Climatic and hydrologic aspects of the 2008 Midwest floods
Between May and June 2008 the Midwest region of the United States (U.S.) experienced record flooding. The event was produced by distinct hydroclimatic conditions that included saturated antecedent soil moisture conditions and atmospheric circulation that guided moist air from the Gulf of Mexico into the area between late May and mid-June. The latter included a well-developed trough over the central/west U.S., a strong Great Plains Low Level Jet (GPLLJ), and unseasonably strong westerlies that promoted upper level divergence in regions of positive vorticity advection. The flooding coincided with a strongly negative phase of the North Atlantic Oscillation linked to the strength of the GPLLJ. The atmospheric flow contributed to flooding within three river basins across nine states. Iowa, southern Wisconsin, and central Indiana located within the Upper Mississippi River Basin (UMRB) and the Wabash River Basin were most impacted and also recorded the greatest anomalies in rainfall. Record rainfall, persistent multi-day precipitation events, high frequency of localized high-intensity rainfall events all contributed to the severity of the flooding. Conditions peaked between May 21 and June 13 when rain fell somewhere within the region each day. River discharge rates reached record levels in June at many locations; return periods throughout Iowa, southern Wisconsin and in central Indiana were estimated to exceed 100 years, and often times 200 years. Record river stage levels were observed during this time in similar areas. Conditions began to recover into July and August. The timing of occurrence of the precipitation and hydrological anomalies towards late spring and into early summer in the Midwest was rather unusual. The 2008 flood event occurred 15 years after the infamous 1993 event. The importance of its occurrence is underscored by the observed increasing trends in extreme and flood-related precipitation characteristics during the 20th century and the anticipated changes under future anthropogenic warming scenarios. If changes in such extremes can be understood or even anticipated, society can begin to take measures towards proactive adaptation and risk management to limit future impacts.
Active Volcano Monitoring using a Space-based Hyperspectral Imager
Active volcanoes occur on every continent, often in close proximity to heavily populated areas. While ground-based studies are essential for scientific research and disaster mitigation, remote sensing from space can provide rapid and continuous monitoring of active and potentially active volcanoes [Ramsey and Flynn, 2004]. In this paper, we report on hyperspectral measurements of Kilauea volcano, Hawaii. Hyperspectral images obtained by the US Air Force TacSat-3/ARTEMIS sensor [Lockwood et al, 2006] are used to obtain estimates of the surface temperatures for the volcano. ARTEMIS measures surface-reflected light in the visible, near-infrared, and short-wave infrared bands (VNIR-SWIR). The SWIR bands are known to be sensitive to thermal radiation [Green, 1996]. For example, images from the NASA Hyperion hyperspectral sensor have shown the extent of wildfires and active volcanoes [Young, 2009]. We employ the methodology described by Dennison et al, (2006) to obtain an estimate of the temperature of the active region of Kilauea. Both day and night-time images were used in the analysis. To improve the estimate, we aggregated neighboring pixels. The active rim of the lava lake is clearly discernable in the temperature image, with a measured temperature exceeding 1100o C. The temperature decreases markedly on the exterior of the summit crater. While a long-wave infrared (LWIR) sensor would be ideal for volcano monitoring, we have shown that the thermal state of an active volcano can be monitored using the SWIR channels of a reflective hyperspectral imager. References: Dennison, Philip E., Kraivut Charoensiri, Dar A. Roberts, Seth H. Peterson, and Robert O. Green (2006). Wildfire temperature and land cover modeling using hyperspectral data, Remote Sens. Environ., vol. 100, pp. 212-222. Green, R. O. (1996). Estimation of biomass fire temperature and areal extent from calibrated AVIRIS spectra, in Summaries of the 6th Annual JPL Airborne Earth Science Workshop, Pasadena, CA JPL Publ. 96-4, vol. 1, pp. 105-113. Lockwood, Ronald B., Thomas W. Cooley, Richard M. Nadile, James A. Gardner, Peter S. Armstrong, Abraham M. Payton, Thom M. Davis, Stanley D. Straight, Thomas G. Chrien, Edward L. Gussin, and David Makowski (2006). Advanced Responsive Tactically-Effective Military Imaging Spectrometer (ARTEMIS) Design, in Proceedings of the 2006 IEEE International Geoscience and Remote Sensing Symposium, 31 July-4 August 2006, Denver, Colorado. Ramsey, Michael S., and Luke P. Flynn (2004). Strategies, insights, and the recent advances in volcanic monitoring and mapping with data from NASA’s Earth Observing System, Jour. of Volcanology and Geothermal Research, vol. 135, pp. 1-11. Young, Joseph (2009). EO-1 Weekly status report for September 24-30, 2009, Earth Science Mission Operations (ESMO) Office, NASA Goddard Space Flight Center, Greenbelt, MD 20771.
