Across the globe this year extreme weather events have caused severe flooding. They've left hundreds of people dead, tens of thousands more affected and billions of dollars worth of damage. New figures from the world's largest re-insurer, Munich Re, reveal a clear trend: flash floods are increasing and so are the resulting costs. It's leading many countries to invest in adaptation projects - ways of reducing the impact of sudden heavy rain, and protect vital infrastructure. Bloomberg's Avril Hong has been to see once such installation - buried deep beneath Singapore.