We spent three weeks auditing Chennai's ₹107.2-crore flood-forecasting system from the outside. Today we're releasing it as Working Paper 1 — openly, with its open questions attached. Here's what it says, in two minutes.
After the 2015 floods, Tamil Nadu bought a Real-Time Flood Forecasting & Spatial Decision Support System (RTFF & SDSS) — rain gauges, river and lake sensors, weather models, ward-level inundation maps — run with IIT Madras oversight, funded through World Bank loan money via TNUIFSL, and promoted as "India's first fully operational" system of its kind. It went live in October 2025, cost ₹107.2 crore by its own launch framing, and its promise is simple: tell neighbourhoods a flood is coming, in time to act.
The first monsoon of its second year, and the public got nothing. On 17–18 October 2026, Chennai's heaviest spell since 2023 flooded roads across north Chennai. The last bulletin the system ever published is dated 30-09-2026. During the flood the portal wouldn't load from abroad, and inside India it showed no current data. The only public predictions were IMD's generic district alerts. (Full evidence: probe note, technical detail in the paper's annex.)
Its whole public record fits in 7 PDFs. No data licence, no API documentation, no public alert feed that has ever carried an alert, and no archive of its own forecasts. You cannot check whether its forecasts were right, because the forecasts aren't published.
Behind the wall, the data exists — and we published it. The system's own map server quietly serves 344 data layers to anyone who asks: 1.7 million sensor readings, flood maps from 2005 and 2015, vendor contracts. We mirrored it and released it openly on Hugging Face. What the state doesn't document, the public can.
The mirror shows decay. On our census day only 22 of 38 flagship rain stations reported fresh data; the city's historic reference gauges have been frozen since May 2025; the ward-level flood "forecast" layer is a static scenario from August 2021.
The money is opaque. ₹71 crore in 2022 became ₹107.2 crore by 2025 (+51%) with no public revision trail. No sanction order, no contract split, no maintenance budget is public. World Bank documents name the programme but never the flagship's results.
This is a working paper, released as a living audit. The open questions are printed in it: the government's right of reply (four letters drafted, not yet answered), the exact provenance of the TN-Alert push during the flood, why the public bulletin chain stopped while the engine ran, and the hosting decision that made the portal vanish for the world during a flood. We grade every claim by evidence, and we'll update the paper as answers come.
Chennai & TN weather bloggers and amateur meteorologists: you kept the city informed when the official system didn't. Check our data, test our method, tell us where we're wrong. The station-level data is yours to use.
Civil society — Arappor Iyakkam and others: the accountability questions here (₹107.2 crore, no forecast archive, no contract disclosure) are RTI-shaped and court-shaped. The paper's 200-question bank is a ready worklist; take it, file it, build on it.
Residents and journalists: the mirror and the live view are public. If your area flooded on 17–18 October and you heard nothing from the "real-time" system, that's a data point too — and we'd like to hear it.
The state (TNSDMA, WRD, TNUIFSL, NIC): the right-of-reply letters are drafted and the register is open. Correct us with documents and we'll publish the correction with the same prominence.
Read the full working paper Live public mirror (CFM Live) Project site & datasets