Marius Necsoiu

Multi-temporal image analysis of historical aerial photographs and recent satellite imagery reveals evolution of water body surface area and polygonal terrain morphology in Kobuk Valley National Park, Alaska

Multi-temporal image analysis of very-high-resolution historical aerial and recent satellite imagery of the Ahnewetut Wetlands in Kobuk Valley National Park, Alaska, revealed the nature of thaw lake and polygonal terrain evolution over a 54-year period of record comprising two 27-year intervals (1951?1978, 1978?2005). Using active-contouring-based change detection, high-precision orthorectification and co-registration and the normalized difference index, surface area expansion and contraction of 22 shallow water bodies, ranging in size from 0.09 to 179?ha, and the transition of ice-wedge polygons from a low- to a high-centered morphology were quantified. Total surface area decreased by only 0.4% during the first time interval, but decreased by 5.5% during the second time interval. Twelve water bodies (ten lakes and two ponds) were relatively stable with net surface area decreases of ?10%, including four lakes that gained area during both time intervals, whereas ten water bodies (five lakes and five ponds) had surface area losses in excess of 10%, including two ponds that drained completely. Polygonal terrain remained relatively stable during the first time interval, but transformation of polygons from low- to high-centered was significant during the second time interval.

Estimating Aquifer Channel Recharge Using Optical Data Interpretation

Recharge through intermittent and ephemeral stream channels is believed to be a primary aquifer recharge process in arid and semiarid environments. The intermittent nature of precipitation and flow events in these channels, and their often remote locations, makes direct flow and loss measurements difficult and expensive. Airborne and satellite optical images were interpreted to evaluate aquifer recharge due to stream losses on the Frio River in south-central Texas. Losses in the Frio River are believed to be a major contributor of recharge to the Edwards Aquifer. The results of this work indicate that interpretation of readily available remote sensing optical images can offer important insights into the spatial distribution of aquifer recharge from losing streams. In cases where upstream gauging data are available, simple visual analysis of the length of the flowing reach downstream from the gauging station can be used to estimate channel losses. In the case of the Frio River, the rate of channel loss estimated from the length of the flowing reach at low flows was about half of the loss rate calculated from in-stream gain-loss measurements. Analysis based on water-surface width and channel slope indicated that losses were mainly in a reach downstream of the mapped recharge zone. The analysis based on water-surface width, however, did not indicate that this method could yield accurate estimates of actual flow in pool and riffle streams, such as the Frio River and similar rivers draining the Edwards Plateau.

New insights on the Salmon Falls Creek Canyon landslide complex based on geomorphological analysis and multitemporal satellite InSAR techniques

Multitemporal satellite interferometric synthetic aperture radar (InSAR) techniques can characterize line-of-sight displacements of active landslide areas with resolution (mm scale) and accuracy comparable to or higher than differential GPS, sensor network, or photogrammetry techniques. This study improves understanding of the rate of movement and the lateral extent of the active domain of a landslide complex within Salmon Falls Creek Canyon near Twin Falls, Idaho. Specifically, we were able to estimate displacement of yearly motion rates in early and late stages of the event by analyzing a collection of archived radar satellite imagery. Small baseline subset (SBAS) InSAR performed better than persistent scatterer (PS) InSAR for analyzing distributed scatterers because of its ability to capture strongly nonlinear displacement rates. In addition, comparison with GPS field measurements showed agreement with InSAR-derived displacements. Geostatistical analysis was used to describe surface and morphometric characteristics of two separate landslides within Salmon Falls Creek Canyon. Each was divided into representative geomorphologic units, and morphometric analysis focused on two key parameters: topographic texture and mean slope. Scarp units are topographically rough because of their greater relief and steep slopes, while a displaced headwall block has retained a smooth topography. Each landslide upper body has a higher topographic texture than the corresponding body unit. Both landslides display a progressive decrease in mean slope from upper body to toe to body. InSAR SBAS results showed that headwall block and transverse scarp of the landslide complex at Salmon Falls Creek Canyon had the highest mean annual velocity in the radar line-of-sight (LOS) direction. Velocity of movement in each landslide toe and body was less, signifying that LOS movement was more active in the upper reaches of the landslides, although lateral translation may have been greater in the body and toe compared to the headwall region due to the curved shape of the landside detachment surface.

Measurement of airborne particle concentrations near the Sunset Crater volcano, Arizona.

