Part 1: NAVD88 Depth Elevation Differences

Results: Deployment #2 (March 2023)

Prior to deploying the second round of HOBO sensors along Money Island, the Stockton Coastal Research Center replaced all internal batteries in an attempt to prevent corrosion during data collection. Unfortunately, there was some complications due to the deployment of the sensors themselves, which rendered sensors 5, 6, 7, & 8 obsolete for this analysis (sensors were not aligned properly with the detached breakwater). Sensor #10 (landward channel) was also rendered obsolete, as it was the only sensor damaged during deployment (corrosion). However, the data for sensor #10 was later recovered by HOBO's manufacture and was provided to the Stockton CRC post data analysis. In general, the second deployment provided adequate data for wave attenuation analysis of detached breakwaters in a wind driven system with sensors 1, 2, 3, 4, 10, 11, 12, 13, & 14 recovered. These sensors allowed for a full tidal coverage of a detached breakwater, the control site, and some wave climate data within the breakwater channels. However, the second deployment occurred during the spring season, to which minimal wave action was observed over the course of deployment due to non-dominant winds and low wind speeds (please see wave and tidal comparison below for full results). This change in winds does provide useful data into the wave dynamics of a wind-driven system, even if the significant differences are not found (seasonal variability).

For a full detached breakwater analysis during the second deployment (sensors 1-4) an average NAVD88 depth difference 0.09 ft was observed between the landward sensors (1&2) in comparison to the seaward sensors (3&4) deployed around breakwater #3. A maximum NAVD88 depth difference was recorded at 0.212 ft (3:34 PM, 3/21/2023), while a minimum of 0.039 ft (7:41 PM, 3/21/2023) was observed. Standard deviation was calculated at 0.44 for these sensors over the course of the 24-hr tidal period. Upon running a T-Test (assuming equal variances), a p-value of 0.312 was returned; stating that there was no significant difference observed between the water levels per & post transmission of the detached breakwater itself. A similar outcome was observed at the control site between sensors 11 & 12 (seaward control) and sensors 13 & 14 (landward control). On average, a NAVD88 depth difference of 0.115 ft was observed throughout the tidal cycle. A maximum difference of 0.252 ft (1:57 PM, 3/21/2023) was observed, while a minimum value of 1.667E-05 (11:38 AM, 3/21/2023) was recorded. A calculated standard deviation value of 0.019 was derived between the control sensors. Statistical analysis (T-Test assuming equal variances) run between the sensor locations observed a p-value of 0.91 which also showed no significant statistical differences in water levels. at the control location.

For the second round of HOBO sensor deployment, sensors 1 (landward breakwater), 9 (landward channel), and 13 (landward control) did display differences amongst water levels/wave climates for the first half of deployment (March 21, 2023 7:00 AM - March 21, 2023 5:18 PM). When comparing sensors 1 & 9, an average NAVD88 depth difference of 0.062 ft was observed, with a maximum difference of 0.228 ft and a minimum of 0.004 ft. The standard deviation was calculated to be 0.023. Statistical analysis (T-Test) provided a p-value of 0.599 when comparing these sensor readings, showing no significant differences between the landward breakwater sensor and the landward channel sensor during collection times. An opposite outcome resulted between sensors 1 & 13, when an average NAVD88 depth difference of 0.101 ft was observed. With a maximum value of 0.205 ft and a minimum of 0.006 ft, the standard deviation was calculated to be 0.019 between these landward sensors and a T-Test (assuming equal variances) returned a p-value of 0.023. Stating that even though there was minimum water level differences in NAVD88 reference depths, there was still a significant difference between the landward breakwater and control readings during the time of collection. A similar outcome was determined when comparing sensors 9 & 13, where the average NAVD88 depth difference was 0.037 ft. The maximum NAVD88 depth difference was 0.249 ft, with a minimum value of 0.007 ft and a standard deviation of 0.021. A T-Test did determine a significant difference in levels with a generated p-value of 0.005. Further statistical analysis (Anova) determine a significant difference present amongst the three landward sensors, with a calculated p-value of 0.016 (F= 4.122 & F-Crit=3.005). 