FLOW DIRECION OF DEBRIS AVALANCHE AT AGUILUCHO-APACHETA VOLCANIC COMPLEX (AAVC), CENTRAL ANDES
Aguilucho-Apacheta (5,581 and 5,283 m a.s.l., respectively) is a volcanic complex located in the Andean Central Volcanic Zone (ACVZ) at 21°50’S and 68°10’W. During its evolution, AAVC underwent a collapse of its eastern part originated by hydrothermal alteration and controlled by tectonic activity present in the zone. This collapse generated a debris-avalanche deposit (DAD) which is distributed towards the eastern flank of the volcanic complex. This DAD has an area of ca. 3 km2, an extended length up to 4.27 km and a relative run-out coefficent (H/L) of 0.23. It is confined between two older andesitic-to-dacitic lava flows and is constituted by andesitic-to-dacitic lavas, hydrothermally altered lava and hydrothermal breccias fragments. The debris-avalanche deposit shows typical hummock morphology. Undisrupted bedding hummocks are observed in the proximal and central zone of the deposit. Towards the distal zone, hummocks fragmented and diminishing their size as they move away from the volcano. Large andesitic-to-dacitic hummocks (4 - 20 m height) can be found at the proximal zones. These proximal hummocks show original bedding of the volcano and are oriented in an E-W trend. Towards the distal part of the deposit small (0.1 to 2 m height) hummocks are found. They are composed by hydrothermally altered lava blocks and trend in a WNW-ESE direction. Hummocks at the central portion are constituted by andesitic-to-dacitic, hydrothermally altered lavas and hydrothermal breccia fragments. These hummocks have heights that vary from 2 up to 4 m and have two major trending orientations which are almost perpendicular: NW-SE and E-W. No Toreva blocks have been observed within this deposit. Ridges and levees also can be found within the deposit. Leveés are located towards the marginal zones climbing up the lava flows that confined the deposit. They are composed by hydrothermal breccias fragments. Orientations of levées change from a ca. E-W direction in the proximal zone to a NW-SE direction towards the central part of the deposit. Ridges are located toward the central zone. These features mark the distal limit of the main body of the deposit. They are constituted by hydrothermally altered lava blocks and hydrothermal breccias fragments, trending in a E-W orientation. Orientation of hummocks, as well as orientation of ridges and leveés, helps to indicate how avalanche was moving while it was flowing. After the collapse, the avalanche was moving in an east-west direction, indicated by proximal hummocks and levées orientation. The avalanche kept this direction until it reached older lava flows erupted towards the eastern side of the volcanic complex. These lava flows channelized and changed the flow towards a NW-SE direction. This generated hummocks and levées which are paralel and ridges and hummocks oriented almost normal to the flow direction at the central zone. At the distal zone the flow was free again, moving in a WNW-ESE orientation.
