Piyush Narang *, Shruti M. Deorah, Ashok Gadgil
Over 250 Indian cities have adopted Heat Action Plans (HAPs), but fewer than a handful include ward-level vulnerability assessments or translate risk data into quantified intervention needs.
Current HAP development requires months of effort per city, a model that cannot scale to 5,000 urban local bodies in a reasonable timeframe. Ward-level assessments require Geographic Information System (GIS) expertise and sustained technical assistance that few cities can access. Scaling heat action planning nationally demands a different approach: near-zero marginal cost, ward-level targeting, and budget-ready intervention estimates.
CHAITRA is a ward-level decision support tool built on Google Earth Engine that can enable state and city officials to accelerate heat action planning, identify wards most at risk and estimate investment needed for different mitigation measures.
Using publicly available satellite imagery, population estimates, and land cover data, it generates heat risk assessments aligned with the Intergovernmental Panel on Climate Change (IPCC), Sixth Assessment Report (AR6) framework (Risk = f (Hazard, Exposure, Vulnerability)). The system produces seven analytical layers — urban heat islands, population heat risk, cool roof priority, tree planting priority, 24-hour heat zones, dense/vulnerable housing, and composite risk index — each translating risk into quantified intervention targets: number of trees, rooftop area for reflective coatings, cooling center capacity, and budget estimates.
Browser-based and requiring no GIS expertise, CHAITRA extends to any city with digitized ward boundaries at near-zero marginal cost.
| Layer | Policy Question | Budget & Action Implication |
| Surface Temperature | Which areas are HOTTER or COOLER than the city average? | Answers: Where are the relative hot and cool spots? Drives: Diagnostic layer for pattern identification. Use to locate cool refuges to protect and hot clusters for intervention targeting. |
| Population Heat Risk | Which wards have the MOST PEOPLE facing dangerous heat conditions? | Answers: How many people must we protect, and where? Drives: Cooling center siting, ambulance staging, medical teams, water distribution plans. |
| Cool Roof Priority | Where are COOL Roofing programs most needed and impactful? | Answers: Where should we invest in cool roofs first? Drives: Subsidy zone designation, procurement scale. |
| Tree Planting Priority | Where is URBAN GREENING most needed and impactful? | Answers: How many trees, where, over what timeline? Drives: Sapling procurement, planting locations (streets, schools, parks), maintenance contracts. |
| 24-Hour Heat Zones | Which wards have PERSISTENT HEAT STRESS across day and night combined with high economic activity? | Answers: Where do night-shift and outdoor workers need protection? Drives: Shaded bus shelters, public water points, rest areas, cool pavement corridors. |
| Dense/Vulnerable Housing | Which wards have the highest concentration of DENSE, LOW-RISE BUILDINGS? | Answers: Which bastis need immediate heat-resilient upgrading? Drives: Community water, sanitation, solar fans, reflective roofing. Links to PMAY/AMRUT. |
| Land Use | What is the DOMINANT LAND COVER in each area? | Answers: Where are built-up, vegetated, water, and barren zones? Drives: Baseline for intervention feasibility, identifies plantable open spaces, waterbody buffer protection, built-area targeting for cool roofs. |
| Heat Risk Index (IPCC) | Which wards need COMPREHENSIVE, bundled intervention? | Answers: Where should we concentrate integrated Heat Action Plan resources? Drives: Ward-level bundled budgets, intervention mix (cool roofs + trees + emergency), phased implementation. |
