8 Oct 2024

Remote Monitoring of Cathodic Protection Systems on Navigable Waterways

Abstract: Cathodic protection is one of the main modes of corrosion prevention for structures in navigable waterways. The rectifier output voltage must be in a specific range to provide effective protection against corrosion. This effort was designed to monitor, predict, and stabilize the efficacy of multiple cathodic protection systems. Copper/copper-sulfate half-cell electrode sensors, water quality sensors, and gauges for rectifier output were connected to modems at multiple locks so the data could be analyzed to create a predictive maintenance algorithm.

11 Sep 2024

Bathymetric Inversion from Unmanned Aircraft System (UAS) Video on Inland Waters, Port Huron, Michigan

Abstract: This Coastal and Hydraulics Engineering Technical Note (CHETN) presents a proof of concept for the use of the cBathy algorithm to estimate bathymetry in an inland water environment. The document summarizes the methods used in collecting and analyzing stationary UAS (unmanned aircraft system) video taken at the Fort Gratiot Lighthouse Park in Port Huron, Michigan, a shoreline overseen by the US Army Corps of Engineers (USACE), Detroit District (LRE). The results presented in this report show that the cBathy algorithm has the potential to measure bathymetry in areas of inland water with sufficient fetch to generate wind swell, similar to how cBathy has been used in open-coast nearshore environments.

11 Sep 2024

Evaluating Topographic Reconstruction Accuracy of Planet Lab’s Stereo Satellite Imagery

Abstract: The goal of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to document initial results to derive topography on the beachface in the northern Outer Banks, North Carolina, utilizing Planet Labs’ SkySat stereo panchromatic imagery processed in Agisoft Metashape. This technical note will provide an initial evaluation into whether Planet Lab’s SkySat imagery is a suitable image source for satellite Structure from Motion (SfM) algorithms as well as whether these data should be explored as a federal beach project monitoring tool. Depending on required accuracy, these data have the potential to aid coastal scientists, managers, and US Army Corps of Engineers (USACE) engineers in understanding the now-state of their coastlines and employ cost-effective adaptive management techniques.

28 Aug 2024

Validation of Daily Snow Water Equivalent for a Watershed Statistics Tool

Abstract: The Watershed Statistics tool is a tool currently being developed for the Remote Sensing and Geographic Information Systems Center of Expertise’s (RSGIS) Extreme Cold Weather web portal and will allow users to easily access and visualize snow water equivalent (SWE) data. The SWE data available on this tool are derived from passive microwave signals acquired by satellite through a technique known as enhanced passive microwave SWE. This analysis used available in situ SWE measurements from snow study sites in four watersheds across the United States and Canada to determine the accuracy of the data available on the tool at the watershed scale. In situ measurements of SWE were compared with the Watershed Statistics tool’s SWE data based on watershed, land cover, and elevation to determine causes if discrepancies between the satellite-based estimations on the tool and ground-based measurements. The extent to which the data available on the Watershed Statistics tool agreed with in situ measurements was highly variable. SWE data available on the Watershed Statistics tool agreed the least with ground-based measurements made at higher elevations and in areas with denser vegetation. The findings of this comparison are consistent with known limitations of the enhanced passive microwave SWE technique.

29 Jul 2024

Rectifying and Stabilizing Planet SkySat Video Collects for Bathymetric Inversions from Space

Abstract: This Coastal and Hydraulics Engineering Technical Note (CHETN) presents the development of a workflow to process Planet SkySat videos collected from space at the US Army Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL), Field Research Facility (FRF), in Duck, North Carolina, to derive wave kinematics and perform bathymetric inversions. The document summarizes the nine 30–60 s* satellite video collections, demonstrates the accuracy of an automated rectification and stabilization workflow, and applies a new short-dwell version of a common inversion algorithm (cBathy) to demonstrate the utility of short-dwell videos from space providing an initial out-of-the-box assessment of errors for one of the collections, and recommends future avenues of research for improving bathymetric predictions.

21 Jun 2024

Multiscale Observation Product (MOP) for Temporal Flood Inundation Mapping of the 2015 Dallas Texas Flood

Abstract: This paper presents a new data fusion multiscale observation product (MOP) for flood emergencies. The MOP was created by integrating multiple sources of contributed open-source data with traditional spaceborne remote sensing imagery to provide a sequence of high spatial and temporal resolution flood inundation maps. The study focuses on the 2015 Memorial Day floods that caused up to US$61 million of damage. The Hydraulic Engineering Center River Analysis System (HEC-RAS) model was used to simulate water surfaces for the northern part of the Trinity River in Dallas, using reservoir surcharge releases and topographic data provided by the US Army Corps of Engineers. A measure of fit assessment is performed on the MOP flood maps with the HEC-RAS simulated flood inundation output to quantify spatial differences. Estimating possible flood inundation using individual datasets that vary spatially and temporally allow an understanding of how much each observational dataset contributes to the overall water estimation. Results show that water surfaces estimated by MOP are comparable with the simulated output for the duration of the flood event. Additionally, contributed data, such as Civil Air Patrol, although they may be geographically sparse, become an important data source when fused with other observation data.

