The scenes in Melbourne over the weekend of extensive flooding, especially in the CBD, didn’t surprise me. Although these were unusual events, I recall reading a report some years ago by the French engineering firm Aegis on the water and sewerage system of Melbourne. Apparently the drainage system in most of inner Melbourne was only designed to accommodate a one in five year storm. In fact some inner areas were designed for a one in two year storm. In contrast, newer areas are designed to cater for a one in one hundred year storm without property damage. They have the space to channel excess stormwater along overland flow paths to parks and creeks whereas in the inner city where the surface is almost entirely impervious the excess tends to flood.