We agree with virtually all Kotarba and Starkel's general comments. In particular the comment that some people tend to take measurements preferentially on the most dynamic elements of relief is well taken. We would however like to respond to some points of detail.
We believe that the figures display the tabulated data (from Saunders and Young (1983) and Young ( 1974)) in a visually satisfactory manner which enables rapid estimates of process or denudation rates for given environmental conditions, assuming that the data itselfpermits this. For example, when Figure 5 is examined carefully, typical ranges of rates of denudation in prescribed climatic and relief conditions are readily yielded. The 'impression of rather chaotic pattern' observed by the critics is dispelled upon close scrutiny of the figures.
It is appreciated that data heterogeneity is a major problem in comparing slope process studies and one which is unlikely to be fully ratified. We thus sympathize with Kotarba and Starkel in that comparison between some studies is not necessarily practical. However, we have to work with what data is available. Not all process or denudation studies contain complete information pertaining to the precise environmental conditions under which they were performed. Despite the substantial volumes of slope process data published, it is still rarely possible to exercise critical comparisons simply on the grounds that this information is incomplete, and the fact that every field site is essentially unique. Hence our classification categories have to be broad to encompass the range of available data. Even with such broad classifications the number of possible environmental permutations exceeds the number actually studied in the field (Young, 1974). This is exemplified by our climatic divisions. In most studies, site climate is not specified, and regional climatic types are preferentially used. In some cases the authors inferred the climate category when it was not specified in the original paper. The sparsity of data from several of the climatic categories precludes further realistic division. The recommendation of Kotarba and Starkel to separate polar (periglacial) and montane cold environments is partly done in the tables. Whilst acknowledging the very real differences between arctic and alpine energy regimes, it can be seeen in the data that slope processes and denudation rates from the two settings exhibit appreciable overlap.
Recognizing the important role of a plant cover, vegetation types were recorded in the original data collection. However, many studies contained no site vegetation information. In a majority of cases, the information that was given was insufficient for classification and comparison purposes and it was therefore excluded.