Debris flow probability and extent vary with infiltration rate and intensity-duration of rainfall: Mt. Mayon, Philippines
Volcanoclastic debris flows or lahars triggered by intense rainfall due to bulking are influenced by surface characteristics that reduce the downward infiltration of groundwater after saturation. Variations in surface cover control storm water runoff, thus affecting the timing and volume of water entering a river channel prone to lahars. Rainfall induced debris flows constitute a serious geologic hazard to communities in many parts of the world. The abundant loose erodible material on volcanoes increases the likelihood and severity of large debris flow events; this combined with dense populations make volcanoes an important area for lahar research and mitigation measures. This study was carried out on the slopes of the Republic of the Philippines most active volcano, Mt. Mayon, in hopes of increasing the understanding of debris flow initiation. Two tipping bucket rain gauges equipped with data loggers were deployed to determine an intensity-duration rainfall threshold during quiescent periods on Mayon. The steady-state infiltration capacities of Mayon’s substrates were determined using a double-ring infiltrometer ponding method. Additional infiltrometer experiments were carried out with an overlying simulated ash layer of 10, 20, 30, 40, 50, and 100 mm in order to quantify the effects of tephra cover on ground infiltration, adding supporting data that decreased infiltration and increased likelihood of debris flow initiation occur after an eruptive event. Finally, sieve analyses of the volcanic substrates were conducted to better understand the variations of infiltration and runoff due to grain size distribution. An intensity-duration rainfall threshold for quiescent periods on Mayon was estimated to be (I=46.2D-0.43). Average infiltration measurements ranged from 5.43-230.83 mm/hr depending on the type of substrate, vegetation cover, and grain size distribution. Simulated ash layers were found to increase initial infiltration (first 10 minutes) but decreased long-term infiltration (minutes - hours) between 2-30%. The average infiltration for each watershed was compared to the estimated volume of the lahars that were produced during Typhoon Reming in 2006, indicating a correlation between infiltration characteristics and debris flow severity.
Ship-based GPS sensing of the 27 Feb 2010 tsunami in the open ocean
The passage of the tsunami from the 27 Feb 2010 Maule, Chile, earthquake was recognized in kinematic GPS solutions from a ship underway in the open ocean. High-rate dual-frequency GPS measurements were collected on the University of Hawaii Research Vessel Kilo Moana, en route from Hawaii to Guam, during the predicted arrival time of the tsunami. Using the Track module of the Gamit software package and a reference GPS site on Maui, 600 km from the ship, kinematic solutions for the ship's track were calculated. A matched filter approach was adopted, with filters generated by extracting the first 1-2 hrs of the sea surface height perturbations predicted by the NOAA Pacific Tsunami Warning Center RIFT model. Even though the predicted maximum height of the passing tsunami was < 10 cm the expected sequence of correlation peaks was generated close to the predicted arrival time. The likelihood of spurious peaks caused by processing artifacts and/or multipath effects currently restricts the use of this technique as a stand-alone detection system, except in the near-field of a major tsunami where simulations show the peaks in sea-level change can be expected to rise significantly above the background noise of the GPS height solutions. Better multipath characterization and mitigation could significantly improve the reliability and performance of this technique. Given the density of commercial shipping traffic on the major Pacific shipping lanes, and the affordability of geodetic GPS systems, this approach shows great promise for augmenting the existing sparse tide-gauge and ocean-bottom pressure sensor networks, providing corroboration of tsunamis and constraints that can be used to fine-tune the source models and improve predictions.
The November 1st, 1755 Tsunami in Morocco: Can Numerical Modeling Clarify the Uncertainties of Historical Reports?
