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Global Archive of Large Flood Events - Notes

The statistics presented in the Dartmouth Flood Observatory Global Archive of Large Flood Events are derived from a wide variety of news and governmental sources. The quality and quantity of information available about a particular flood is not always in proportion to its actual magnitude, and the intensity of news coverage varies from nation to nation. In general, news from floods in low-tech countries tend to arrive later and be less detailed than information from 'first world' countries. Here are some category-specific notes to be aware of when you are using our data:

DFO# - An archive number is assigned to any flood that appears to be "large", with, for example, significant damage to structures or agriculture, long (decades) reported intervals since the last similar event, and/or fatalities.

GLIDE# - GLobal IDEntifier Number. A globally common Unique ID code for disasters.

Country - Primary country of flooding. Other affected countries are listed in three separate fields to the right of the main Country column.

Locations - Includes names of the states, provinces, counties, towns, and cities.

Rivers - Names of rivers.

Begin - Ended - Ocassionally there is no specific beginning date mentioned in news reports, only a month; in that case the DFO date will be the middle of that month. Ending dates are often harder to determine - sometimes the news will note when the floods start to recede. We make an estimate based on a qualitative judgement concerning the flood event.

Duration - Derived from start and end dates.

Known Dead - News reports are usually specific about this, but occasionally there is only mention of 'hundreds' or 'scores' killed; in this case we estimate as follows: "hundreds"=300; "scores"=30; "more than a hundred =110 (number given plus 10%). If there is information on the number of people 'missing', the DFO does not include them in the total of deaths. We require an exact number for analytical purposes, but caution that our numbers are never more than estimates.

Number Displaced - This number is sometimes the total number of people left homeless after the incident, and sometimes it is the number evacuated during the flood. News reports will often mention a number of people that are 'affected', but we do not use this. If the only information is the number of houses destroyed or damaged, then DFO assumes that 4 people live in each house. If the news report only mentions that "thousands were evacuated", the number is estimated at 3000. If the news reports mention that "more than 10,000" were displaced then the DFO number is 11,000 (number plus 10%). If the only information is the number of families left homeless, then DFO assumes that there are 4 people in each family.

Damage (US $) - This number is never more than an estimate and we use no independent criteria for determining such. Instead we accept the latest and apparently most accurate number available in all the relevant sources.

Main Cause - One of eleven main causes is selected: Heavy rain, Tropical cyclone, Extra-tropical cyclone, Monsoonal rain, Snowmelt, Rain and snowmelt, Ice jam/break-up, Dam/Levy, break or release, Brief torrential rain, Tidal surge, Avalanche related. Information about secondary causes is in the Notes and Comments section of the table.

Severity Class - Assessment is on 1-2 scale. These floods are then divided into three classes. Class 1: large flood events: significant damage to structures or agriculture; fatalities; and/or 1-2 decades-long reported interval since the last similar event. Class 1.5: very large events: with a greater than 2 decades but less than 100 year estimated recurrence interval, and/or a local recurrence interval of at 1-2 decades and affecting a large geographic region (> 5000 sq. km). Class 2: Extreme events: with an estimated recurrence interval greater than 100 years.

Geographic Flood Extents (sq km) - This is derived from our global map of news detected floods. Polygons representing the areas affected by flooding are drawn in a GIS program based upon information acquired from news sources. Note: These are not actual flooded areas but rather the extent of geographic regions affected by flooding.

Magnitude (M) - Flood Magnitude =LOG(Duration x Severity x Affected Area)

Notes and Comments - Name of associated typhoon, hurricane or storm. Notes on the weather associated with the flood event, if floods were accompanied by landslides, or if floods were caused or exacerbated by dam or levy failures. Notes of recurrance intervals, record flooding or rainfall. Notes on infrastructure and agricultural damages, including hectares of crops or arable land flooded, or total amount of land flooded. Breakdowns of dead and displaced by country or region. Direct quotes of interesting information from news and UN sources.

If there is no information for a particular category available in our sources, then the cell is empty.

GIS Files - Available in Mapinfo interchange format. Each flood event in the Register of Major Flood Events table has an associated GIS polygon representing the area affected by the flooding in that event. The same news and governmental sources that are used to complete the entries in the tables are used to determine an approximate geographic area that is affected by the flood event; this should not be confused with actual areas of inundation. When DFO has obtained satellite data and produced a Rapid Response Inundation Map for an event a link to that map is provided in the Country column of the Register of Major Flood Events.

 

 

 

 


Direct Questions to:
Bob Brakenridge
Elaine Anderson


 

This work is made possible by data obtained by NASA, JAXA, ESA, and other space agencies, and by funding support from the Earth Surface and Interior Focus Area and the Applied Sciences Program, Science Mission Directorate, NASA, and from the European Commission, through the GDACS project, Joint Research Centre, Ispra, Italy.

 
     

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