Disaster Relief and Emergency Assistance Act)

Based on the region’s geologic features, soil surveys and weather conditions, federal officials rate landslides as highly probable in Western North Carolina. These risk assessments were disseminated to 21 mountain county governments in 1998.

Even though the North Carolina legislature allocated funding for 19 counties, FEMA has determined that detailed landslide hazard maps are critical for the following counties:

Alleghany, Ashe, Avery, Buncombe, Burke, Caldwell, Cherokee, Clay, Graham, Haywood, Henderson, Jackson, McDowell, Macon, Madison, Mitchell, Surry, Swain, Transylvania, Watauga, and Yancey.

Only three county landslide hazard maps have been published: Macon 2006, Watauga 2008 and Buncombe 2009. The North Carolina Geological Survey is working on Henderson and Jackson County maps.

Haywood County Landslide Hazard Map

During the same time frame that legislators were stating “such maps are not readily available” Anne Carter Witt, a North Carolina State University graduate student, was using government documents to complete her 2005 dissertation on Western North Carolina landslides.
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In order to compare risk modeling programs for her landslide predictability thesis, Ms. Witt chose
Haywood County for its rugged topography and the dispersed nature of the inventoried debris flows in the county. Both programs calculated 705.4 km² (49%) of Haywood County to be unstable. SHALSTAB calculated slightly more of the county as unstable (870.3 km² or 61%) than SINMAP (740.5 km² or 52%).)
Reference: “USING A GIS (GEOGRAPHIC INFORMATION SYSTEM) TO MODEL SLOPE INSTABILITY AND DEBRIS FLOW HAZARDS IN THE FRENCH BROAD RIVER WATERSHED, NORTH CAROLINA.”

Haywood County Mountain Real Estate

It is not known when the complete Haywood County landslide hazard map series will be released. Ms. Witt used the stability index map for her thesis. The Haywood County slope movement/deposits and downslope hazard maps are missing.

Landslide maps are vital. Without these references, Haywood County Realtors are likely selling hazardous home sites.

Western North Carolina Mountain Real Estate Declared Landslide-Hazardous

The Federal Emergency Management Agency has determined that disastrous landslide events are probable in the following Western North Carolina counties:

Alleghany, Ashe, Avery, Buncombe, Burke, Caldwell, Cherokee, Clay, Graham, Haywood, Henderson, Jackson, McDowell, Macon, Madison, Mitchell, Surry, Swain, Transylvania, Watauga, and Yancey.

This hazardous-land assessment dates from 1998.

When it Rains

National Weather Service Bulletin— September 21, 2009
The recent heavy rainfall across the area from Macon County to Henderson County North Carolina has increased the risk of slope failures and landslides if more heavy rain develops across the southern mountains today. An additional two or three inches…if it falls in a of period of one or two hours…could be enough to trigger slope movements…especially where hillsides have been modified by human activity.

This National Weather Service notification serves as warning that Western North Carolina landslides and slope failures are expected events during periods of heavy rainfall.
Western North Carolina Mountain Real Estate

Western North Carolina mountain home sites are presently being marketed and sold as no-risk real estate. The reality is, the aforementioned counties are undergoing extensive landslide mapping. Of the 19 counties listed, three have been mapped: Macon 2006, Watauga 2008 and Buncombe 2009. Geologic studies focus on steep slope (land on or above a 15% grade), soil surveys and prior landslide events.

Western North Carolina real property is not insurable for landslide losses.