Flood History Explorer

Explore historical flood events at any location worldwide. View flood seasonality, precipitation trigger thresholds, and event density from 2.6 million news-extracted records (2000-2026).
Data: Google Groundsource (Mayo et al., 2026) | CC-BY-4.0








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Flood Episodes
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Reports Displayed
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Avg Duration
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Peak Flood Month
Monthly Flood Seasonality
Episode counts by start month. Peak month highlighted. Event counts reflect expanding news coverage over time, not actual flood frequency changes.
Flood Trigger Thresholds
Rainfall levels that historically preceded flooding at this location, derived from ERA5 reanalysis data. The 3-day cumulative trigger is the most actionable metric for weather-based flood alerts.
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mm peak daily
Peak Single-Day Rainfall
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mm in 3 days
Typical Flood Trigger
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mm over 7 days
7-Day Cumulative Buildup
Analyzing flood records…
Click anywhere on the map to search that location.
Flood Events
Date Duration Area (km²) Distance (km)
Search a location to see nearby flood events
Data Sources
Flood events: Google Groundsource (Mayo et al., 2026). 2.6M flood events extracted from 5M+ news articles using Gemini. Licensed under CC-BY-4.0.
Precipitation thresholds: ERA5 reanalysis via Open-Meteo Archive API. Cross-referenced with historical flood episodes to derive empirical rainfall triggers.
Episode clustering: Independent flood episodes identified using a 7-day gap rule. Statistics are computed on the full dataset; the events table displays up to 500 nearest events.

How It Works

1
Enter Coordinates
Type latitude and longitude, click a preset city, or click directly on the map.
2
View Flood History
See flood episodes, seasonality patterns, and event density within a 10 km radius.
3
Analyze Triggers
Review ERA5-derived precipitation thresholds that historically trigger flooding at this location.

Frequently Asked Questions

What is the Flood History Explorer? ▼
The Flood History Explorer is a free interactive tool that lets you query historical flood events at any location worldwide. It analyzes 2.6 million news-extracted flood records from 2000 to 2026 to show flood frequency, monthly seasonality, precipitation trigger thresholds, and event density maps within a 10 km radius of your chosen coordinates.
Where does the flood data come from? ▼
The flood data comes from the Google Groundsource dataset (Mayo et al., 2026), which used Gemini to extract flood events from over 5 million news articles worldwide. The dataset covers 150+ countries from 2000 to 2026 and is licensed under CC-BY-4.0. Precipitation thresholds are derived from ERA5 reanalysis data via the Open-Meteo Archive API.
What are flood trigger thresholds? ▼
Flood trigger thresholds are empirical precipitation values derived by cross-referencing ERA5 daily rainfall data with historical flood episode dates at a given location. The tool shows three metrics: peak single-day rainfall, maximum 3-day cumulative rainfall (the most actionable for weather forecasts), and 7-day buildup. Each metric shows the median (P50) and interquartile range (P25-P75) across all matched episodes.
How is the seasonality chart calculated? ▼
The seasonality chart counts independent flood episodes by their start month. Raw news reports are clustered into independent episodes using a 7-day gap rule, so one prolonged flood event counts once regardless of how many news articles covered it. The peak month is highlighted in dark blue.
How accurate is news-extracted flood data? ▼
News-extracted flood data provides excellent global coverage but has known limitations. Event counts increased 800-fold from 2000 to 2024, reflecting expanding news digitization and satellite detection capabilities rather than actual flood frequency changes. The data overrepresents countries with high digital news coverage and underrepresents rural or developing regions. Event boundaries are often approximate city or district polygons rather than precise satellite-derived flood extents.