Indicators of Agglomeration: Using Population Density Grids to Assess Growth Momentum in Identifying the Emerging City of Drogheda with Laytown-Bettystown-Mornington (LBM).

Brian Hughes, Dublin Institute of Technology

Document Type Report

Academic research paper, April 2016.


In earlier research literature this author deployed both population size and daytime working population data as measures of potential settlements, for selection as comparable growth centres for the National Spatial Framework, vide Hughes (2013). An identified problem, encountered in defining urban settlements and that of their spatial extent, is the dilemma of opposites; of being able to distinguish between the physical ‘separation’ and the agglomerating ‘contiguity’ of discrete settlements. Focusing on linear distance as its principal ‘separation’ measure, the United Nations provides a limiting description, for separation, in the task of quantifying singular urban fields of agglomeration and thus in identifying processes of city formation. In contrast, The World Bank advocates three ‘D’s which, in addition to Distance and Division, includes Density (2009). Particularly for Ireland as a sparsely-populated country this latter measure assumes particular importance, especially given Ireland’s scarce number of large settlements and their linear distances from each other. The Central Statistics Office (CSO) now has the facility for grid-enabled data, which can be used in distinguishing between examples of scattered morphology of sparsely-populated ribbon development in contrast to that which can identify densifying urbanisation.

Prior to the availability of the 2016 census population results this paper investigates and applies population grid data measures based on the CSO grid-based demographic data from the 2011 census. Applied to a real-life example, this technique facilitates the further research objective of identifying Ireland’s emerging sixth city, the east coast agglomeration of Drogheda with Laytown-Bettystown-Mornington (LBM). In its census of 2011, the CSO adopted the United Nations updated convention for Settlement distancing in its application of the ‘100 Metre’ rule for settlement separation. This is applied to habitable buildings, including both residential and non-residential structures. The rationale for its use is …to avoid the agglomerating of adjacent towns caused by the inclusion of low density one off dwellings on the approach routes to town. CSO 2011 Census, Area Volume, Appendix 1.

Analysing the agglomeration of LBM with Drogheda and in comparing this with that of Blackrock (Louth) with Dundalk, on the basis of the EU Grid criteria this Paper concludes by noting the need to distinguish between physical separation and that of physical agglomeration and proximity densification, especially for governance and local administration purposes in this new Putting People First era of local governance rationalisation.