The effects of the Hurricane Agnes flood on channel geometry and sediment discharge of selected streams in the Susquehanna River basin, Pennsylvania

The Hurricane Agnes flood seems to have hardly changed the channel geometry of the Pennsylvania streams studied in this report. The 10 sites studied generally showed that the width of the stream channels had been changed little by the flood and that streambed altitudes had been lowered less than a foot (0.3 m). The velocity of the streams at a given discharge had decreased. In comparison, the sediment deposited by the December 1964 flood in northwestern California commonly raised the streambed altitudes several feet. The differences in the effects of the two floods may have been produced by the availability of sediment for transport, by the relative size of sediment carried in suspension or bedload, or by the relative magnitudes of the floods.