Iowa Code § 670.3: Actual knowledge of defect as defense.

In any action subject to the provisions of this chapter, an affirmative showing that the injured party had actual knowledge of the existence of the alleged obstruction, disrepair, defect, accumulation, or nuisance at the time of the occurrence of the injury, and a further showing that an alternate safe route was available and known to the injured party, shall constitute a defense to the action.