20 Jun 2024

Spatial Variations in Vegetation Fires and Emissions in South and Southeast Asia during COVID-19 and Pre-pandemic

Abstract: Vegetation fires are common in South/Southeast Asian (SA/SEA) countries. However, few studies focused on vegetation fires and the changes during COVID compared to pre pandemic. This study fills an information gap and reports total fire incidences, total burnt area, type of vegetation burnt, and total particulate matter emission variations. Results from the short term 2020 COVID versus 2019 non COVID year showed a decline in fire counts varying from -2.88 to 79.43%. The exceptions in South Asia include Afghanistan and Sri Lanka, and Cambodia and Myanmar in Southeast Asia. The burnt area decline for 2020 compared to 2019 varied from -0.8% to 92% for South/Southeast Asian countries, with most burning in agricultural landscapes than forests. Several patches in S/SEA showed a decrease in fires for the 2020 pandemic year compared to long term 2012–2020 pre pandemic record, with Z scores greater or less than two denoting statistical significance. However, on a country scale, the results were not statistically significant in both S/SEA, with Z scores ranging from -0.24 to -1, although most countries experienced a decrease in fire counts. The study highlights variations in fires and emissions useful for fire management and mitigation.

13 Jun 2024

Quantifying Coastal Evolution and Project Performance at Beaches by Using Satellite Imagery

Abstract: Accurately delineating the shoreline is crucial for tracking coastal evolution, community vulnerability, storm impacts, and for coastal management decision-making. However, existing shoreline measurement methods are often time-consuming and expensive and therefore, USACE Districts are often forced to narrow areas of interest or monitoring frequency, decreasing the likelihood of making data-driven management decisions, especially over regional scales. In the last decade, space-borne earth observations have captured images subweekly, and can potentially be used for shoreline monitoring. This work investigated the Python-based CoastSat toolkit and compared the shorelines derived from publicly available satellite imagery to ground truth surveys at 37 sites across the nation chosen in coordination with Districts. Mean horizontal errors ranged from 4.21 to 20.58 m with an overall mean of 11.32 m. Tidal corrections improved accuracies at 82% of sites. The CoastSat slope function was tested and there were negligible differences in shoreline accuracy when compared with user-defined slopes Twenty-year satellite-derived trends generally align well with ground truth trends. The satellite approach identified quantifying storm impacts/recovery, beach nourishment equilibration, diffusion and decay, shoreline response to nearshore berm placements and decadal shoreline evolution at the evaluated district sites. Work is ongoing to transition to a user-friendly software tool.

14 May 2024

Snow-Impacted National Inventory of Dams by GAGESII Watershed

Abstract: This Engineering Research and Development Center (ERDC) Technical Note describes the development of a set of locations within the contiguous United States (CONUS) where snowmelt is a component of the annual streamflow. The locations are selected from the US Geological Survey (USGS) Geospatial Attributes of Gages for Evaluating Streamflow II (GAGESII) and National Inventory of Dams (NID) data sets. The 30-year normal snow regimes were used to identify all GAGESII watersheds that have any of the basin delineated as transitional (rain/snow), snow dominated, or perennial snow zones. NID dams that are within snow affected GAGESII watersheds are included in the data set. The purpose of this ERDC Technical Note is to describe the development of a comprehensive data set of CONUS GAGESII and dam infrastructure affected by snow changing regimes.

7 May 2024

Spherical Shock Waveform Reconstruction by Heterodyne Interferometry

Abstract: The indirect measurement of shock waveforms by acousto-optic sensing requires a method to reconstruct the field from the projected data. Under the assumption of spherical symmetry, one approach is to reconstruct the field by the Abel inversion integral transform. When the acousto-optic sensing modality measures the change in optical phase difference time derivative, as for a heterodyne Mach–Zehnder interferometer, e.g., a laser Doppler vibrometer, the reconstructed field is the fluctuating refractive index time derivative. A technique is derived that reconstructs the fluctuating index directly by assuming plane wave propagation local to a probe beam. With synthetic data, this approach is compared to the Abel inversion integral transform and then applied to experimental data of laser-induced shockwaves. Time waveforms are reconstructed with greater accuracy except for the tail of the waveform that maps spatially to positions near a virtual origin. Furthermore, direct reconstruction of the fluctuating index field eliminates the required time integration and results in more accurate shock waveform peak values, rise times, and positive phase duration.