Coastal communities in the Atlantic marine limit of Morocco risk of inundation by regional and local tsunamis generated in the SW Iberia zone. Tsunami catalogs indicate that this area was the place of several tsunami events since historical time. Among them, the 1755 tsunami remains the largest eye witnessed historical event in the North East Atlantic area. Historical documents described, in some details, the generated waves along the coasts of Portugal, Spain and Morocco. They mentioned that the tsunami run-up has reached 15 m and the wave amplitude was as height as 26 m in some locations. However, these values of wave heights, run-up and inundated areas may were overestimated as it was revealed in the recent published critical studies of historical documents focused on the Gulf of Cadiz area. One of the coastal segments where the reported historical data, related to the 1755 event, are uncertain is the city of Mazagão, actually El-Jadida, located at the SW of Moroccan Atlantic coast. The present study seeks to numerically evaluate the tsunami impact along the El-Jadida coastal segment in order to clarify the uncertainties of the historical reports. A detailed numerical modeling of the tsunami waves evolution onshore and offshore El- Jadida site has been conducted. The digital terrain model (DTM) considered in this study is a reconstruction of the paleo-DTM of El-Jadida site in the 1750s, that we have computed from the paleo-bathymetric/topographic carts available before 1755. Earthquake scenarios of magnitude ~8.5 have been considered to represent a 1755-like event. Results in term of wave heights, maximum run-ups, high resolution inundation maps and flow limits for the study area have been presented for each candidate scenarios. Reliability of historical reports has been discussed in light of the comparison of these reports with the worst tsunami impact in El-Jadida obtained from numerical modeling. Keywords: 1755 tsunami; Morocco; tsunami modeling; historical data.
Emergency Satellite Image Delivery through International Charter ‘Space and Major Disasters’
Rapid acquisition and availability of satellite imagery is an essential component of effective response to many types of disasters such as floods, earthquakes, landslides, and other natural or human-induced disasters. The International Charter ‘Space and Major Disasters’ provides a unified system of space-based data acquisition, image analysis, and derived information delivery to those affected by natural or man-made disasters. As a member of the International Charter, the USGS helps to ensure the rapid collection and availability of a diverse set of space-based image data resources for US as well as non-US disaster events. Recent International Charter activations by USGS have included the Earthquake in Haiti, Gulf of Mexico Oil Spill, and flooding in Pakistan. In all cases, an immediate activation through the International Charter helped to ensure timely availability of satellite data from many international sources for use in the response and recovery efforts. The International Charter was initiated in November 2000, and since that time has grown to include 10 member agencies and their associated space assets. Each member agency has committed resources to support the provisions of the Charter, thus helping to mitigate the effects of disasters on human life and property. For each member agency involved in an event response, participation in the Charter provides access to member space agency resources, and to data from satellites operated by member countries. Such access greatly enhances our ability to respond to disasters as they occur globally, as well as to those that occur within the United States. This presentation will provide an overview of the International Charter organization and provide technical details on the assets and capabilities available for emergency response through the current US membership in the Charter. Examples from the 2010 activations in Haiti, Gulf of Mexico, and Pakistan will also be discussed to demonstrate the importance of having a diverse and robust set of internationally based space-borne assets available for disaster response.
Development of an Integrated Model for the Assessment of Climate Change Adaptation Methods Relating to the Preservation of Urban Coastal Cultural Heritage
The Government Accountability Office’s report, Climate Change Adaption, examines federal, state, local, and international mitigation actions for climate change and sea-level rise. The report specifically addresses the dearth of Site-Specific Information relating to the effects of climate change on a localized scale and the challenges this poses for the development of adaption strategies. We are developing a model that will begin to regionalize climate change projections for the purpose of projecting the effects of climate change on coastal cultural heritage. As global sea level increases, so too will the number of historically significant landscapes that are threatened due to sea-level rise. Because of this, historical preservationists will require a greater availability of pertinent information in order to contend with the threats posed by climate change and rising sea levels. These threats will have a far greater impact on Low Elevation Coastal Zones (LECZ) areas. The US ranks third for land mass classified as LECZ and has an estimated population of 22 million people living within these regions. Many of these areas have had high population densities due to the concentration of marine fishery resources, ease of transportation, and agricultural associations with river deltas. These areas have acted as catalysts for the evolution of various societies and cultures, and contain a concentrated stratification of cultural heritage deposits. The development of models for the assessment of spatial/temporal impacts of climate change on coastal cultural heritage will play a significant role in defining long-term preservation needs on a regional scale. We are coordinating ground water seepage models, tidal estuary models, and the regionalized Global Climate Models with localized geophysical assessments and GIS data sets. Through the digitization and rectification of various contemporary and historical maps we have developed a GIS data set that reflects the evolution of the Strawbery Banke, a living history museum in Portsmouth, N.H., located close to the Piscataqua River tidal estuary, over 200 years. Particular attention is paid to Puddle Dock; a tidal inlet that was filled in the early 1900’s and lies at the heart of the facility. A Ground Penetrating Radar (GPR) survey of Puddle Dock was conducted to provide data on seepage characteristics during high and low tides. This information is increasing our understanding of the role that tidal pressure and the intrusion of the saltwater/freshwater interface plays on shifting the height of the ground water lense. The data derived from the model and its coordination with the high resolution GIS data set will allow preservationists to better determine the impacts of potential inundation, storm surge, or flooding on defined areas of particular historical significance.
