Strategies for Enhancing the Thermal Environment of Street Spaces in Ancient Canal Towns Based on the Design of Water-Friendly Spatial Diversity

Many ancient canal towns are distributed in southern China, serving as popular tourist destinations. However, these towns experience intense summer heat, with poor thermal comfort in their street spaces. Studying the thermal comfort of historical districts is therefore crucial for promoting tourism development. This research focuses on the Xiaohe Street Historical District, employing ENVI-met software v5.7 for the simulation analysis. Targeting waterfront spaces in ancient town historical districts, nine simulation scenarios were established to systematically compare the thermal environmental impacts of different widths, locations, and configurations of waterfront spaces. The key findings include the following. The waterfront space width shows a positive correlation with thermal environment improvement—wider spaces yield a more significant enhancement. However, when the width exceeds 5 m, a further expansion to 7 m shows a limited impact on the temperature, humidity, and wind speed, with diminishing returns. Distributed versus concentrated layouts of waterfront spaces show negligible differences in temperature and humidity regulation, but concentrated arrangements significantly enhance the street-level wind speed. Thus, under equivalent total width conditions, concentrated large-scale waterfront spaces are recommended. Installing shading facilities in waterfront spaces can effectively reduce the site temperature by over 2 °C. Aligning waterfront spaces with ventilation corridors substantially improves the wind speed, thereby enhancing thermal comfort. Through quantitative analysis, this study provides a scientific basis for optimizing thermal environmental design in canal-side historical districts. The findings offer practical guidance for similar renovation projects in canal historical districts.