Statutory authority: this is a complete defence if the accumulation of the thing was statutorily sanctioned.
Plaintiffs Consent or benefit: the plaintiff cannot complain of the escape if he benefits from the accumulation or expressly or implied consented to it.
Contributory negligence: this defence is available to the defendant if they plaintiff contributed to the escape. Its effect is to reduce the amount payable as damages.
Strangers or third parties: the defendant is not liable if the escape was occasioned an unforeseen act of a stranger.
Act of God: this defence may be relied upon if the escape is wholly attributable to natural causes. The circumstances must be such that human foresight could not have recognized the escape as a possibility.