Methodologies For The Estimation Of Sustainable Settlement Size

Final Report - ERTDI report 4 - Moles at al

Summary: Identifies key links between sizes of settlements and their sustainability.

Executive Summary

This project aimed to identify the key links between the size of settlements and their sustainability. It was intended to provide information on the development of spatial policies emerging from the National Spatial Strategy relating to optimal ways in which to accommodate Ireland's growing population in a manner consistent with balanced regional development and environmental sustainability.

2.1 Environmental issues

• Transport: there is a clear relationship between settlementsize and use of public transport. There is athreshold population (ca. 20,000–30,000) at whichinternal bus services become more viable.
• Energy and climatic emissions: energy use in buildingsis related to urban density, and climate emissionsdepend on the energy source. However,settlement size is linked to the viability of combinedheat and power units with distributed heating.
• Waste and resource use: larger settlements generatemore waste per person, but also enable higher ratesof recycling.
• Water quality and treatment: larger settlements aremore likely to afford full tertiary sewage treatment,with consequent improvements in local water quality;there is a minimum population threshold of about1000 for viability of secondary treatment.
• Urban quality: congestion and noise both increase inlarger settlements (though there are important Irishexceptions), but open space access is generally betterin smaller settlements.

Full executive summary in report.