Noda City, Japan -A little bit of thumping sound and you can hear an echo emanating from the immense underground discharge channel – an engineering marvel built to alleviate the rising of flood waters in the Naka and Ayase river basins. It is the world's largest underground flood water diversion facility built in Kasukabe city in Saitama Prefecture, to mitigate overflowing of the city's major waterways and rivers during rain and typhoon seasons. Over 30,000 homes are now prot