In what circumstances will a municipality be found liable for the nuisance caused by cutting through a natural watershed?

In McCallum, the plaintiffs argued the municipality had created a continuing nuisance by cutting through a natural watershed and allowing water to invade, overload and overflow the plaintiffs’ ditch. Fisher J.A. dismissed the claim because the plaintiffs had consented to the municipality’s actions: 11 … Nevertheless, the consent of the appellants to the act is a primary factor to be considered in an action seeking to make the respondent liable for a nuisance and damages alleged to be the consequences of the act consented to and I think it is contrary to common sense and common justice that the appellants should now be able to complain of the consequences of an act, the doing of which they sanctioned, and successfully base an action for nuisance thereupon, to the prejudice of those who have acted upon their sanction. 12 … the principle underlying the judgment of Lord Campbell, L.C. in Cairncross v. Lorimer (1860) 3 Macq. H.L. 827, 3 L.T. 130, referred to by the learned trial Judge, while expressed in language applicable to the special facts of that case, may, I think, be applied in its general sense to the facts of the present case. In the Cairncross case the Lord Chancellor said: The doctrine will apply which is to be found, I believe, in the laws of all civilized nations, that if a man, either by words or by conduct, has intimated that he consents to an act which has been done, and that he will offer no opposition to it, although it could not have been lawfully done without his consent, and he thereby induces others to do that from which they otherwise might have abstained — he cannot question the legality of the act he had so sanctioned — to the prejudice of those who have so given faith to his words or to the fair inference to be drawn from his conduct. [Emphasis Added]