ABSTRACT
This chapter reviews the development of scree slopes and considers three aspects: debris input from the headwall, scree slope accumulation and form, and subsequent long-term behavior through weathering. Supply of debris from the headwall is largely controlled by weathering along discontinuities, though climatic processes act as immediate trigger mechanisms. Consequently, any study of headwall slope development must take account of the rock structure if meaningful relationships between form and process are to be made. The subscree rock slope profile is theoretically convex in form, resulting from recession of the headwall and protection of the buried face. In practice, previous slope form often masks this theoretical trend. Models of scree slope accumulation must explain frequently observed slope characteristics, principally a straight profile with basal concavity, and downslope fine to coarse particle sorting. A rockfall model is consistent with these characteristics, the basal concavity resulting from an exponential distribution of downslope travel distances. Sorting is due to greater frictional resistance of smaller particles. The frictional resistance of a moving particle is dependent on particle shape and surface characteristics. Weathering of scree deposits may cause considerable changes in particle properties, such as particle size, grading, and shape. Relatively small changes in material strength may result, however, and the most important effect of weathering will be to reduce hydraulic conductivity. Ultimately this may lead to instability, which, for a number of reasons, is most likely to occur at the top of the scree slope, in contrast to regolith-covered hillsides.
