Progression of erosion and waves near the shoreline during a berm erosion

Two extremely large events of berm erosion were observed during the field experiments carried out at Hasaki by employing twenty some ultrasonic gages near the shoreline between Jul. 12 2002 - Jul. 21 2006 and Jul. 24 2008 - Oct. 29 2008. One was caused by a Typhoon waves and the other by a winter storm. Both erosions show complete disappearance of berm profile within a few hours when large waves with significant long period waves attacked well-developed berm profile during rising tides. However one of them shows erosion advancing onshore-ward creating beach cliff like profile while the other show almost instantaneous erosion of whole berm profile. Both erosions stopped when beach profiles become uniformly mild slope.