Evaluation of the Wave Absorber at Pentwater, Michigan

This discussion compares incident and transferred energy for gages located within the Pentwater, Michigan boat channel. Comparisons are made primarily by examining the differences in the incident and transferred significant wave height, (Hm0). Other comparisons use spectral results. Spectral analysis allows the energy of the total wave record to be broken down into discrete frequency bands. Energy inside and outside the wave absorber may then be compared and a transfer factor for each discrete frequency can be determined. Incident, (lakeside of absorber) and transferred (harborside of absorber) wave data were collected within the Pentwater, Michigan boat channel. Non-directional, internally recording gages, each mounted about 6 inches off the bottom were deployed as indicated in figure 1. The incident gage is MI002 and is identified as Northwest Channel. This gage was deployed in 11 feet of water and was located 121 feet west of west edge of north wave absorber. The harborside gage is MI004 and is designated as Northeast Channel. MI004 was deployed in 8 feet of water, 72 feet east of east edge of north wave absorber. The purpose of this data collection effort was to determine characteristics of the wave absorber located at the western end of the channel. Wave gages were set to collect hourly using subsurface pressure sensors, however, MI004 collected every 26-32 minutes throughout the study. The sample rate for these sensors was 2 Hz and the burst length was 1024 seconds.