Geotechnical Risk Associated with Hillside Development

Slope instability has been a problem in both house and sub-divisional development on hillsides in the Newcastle-Sydney-Wollongong region for some time. Instability in its geotechnical sense is dramatically observed as lands lips, landslides and mudflows and these phenomena have been recorded in the region at least since the turn of the century. Slope instability has become particularly evident in the past 30 years with the more intense development of available land and the greater acceptance of, and even preference for, house sites on steeply sloping land. In the most severe problem areas land instability has led to the destruction of houses, whilst in other cases the development of large areas has been severely restricted.

Members of the Sydney Group of the Australian Geomechanics Society have been particularly aware of the problems and in 1985 a sUb-committee was established to develop a risk classification for slope instability and to provide guidelines for hillside construction. The sub-committee subsequently prepared a classification and terminology system which can be uniformly used by geotechnical consultants and which can be readily understood by landowners as well as council engineers and surveyors, structural engineers and architects.