POTHOLES-crib dam instance

here you see what may be the remains of an old crib dam.   A crib dam is a man made structure of interlocking timbers (much like a log home) which is laid across a creek bed and filled with stones.  The intention of this crib dam may have been to regulate water flow and redirect water to a trench for use elsewhere.  As you can see, the crib dam continues to sufficiently regulate water flow.  But when water levels are high, the excess water begins to spill over the edges and create new pathways. 

The spillage on each side of the crib dam exhibits much more force on the underlying rock than the water that flows as intended through the dam.  Evidence for the amount of energy created by the water is found at the bottom tier, on the left side.  Looking closely, you may see a portion of a pothole.   A pothole is a circular or cylindrical hole in the riverbed which is produced by force of water and abrasion.  A pothole is formed when a circular current of water carrying small pebbles and sediment begins to wear away a rock surface. The force of water and the sediment it carries is greater than the resistance of the rock. Once the process has begun, it continues and the rock in that location continues to erode away.

Geologists associate potholes with large volumes of very turbulent water.  Most often they are thought to be associated with the melt water of a glacier.   This is likely the case here at Hungarian Falls, as we can point to additional evidence to demonstrate that glacial activity in this area was prominent in the last 1-2 million years.  As glaciers advanced, they scoured out the softer sediment, essentially wiping this area clean of any loose rock, and carrying it along.  The sediment being moved by the glacier, along with the structure of the underlying bedrock, together created the potential for potholes.  As glaciers retreated, and melting waters turned to phenomenal rivers, the sediment that they carried along with them did the work of carving out the hole in the creek bed.