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 settlement size and use of public transport. There is a threshold population (ca. 20,000–30,000) at which internal bus services become more viable.
• Energy and climatic emissions: energy use in buildings is related to urban density, and climate emissions depend on the energy source. However, settlement size is linked to the viability of combined heat and power units with distributed heating.
• Waste and resource use: larger settlements generate more waste per person, but also enable higher rates of recycling.
• Water quality and treatment: larger settlements are more likely to afford full tertiary sewage treatment, with consequent improvements in local water quality; there is a minimum population threshold of about 1000 for viability of secondary treatment.
• Urban quality: congestion and noise both increase in larger settlements (though there are important Irish exceptions), but open space access is generally better in smaller settlements.

Full executive summary in report.