A new USGS assessment of 30 extraordinary floods between 1927 and 1978 found that the peak discharges for two of them were revised upward. One of those two extraordinary floods was in Bronco Creek, Arizona.
The USGS report has to be ordered, so I didn’t find the details online of just how large the revised flood peak flow was.
A big part of the USGS study deals with the reliability of peak flow measurements and errors in data collection and processing.
The study concludes that “Within the U.S. Geological Survey, new approaches are needed to collect more accurate data for floods, particularly extraordinary floods. In recent years, significant progress has been made in instrumentation for making direct discharge measurements. During this same period, very little has been accomplished in advancing methods to improve indirect discharge measurements.”