India Cyclone Zone Map — IS 875 (Part 3) Annex A
Identify cyclone-exposed regions and the k4 amplification factor per IS 875 (Part 3):2015 Annex A. Five exposure tiers from Inland (k4 = 1.00) to Severe (frequent landfalling cyclones). Click any coastal city or anywhere on the map for site-specific design implications.
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Cyclone-prone classification
India's coastline is split into Bay of Bengal (East) and Arabian Sea (West) cyclone regimes. The Bay accounts for ~75% of landfalling tropical cyclones; the Arabian Sea for the rest. Severity classes here track the frequency + intensity of historical cyclones recorded by IMD and the design implications in IS 875.
Design checks by severity
- Inland (k4 = 1.00): No cyclone amplification needed. Standard IS 875 wind design.
- Low (k4 = 1.15): West coast 30-60 km inland strip. Apply for residential.
- Moderate (k4 = 1.20): West coast 0-30 km. Industrial / commercial design.
- High (k4 = 1.30): East coast 0-60 km, frequent landfalls. Buildings, gantries, water tanks.
- Severe (k4 = 1.30+ surcharge): Direct cyclone-landfall corridor — Odisha, Bengal, Gujarat coast. Design for cyclone shelter, anchored roof framing, debris-impact load. Reference NDMA guidelines + IS 13827.
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IS 875 (Part 3):2015 — Wind Loads · Wind Speed Zone Map · Seismic Zone Map
Frequently asked questions
Which Indian cities are most cyclone-prone?
East-coast cities — Visakhapatnam, Puri, Bhubaneswar, Brahmapur, Chennai, Kolkata — face frequent landfalling cyclones from the Bay of Bengal (1-2 per year on average). Gujarat coast (Bhuj, Gandhidham, Porbandar, Jamnagar) faces Arabian Sea cyclones (1 every 3-5 years). Andaman & Nicobar islands sit on multiple tropical-cyclone tracks.
What is the k4 cyclone factor in IS 875?
k4 is a cyclone-importance multiplier applied to basic wind speed (Vb) within 60 km of cyclone-prone coast. Per IS 875 Part 3 Cl. 6.3.4: k4 = 1.00 (general industrial), 1.15 (residential), 1.30 (cyclone shelters, hospitals, schools, fire stations, lifelines). Combined with coastal Vb of 50-55 m/s, design wind speeds reach 65-72 m/s.
Are West Coast cities cyclone-prone too?
Yes, but at lower frequency than East Coast. Mumbai, Goa, Mangalore, Kochi face Arabian Sea cyclones every 3-5 years. Recent examples: Cyclone Tauktae (May 2021) hit Gujarat-Maharashtra-Goa; Cyclone Nisarga (June 2020) made landfall near Mumbai. Apply k4 = 1.15-1.20 for design.
Does cyclone factor apply to inland cities?
Per IS 875, k4 applies within 60 km of designated cyclone-prone coast. Inland cities like Pune, Bengaluru, Hyderabad, Nagpur do not require k4 amplification. However, cyclone remnants (post-landfall) can produce locally-high gusts; site-specific assessment is recommended for tall structures within ~150 km of coast.
What's the difference between IS 875 wind speed and cyclone zone?
IS 875 Fig 1 gives Vb (basic wind speed) for non-cyclonic 50-year wind. Annex A identifies cyclone-prone strips where actual cyclone gusts exceed Vb. The k4 factor in Cl. 6.3.4 amplifies Vb in cyclone zones to account for these high-energy events. Use both: Vb from Fig 1 + k4 from Annex A.
Cyclone classification combines IS 875 Annex A guidance with IMD historical track data (1900-2024 landfalling cyclones). For coastal sites within 1 km of high-water mark, apply site-specific surge + storm-water load assessment beyond the standard k4 factor.