NRT Global Flood Products

Summary

Updates

April 6, 2026: A reprocessed historical archive of the MODIS flood product (MCDWD_L3) covering 2003-2025 was released, along with an ongoing archive of the NRT MODIS flood product, from January 2026 onward (MCDWD_L3_NRT). Both are available from LAADS DAAC. Please see the section below — MODIS Historical Reprocessed Archive Product Details — for more information. 

Dec. 11, 2025: Both MODIS and VIIRS products were updated to Release 1.1 (User Guide revision F), with the addition of recurring flood classification. This tool helps discriminate unusual flooding from recurring flooding, which is defined as flooding that has been observed in the same location in roughly one third of the years in the reprocessed 22-year archive (2003-2024). (Please see the User Guide for details.) The VIIRS product was updated to use the final cross-calibrated surface reflectance for NOAA-21; this was an upstream update to the VJ209 surface reflectance product. The FLOOD viewer was also released to assist end users with evaluating this and other flood products. 

April 16, 2025: VIIRS product Beta 1 was published (User Guide Revision E) and HDF product files were made available (including Geotiff files). The product was also added to Worldview. In this Beta 1 release, we used the preliminary calibration for NOAA-21 surface reflectance. 

The MODIS and VIIRS products use the same overall algorithm and processing, with a few differences.

• Resolution: MODIS source imagery is nominally at ~250 m resolution for the primary red and near-infrared bands, while the VIIRS source imagery is 375 m resolution. To simplify adapting the code to work for VIIRS, the incoming VIIRS data is resampled to the same ~250 m latitude/longitude grid as the MODIS product.
• Observation times: Until 2022, the nominal equatorial overpass times for MODIS were 10:30 a.m. for Terra and 1:30 p.m. for Aqua. As the satellites reach end-of-life, fuel supplies have been exhausted, and overpass times had drifted to about 9:30 a.m. and 3:00 p.m., respectively, as of December 2025. They will continue to drift. All VIIRS instruments only provide afternoon observations, nominally ~1:30 p.m., although currently NOAA-20 and NOAA-21 are separated by about 50 minutes. The 50 minute separation was found to be sufficient to improve the product, compared to using data from only a single VIIRS instrument. But the VIIRS product is expected to be of somewhat lower quality than the MODIS product due to loss of the less cloudy morning observations provided by Terra.
• Current day files: The MODIS MCDWD product files are updated in-place as new observations are received and processed throughout the day. The user must check timestamps on the files to determine if they have been updated. For VIIRS, there is a separate hourly cumulative product generated for the current day: VCDWDG. The filenames have an additional element indicating the hour of production. For example: VCDWDG_L3_NRT.A2025063.2000.h08v06.002.h5 was generated at 20:00 (GMT). For a given tile, there will likely be two to four such files generated over the course of a day, as additional observations intersecting that tile are received. Thus, a user interested in the product for the current day should select the file with the highest hourly timestamp. It will incorporate all data received to that point in the day. The file generated with what would be a 2300 timestamp contains all the data received for the day, so is generated as the final VCDWD product, not as VCDWDG (and so will be located in the VCDWD download directories).  
• HDF format: The MODIS product is generated in EOS-HDF4 (with .hdf file extensions), while the VIIRS product is in EOS-HDF5 (with .h5 extension).

MODIS NRT Product Details

MODIS Historical Reprocessed Archive Product Details

In addition to the NRT MODIS flood product, a reprocessed historical archive (2003-2025) is available via LAADS. 

Key differences: The NRT product (MCDWD_L3_NRT) uses expedited geolocation and atmospheric inputs to meet rapid delivery requirements, while the reprocessed archive (MCDWD_L3) uses standard science-quality inputs for improved long-term consistency. Both use the same underlying algorithm and provide the same flood map layers. See the product description document for additional details. Note that the historical product is only available as HDF files.

VIIRS NRT Product Details

Support

• User Guide, Revision F, Dec. 11, 2025: MODIS/VIIRS NRT Global Flood User Guide
• Contact Earthdata Support
• To be notified of updates, please email floodmap-join@lists.nasa.gov (no text or subject required)
  • To unsubscribe: e-mail floodmap-leave@lists.nasa.gov (no subject or text is required)
• Main POC - Dan Slayback, NASA Goddard Space Flight Center

Data Access/Download

View the flood data in Worldview, as well as the "Assessing Floodwaters" tour story.

The FLOOD Viewer web tool allows advanced users to easily compare MODIS and VIIRS flood products, including 1-day composites, with other flood products such as the NOAA-GMU VIIRS product and the NASA OPERA surface water products. 

HDF and GeoTIFF Product Downloads: 

Product downloads require free registration with the Earthdata Login registration system.

Automated and bulk download instructions.

