Does the natural watercourse rule include a reasonableness element?

Defendants argue that the natural watercourse rule does not include a reasonableness element and should remain the law. They contend that the rationale on which the rule is based remains valid, and that application of the Keys v. Romley rule of reasonableness would create a virtual strict liability for public entities owning streets, storm drains, or other water-impervious improvements. Public entities, they claim, would bear extraordinary liability solely because storm waters falling on their thoroughfares ultimately reach a natural watercourse. The natural watercourse rule, they argue, properly permits the natural and intended usage of the creeks and waterways as a means of discharging the waters which would normally be conveyed therein.