Walkable by nature? Adding green and blue space to walkability indices and assessment of socioeconomic inequalities.

Abstract

Green and blue spaces protect against heat exposure and provide opportunities for physical activity, social connection and psychological restoration. However, few studies combine green and blue space with walkability indices, potentially under-estimating levels of socioeconomic inequity. We aimed to create walkability indices that included green and blue walkability and compared these with conventional walkability methods. Walkability network buffers (400m, 800m, 1600m) around Australian Bureau of Statistics (ABS) mesh blocks were created for one large (Sydney) and two smaller cities (Newcastle, Wollongong). Estimates were made of network walkability areas using: 1) population density; 2) street connectivity; 3) destination availability; 4) street and park tree canopy percentage; and 5) blue space percentage (determined by a 10m buffer around coastlines/water bodies, and a 50m buffer around beaches). Z-scores for each of the five domains were calculated and used to create five walkability index models. Choropleth and bivariate maps were analysed for spatial patterns. Spearman's rank correlation coefficient was analysed between socioeconomic disadvantage and measures of walkability with and without green and blue space embellishment. For all three cities together at the 1600m scale, green + blue walkability was moderately associated with low socioeconomic disadvantage (Rho = 0.5163, p-value<0.0001). In comparison, conventional walkability was negligibly associated with more disadvantaged areas (Rho = -0.0680, p-value<0.0001). For Sydney, conventional walkability and green + blue walkability were weakly but positively related at 1600m, but had a negligible relationship at 400m. Incorporating measures of green and blue space reveals greater levels of socioeconomic inequality in walkability than previously recognised. Spatially targeted investment in green and blue space is accordingly indicated to better balance socioeconomic inequalities in walkability. Incorporating blue and green infrastructure into walkability indices could also assist in global heat mitigation to reduce urban heat islands.