Late 20th Century Deep-seated Vertical Motions in New Orleans and implications for Gulf Coast Subsidence
Subsidence of the Mississippi River delta and adjoining coastal areas is widely thought to be dominated by compaction of Holocene sediments. Current public policies regarding hurricane protection and ecosystems restoration are founded on this interpretation. To test this hypothesis, monuments that penetrate the entire Holocene section were measured using geodetic leveling and water gauges attached to bridge foundations. Results show that the entire sampling area subsided between 1955 and 1995 in amounts unanticipated by previous models. Subsidence due to processes originating below the Holocene section locally exceeded 0.9 m between 1955 and 1995. The maxima of deep subsidence occurred in the urbanized and industrialized sections of eastern New Orleans. Subsidence decreased away from urbanized areas and north of the belt of active basin margin normal faults; this decrease in subsidence continued to the north and east along the Mississippi coast. These independent measurements provide insights into the complexity and causes of modern landscape change in the region. Modern subsidence is clearly not dominated solely by shallow processes such as natural compaction, Deep subsidence occurring east and north of the basin margin faults can be explained by regional tectonic loading of the lithosphere by the modern Mississippi River delta and local groundwater withdrawal. Sharp, local changes in subsidence coincide with strands of the basin margin normal fault system. Deep subsidence of the New Orleans area can be explained by a combination of groundwater withdrawal from shallow upper Pleistocene aquifers, the aforementioned lithospheric loading, and non-groundwater-related faulting. Subsidence due to groundwater extraction from aquifers ~160 to 200 m deep dominated the urbanized areas from ~1960 to the early 1990s and is likely responsible for lowering flood protection structures and bridges in the area by as much as ~0.8 m.
Water Induced Hazard Mapping in Nepal: A Case Study of East Rapti River Basin
This paper presents illustration on typical water induced hazard mapping of East Rapti River Basin under the DWIDP, GON. The basin covers an area of 2398 sq km. The methodology includes making of base map of water induced disaster in the basin. Landslide hazard maps were prepared by SINMAP approach. Debris flow hazard maps were prepared by considering geology, slope, and saturation. Flood hazard maps were prepared by using two approaches: HEC-RAS and Satellite Imagery Interpretation. The composite water-induced hazard maps were produced by compiling the hazards rendered by landslide, debris flow, and flood. The monsoon average rainfall in the basin is 1907 mm whereas maximum 24 hours precipitation is 456.8 mm. The peak discharge of the Rapati River in the year of 1993 at station was 1220 cu m/sec. This discharge nearly corresponds to the discharge of 100-year return period. The landslides, floods, and debris flows triggered by the heavy rain of July 1993 claimed 265 lives, affected 148516 people, and damaged 1500 houses in the basin. The field investigation and integrated GIS interpretation showed that the very high and high landslide hazard zones collectively cover 38.38% and debris flow hazard zone constitutes 6.58%. High flood hazard zone occupies 4.28% area of the watershed. Mitigation measures are recommendated according to Integrated Watershed Management Approach under which the non-structural and structural measures are proposed. The non-structural measures includes: disaster management training, formulation of evacuation system (arrangement of information plan about disaster), agriculture management practices, protection of water sources, slope protections and removal of excessive bed load from the river channel. Similarly, structural measures such as dike, spur, rehabilitation of existing preventive measures and river training at some locations are recommendated. The major factors that have contributed to induce high incidences of various types of mass movements and inundation in the basin are rock and soil properties, prolonged and high-intensity rainfall, steep topography and various anthropogenic factors.
