Changes in the visual preference after stream remediation using an image power spectrum: Stone revetment construction in the Nan-Shi-Ken stream, Taiwan

This paper investigates changes in the visual perception of a stream landscape due to remediation work (i.e., the construction of a stone revetment, which is a common ecological engineering technique in Taiwan) in the Nan-Shi-Ken stream. Various images of the Nan-Shi-Ken streambank before and after remediation were collected. The visual preference (PP) and perceived naturalness (NN), which were selected as indices of visual perception, were quantified using a questionnaire survey. The image characteristics were analyzed by the image spectrum method and presented by the spectrum-frequency slope (SS). Furthermore, the relationship between SS and the visual perceptual reaction was presented. The results of this study demonstrate that PP and NN increase with increasing vegetative cover on a stone revetment after stream remediation. PP and NN were highly correlated with SS and proportional to SS. SS provides an index to assess PP or NN for a stream landscape change due to variation in vegetation.