Urban building designs trap heat by blocking natural wind flow in Indian cities

UPDATE - follow-up to Letting the wind flow freely is the secret to cooling our cities: Dense high-rise construction, high compound walls, and paved surfaces across Indian metropolitan areas are slowing near-surface wind speeds and intensifying urban heat stress.

Urban Design and Heat

Wind speed near the ground has been dropping worldwide since the 1980s in a trend known as terrestrial stilling. Amruthraj M.N., a consultant at the Indian Institute for Human Settlements in Bengaluru, points out that pedestrian levels roughly 10 metres from the ground experience this reduced wind speed. Dense buildings, high compound walls, and podiums block natural wind corridors, while asphalt and concrete replace vegetation and reduce cooling evaporation.

Wind Behaviours

When tall buildings interrupt wind flow, air can either create sheltered hot pockets or funnel through narrow gaps into sudden gusts via the Venturi effect. Winds slamming into towers can also trigger downdraughts, pushing air down into strong gusts. However, Prasad Vaidya of IIHS notes that establishing direct causal links between urban warming and stilling remains difficult without comparative studies.

Context

Urban planning rarely incorporates computer-based fluid dynamics simulations to test wind patterns due to high costs and technical demands. Experts suggest using satellite data and ventilation maps to improve airflow and combat trapped pollution and heat in cities like Chennai and Mumbai.