How visible are the valley slopes in the city? A viewshed analysis in the urban agglomeration of Liège

Valley slope is a cultural and ecological resource of many cities that has gained attention in recent decades. Even if valley slopes are the background of numerous cities, they are scarcely considered by 'Viewshed Analysis'. In urban areas, the focus is on the visibility of individual biotic or abiotic elements, such as trees or buildings, assessing the impact of isolated components rather than understanding the place's topography. This contribution experiments with valley slope viewshed analysis through a case study of Liège's urban agglomeration. We propose a methodology articulated through the combination of GIS mapping, statistical analysis and photographic survey to address gaps related to the identification of valley slopes' visibility in an urban agglomeration and to investigate the elements of urban form that influence its visibility. The research highlights different degrees of valley slope visibility and different ways of urban form influencing it.