Remote Sensing Based Flood Mapping for Disaster Management Applications
Flooding is among the most destructive and costly natural disasters faced by modern society. The disaster management community requires flood extent information with very little latency and frequent updating. With the advent of near real time satellite data acquisition and rapid processing and distribution techniques, there is every reason to develop and deploy an automated system for near real time flood map production. Funded by a NASA Applied Sciences grant to conduct a “feasibility study”, the authors have developed the algorithms and methodology necessary to automate the production of global near real time flood maps based on remote sensing data from the MODIS instruments on the NASA AQUA and TERRA satellites. A number of challenges to developing a useful product have been addressed by this applied research, including minimizing product latency, identifying water in the data scenes and distinguishing flood water from “normal” water levels, minimizing the impact of data loss due to cloud and cloud shadow, and providing context. We provide an overview of the data sources used, the algorithms employed, the processing techniques, the initial results, and the validation approach.
Geomagnetic Effect Caused by 1908 Tunguska Event
The analysis of the magnetograms of Irkutsk observatory on the 30th June 1908 showed that the explosion of Tunguska bolide was accompanied by variations of the Earth’s magnetic field, which were being continued for several hours . Irkutsk geophysical observatory is located approximately in 950 km to the southeast from the point of Tunguska explosion and it was nearest point, where the continuous recording of the components of the geomagnetic field was in progress. We suppose that it was caused by magnetic field of the current system, generated in the E-layer of ionosphere by gas dynamical flow after the Tunguska explosion . Plunging through the atmosphere, cosmic body forms a hot rarefied channel behind it; the hydrostatic equilibrium of pressure in the channel becomes broken. The particles of the body vapor and atmospheric air, involved in the motion, lift along this channel upward (so-called plume). In the rarefied layers of the atmosphere they move along the ballistic trajectories in the gravitational field. While falling down gas loses its kinetic energy in dense layers of the atmosphere, which is converted into thermal energy. Then the reflected shock wave is formed. The gas heated in it rises up and all these processes repeat. The effects of heating and ionization of gas at height of 100 km, caused by the oscillations in the atmosphere, can lead to a distortion of the existing current system in ionosphere and generation of new ones. Since the Tunguska body had an oblique trajectory, the plume was ejected in the direction opposite to motion of Tunguska body and provided ionized region at the distance about 700 km from the epicenter at time moment 400 seconds after explosion. Gas dynamical simulation and estimates of the plume parameters have been fulfilled to calculate conductivity profiles and the electric field. Magnetic field of the induced current system has been obtained by the numerical simulation of Maxwell’s equations. Analysis of calculation results of this current system shows that an unique azimuth of trajectory of the body exists, for which the variations of all three components of the geomagnetic field do not contradict to the observation data. This azimuth is equal to 306 degrees, while other estimates are in the range of 290-344 degrees. This idea of the atmospheric plume ejected along the trajectory and ionization in the upper atmosphere, caused by the following atmospheric oscillations, could explain the geomagnetic effect both in general and locally in Irkutsk observatory: the time delay and the variations of all magnetic field components. Binding of simulation results of observation data also allows us to select the unique trajectory azimuth for Tunguska body. References:  Ivanov K.G. The Geomagnetic phenomena, which were being observed on the Irkutsk magnetic observatory, following the explosion of the Tunguska meteorite //Meteoritika. 1961. Iss. XXI. P.46-49 (in Russian).  Losseva T., Merkin V., Nemtchinov I. Estimations of the Aeronomical and Electromagnetic Disturbances in the E-layer of the Ionosphere, caused by Tunguska Event // AGU Fall Meeting. 1999. SA32A-09.
