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Rice plants transport air (oxygen) from the leaves to the roots, so rice can survive and grow in flooded fields as long as at least some leaves stick out of the water. However, complete submergence cuts the oxygen supply and most rice varieties die within a few days. When submergence happens at flowering, fertilization cannot occur and complete yield loss is the consequence even if the plants survive.

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When rice is most vulnerable

Any stage where the canopy is fully submerged. Submergence during flowering causes complete yield loss even when plants recover.

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How submergence shows in satellite data

  • Sudden NDVI collapse in the days after heavy rain, concentrated in low-lying or flood-prone zones.
  • Water in the imagery replaces canopy - NDWI rises sharply at the same time NDVI drops.
  • Very different signature from drought (slow NDWI-then-NDVI decline) and salinity (patchy but stable).
  • If canopy leaves remain above water, NDVI may only dip briefly and recover; if fully submerged for more than a few days, recovery is limited.

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Reduce the damage by

  • Choosing adequate cultivars - tall and/or submergence-tolerant varieties.
  • Adjusting the planting time to fit in the hydrological fluctuations in the area.
  • Double transplanting - seedlings are transplanted two times to have tall seedlings for areas with medium deep flooding risk.

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Set an alert for early warning

Turn the diagnosis into a trigger. Go to the Alerts page and configure a rule so heavy-rain events on flood-prone fields notify you before the imagery even confirms the submergence.
Recommended settings for submergence on rice:
  • Weather alert - excessive rainfall exceeding your defined threshold, so you can pre-position response before imagery even confirms.
  • NDVI drop alert - trigger on a drop of 0.20 or more between consecutive passes in flood-prone fields. The drop alone is not the finding. On a flood-prone field a sudden NDVI drop is at least as likely to be a flood pulse as crop damage — Rice Ecosystems says to cross-check NDWI and recent rainfall before flagging one. So the alert opens a watch, and the finding is raised only if NDVI fails to recover on the following pass. Water that drains leaves a canopy that climbs back; water that stayed long enough to kill does not.
  • New Imagery alert during the monsoon or flood season, so you review recovery within hours of each new pass.