SLOPE PROCESSES AND GEOLOGICAL HAZARDS IN THE OHIO RIVER VALLEY NEAR HANOVER, JEFFERSON COUNTY, INDIANA

Slopes, terraces and active floodplains of the Ohio River Valley (ORV) have been subjected to extensive and (often) unwise agricultural, industrial and residential development. To assist local developers and land-use planners in making sound development decisions, we have constructed a GIS of the landforms and geological hazards in the vicinity of Hanover, Indiana, a natural geological laboratory of Hanover College. We distinguish seven main landforms: poorly drained level uplands; minor upland floodplains, shoulder slopes, slope faces and bedrock ledges, foot slopes, alluvial terraces, and active floodplain of the Ohio River and tributary valley streams. Development on the level uplands is limited by poor drainage associated with the presence of an extensive fragipan horizon. Shoulder slopes along the rim of the ORV offer some of the best sites for residential development, but developers have engaged in unsightly clear-cutting. The long steep ORV slope faces, underlain by a combination of shaley Ordovician bedrock and ledge-forming Ordovician and Silurian carbonate units, experiences pervasive creep as well as occasional rock fall and soil slip. In many places, the lower portion of these slopes is underlain by thick colluvium, the topmost portion of which has been excavated for paved roads. Additionally, major ravines cut into these slopes have experienced flash flooding and debris flow activity, resulting in the formation of broad colluvial fans at the foot of the slopes. These fans, which are incised, grade into minor active floodplain surfaces that lie below the level of the lowest (youngest) alluvial terrace. Except near the foot slopes, which host a number of homes susceptible to damage from all of the above-mentioned forms of mass wasting, the two alluvial terraces exhibit very low potential for mass wasting, but during floods they are cut off from the uplands. Finally, numerous dwellings and businesses occur on the active floodplain of the Ohio River, near a cliff face in sandy alluvium along the edge of the channel.

A prime objective of undergraduate earth science education at Hanover College is developing awareness of local landforms and geological hazards, and this objective should probably be expanded to include local non-student residents.