The Indiana Geological and Water Survey at Indiana University has been publishing critical research that addresses landslide risks across the Hoosier state. New high-resolution imagery and digital elevation measurements being collected by the Indiana Geographic Information Office will aid this work.
The Indiana Geological and Water Survey is undertaking landslide risk assessments and creating a landslide inventory across central and southern Indiana according to the schedule shown in the map above. Dots represent documented landslide locations so far. Work that started in 2023 covered Hoosier National Forest properties (darkest gray shading); work that started in 2024 covered the entirety of the Bedford, Jasper, and Tell City. Graphic by Casey Jones, Indiana Geological Water Survey." src="https://news.iu.edu/live/image/gid/2/width/500/height/813/20663_landslides.png" title="landslides-map" srcset="https://news.iu.edu/live/image/scale/2x/gid/2/width/500/height/813/20663_landslides.png 2x" data-max-w="1200" data-max-h="1950" loading="lazy" data-optimized="true"/>
The Indiana Geological and Water Survey is undertaking landslide risk assessments and creating a landslide inventory across central and southern Indiana according to the schedule shown in the map above. Dots represent documented landslide locations so far. Work that started in 2023 covered Hoosier National Forest properties (darkest gray shading); work that started in 2024 covered the entirety of the Bedford, Jasper, and Tell City. Graphic by Casey Jones, Indiana Geological Water Survey.
States with more severe topography than Indiana - like Washington, Oregon and Kentucky - have been mapping landslides for years using light detection and ranging, or lidar, according to Victoria Leffel, the lead researcher on this project at the Indiana Geological Water Survey.
A statewide Indiana lidar imagery set released in 2020 marked a turning point for Indiana. That data, collected over four years and captured at a more detailed scale than a prior set released in the early 2010s, enabled researchers to develop three-dimensional models that revealed landslide sites with greater clarity. A new, third data set, to be collected at an even finer resolution over the next three years, will deepen the data well.
"It offers the promise to see potential landslide movement over time, which is exciting," Leffel said.
Since joining the survey in 2022, Leffel has been working to create the first statewide landslide risk maps for Indiana using this lidar data. Her research so far - outlined in the reports "Highway Landslide Hazards in Indiana - Construction and Analysis of a Landslide Inventory" and "Landslide Hazard Mapping and Inventory of the Hoosier National Forest Using LiDAR Data" - has been published in the open-access Indiana Journal of Earth Sciences in 2024. More of her research is expected to be released over the next two years.
Lidar uses a laser scanner and GPS to measure distances by transmitting brief pulses of light to the ground. The data are used to create 3D models of surfaces. Geologic mappers, hydrologists and other scientists can use lidar and related data to track changes over time along coastlines and streambanks; at abandoned mines; or from natural hazards such as karst (caves and sinkholes), landslides, volcanoes and earthquakes.
Indiana is at a lower risk of landslides and rockfalls than other parts of the country, but parts of this state are more susceptible than others because of their topography, precipitation and underlying geology. Southern Indiana contains some of those higher-risk areas.
In February 2024, Leffel was called to Clifty Falls State Park in Madison after a 7- to 8-foot-tall chunk of limestone fell near a popular trail and tunnel. The Indiana Department of Natural Resources has kept the tunnel closed after a report Leffel provided warned of further rockfalls due to the weathering of the shale underneath. Later in the spring, while verifying in person what she was seeing on lidar, Leffel and her field team came across dozens of areas on public forest lands in southern Indiana where landslides had occurred, including some near trails and a dam.
Leffel's first study concluded that bedrock geology and the lack of a glacial cover are closely related to the occurrence of landslides, with predominately shale bedrock, variable topography and groundwater fluctuations contributing to landslide development and incidence.
Understanding the factors that lead to landslide risks can help builders, public emergency managers and residents make better informed decisions.
"It's tricky," Leffel said. "The New Albany Shale has a low landslide susceptibility, but the Kope Formation has a high landslide susceptibility, so it's not like you can just say, 'You can't build with shale.' Understanding how it weathers and behaves over time under varying conditions is a key consideration in roadway construction."
Her current project, funded by a $45,439 grant from the U.S. Geological Survey, is focused on finding and mapping landslide hazards in a 15-county, 4,200-square-mile area of southeast-central Indiana. In addition to a landslide inventory of the area, one outcome, expected this fall, will be developing landslide maps for the state parks in those counties to aid in land management and educational outreach.
An additional grant application under review would fund the creation of a comprehensive, publicly accessible landslide inventory for south-central Indiana, covering parts of 13 counties. That inventory would pull in not only lidar data but also records related to Indiana transportation infrastructure dating back to the 1940s, as well as Indiana Geological and Water Survey data from past bedrock mapping projects.
"While the proposed and future project boundaries are subject to change," Leffel said, "our current goal is to eventually map landslide risk for all areas of the state south of the Wisconsin Glacial Boundary" - approximately south of Interstates 70 and 74.
"Landslides in Indiana go beyond simple erosion; they involve the movement of soil and rock on a large scale," she said. "Although most are slow-moving and lack the dramatic impact of the fast-moving landslides often seen in news stories, these gradual events still pose significant maintenance challenges."
