tumbling bay

from The Collaborative International Dictionary of English v.0.48

Tumbling \Tum"bling\,
   a. & vb. n. from {Tumble}, v.
   [1913 Webster]

   {Tumbling barrel}. Same as {Rumble}, n., 4.

   {Tumbling bay}, an overfall, or weir, in a canal.
      [1913 Webster] Tumbrel