Patch–Street Coupling for Heat-Relief Placement of Small Urban Green Spaces in Temperate Neighbourhoods

Abstract

Heat adaptation of compact temperate neighborhoods usually relies on green spaces since additional land to accommodate larger parks is scarce. The heat mitigation capacity of such spaces cannot be estimated just in terms of their surface areas. One-hectare intervention may perform like a shade destination, cooling interface with streets, or both depending on patch division, compactness, grouping, width of streets, and direction of streets. Street-Coupled Thermal Allocation (SCTA) methodology is utilized in order to find out which one-hectare layout suits best each of four neighborhood morphologies when pedestrians’ heat stress is considered the goal of urban planning. Numerical parameter sets incorporate four types of streets and eight types of one-hectare layouts. Four street types, designated as T1 to T4, vary in street area share, height-to-width ratio, and orientation composition. Eight layouts of one hectare, referred to as S1 to S8, differ in patch area, total patch number, shape index, grouping property, and association with wide and narrow streets. Calculation is performed separately in respect of Local Green Refuge Score and Street Cooling Transfer Score with further aggregation of these two scores with coefficients 0.55 and 0.45, respectively. It turned out that grouped and compact layouts (S7, S8) ensure maximum performance with regard to local refuge, and grouped wide streets provide maximum cooling transfer capacity (S1, S3). Combining the two scores yields maximum values in favor of S1 layout within T1, T2, and T4, equaling to 0.719, 0.689, and 0.740, respectively. Layout S8 wins in terms of SCTA score for T3 with score equaling to 0.721 and also proves to be very effective for T4 neighborhood morphotype with SCTA value of 0.730. Layout S3 maintains its good performance throughout and reaches 0.728 in case of T4 type of morphology. The results suggest that one-hectare green space layout optimization is a morphology-related task, whereby grouping and wide streets are more appropriate for the street cooling transfer goal, while compact cross-street placement is better for diagonal morphology.