In a suit seeking damages for inverse condemnation, nuisance, and trespass when erosion to plaintiff-owner's property was caused by water discharged from a storm drain, summary judgment for defendant-city is reversed where: 1) the critical inquiry was not whether the entire system was a public improvement, but rather whether city acted reasonably in its maintenance and control over those portions of the drainage system it does own; and 2) accordingly, there were triable issues of material fact.