Graphic 4: Displays the average NAVD88 depths between the landward breakwater sensors (1 & 2) and the seaward breakwater sensors (3 & 4) during the second HOBO sensor deployment (March 2023).

Part 2: Wave Attenuation Percentages of Detached Breakwaters

Calculating the percent differences in water levels on the theoretical plane is where wave attenuation numbers become visible (please see Methodology page for full details of percent difference equations). When comparing sensors 2 (landward breakwater) and 4 (seaward breakwater) from the first deployment of HOBO sensors (November 17-18, 2022), an average percent difference of 20% was observed during data collection (1:20 AM - 11:36 AM 11/18/2022). This percentage infers that the detached breakwaters attenuated roughly 20% of the incoming wave energy along Money Island during time of collection (please see graph below). A maximum attenuation percentage of 48% was calculated at 11:12 AM (11/18/2022), while a minimum attenuation of 11% was noted a multiple times between 4:00 AM and 5:00 AM on November 18, 2022. These percentages fluctuated due to the meteorological and tidal influences present during deployment. The maximum attenuation of 48% occurred 36 minutes after the predicted low tide (from NOAA's tide prediction) at 10:36 AM (see images below), when winds were roughly 14-15 knots in a West direction. In contrast, the minimum attenuation percentages of 11% were observed around high tide scenarios (predicted at 4:35 AM on 11/18/2022), with winds roughly 17-20 knots in a West/West-Southwest direction. Which is expected due to the detached breakwaters being partially submerged, which would generate high attenuations during low tides and low percentages during high tides.

When analyzing the percent differences between sensors 5 (landward breakwater) and 7 (seaward breakwater) an average attenuation percentage of 14% was calculated based on the sensor depth values observed between 3:00 PM (11/17/2022) and 1:20 AM (11/18/2022). The maximum wave attenuation was roughly 28% at 10:45 PM (11/17/2022), with a minimum percentage of 7% observed between 3:00 PM and 5:00 PM on November 17, 2022 (please see graph below). Again, these values coincide directly with the collected meteorological and tidal data collected for Money Island. The maximum attenuation value was observed during low tides (predicted 10:29 PM) with winds approximately 16-18 knots in a Westerly direction, while the minimum attenuation occurred during high tides (predicted at 3:52 PM) with winds approximately 17-20 knots in a West/West-Northwest direction. A quick percent difference calculation between sensors 2 (landward breakwater) and 10 (landward channel) yielded an average difference of 7% during collection. Although this is not an theoretical wave attenuation percentages, this result states that the wave climate within the channel is roughly 7% higher on average in comparison to the sensors located landward of a breakwater. Which, can be accredited to no wave energy attenuation within the channel, and increased waves due to refracted waves. A maximum difference of 15% and a minimum difference of 4% was calculated between sensors 2 & 10. 

While the data analyzed from winter deployment of HOBO sensors yielded results comparable to the Stockton University Coastal Research Center's anticipated wave attenuation from the partially submerged breakwater (estimated 20%), the spring deployment provided opposite values. Due to the high attenuation results calculated from poor winds and low tides overall, the maximum difference values were not utilized from the second deployment of HOBO sensors. Winds were dominant from the Southeast (average speed of 4 knots), with low tides predicted around -0.5 (ft). Any slight changes around Mean Sea Level (MSL) generated significant attenuation percentages due to the dependency of "average" water levels for results. For the landward (1 & 2) and seaward (3 & 4) sensors implemented around breakwater #3, an average percent difference (wave attenuation) was calculated at 5% during the full 24-hr HOBO sensor deployment, with a minimum percent difference of <1%. In comparison, the control sensor locations (sensors 11-14) yielded an average difference of 2%, with a minimum value of 0% for the full 24-hr coverage. From analyzing all the landward sensors (1, 9, & 13) average percent differences of 3% (1 vs. 9), 6% (1 vs. 13), and 2% (9 vs. 13) were calculated. All of these percentages directly resulted from the poor wind and low tidal conditions during the second deployment. Although, the percentages do infer that wave attenuation does still occurs during the spring season, however, the attenuation is minimum in comparison to the winter season.

Part 3: Tidal Data

Part 4: Meteorological Data