Net Shore-Drift of Mason County, Washington

Winds from various directions cause waves which transport sediment along the shore. Over a relatively long time interval, sediment is moved in one predominant direction, which is the direction of net shore-drift. Variations in shoreline orientation cause shore drift to occur in discrete, essentially independent, drift cells. By the specific identification of a number of established geomorphic and sedimentological shore drift indicators, drift cell boundaries can be delineated and the directions of net shore-drift determined. These indicators include changes in bluff morphology, beach width and slope, sediment-size gradation, identifiable sediment, deposition and/or erosion at shore drift obstructions, direction of spit growth and stream diversions, and nearshore bar orientation. Using these shore drift indicators, 136 drift cells have been mapped and described for the Mason County portions of Hood Canal and southern Puget Sound. Net shore-drift along most of the Mason County shore is generally northward, which reflects the influence of more frequent and stronger winds from southerly directions. Areas of southward net shore-drift occur where fetch from the south is limited. Shore drift in insignificant along parts of the shore where fetch is limited in all directions, where wave energy is diminished by shallow water or man-made barriers, or where cliffs or bluffs extend to deep water.