The use of fractional acre plots to predict soil loss from a mountain catchment

In 1941 the Government passed the Soil Conservation and Rivers Control Act which set up Catchment Boards and Commissions to (inter alia) conserve soil resources and prevent damage by erosion. In view of the accepted extent and severity of erosion, and in the intensity of former debates, it is a matter of some surprise that there were, and still are, no measurements relating to the stability of soils on steep slopes. While this lack of data has been a handicap in the past it will without doubt become a greater barrier to progress in the future. In recent years a few investigations have been made of materials and techniques for the revegetation of high altitude eroded lands. (O’connor and Lambrechtsen, 1967; Nordmeyer, pers comm; Dunbar, 1967.) However, before the results from studies such as these can be used in action programmes it will be necessary to know the benefits of such work in terms of reduced soil loss or surface water runoff. It was therefore decided to set up a study which, it was hoped, would determine the extent of soil movement within one mountain catchment, and assess the influence of plant cover and type on soil stability. To carry out such a study, a number of possible techniques were considered, but the fractional acre runoff plot method appeared to have a number of advantages which could not be overlooked. The most important were that the technique had been used under diverse conditions in the United States for nearly 50 years with apparent success. In addition the plots were inexpensive, easy to install, and could provide information in relatively short time periods. Elsewhere the author has reviewed the use of runoff plots in erosion research (Hayward, 1967b) and critically discussed some of the major deficiencies of experimental design common to most studies (Hayward 1969). This study attempted to rectify the major deficiencies of design, and use the plots to sample the erosion behaviour of the subareas of a small mountain catchment. It was hoped that the erosion behaviour of the sub-areas and the catchment could be predicted from the behaviour of this sample.