What is the obligation of a private landowner to prevent a natural disaster from occurring on their land?

Megaw L.J. went on to analyze the nature of the obligation in terms of the principles in Rylands v. Fletcher (1868), L.R. 3 H.L. 330 and concluded that the obligation is not one of strict liability. He further discussed and dismissed the notion that Rylands v. Fletcher stands for the proposition that there can be no liability for naturally occurring phenomena. Rather, he concluded that there cannot be strict liability for naturally occurring phenomena. He held that the obligation is one which requires the occupier to use reasonable care in relation to risks he is either aware of or of which, as a reasonably careful landowner, he ought to be aware.

Having determined that a duty of care could be imposed, the court concluded that there were no policy reasons which precluded recognition of the duty because the scope of the duty was limited, not only by the usual limits associated with determining liability in negligence but also by a consideration of economic reasonableness. Megaw L.J. outlined the limit of the occupier’s duty in these words (at p. 35): This leads on to the question of the scope of the duty. This is discussed, and the nature and extent of the duty is explained, in the judgment in Goldman v. Hargrave. The duty is a duty to do that which is reasonable in all the circumstances, and no more than what, if anything, is reasonable, to prevent or minimise the known risk of damage or injury to one’s neighbour or to his property. The considerations with which the law is familiar are all to be taken into account in deciding whether there has been a breach of duty, and, if so, what that breach is, and whether it is causative of the damage in respect of which the claim is made. Thus, there will fall to be considered the extent of the risk. What, so far as reasonably can be foreseen, are the chances that anything untoward will happen or that any damage will be caused? What is to be foreseen as to the possible extent of the damage if the risk becomes a reality? Is it practicable to prevent, or to minimise, the happening of any damage? If it is practicable, how simple or how difficult are the measures which could be taken, how much and how lengthy work do they involve, and what is the probable cost of such works? Was there sufficient time for preventive action to have been taken, by persons acting reasonably in relation to the known risk, between the time when it became known to, or should have been realised by, the defendant, and the time when the damage occurred? Factors such as these, so far as they apply in a particular case, fall to be weighed in deciding whether the defendant’s duty of care requires, or required, him to do anything, and, if so, what.