The Neuse River Estuary (NRE) located in eastern North Carolina is experiencing shoreline bluff retreat and corresponding nearshore bathymetric change due to increasing storm events such as hurricanes. Monitoring changes in nearshore bathymetry can aid in understanding sediment flux for management and restoration purposes. New remote sensing devices such as small Unoccupied Surface Vehicles (sUSV) allow for on-demand repeat bathymetric surveys of shallow nearshore environments where larger vessels cannot reach. This study uses a sUSV equipped with a single beam echosounder to investigate nearshore morphological changes in the NRE. Two Real-time Kinematic Global Navigation Satellite Systems (RTK-GNSS) and sUSV surveys were carried out in February and April 2022. For each of the two surveys, three Bathymetric Elevation Models (BEMs) were generated using Empirical Bayesian Kriging (EBK), Global Polynomial Interpolation (GPI), and Spline. EBK achieved the best result for both surveys based on conditions observed in the field as well as a vertical Root Mean Square Error (RMSE) of 0.21 m for February and 0.16 m for April. Wave and weather sensors were installed for this study to help determine potential causes of morphological changes. While both months had similar average wind speeds (average 5-10 m/s), their directions were different (Northeast and South directions for February and Southwest direction for April). As can be expected in a wave dominated estuary with these observed wind speeds, wave depth minimum and maximum ranges were small, which ranged 0.02 cm for February and 0.03 cm for April. Short term changes in the nearshore bathymetry were negative resulting in erosion with no estimated deposition. Bathymetry loss ranged from 0.3 to 0.69 m between February and April, and the observed wind and wave data indicate these changes were likely due to another contributing factor such as currents. To assist future work using sUSVs in shallow nearshore estuarine environments, a workflow of best practices when conducting sUSV surveys was also developed in this study. It is anticipated that the results will provide useful information for researchers conducting sUSV surveys as well as understanding the causes of nearshore morphological change in shallow estuarine environments.

Date: June 27, 2022
Time: 10:00 am
Place: https://ecu.webex.com/ecu/j.php?MTID=m200716ca1baf2fd63e9723450e18d482
Meeting number: 2620 113 6592
Password: qKutbBTA273 (75882282 from phones)
Join by phone: +1-415-655-0003 US Toll; Access code: 2620 113 6592

Advisor: Dr. Hannah Sirianni
Committee: Drs. Scott Lecce and Thad Wasklewicz

Watch Jessica Richter present her research at the NC Space/Sea Grant as a lightening talk.

Guan, S., Sirianni, H., Wang, W., Zhu, Z. (2022) sUAS monitoring of Coastal Environments: A Review of Best Practices from Field to Lab. Drones. 6(6), 142, https://doi.org/10.3390/drones6060142 (Journal Article: IF: 5.532).

Abstract

This review article aims to synthesize and illustrate best practices used to collect and process sUAS data of coastal environments. To assist with this objective, we reviewed recent review articles that focus on sUAS applications in coastal environments and include topics such as regulations, sensors, platforms, calibration, validation, and data processing. Based on the best practices identified from these review articles in addition to the current literature, we illustrate a step-by-step workflow that can be used for either conducting sUAS surveys or sUAS data processing, or both.

Figure 2. A 17-step workflow using best practices for processing sUAS photo-based surveys of coastal environments.