Field observation of morpho-dynamic processes during storms at a Pacific beach,Japan: Role of long-period waves in storm-induced berm erosion |
| |
Authors: | Masaru MIZUGUCHI Katsumi SEKI |
| |
Institution: | *1Department of Civil and Environmental Engineering, Chuo University, Tokyo, Japan.;*2Marine Information Group, Port and Airport Research Institute, Yokosuka, Kanagawa, Japan. |
| |
Abstract: | Many ultrasonic wave gages were placed with a small spacing across the swash zone to monitor either sand level or water level. Continuous monitoring conducted for a few years enabled the collection of data on the change in wave properties as well as swash-zone profiles. Data sets including two cases of large-scale berm erosion were analyzed. The results showed that 1) shoreline erosion started when high waves with significant power in long-period (1 to 2 min.) waves reached the top of a well-developed berm with the help of rising tide; 2) the beach in the swash zone was eroded with higher elevation being more depressed, while the bottom elevation just outside the swash zone remained almost unchanged; and 3) erosion stopped in a few hours after the berm was completely eroded or the swash-zone slope became uniformly mild. These findings strongly suggest that long waves play a dominant role in the swash-zone dynamics associated with these erosional events. |
| |
Keywords: | field observation berm erosion sediment transport long period waves Hasaki pier swash process |
|
|