Evaluating urban heat adaptation strategies for extreme heatwaves in complex terrain: A case study of Grenoble, France

Urban heat adaptation strategies are critical for mitigating the impacts of ex- treme heat events in cities, particularly as climate change exacerbates their intensity and frequency. This study evaluates a set of adaptation strategies during the 2023 heatwave in Grenoble, France, using the WRF model with the BEP+BEM urban canopy scheme. Eight scenarios are simulated, including increased vegetation, reflective surfaces, enhanced building insulation, permeable surfaces, and combined strategies, assessing their effects on air tem- perature, thermal comfort (UTCI), and energy demand. The results highlight that strategies involving vegetation, reflective surfaces, and building insulation are particularly effective in reducing temperatures and improving thermal comfort, with tree-based interventions show- ing the greatest impact. Combined strategies enhance these effects, providing near-additive reductions in heat stress, especially during the day, and improving both outdoor and indoor conditions. Building-focused interventions (e.g. insulation) significantly lower energy de- mand, whereas ground-based strategies (e.g. permeable ground) primarily improve outdoor thermal comfort. Urban morphology strongly influences the effectiveness of these measures, with densely built areas benefiting the most. This work emphasizes the importance of inte- grating diverse strategies to address urban heat, bridging immediate mitigation efforts with long-term resilience planning.