What is "ponding"

n. (context construction geology English) The excessive accumulation of water at low-lying areas that remains after 48 hours after the end of rainfall under conditions conducive to drying. vb. (present participle of pond English)

Ponding is the (typically) unwanted pooling of water, typically on a flat roof or roadway. Ponding water accelerates the deterioration of many materials, including seam adhesives in single-ply roof systems, steel equipment supports, and particularly roofing asphalt. On low-slope asphalt roofs, ponding water allows the oil solvent components of the asphalt to leach out and evaporate, leaving the the roof membrane brittle and susceptible to cracking and leaking in the ponding location.