Hamilton County, Ohio and the Greater Cincinnati area, including the tri-state region of northern Kentucky, southwestern Ohio, and southeastern Indiana have been plagued with extensive landslide activities, gaining the reputation of being one of the most landslide prone areas in the nation. The estimated cost of landslide related damages in Hamilton County alone is approximately $14 per capita per year. The underlying geology of Hamilton County (including substantial area of tri-state region) consists of shales and limestones of Middle and Late Ordovician age. By and large, the shale in the bedrock sequence disintegrates upon exposure to air and water whereby colluvial soils are formed. The overlying colluvium, derived from this weathering process, is unstable and have been historically slow moving and may be triggered by improperly constructed developments, heavy rains, and vibrations. The characteristics of these types of movements are considered herein along with laboratory direct shear test results. It is plausible that the stability analysis of colluvial slopes should be based on the residual shear strength.
Landslides are a persistent cause of damage to properties and nuisance to the public in several areas of Ohio. In particular, the economic impact from landslide damage is significant in Hamilton County and metropolitan Cincinnati area including the tri-state region of southwest Ohio, northern Kentucky, and southeast Indiana. During the period of 1927–30, landslides along Riverside, located west of downtown Cincinnati, destroyed nearly 40 homes, reported Von Schlichten in 1935 [3]. In 1974, a massive landslide was triggered on Mt. Adams in conjunction with the construction of Interstate Highway I-471 [4]. The cost of this single landslide has been estimated at ~44.5 million dollars (in 2005 dollars). In 1982, a map produced by the United States Geological Survey (USGS) revealed that an area within the tri-state region, up and down the Ohio River, was identified to have the highest landslide activities in the U.S. [1]. In 1996, a very wet year in tristate, it was publicized that the local engineers were working on over $10,000,000 in landslide repairs throughout Hamilton County [2]. During late spring of the same year (1996), another large landslide was triggered due to excessive rainfall in the Lawyers Pointe Subdivision in Anderson Township. The impact of the reference landslide was extensive, covered a surface area of approximately 10 acres, shifted nearly 500 ft long section of Lawyers Pointe Drive, and damaged utilities within the public right-of-way [5]. The above case histories present a potpourri of landslide incidences that exemplify the nature of recurrent mass movements in the tri-state region. Fittingly, the Greater Cincinnati has been referred to the "Landslide Capital of the Nation [6]." By and large, the topography of the area is characterized by a gently rolling upland surface, dissected by deep valley cuts of the Ohio River and its major tributaries along with flood plains and terraces of the rivers.