Multiple meteoroid impacts in Antarctica at 481,000ky: a possible cause for the mid-Brunhes Event/MIS 11 Stage via the disruption of the West Antarctic Ice Sheet?
An early (1960s) gravity traverse over Wilkes Land in Antarctica yielded an unusual gravity profile: free air anomaly to -158mgal, steep negative free air gravity anomaly gradients (to 4.71 mgal/km), etc. The profile was not characteristic of those related to mantle or geologic crustal variations. Further, the lack of isostatic compensation, known rebound rates and locally crevassed ice lent to the suggestion the profile represented some recent process. The profile gave indication of apparent rim structures with an interior peak beneath the ice. The only interpretation at the time that appeared to reconcile the incongruities was the suggestion the profile represented a recent major bolide impact. Later radio-sounding work yielding craterform features that strengthened the hypothesis. More recent geophysical surveys, however, show a dominant cluster of negative free air gravity anomalies throughout Antarctica, spread across the East and West Antarctic structural boundary, i.e., the Transantarctic Mountains, the Ross Embayment and crossing into the continental-oceanic boundary. The geographic spread of these anomalies lies athwart contrasting geological provinces, making it difficult to assign the cause of these anomalies to any processes that might attend one geological regime. In addition, these anomalies lie within what might be postulated to be a bolide scatter ellipse. These gravity anomalies as well as aeromagnetic anomalies do not depart significantly from those of known impact sites (deviations are attributable to glacial scour). We therefore modified the earlier suggestion of one impact to that of multiple impacts. Three independent groups recently report that a major meteoritic event did occur in Antarctica at 481kyr. These reports arose from studies of 2 deep ice cores, Core Fuji and Dome C Core, and from the discovery of significant ablation debris in the Transantarctic Mountains indistinguishable from the anomalous extraterrestrial particles found in the cores and of the same age. The indication is that this impact event affected an area of around 6 million square kilometers if not more. The date of 481,000 years for the impacts as implied by the Transantarctic Mountains ablation debris and the ice cores place them at the mid-Brunhes event, i.e., the onset of MIS 11, which is characterized by the replacement of a heavy glacial with an unusually long and warm interglacial interval and a major marine transgression (sea levels > 20m above present). The collapse of a major ice sheet has to be inferred in order to produce similar high sea-levels. As this deglaciation is not associated with an early CO2 peak nor does it seem attributable to Milankovitch mechanisms, it is tempting to suggest that the initiator of MIS11 is the disruption of the Antarctic Ice Sheets by major bolide impacts with attendant loss of the West Antarctic Ice Sheet. There may be possible analogs here that have relevance to mankind’s present environmental issues.
Surrogate Models and Uncertainty Quantification for Hazard Map Construction
Computer models of hazardous phenomena, such as floods, hurricanes, and avalanches, are very expensive to run, and each run produces an enormous amount data. For example, a flood model output consists of water depth and velocity at every point in a large grid, at every instant of time. Furthermore, these models often require speci[|#12#|]fication of several parameters that may not be well characterized, and initial and boundary data that is likewise poorly specifi[|#12#|]ed. These inputs include for instance digital elevation models to represent terrain. Given the high dimension of uncertain features, a study of hazard risk using Monte Carlo type procedures for such models will be prohibitively expensive even with high end supercomputers. We present here systematic procedures that allow the construction of hazard maps based on surrogate models of the physical phenomena created by using a small ensemble of O(100) large scale computer simulations. We introduce the idea of hierarchical global and local (in parameter space) surrogates combined systematically to allow us to quantify uncertainty in the simulation outputs. This characterization may then be used as an easily computable indicator of potential hazard. We present the construction of hazard maps for large scale volcanic flows as an example.
Hazard analysis of potential flows at Mammoth Mountain, CA using input uncertainties in digital elevation model, frictional resistance to flow and initiation location and volume (8 dimensional input).