NRT products are available from a primary server and a backup server:

• Primary LANCE server 
• Backup/Secondary Lance server

MODIS HDF Files

For MODIS HDF files navigate to: NRT Data → allData → 61 → MCDWD_L3_NRT or navigate to:
https://nrt3.modaps.eosdis.nasa.gov/archive/allData/61/MCDWD_L3_NRT

VIIRS HDF Files

For VIIRS HDF files navigate to NRT Data → all Data → 5200 → VCDWD_L3_NRT (VCDWDG_L3_NRT for hourly) or navigate to:
https://nrt3.modaps.eosdis.nasa.gov/archive/allData/5200/VCDWD_L3_NRT

MODIS GeoTIFFs

For MODIS GeoTIFFs (one for each of the four flood composite products in each HDF file)
navigate to: NRT Data → allData → 61 → MCDWD_L3_F<X>_NRT (where X is the composite of interest: 1, 1C, 2, or 3) or navigate to:

https://nrt3.modaps.eosdis.nasa.gov/archive/allData/61/MCDWD_L3_F1C_NRT
https://nrt3.modaps.eosdis.nasa.gov/archive/allData/61/MCDWD_L3_F1_NRT
https://nrt3.modaps.eosdis.nasa.gov/archive/allData/61/MCDWD_L3_F2_NRT
https://nrt3.modaps.eosdis.nasa.gov/archive/allData/61/MCDWD_L3_F3_NRT

VIIRS GeoTIFFs

For VIIRS GeoTIFFs (one for each of the four flood composite products in each HDF file)
navigate to: NRT Data → allData → 5200 → VCDWD_L3_F<X>_NRT (where X is the composite of interest: 1, 1C, 2, or 3) or navigate to:

https://nrt3.modaps.eosdis.nasa.gov/archive/allData/5200/VCDWD_L3_F1C_NRT
https://nrt3.modaps.eosdis.nasa.gov/archive/allData/5200/VCDWD_L3_F1_NRT
https://nrt3.modaps.eosdis.nasa.gov/archive/allData/5200/VCDWD_L3_F2_NRT
https://nrt3.modaps.eosdis.nasa.gov/archive/allData/5200/VCDWD_L3_F3_NRT

MODIS Historical Archive

For access to the reprocessed historical archive (MCDWD_L3, 2003–2025), navigate to LAADS:
https://ladsweb.modaps.eosdis.nasa.gov/archive/allData/61/MCDWD_L3/

Additionally, the MODIS NRT product will be archived on LAADS from January 2026 onward. Note these are simply the original NRT files (MCDWD_L3_NRT) and have not been reprocessed as the above 2003-2025 archive has. 
https://ladsweb.modaps.eosdis.nasa.gov/archive/allData/61/MCDWD_L3_NRT/

Tile Map

Citations and Disclaimer

Citation for the MODIS NRT product: 

NRT MODIS/Aqua+Terra Global Flood Product MCDWD_L3_NRT distributed from NASA LANCE. Available online [https://www.earthdata.nasa.gov/global-flood-product]. doi:10.5067/MODIS/MCDWD_L3_NRT.061

Citation for the reprocessed historical archive (MCDWD_L3, 2003–2025):

MODIS Aqua+Terra Global Flood Product MCDWD_L3 (Reprocessed Archive) distributed from NASA LAADS DAAC. Available online [https://www.earthdata.nasa.gov/global-flood-product]. doi: 10.5067/MODIS/MCDWD_L3.061

Citation for the daily VIIRS product: 

VIIRS/JPSS1+JPSS2 Daily L3 Global Flood Composite 250m Linear Lat Lon Grid NRT (VCDWD_L3_NRT) distributed from NASA LANCE. Available online [https://www.earthdata.nasa.gov/global-flood-product]. doi:10.5067/VIIRS/VCDWD_L3_NRT.002

Citation for the hourly VIIRS product: 

VIIRS/JPSS1+JPSS2 Hourly Cumulative L3 Global Flood Composite 250m Linear Lat Lon Grid - NRT (VCDWDG_L3_NRT) distributed from NASA LANCE. Available on-line [https://www.earthdata.nasa.gov/global-flood-product]. doi:10.5067/VIIRS/VCDWDG_L3_NRT.002

Please see the LANCE Disclaimer on our Data Use Policy page.

Legacy NASA NRT Global Flood Mapping Product

From 2012 through 2022, we generated a precursor legacy NASA NRT Global Flood Mapping Product. Although similar, the product had slightly different characteristics (tile naming; pixel size) and output products (including a graphic product and a 14-day product). The legacy product used a “MWP” filename prefix, such as “MWP_2022123_080E030N_3D3OT.tif.” Users transitioning from using the legacy product to the new LANCE MCDWD product should review the User Guide Appendix for relevant differences.

Frequently Asked Questions

Which product will show me the water for a particular flood event?

