Groundwater erosion on Rialto Beach, Washington 

During high tides on Rialto Beach gravel and sand are pushed up on the shoreline. As the tide recedes, groundwater and sometimes coastal streams will run downward through the sediments, creating erosional features as seen in this video. I've been attempting to find a proper geological term for these features, and the best I've come up with so far is a gully. On Rialto, these erosional features are temporary, so being there at the right time to see them was a bit of good luck.