In Sheffet v. County of Los Angeles (1970) 3 Cal.App.3d 720, the question before the court was whether substantial evidence supported the lower court's finding that the lower landowner had acted reasonably while the upper landowner had acted unreasonably. Indeed, the appellate court observed that it was bound by the trial court's decision unless substantial evidence did not support the trial court's finding on reasonableness. (Id. at pp. 728, 731, 741.) In Sheffet, the court imposed liability on the upper landowner because that party had engaged in some affirmative conduct creating the flooding problems and the adjacent property owner's actions had been reasonable. (Sheffet, at pp. 726-727, 731-732 county liable in inverse condemnation for damages from overflow of surface waters from public streets onto plaintiff's property where county approved subdivision and drainage system, plaintiff acted reasonably in relation to his property, and damage to adjacent property resulted from improvements)