LANDSLIDING IN ALLEGHENY COUNTY, PENNSYLVANIA: CHARACTERISTICS, CAUSES, AND CURES (SLOPES, DELPHI

Allegheny County, Pennsylvania has long been acknowledged as being in a region prone to landsliding. The numerous slope movements that occur in the county typically result from the combination of natural conditions and activities of man. Although not generally life-threatening, these slope failures have been costly to the public and private sectors both in time and money. To help alleviate the impact of slope failures in the county, there is a need for some method to better evaluate the potential for slope movement in the preliminary stages of a project before data from laboratory testing, subsurface investigations, etc. are available.;In trying to establish such a method, over 700 slope movements were inventorized and over 200 of these slope failures were field visited. A computerized database was developed containing information on the variables thought to be responsible for the movements.;To provide some degree of predictability, a groups of experts on landsliding in Allegheny County was asked to rate the variables responsible for slope movements in the county. The Delphi technique was used to obtain a consensus from this group on the importance of each variable.;An empirical model was developed to describe the slope-movement process with input data for the model being structured so that it can be obtained from information collected during a typical office study and field reconnaissance. The model was used to establish ranges of slope-movement potential for areas within the county.;The use of this empirical model appears to be a promising method for evaluating the potential for slope movements in the county. The procedures used to develop the model could act as a guide for other investigators attempting to formulate models for other developed areas.;Various methods were presented for landslide-hazard mitigation in the county but most are probably not likely to be utilized because of the costs associated with their implementation. The need for more consideration of the social, economic, political, and cultural attitudes and conditions in this region when developing mitigation methods was also identified.