ponding

1. 1
   noununcountable

   The collection of water on a flat roof that fails to drain off, which can eventually cause leaks.

   Poor drainage left ponding across half the building's roof for days.

   Repeated ponding had weakened the membrane until water seeped into the offices below.

   Similarpooling

   Note

   On a roof the word loses its stopwatch. The drainage engineer's sense requires water to linger 48 hours, but here any water that sits on a flat roof instead of running off counts. The worry shifts from the ground to the roof covering beneath the water, which gives way to leaks the longer ponding is left alone.

2. 2
   noununcountable

   The excessive buildup of water in low-lying areas that remains 48 hours after rain ends, even under conditions that would normally allow drying.

   Engineers mapped areas of ponding across the floodplain after the monsoon.

   Persistent ponding in the lowlands delayed planting for several weeks.

   Similarwaterlogging, pooling

   Note

   This is a drainage engineer's term, not a casual word for puddles. The 48-hour clock is what turns standing water into ponding. Water that outlasts weather fit for drying points to poor drainage or to soil that lets little through. The word is usually uncountable, so writers speak of areas of ponding or persistent ponding rather than counting pondings.

3. 3
   verb

   Present participle of pond.

   Rainwater was ponding against the foundation, so they dug a drainage trench.

   Meltwater kept ponding on the trail, turning it to mud.

   Note

   The verb form works both without an object and with one. Water is ponding when it collects and stands. In the transitive senses an object follows, and ponding a stream means damming it. The form once also meant pondering, a use now obsolete. As a gerund it shades into the drainage term, so only the sentence shows whether it is verb or noun.

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