The valley pre-flood
The valley is shown in two time periods. In the time-slips into the past, Sadie finds herself in a very different Victoria where the lake that she knows was not there yet. The flood is the doing of her own great-grandfather, it turns out, so by analyzing the imagery of the valley pre-flood, she learns the exact value of his actions. She does not get to enjoy the valley in the present because her own patriarch destroyed it with water. She even finds magical ruins that are eventually destroyed.
The valley post-flood
This is actually the imagery of the status quo in the book. To Sadie, the valley has always been full of water, but that was not the case until her own great-grandfather executed a plan to flood it. The difference between the imagery is also a symbol for time, because each imagery—before and after the flood—can be used by contrast to determine the flow of time (which is an important part of the prose). Put plainly, the flood is an imagery which reminds Sadie whether she is in the past or present.
Modernization
Sadie comes from a modern world, so when she goes back to a time during Australia's economic development, in the 1930's, she realizes that her great-grandfather is a hero. He builds businesses and through his professional network, he helps supply the town through his store the various things they need by importing goods. But, the imagery has a dark side; when confronted with a naturalistic point of view, the businessmen kill the naturalist and continue with progress.
Nature
Natural imagery covers a wide span of the novel. The talking crows are symbols of nature, and Sadie is prone to lengthy appreciations of nature herself. She observes well and properly perceives the absurdity of nature. When she travels back in time, it is nature that she discovers, nature that would have been preserved into her own present day if not for the sins of her forefathers. The natural imagery is best symbolized by the Aboriginal employee who is murdered for alleging that nature is sacred.
