Methodology

Current data sources

• Flood hazard: modeled using a weighted overlay of six environmental layers, rainfall (25%), distance from major rivers (20%), slope (20%), elevation (15%), land use and land cover (10%), and soil type (10%). Each layer is reclassified into five hazard zones and combined into a single flood hazard index, built from Copernicus DEM elevation and slope, OpenStreetMap river networks, Open-Meteo reanalysis rainfall data, ESA WorldCover land cover data, and ISRIC SoilGrids soil data. You can adjust each factor's weighting yourself on the map's Flood layer panel; the map recomputes the hazard picture live as you do.

• Earthquake hazard: modeled using a weighted overlay of fault line proximity (Global Earthquake Model active faults database), historical earthquake density (epicenter data from the Humanitarian Data Exchange), geology and lithology (ICIMOD), and a soil amplification layer (Vs30) derived from slope using the Wald and Allen (2007) proxy method. Combined into five hazard zones from very safe to very high hazard.

• Air quality: live station data from the World Air Quality Index (WAQI) network across Kathmandu Valley, refreshed every 30 minutes. A ward is coloured using its nearest active station when that station is within 4 km, wards farther away show no data rather than an estimated value. Classified into six AQI categories using US EPA breakpoints.

• Ward boundaries: official administrative boundaries covering Kathmandu, Lalitpur, and Bhaktapur districts.

A note on confidence

These are modeled estimates, not direct measurements at every point. Flood and earthquake hazard zones are ward-level approximations built from multiple weighted environmental layers, not precise point-level readings. Air quality values reflect the nearest monitoring station within 4 km, so a ward's reading is only as precise as that station, and wards beyond 4 km of any station show no data rather than an estimate.

This is v1 of the atlas. As better local data becomes available, through municipal partnerships, new surveys, or research collaborations, individual wards and layers will be updated and the confidence behind them will improve.