The catchment of the Georges River is extensive and covers\r almost 1000 square kilometres. Although major floods\r generally result from prolonged heavy rainfall in the\r upper part of the catchment there is generally little\r advance warning of major floods.\r \r In fact, warning of the transition of a flood from\r nuisance status to a major 1 in 100 year event, could be\r typically of the order of only 3 to 4 hours. As a\r consequence there would be only limited opportunity for\r effective evacuation of the Moorebank-Milperra floodway, a\r situation which is compounded by the fact that road access\r into the area is cut at an early stage of a flood.\r \r Major flooding has posed a potential threat to development\r adjacent to the Georges River since the earliest days of\r settlement. A major flood was recorded in 1873 and\r several other large floods occurred prior to the turn of\r the century. However, the river has been relatively flood\r free throughout the twentieth century with the only\r significant flood occurring in 1956. Since then only\r minor floods in 1961, 1964, and 1978 have been\r experienced.\r \r This report addresses the impacts of the 20, 50 and 100\r year floods on the Milperra floodway. These impacts are\r presented primarily in terms of depths of inundation and\r flood velocities through the residential area. Table 1\r compares depths for these events with those which would\r have been experienced during the floods of 1873, 1875,\r 1889, 1956, 1961, 1964 and 1978.

The catchment of the Georges River is extensive and covers almost 1000 square kilometres. Although major floods generally result from prolonged heavy rainfall in the upper part of the catchment there is generally little advance warning of major floods. In fact, warning of the transition of a flood from nuisance status to a major 1 in 100 year event, could be typically of the order of only 3 to 4 hours. As a consequence there would be only limited opportunity for effective evacuation of the Moorebank-Milperra floodway, a situation which is compounded by the fact that road access into the area is cut at an early stage of a flood. Major flooding has posed a potential threat to development adjacent to the Georges River since the earliest days of settlement. A major flood was recorded in 1873 and several other large floods occurred prior to the turn of the century. However, the river has been relatively flood free throughout the twentieth century with the only significant flood occurring in 1956. Since then only minor floods in 1961, 1964, and 1978 have been experienced. This report addresses the impacts of the 20, 50 and 100 year floods on the Milperra floodway. These impacts are presented primarily in terms of depths of inundation and flood velocities through the residential area. Table 1 compares depths for these events with those which would have been experienced during the floods of 1873, 1875, 1889, 1956, 1961, 1964 and 1978.