Assessment of the Buffer-Induced Setback Effects on Riparian Scenic Quality by Digital Tools

Under a typical riparian landscape structure where a vegetated buffer is sandwiched between a greenway trail and the river bank or lake shore, a trail user's perceptions about riparian scenic quality are influenced by, among other factors, buffer-induced setback effects. As a trail is set back to leave enough space for the vegetated linear area, both the subject and the composition of a trail user's viewshed can change significantly. This may in turn affect his or her perceptions of the lakescape or riverscape. For greenway trail planners, the buffer-induced setback effects become most relevant when they have the option of allocating trails behind either a legislature-regulated buffer with constant width or a scientifically recommended buffer of variable width. In North Carolina's Piedmont region, the discrepancy in width between constant and variable buffers may range from 10 to 200 m, large enough to cause significant visual variances. In this paper a method to investigate these setback effects is presented. Based on Shafer's landscape-photography approach, a technique called BISEA (buffer-induced setback effect assessment) is designed to inquire and represent two pieces of information about the setback effects. These are: (1) the subject and composition changes in prospective trail users' viewsheds caused by buffer-width variations; and (2) the impacts of these changes on riparian scenic quality as perceived by trail users. Implementation of the method is facilitated by a computer-based support system that comprise tools for landscape photography (a digital camera), survey [a global positioning system (GPS) receiver], image processing (a digital image-processing program), database management and visualization (a GIS), and scenic quality assessment (a spreadsheet program).