Cause
- Prolonged monsoon rain (northeast monsoon Nov-Feb) on flat blocks
- Blocked or silted drainage in mature stands (drains not maintained)
- Clay subsoil creating a perched water table
- Low-lying blocks near rivers or in coastal reclaimed land
- Compaction from heavy machinery (harvester tractors, replanting equipment)
Effect
Field signs:
- Standing water in furrows and inter-rows 24+ hours after rain
- Yellowing older leaves progressing to whole canopy
- Reduced latex flow, watery latex
- Root collar rot (soft, black, foul-smelling)
- Elevated incidence of white root and red root 3 to 6 months after waterlogging events
Satellite signals
Waterlogging often coincides with heavy cloud cover, so radar (Sentinel-1) is more reliable than optical during monsoon.
Action
1
Clear the drains first
Before diagnosing anything else, walk the block boundary and inspect the main drains. Silted or blocked drains cause 80% of waterlogging events on mature blocks.
2
Inspect low spots and map the extent
Use the Field Walk Protocol. Record standing-water depth and duration, and mark trees showing yellowing.
3
Root-disease sweep 2 months later
Waterlogged blocks have elevated root-disease risk. Schedule a targeted white root sweep 8 to 12 weeks after the event, focused on the affected zones.
4
Long-term drainage
On chronic blocks, cut secondary drains or install subsurface drainage. In replanting, install a proper drainage grid before planting.
5
Suspend tapping on severely affected trees
Trees with confirmed root collar rot should not be tapped. Rest the panel and consider felling if canopy loss exceeds 50%.