Role of soil joints in causing bluff erosion along the Lake Erie shoreline, northeast Ohio
Thomas A. Highman, and Abdul Shakoor
Vadose Research, North Canton, OH, United States
Kent State University, United States
Bluff erosion along the Lake Erie shoreline in Ohio is a major environmental problem causing extensive damage to homes, agricultural land, and lakeshore roads. The most extensive erosion takes place in areas where the bluffs are made of well-jointed, overconsolidated, glacial till material (CL; ML-CL) that is overlain by lacustrine silts (ML) or silty clays (CL). In order to investigate the effect of soil joints on bluff erosion, four sites, all characterized by the presence of well-developed joints, were selected between Painesville, Ohio, and the Ohio-Pennsylvania border. The detailed line survey technique was used to measure orientations and other aspects (continuity, spacing, surface features, aperture, nature of infilling material, presence or absence of water) of the joints at the four sites. Erosion rates were monitored on a bi-weekly basis for a period of one year, using equally spaced pegs on the bluff face. Photographs were taken frequently to aid in monitoring of bluff erosion. Results indicate that bluff erosion in the study area is greatly influenced by the presence of joints in the glacial till. The joints enhance erosion by providing pathways for water movement in both horizontal and vertical directions which, in turn, leads to widening of the joint openings and piping of the overlying silty material. The buildup of pore pressure along the joints, after a prolonged rainfall or a sudden snowmelt, also contributes to bluff instability. In the toe area, wave attack results in the formation of notches, cavities, and concave zones. Erosion at the bluff toe, accelerated by soil joints, initiates block falls and planar slides along the pre-existing joint surfaces above the toe area. The slump and flow type failures that occur in the overlying lacustrine material are a consequence of the joint-promoted failures in the underlying till. Thus, any remedial measures that are undertaken to minimize bluff erosion along Lake Erie must take into account the effect of soil joints.
This record provided courtesy of AGI/GeoRef.
