I am no expert, but I would think that what you can see in this picture is one reason why it floods so easily during storms in Bangkok. Residue cement from a nearby building site has flown down into this drain. That’s not all. A lot of sand and bricks from last year’s flood walls have also been dumped down the drain. I saw some people do it with my own eyes. Between this and rubbish being dumped in the gutter, no wonder Bangkok floods after ten minutes of rain.