Evolution of Edges and Porosity of Urban Blue Spaces: A Case Study of Gdańsk

Current waterfront studies focus mainly on a land-based perspective, failing to include the water side. Water is, however, not just a resource for port and industrial purposes and an edge to the waterfront; it is also a feature of the waterfront and the complex relation between water and city. Thus, the article suggests that water-land edges need to be re-contextualised, taking into consideration also their shape, functionality, and evolution over time. This article therefore introduces the concept of urban blue spaces, that is, spaces that include at least one land-water edge, such as a shoreline or river edge. The types and character of these edges define the porosity of urban blue spaces: Spaces with easy connections, such as boulevards or parks, are highly porous, while fenced areas have low porosity. The research first analyses the existing literature on the spatial and functional characteristics of the land-water edge in port cities, and explores existing typologies of urban blue spaces. The results of this investigation are used to examine the most iconic urban blue space of Gdańsk, the Motława river, over the last 1000 years. The case study shows that the porosity of the Gdańsk urban blue space has been increasing over time, in line with its spatial and functional development from an undeveloped riverbank to a ‘gated’ port and industry area, to urban living spaces today. The article thus presents the whole breadth of urban blue spaces through the case study of the Motława river urban blue space. The spatial evolution of the urban blue space is depicted through the transformation of its land-water edge—from a natural sloping edge to the dominance of vertical edged structures or ones overhanging the surface of the water, to the emergence of spatially ‘blurred’ sloping, slanted, terraced, and floating structures, partially independent of the riverbank. The transformation of the structure of the Motława urban blue space edges increased its complexity over time, from a single-edge structure to a double and multiple-edged one.