How does Tayeb Salih use imagery in Season of Migration to the North?

Imagery:

"'Had your father lived,' she said to me, 'he would not have chosen for you differently from what you have chosen for yourself. Do as you wish, depart or stay, it's up to you. It's your life and you're free to do with it as you will. In this purse is some money which will come in useful.' That was our farewell: no tears, no kisses, no fuss. Two human beings had walked along a part of the road together then each had gone his way. This was in fact the last thing she said to me, for I did not see her again."

"And the river, the river but for which there would have been no beginning and no end, flows northwards, pays heed to nothing; a mountain may stand in its way so it turns eastwards; it may happen upon a deep depression so it turns westwards, but sooner or later it settles down in its irrevocable journey towards the sea in the north."