In City of Keller v. Wilson, 168 S.W.3d 802, 813 (Tex. 2005), the city approved a developer's drainage ditch ending at one edge of a privately owned property not connected to a culvert the city built at the opposite edge of the property to receive rainwater runoff. 168 S.W.3d at 808.
The supreme court distilled what the property owners had to prove: "The critical question in this case was the City's state of mind--the Wilsons had to prove the City knew (not should have known) that flooding was substantially certain." Id. at 829.
The supreme court explained why the record failed to show there was evidence the city knew that flooding the private property was substantially certain from the storm water discharged through the drainage system:
"Moreover, when a case involves scientific or technical issues requiring expert advice (as this one does), jurors cannot disregard a party's reliance on experts hired for that very purpose without some evidence supplying a reasonable basis for doing so. Here, it was uncontroverted that three sets of engineers certified that the revised plans met the City's codes and regulations--and thus would not increase downstream flooding. The same firm that drew up the original Master Plan certified the revised one; unless the City had some reason to know the first certification was true and the second one was false (of which there was no evidence), there was only one logical inference jurors could draw." Id.
Even though the property owners presented expert testimony that the flooding was inevitable, the court still required evidence that the governmental entity knew this fact, stating, "None of the evidence cited by the court of appeals showed the City knew more than it was told by the engineers. The Wilsons' expert testified that flooding was (in his opinion) inevitable, but not that the City knew it was inevitable." Id.