To be technical, you could say the river is nearing flood stage. In everyday conversation, just simply say the river is high. "I am returning to my car" has a formal tone. To express the same thought in a more casual manner, say "I'm going back to my car." You would usually only say "I return to my car" if you were describing a habitual action.

The water in the river is high. この川の水位(すいい)は高い。 水位➡️water level 変える(かえる) to change 帰る(かえる) to go home, to return(to home country, hometown, where you were feeling it's home) 変える、変えます、変えて 帰る、帰ります、帰って I return to my car. You'd better use 戻る(もどる). もどる means to go back, return to where you were. Doesn't need to be home. もどる、もどります、もどって 車にもどります。I return to my car. 車にもどっています。I'm returning to my car.