Tennessee is known for its diverse landscape that can be divided into three regions: the rugged mountains in the east, the rolling hills in the middle, and the fertile flat plains in the west. Indeed, the Volunteer State is a truly beautiful place. Yet, hidden beneath this lovely scenery is the ugly face of a persistent geological hazard: Tennessee mudslides.
Mudslides Vs. Landslides
You’ve most probably heard of “landslides,” but how about mudslides? They sound like the same thing, but are they? Here are the differences between the two.
All About Landslides
Landslides are “the downslope movement of earth materials (rock, debris, and soil) at rates that range from inches per year to tens of miles per hour,” according to the U.S. Geological Survey (USGS). So, some landslides can outrun a person, but others you’d hardly even notice.
This downward movement is caused by disturbances in the natural stability of a slope, which almost always is due to multiple causes, including:
- Heavy rain,
- Snowmelt
- Changes in water level,
- Stream erosion,
- Changes in ground water,
- Earthquakes
- Volcanic activity, such as eruptions,
- Disturbance by human activities, or
- Any combination of these factors.
What are Mudslides?
A mudslide is a common type of fast-moving landslide that tends to flow in or follow channels like a river. It occurs because of a specific factor, namely, the rapid accumulation of water or saturation of the ground in a slope such as what happens after a heavy rain.
This is the main difference between landslides and mudslides: the liquefaction occurring in the material. Liquefaction is a phenomenon where saturated, loose, granular soil temporarily loses strength and behaves like a viscous liquid.
Because the soil is saturated with water and due to internal water pressure, the soil grains lose their friction and results in the previously solid material now flowing like a liquid. As such, mudslides frequently occur during wet seasons.
While excess rain fills the rock, earth, and debris with water, mudslides are typically triggered by natural disasters, such as an earthquake. They can also be caused by disturbances in hillsides due to wildfires, heavy logging and deforestation, rapid use or modification of the land, and other human activity which result in the destruction of vegetation on slopes. Water still permeates the burnt ground, according to a study, but without vegetation that helps hold the loose soil together, the saturated ground falls down the slope in a mudslide.
Areas in Tennessee Most At-Risk of Mudslides
According to the U.S. Centers for Disease Control and Prevention (CDC), the following areas are more likely to face the threat of landslides or mudslides:
- Areas where wildfires or human modification of the land have destroyed vegetation,
- Areas where landslides have already occurred before,
- Steep slopes and areas at the bottom of slopes or canyons,
- Slopes that have been altered for construction of buildings and roads,
- Channels along a stream or river, and
- Areas where surface runoff is directed.
Tennessee Counties With High Risk of Mudslides
In 2024, Truck Parking Club, which provides monthly truck parking, conducted a county-level data mapping to determine which areas in the state were susceptible to landslides. Here’s what they found out:
- Counties within mountain ranges are highly susceptible to landslides. Out of the 95 counties in Tennessee, 77 counties are susceptible to landslides, 20 of which have more than 90% of their land at risk of landslides.
Tennessee Counties with the Highest Risk of Landslides
| County | % of Land Susceptible to Landslides |
| Hancock County | 98% |
| Claiborne County | 96% |
| Campbell | 96% |
| Unicoi County | 96% |
| Union County | 95% |
| Johnson County | 95% |
| Carter County | 95% |
| Sevier County | 94% |
| Cocke County | 94% |
| Grainger County | 94% |
| Scott County | 93% |
| Anderson County | 93% |
| Roane County | 88% |
| Monroe County | 88% |
| Morgan County | 88% |
| Hamblen County | 85% |
| Greene County | 85% |
| Blount County | 85% |
| London County | 82% |
| Fentress County | 81% |
| Jefferson County | 81% |
| Knox County | 81% |
| Cumberland County | 71% |
Source: Truck Parking Club
- Slopes with weak or fractured soil are also likely to experience landslides. A good example of this are areas with a history of strip mining. Eastern Tennessee’s Appalachian coal mining locations fit this description. Mining activities leave behind waste rock and combined with increasing stream flows and heavy rainfall can produce landslides.
Consequences of Mudslides
Mudslides can compromise slope stability and bury roads and lead to their closure. They can also wash out bridge foundations and severely damage railways, power transmission lines, and other infrastructure. These problems can lead to prolonged closure, service disruption, costly repairs, and safety and health hazards.
Speaking of health hazards, the CDC states that landslides and debris flows result in 25 to 50 deaths annually. In addition, mudslides can also lead to:
- Trauma caused by rapidly moving water and debris,
- Injury or illness from broken electrical, water, gas, and sewage lines, and
- Endangerment of motorists and disruption in transport and access to health care due to disrupted roadways and railways.
Warning Signs of Mudslides
While mudslides are hard to predict and may happen without any warning, some come with clues. There might be features on the landscape and unusual sounds that indicate an impending mudslide. Here are the warning signs you should look out for, according to the USGS:
| Signs of a potential landslide: |
| New cracks, bulges, or other deformation in the ground, roadways, or other surfaces. The appearance of flowing water on a slope or water ponding where this has never occurred before. Sagging or taut utility lines caused by leaning utility poles, deformed fences, or tilting of trees on a hillside. Sticking windows or doors; new cracks in walls, ceilings, or foundations. Broken or leaking utilities, such as water, septic, or sewer lines. Separation of structures from their foundation or soil pulling away from the foundation. Abnormal changes in water well levels. |
| Signs of a moving landslide: |
| Sounds of cracking or breaking wood, knocking boulders, groaning of the ground, or other unusual sounds, especially if the sound increases. A loud rumble and ground vibrations, like the sensation of a passing freight train. A sudden change in stream water levels, especially during or right after an intense or prolonged storm event. |
Tennessee’s mudslides are a natural part of its changing landscape, but they are becoming more frequent and costly.By understanding the unique geology of the region and the factors that trigger mudslides, Tennesseans can better prepare for a future on these unsteady slopes.