Abstract
The article deals with the evaluation of the visual impact arising from quarrying, mining and civil engineering works that involve extensive surface excavation. An indirect method has been formerly proposed to quantify the level of visual impact (Lvi) based on the two physical variables that define the magnitude of change in a natural landscape: the solid angle subtended by the visible alteration from a given viewpoint (Ωv) and the chromatic contrast between the alteration and the surrounding landscape (ΔEμ). These two objective variables are determined by elaborating the digital images of the landscape under investigation, taken from the most representative viewpoints. The Lvi indicator has proven to be highly correlated with the judgement values expressed by potential observers and thus may represent a valuable operative tool in the environmental impact assessment (EIA) procedures, both for the proponent of new projects and for the governmental authorities in charge of decision-making. This article describes a further development of the Lvi method, which aims at improving the repeatability of the impact evaluation by eliminating some critical issues related to the definition of both the excavation limits and the natural comparison surfaces representing the natural landscape. To that end, the original calculation code has been implemented with two image segmentation algorithms, which objectively designate the areas within the picture to be used for the automatic calculation of the impact level Lvi. The updated code has been validated against the original Lvi method, thus confirming the suitability of the revised methodology to represent the perception of potential observers.
Highlights
The visual impact defines the modification of a given visual resource and the consequent effect on the perception of potential observers
The updated code has been applied to eight cases of surface excavation and the results were found in accordance with those obtained with the original level of visual impact (Lvi) method, confirming the suitability of the revised methodology to represent the perception of potential observers (Dentoni and Massacci 2007)
The level of visual impact Lvi is defined by Eq (1), where Ωv is the solid angle subtended by the visible altered area from a given viewpoint, Ω0 (8,46·10–8 sr) is the human visibility threshold in a black and white (BW) colour space, ΔEμ is the mean value of the chromatic contrast between the quarry and the surrounding landscape, and ΔEBW is the chromatic contrast between black and white
Summary
The visual impact defines the modification of a given visual resource and the consequent effect on the perception of potential observers. The updated code has been applied to eight cases of surface excavation and the results were found in accordance with those obtained with the original Lvi method, confirming the suitability of the revised methodology to represent the perception of potential observers (Dentoni and Massacci 2007).
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