Origin and Significance of Openwork Gravel

Openwork gravel, without interstitial sand, is found associated with stream deposits of well-graded sand and gravel in innumerable exposures throughout the Pacific Northwest. A study of the relationships suggests that. openwork gravel is deposited by swift streams on the downstream face of a gravel bar or as sloping beds on a delta face. Vortex action may be partly responsible for the absence of sand in the deposit. Openwork gravel is of significance in engineering works involving water because of its common occurrence, the usual lenticular shape of a deposit, and its extremely high permeability.