Direct measurements of airborne particle mass concentrations or mass loads are often used to estimate health effects from the inhalation of resuspended contaminated soil. Airborne particle mass concentrations were measured using a personal sampler under a variety of surface-disturbing activities within different depositional environments at both volcanic and nonvolcanic sites near the Sunset Crater volcano in northern Arizona. Focused field investigations were performed at this analog site to improve the understanding of natural and human-induced processes at Yucca Mountain, Nevada. The level of surface-disturbing activity was found to be the most influential factor affecting the measured airborne particle concentrations, which increased over three orders of magnitude relative to ambient conditions. As the surface-disturbing activity level increased, the particle size distribution and the majority of airborne particle mass shifted from particles with aerodynamic diameters less than 10 &mgr;m (0.00039 in) to particles with aerodynamic diameters greater than 10 &mgr;m (0.00039 in). Under ambient conditions, above average wind speeds tended to increase airborne particle concentrations. In contrast, stronger winds tended to decrease airborne particle concentrations in the breathing zone during light and heavy surface-disturbing conditions. A slight increase in the average airborne particle concentration during ambient conditions was found above older nonvolcanic deposits, which tended to be finer grained than the Sunset Crater tephra deposits. An increased airborne particle concentration was realized when walking on an extremely fine-grained deposit, but the sensitivity of airborne particle concentrations to the resuspendible fraction of near-surface grain mass was not conclusive in the field setting when human activities disturbed the bulk of near-surface material. Although the limited sample size precluded detailed statistical analysis, the differences in airborne particle concentration over 900-y weathered volcanic and nonvolcanic deposits appeared to be potentially significant only under heavy surface disturbances.

A new methodology to monitor soil moisture over a complex arctic environment, Kobuk River valley, Alaska

Frozen ground is a sensitive indicator of environmental change. In this study, we examine the relevance of L-band synthetic aperture radar (SAR) data for extracting information on frozen ground, above discontinuous permafrost, in the Kobuk River valley, Alaska. A new methodology based on multi-temporal image acquisition is presented. This approach uses Ohs model with image acquisition during the period of frozen ground, and incorporates a vegetation model during the thawing period. The methodology is optimized to retrieve not only the soil moisture content but also the albedo and the extinction coefficient of the vegetation layer. Estimated soil moisture maps produced for one year reveal high values in late spring in response to snowmelt, rainfall, and spring vegetation growth. Low values in late summer/early fall are in response to seasonal rainfall variation, increased evapotranspiration, and the end of the growing season. These results provide insights for monitoring change in complex arctic environments.

Using TerraSAR-X satellite data to detect road age and degradation

Analysis of satellite-acquired synthetic aperture radar (SAR) data provides a way to rapidly survey road conditions over large areas. This capability could be useful for identifying road segments that potentially require repair or at least onsite inspection of their condition due to changes in vehicular traffic associated with change in land use. We conducted a feasibility study focused on urban roads near the Southwest Research Institute (SwRI) campus in San Antonio, Texas. The roads near SwRI were affected by heavy truck traffic, they were easily inspected, and the age and construction of the pavement was known. TerraSAR-X (TSX) SpotLight (ST) satellite data were used to correlate radar backscattering response to pavement age and condition. Our preliminary results indicate that TSX radar imagery can be useful for detecting changes in pavement type, damage to pavement, such as cracking and scaling, and, occasionally, severe rutting. In addition, multitemporal interferometric analysis showed patches of settlement along two roads south of the SwRI campus. Further development of an automated approach to detect degradation of roads could allow transportation departments to prioritize inspection and repair efforts. The techniques also could be used to detect surreptitious heavy truck traffic in areas where direct inspection is not possible.

Historical Rail Accident Analyses Identifying Accident Parameters That Could Impact Transportation of Spent Nuclear Fuel

As the regulatory authority for transportation of spent nuclear fuel (SNF) in the United States, the Nuclear Regulatory Commission (NRC) requires that SNF transportation packages be designed to endure a fully engulfing fire with an average temperature of 800 °C (1,475 °F) for 30 minutes, as prescribed in Title 10 of the Code of Federal Regulations (CFR) Part 71. The work described in this paper was performed to support NRC in determining the types of accident parameters that could produce a severe fire with the potential to fully engulf a SNF transportation package. This paper describes the process that was used to characterize the important features of rail accidents that would potentially lead to a spent nuclear fuel transport package being involved in a severe fire. Historical rail accidents involving hazardous material and long duration fires in the United States have been analyzed using data from the Federal Railroad Administration (FRA) and the Pipeline and Hazardous Materials Safety Administration (PHMSA). Parameters that were evaluated from this data include, but were not limited to, class of track where the accident occurred, class of hazardous material that was being transported, and number of railcars involved in the fire. The data analysis revealed that in the past 34 years of rail transport, roughly 1,800 accidents have led to the release of hazardous materials resulting in a frequency of roughly 1 accident per 10 million freight train miles. In the last 12 years, there have only been 20 accidents involving multiple car hazardous material releases that led to a fire. This results in an accident rate of 0.003 accidents per million freight train miles that involved multiple car releases and a fire. In all the accidents analyzed, only one involved a railcar carrying Class 7 (i.e., radioactive) hazardous material (HAZMAT).Copyright