Exurbanization and Landslides

The Coweeta Hydrologic Lab and the Coweeta LTER draw on the knowledge of scientists from a variety of disciplines, including geography, ecology, anthropology and forestry. One benefit of this multi-disciplinary approach is that it allows for the identification of trends and processes happening simultaneously, that might otherwise only be considered separately. For Macon County and southern Appalachia, two of these trends are exurbanization and climate change.

Today’s column draws on investigations into these two trends in Macon County and what their interaction might mean for the county’s future in terms of landslides and other debris flows.

As we’ve noted in previous columns, one way regional climate change occurs in Macon County is through changing precipitation patterns. Recent research at the Coweeta Hydrologic Lab indicates that extreme wetness and extreme dryness will increase in the future. In other words, heavy precipitation and extreme drought are projected to worsen.

Soil scientists have long known that unusually heavy precipitation events destabilize mountain soils and can trigger landslides and other debris flows.

Maconians know this well, too, with rain-related landslides recently on Wayah Bald and the tragic 2004 Peeks Creek slide. Drought doesn’t directly contribute to landslides although severe drought can destabilize soil structure so that it is more vulnerable to future extreme rainfall events. This makes the threat of landslides even greater. Climate scientists’ forecast of increasingly extreme drought coupled with extreme precipitation events means that Maconians should take care in the landslide-prone areas of the county in the coming years.

Urban growth in Macon County further complicates this situation. The county’s population growth is driven by older in-migrants from out-of-state who are attracted by the county’s amenities. Macon County’s population has more than doubled since 1970 and from 2000-2010, it posted a 13.8% rate of population growth, most of which was due to non-Maconians moving to Macon County.

The Macon County tax database provides information on where people are purchasing existing and building new homes and the North Carolina Geological Survey’s Landslide Hazard Maps shows areas of the county that are in high, moderate, and low risk for landslide hazards. Combining these two sources of information reveals that from 1993 to 2012, 7 percent of annual sales of Macon County homes were located in high and moderate risk landslide zones. These sales are partly driven by out-of-state owners who are more likely than in-state owners to own properties in high and moderate risk zones. Ultimately, residential development is growing in all areas of the county, though, including high and moderate landslide risk zones.

The bottom line is that there is research that indicates a future of increasing precipitation and drought conditions that can trigger landslides, even as more people are purchasing property in the landslide-prone areas of Macon County.

Landslides caused by human disturbance like residential development and road construction only make this situation even more important to be aware of. Whatever the case, though, Maconians should educate themselves and others about the potential for landslides impacting their county, neighborhoods, developments, and property, especially in the high and moderate zones of the Landslide Hazard Maps.

The Coweeta Listening Project website, https://listening.coweeta.uga.edu, has scientific articles, resources, and maps, including the USGS landslide hazard maps, that can help. As always, we’d love to hear your thoughts, comments, and concerns on other ways climate change and exurbanization are changing Macon County and southern Appalachia.


This column is produced by members of the Coweeta Listening Project (CLP), a branch of the Coweeta Long Term Ecological Research Program. Views expressed here are not representative of the USDA Forest Service or the Coweeta Hydrologic Lab. Please share questions, comments, or suggestions for future topics at cwtlistn@uga.edu or Coweeta Listening Project, UGA, 210 Field St., Room 204, Athens, Georgia 30602.


Original Citation: The Coweeta Listening Project. Franklin Press. Column on "Science, Public Policy, Community." Page B4. May 10, 2013.