Piña-García, F.; de Luis-Ruiz, J.M.; Castillo-López, E.; Pereda-García, R., and Pérez-Álvarez, R., 2019. Demarcation of coastal municipalities in Spain. Journal of Coastal Research, 35(2), 305–313. Coconut Creek (Florida), ISSN 0749-0208.

The demarcation of municipalities is essential for an adequate functioning of local administrations and the exercise of other public functions, such as jurisdiction, spatial planning, and urbanism. This research emphasizes the definition of municipalities in coastal areas, understanding that the beaches and the maritime–terrestrial zones are part of them. The limits of the beaches and the maritime–terrestrial zones are hard to determine, and the hydrographic zero is defined as an abstract line that separates terrestrial from marine. This line is difficult to define and even worse to materialize as it is a fractal object (too irregular for a geometric definition) and, in some cases, undergoes great changes through time. By analogy with what is done with normal baselines, which allow straight lines, or with the demarcation of the inner limit of the maritime–terrestrial public domain, it is proposed to identify the border of the municipality as a polygonal line whose vertices are defined by coordinates. A strictly administrative demarcation is thus proposed, which should neither modify the maritime–terrestrial public domain nor affect the inner waters or the territorial sea. As a result of the application of this methodology, the boundaries of a municipality would be defined and, therefore, its area. The proposal is applied to a practical case: the municipality of Ribamontán al Mar (Cantabria, Spain). Both the ambiguity of data and the imprecisions among the several sources of information regarding its boundary with respect to the sea are analyzed. A polygonal line defined by coordinates is proposed. This procedure could be generalized for the boundaries of any coastal municipality.