25' - Extreme flood, extensive residential flooding begins, especially upstream from Union Street bridge. Some evacuations necessary. Serious flooding upstream through Portville. Dikes overwhelmed.<br><br>23' - Major flood, protective dikes begin to be topped. Some roadway flooding in residential areas of city begins, especially upstream. Serious flooding in areas unprotected by dikes including portions of Portville.<br><br>17' - Moderate flood, water affects Riverview School of Aviation, 1.5 miles upstream of Union Street bridge. Local flooding occurs in areas unprotected by dikes including portions of Portville upstream.<br><br>12' - Flood stage, flooding possible on Union Street in Allegany and East Riverside Drive 1 to 3 miles upstream of Olean. Some farm lands along the river are also impacted.<br><br>10' - Action stage, high flows. No flooding.<br><br>