I watched over the last few years the widening of Sukhumvit road southwards from Jomtien...I particularly noticed that the drainage pipes were half full of crud,sand,rocks,road building detritus and common old garden rubbish thrown from passing cars or blown by the wind as soon as they were laid then the grading/leveling machines pushed even more crud in....first big rains 2 lanes of flood water in both directions at certain locations.
The left hand lane flooding being quite deep, there was also signs of the "popular belief" that water flows up hill !