Geology topics

Adam LeWinter

Publications and source records attributed to Adam LeWinter.

3 recordsLinked to original sources

USGS2019

Near-field remote sensing of Alaskan Rivers

The U.S. Geological Survey (USGS) Geomorphology and Sediment Transport Laboratory (GSTL), in collaboration with the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL), acquired remotely sensed data from several Alaskan rivers in 2017 and 2018 with the goal of developing a methodology for measuring streamflow from a helicopter. CRREL operates a custom airborne lidar system that can be deployed in a helicopter-based pod (HeliPod). Data were collected with the HeliPod near existing USGS streamflow information stations on the Knik, Matanuska, Chena, and Salcha Rivers in both 2017 and 2018. Sites on the Tanana and Snow Rivers were added in 2018. In 2018, the HeliPod was modified to accommodate both a thermal infrared and a visible camera. The cameras were integrated with the flight management software to simultaneously acquire imagery with lidar. The Global Navigation Satellite System (GNSS) and inertial measurement unit (IMU) in the HeliPod were used to compute trajectories with precise position and orientation information needed for image orthorectification. The HeliPod sensors provide data for measuring river channel characteristics. Lidar can map the elevation of the water surface and thus be used to measure water-surface slopes and return intensity can be used to delineate the extent of the wetted river channel. Various approaches are currently being evaluated to estimate surface flow velocity from visible and thermal image time series. In this paper, we examine and compare water-surface elevation returns and slopes derived from the HeliPod lidar and found good agreement with measurements made using conventional field-based techniques.

Alaska↗

USGS2018

High resolution measurement of levee subsidence related to energy infrastructure in the Sacramento-San Joaquin Delta

We assess flood overtopping potential (when flood water elevation exceeds levee elevation) to the levees surrounding the islands in the interior of California's Sacramento-San Joaquin Delta. Because critical natural gas infrastructure is susceptible to overtopping-related disruption, we focus our analysis on regions that are crossed by the network of the state's natural gas pipelines. We use laser scanning data collected during 2015-2016 to estimate subsidence rates since 2007 when an earlier, Delta-wide, airborne laser-scanning topographic dataset was collected. For each levee studied, we combine: (1) the estimated subsidence rate, (2) a conservative range of sea-level rise projections and, (3) an estimate of the 100-year freshwater flood stage to project the time until exceedance of the federal levee height standard (PL84-99). We find that subsidence rates vary from 0-5 centimeters per year (cm/yr) with mean values of ~1-2 cm/year. Local gradients in subsidence can be on the order of cms/yr over a distance of 10s of meters parallel to the levee crests, and these types of gradients are present near some pipeline crossings. The Sherman Island region has subsidence rates close to a factor of 2 greater than other areas considered. Our projections indicate general ranges of exceedance date from about 2060 (fast sea-level rise scenario) to 2080 (slow sea-level rise scenario) with some places projected to exceed threshold by about 2050.

California↗

USGS2017

Sculpted by water, elevated by earthquakes—The coastal landscape of Glacier Bay National Park, Alaska

Within Glacier Bay National Park in southeastern Alaska, the Fairweather Fault represents the onshore boundary between two of Earth’s constantly moving tectonic plates: the North American Plate and the Yakutat microplate. Satellite measurements indicate that during the past few decades the Yakutat microplate has moved northwest at a rate of nearly 5 centimeters per year relative to the North American Plate. Motion between the tectonic plates results in earthquakes on the Fairweather Fault during time intervals spanning one or more centuries. For example, in 1958, a 260-kilometer section of the Fairweather Fault ruptured during a magnitude 7.8 earthquake, causing permanent horizontal (as much as 6.5 meters) and vertical (as much as 1 meter) displacement of the ground surface across the fault. Thousands to millions of years of tectonic plate motion, including earthquakes like the one in 1958, raised and shifted the ground surface across the Fairweather Fault, while rivers, glaciers, and ocean waves eroded and sculpted the surrounding landscape along the Gulf of Alaska coast in Glacier Bay National Park.

Alaska↗