We recommend that users read section 7.1 (Usage Notes) of the User Guide to better understand the caveats for use of the product. Buildings, canopy cover, clouds, and cloud shadows can obscure flood detection. Terrain shadow, cloud shadow, and volcanic rock also can lead to false-positive flood detections. It is also helpful to examine the corresponding reflectance imagery in NASA Worldview to determine the level of cloudiness on the dates of interest, and thus potential sources of false-positives (cloud or terrain shadow) or false negatives (cloud obscuration or other data gaps). 

Why can I only see the 2- and 3-day products in Worldview? 

The 1-day product has more false positive flood detections so, to avoid misinterpretation, only the 2- and 3-day products are currently available in Worldview. The 1-day is available in the full HDF product file and as separate GeoTIFF files.

What caveats should be considered when using the flood mapping product? 

Incorrect reference water may result in flood false positives. Figure 1 shows a reservoir in Cambodia formed after the completion of the Lower Sesan II dam in 2017. Prior to Release 1, this reservoir was routinely reported as a flood. With the updated reference water layer (see User Guide section 3.5) this is no longer occurring; the reservoir is now reported as “surface water.” But similar situations will occur with other newly constructed reservoirs until they have been filled for about 3 years. Note that even then, if the reservoir levels vary seasonally or yearly, some edge areas may be reported as floods if the new reference water layer has not captured its maximal extent. 

Volcanic lava fields will often trigger the water detection algorithm because, like water, they are optically very dark. The user guide shows an example from the Craters of the Moon area of south-central Idaho.

Clouds and terrain shadows can lead to false positives. Please see section 8 of the User Guide for more information and examples.

Why was a particular flood not detected?

The usual culprit is clouds: If an area is too cloudy for the sensors to observe the land surface at its overpass times during a flooding event, the flood will not be reported. Or if the flood water was not present at the overpass times (e.g., flash floods that may last only a few hours), it may not be detected. For the MODIS product, overpass times are currently ~9:30 a.m. (Terra) and 2:30 p.m. (Aqua) mean local time. For the VIIRS product, they are ~1:30 p.m. (NOAA-21) and ~2:20 p.m. (NOAA-20).

Additionally, a flood may not be captured if it is small in extent (MODIS pixels are approximately 250 m, and VIIRS ~375 m), under canopy cover (trees will obscure underlying water), or in urban areas (where streets may be flooded, but there is a larger proportion of non-flooded rooftops).

Can I get a GeoTIFF of the flood product?

Yes, the four individual flood composites in the product HDF file are available as individual GeoTIFF files. Please see links in the Data Download section of this guide.

What is the best way to obtain the flood product?

It is recommended that users view the 2- and 3-day flood products in Worldview, as this allows rapid browsing of relevant dates and the user can also view the relevant corrected reflectance imagery, making clouds and any anomalies in the imagery easier to evaluate. 

See Data Download for more information on obtaining product files.  

What is the difference between the 1-, 2-, and 3-day products?

The table below highlights the key differences between the various 1-, 2-, and 3-day composite products. Visual examples can be found in the user guide.

Why are there two 1-day products? Which should I use?

The 1-day CS product has cloud shadow masks applied to the water detections to help remove cloud-shadow false positives. However, these masks can be inaccurate, and thus may potentially remove real water or they may not remove all cloud shadow. In general, it is recommended that the 1-day product is used only if either: the most timely information is needed or there are no potential cloud concerns. If there are clouds and the most timely information is required, then both 1-day products should be evaluated along with the visible imagery (most easily done via Worldview) to determine which provides the most useful information.

Why does a known reservoir show up as flooded?

The reference water layer tells us where “normal” water is expected to be observed: rivers, lakes, reservoirs, oceans. The current reference water layer is generated from the previous five years of the annual MOD44W product (see section 3.5 of the User Guide). After a new reservoir is constructed, it is expected it will continue to show up as “flood” in the product for up to three years. If the reservoir is more than three years old but continues to show up as “flood,” this is likely because the water levels vary enough seasonally or from year to year to prevent it from being identified in the MOD44W surface water product. Users could use a custom water mask to reclassify reported flood and surface water pixels accordingly.

What are the differences between the new LANCE flood product and the legacy flood product?

The LANCE MODIS MCDWD 1-, 2-, and 3-day composite products are considered comparable with the legacy product, although the MCDWD has some additional features. Most notably, as of Release 1, the reference water layer has been updated, which greatly reduces the number of falsely reported floods from new reservoirs. The MCDWD also has an additional topographic mask (HAND) applied, which greatly reduces terrain shadow false-positives in mountainous areas (see User Guide section 3.4.2). The flood layer’s pixel values also changed – see the table below. See the User Guide for more information. 

Note that the legacy product did not have the “recurring flood” class.