With the recent landslide tragedy in Washington state I think it’s a good time to remind people of the risks here in North Carolina. The risk here is much higher than many people might think. The highest risks are located in the mountains and foothills of North Carolina but there are smaller scale risks even across parts of the piedmont.
National Landslide Hazards map:
Closer view notice the red area through Gaston and Mecklenburg counties:
Highest Risk Areas:
Last year (2013) the NC Geological Survey estimated that there were almost 300 damaging landslides in the state. That was the most since 2004 when we had back to back Tropical Storms Frances and Ivan. Which back then caused on the upwards of 400 landslides in the state.
As you may suspect weather plays a huge role in these landslides and is part of the reason the Carolinas are so vulnerable to slides. The steep elevation changes combined with development and our frequent heavy rains all lead to an increased danger.
There is a very high correlation of heavy rainfall events and landslides in Western North Carolina. Due to the amount of rain saturating the soil on many of these steep slopes in the western part of the state.
Watauga County leads the state in number of known landslides. Mainly because of the amount of steep terrain and development in the county. The risk there is highest, but Macon, Haywood and Buncombe counties also have very high risks due to development on slopes and heavy rain risks. Though just about any county in the mountains could see a slide.
Watauga County landslide potential:
What about Charlotte?
The combination of development and the soil type also plays a huge role in landslide risks. Across the Charlotte metro the risk is higher due to the combination of soil type and development. The elevation might not be as high in parts of the piedmont as the mountains but there is still a lot of elevation change within the county.
The types of slides in Mecklenburg county are smaller but can damage foundations and cause property damage. Anywhere you see retaining walls there is a risk. the county with so many steep slopes and development the threat for smaller slides might just be a way of life across Charlotte.
The number of small creeks and elevation change across the county make it an area susceptible to landslides. Here is a topography map made using LIDAR of Mecklenburg county.
Earthquakes as triggers:
I am amazed on how people in the Carolinas don’t realize the Earthquake risk here as well. Now this isn’t California but we still get minor quakes and anywhere you have mountains you can expect the ground to be moving a bit. Combine that with the risk centered around Charleston and you have an added trigger for landslides. If we ever get the combination of heavy rains and a small tremor we could see numerous slides in the Western Carolinas.
Earthquake Risk Map:
So is this something we need to worry about? Living in a beautiful state with elevation changes does have it risks. Development needs to be done in the right spots and home and landowners should be aware of the risks. When ever we get heavy rains like we saw last year or during the hurricane season we should be extra cautious of the risks for th landslides.