SMH reports that the risk for natural disaster in Sydney is higher because of development on flood plains of the several rivers that criss cross the city – the Georges, Cooks and Hawkesbury. This corresponds with discussions I’ve had with hydrological engineers. They note that it would be better to have parklands and sporting fields than residential housing on the flood plains. I’d be curious to know how many people are living on flood plain in Sydney today. The interaction between storm event and associated relations between rainwater, seawater and waste water combine to shape the potential risk.