ASPECTS OF THE GEOMETRY OF RIPARIAN BUFFER STRIPS AND ITS SIGNIFICANCE TO FORESTRY OPERATIONS

A stream buffer strip is an area within a defined distance from a stream in which land use activities are restricted for stream protection purposes. This study used a sophisticated Geographic Information System to examine the extent, distribution, and boundary properties of land defined by buffer strips of differing widths. The prototype catchment studied was the mountainous 65 km(2) Tarago River catchment in eastern Victoria. The West Tarago River is a fourth-order stream network. This was accurately delineated using the topographic map supplemented by high quality aerial colour transparencies. This showed that the map had inadequate detail of smaller streams. The streams had a branching network with an overall fractal dimension (measure of complexity) of 1.75, although the fractal dimension of the individual stream reaches was only slightly greater than one. The area of land occupied by buffers increased substantially with increasing width of buffers, with 95% of the catchment occupied by buffers of 300 m width. As buffer width increased to 100 m, many areas became entrapped by buffers and hence became effectively inaccessible. Individual boundaries reached their greatest complexity at 10 m buffer width, but the buffer/non-buffer network achieved greatest complexity at 100 m buffer width. Small buffers had a very high perimeter/area ratio. As buffer width increased the perimeter/area ratio of non-buffer areas slowly increased, reflecting that non-buffer areas were becoming smaller and more fragmented.