High resolution seascape visibility tool for aquaculture marine spatial planning

Aquaculture is recognized as the fastest-growing animal production system worldwide. However, it often encounters public opposition due to the visual impact of fish farm infrastructures, which represents a significant constraint in policy decisions related to the allocation of marine areas for aquaculture development. This study presents the r.wind.sun_aqua tool, an adaptation of the open-source r.wind.sun module for GRASS GIS, designed to identify marine areas suitable for aquaculture based on visual impact, thereby supporting the integration of aquaculture development within the landscape. The tool combines viewshed analysis with a quantification of distortion of observed objects in the visual field, generating a Non-dimensional visual impact Index (NI) to represent human perception of aquaculture structures. A high-resolution LiDAR Digital Surface Model (DSM) is used as input, ensuring precise and reliable evaluations.

The tool was tested in the Gulf of Gaeta (Italy), an area that hosts, among others, fish and shellfish aquaculture, tourism, high-value landscapes, and cultural heritage sites. The average NI was calculated for the locations of existing fish farms and four potential new aquaculture sites. Based on high-resolution NI maps, existing fish farms were found to have a greater impact on the seascape visibility of the Gulf of Gaeta compared to the proposed new farming sites.

The r.wind.sun_aqua tool proved effective in assessing and quantifying the visual impact of fish farming facilities on coastal landscapes. It is currently being developed into a user-friendly, open-source QGIS plugin to assist non-experts in analysing the visual impact of aquaculture on coastal areas.