Bengaluru - Flood risk399 hotspots - 163 primary drains - 870 secondary drains - KSRSAC via OpenCity (Nov 2025)

Bengaluru's flood risk

Bengaluru sits on a ridge that drains into three valleys - Vrishabhavathi (west), Koramangala-Challaghatta (south-east), and Hebbal-Nagavara (north). When monsoon rainfall exceeds the storm-drain network's capacity, water backs up at the named hotspots on this map. The 2022 monsoon submerged Whitefield / Manyata Tech Park / Outer Ring Road East for days; the 2024 events extended into Yelahanka and Bommanahalli.

What this map shows

163 primary stormwater drains (rajakaluves) - the main BBMP-wide drainage spine, NGT-protected with a 50 m buffer order.
870 secondary drains - feeder network connecting wards to the rajakaluves.
70 named flood-prone localities - BBMP's curated list of named hotspots with documented flooding history (e.g. Bhadrappa Layout, Sampangirama Nagar).
129 named low-lying areas - additional KSRSAC dataset of named low-elevation neighbourhoods (e.g. JRD Tata Nagar, Devi Nagara).
200 unnamed vulnerable points - KSRSAC's broader vulnerability layer; toggle off by default because the unnamed cloud crowds out the named-locality story. Named-locality cross-reference is a follow-up RTI to BBMP.

Data we don't have

5 / 10 / 25 / 50 / 100 / 200-year return-period polygons. The DST-funded IISc-KSNDMC Urban Flood Model (Current Science vol. 120 no. 9, May 2021) produces these by valley but the underlying rasters aren't republished. Acquisition path: RTI / partnership ask through T.V. Ramachandra's group at IISc CES.
Tertiary drains (~5,800 features). Available from KSRSAC as a 17 MB GeoJSON - too heavy for raw browser load; queued for a PMTiles follow-up.
Live rainfall + SWD water-level. KSNDMC has 100 ARG + 12 AWS + 25 SWD sensors inside BBMP at 15-minute cadence. The Bengaluru Megha Sandesha app surfaces "now" only - bulk historical and a public REST feed are partnership-only.
BBMP rajakaluve survey-number GIS. KSRSAC's primary-drains KML here is the public summary; the underlying survey-number-resolution dataset stays with BBMP SWD Department. RTI ask logged.

External monitoring sources

KSNDMC - Karnataka SDMA - 100 ARG / 12 AWS / 25 SWD sensors in BBMP, 15-min cadence (live via Megha Sandesha app)
ISRO Bhuvan - satellite flood-inundation layers for major historical events (2005, 2022, 2024)
World Bank P506272 - Karnataka Water Security & Resilience Program ($426M, 2025) - references 372 flood hotspots 2013-2020 + 183 lakes as balancing reservoirs
IISc CES - T.V. Ramachandra urban-flood papers - valley-wise catchment + low-lying-ward analysis (ETR114 / ETR123 / ETR131)
BMTPC Vulnerability Atlas - Karnataka district-level flood hazard map (national context)

All spatial data on this page is sourced from OpenCity Bengaluru, which republishes KSRSAC's public-domain KMLs. Last source refresh: 27 November 2025.

See /bangalore/about for the full data-source index and the IISc partnership ask logged as a Tier-1 follow-up.