Surface velocity computation of debris flows by vector field measurements

2000 ◽  
Vol 25 (9) ◽  
pp. 741-744 ◽  
Author(s):  
H. Inaba ◽  
Y. Itakura ◽  
M. Kasahara
Keyword(s):  
Vector Field ◽  
Debris Flows ◽  
Field Measurements ◽  
Surface Velocity

Experiments on the stability and transition of wind-driven water surfaces

2001 ◽  
Vol 446 ◽  
pp. 25-65 ◽  
Author(s):  
FABRICE VERON ◽  
W. KENDALL MELVILLE
Keyword(s):  
Surface Current ◽  
Field Measurements ◽  
Surface Flow ◽  
Transition To Turbulence ◽  
Surface Velocity ◽  
Small Scale ◽  
Gas Transfer ◽  
Water Surfaces ◽  
Langmuir Circulations ◽  
The Stability

We present the results of laboratory and field measurements on the stability of wind-driven water surfaces. The laboratory measurements show that when exposed to an increasing wind starting from rest, surface current and wave generation is accompanied by a variety of phenomena that occur over comparable space and time scales. Of particular interest is the generation of small-scale, streamwise vortices, or Langmuir circulations, the clear influence of the circulations on the structure of the growing wave field, and the subsequent transition to turbulence of the surface flow. Following recent work by Melville, Shear & Veron (1998) and Veron & Melville (1999b), we show that the waves that are initially generated by the wind are then strongly modulated by the Langmuir circulations that follow. Direct measurements of the modulated wave variables are qualitatively consistent with geometrical optics and wave action conservation, but quantitative comparison remains elusive. Within the range of parameters of the experiments, both the surface waves and the Langmuir circulations first appear at constant Reynolds numbers of 370 ± 10 and 530 ± 20, respectively, based on the surface velocity and the depth of the laminar shear layer. The onset of the Langmuir circulations leads to a significant increase in the heat transfer across the surface. The field measurements in a boat basin display the same phenomena that are observed in the laboratory. The implications of the measurements for air–sea fluxes, especially heat and gas transfer, and sea-surface temperature, are discussed.

scholarly journals Inundation, flow dynamics, and damage in the 9 January 2018 Montecito debris-flow event, California, USA: Opportunities and challenges for post-wildfire risk assessment

Geosphere ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 1140-1163 ◽  
Author(s):  
J.W. Kean ◽  
D.M. Staley ◽  
J.T. Lancaster ◽  
F.K. Rengers ◽  
B.J. Swanson ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Field Measurements ◽  
Economic Loss ◽  
Flow Dynamics ◽  
Dynamic Constraints ◽  
Fire Debris ◽  
Velocity Information ◽  
Intense Burst ◽  
Comprehensive Framework

Abstract Shortly before the beginning of the 2017–2018 winter rainy season, one of the largest fires in California (USA) history (Thomas fire) substantially increased the susceptibility of steep slopes in Santa Barbara and Ventura Counties to debris flows. On 9 January 2018, before the fire was fully contained, an intense burst of rain fell on the portion of the burn area above Montecito, California. The rainfall and associated runoff triggered a series of debris flows that mobilized ∼680,000 m3 of sediment (including boulders >6 m in diameter) at velocities up to 4 m/s down coalescing urbanized alluvial fans. The resulting destruction (including 23 fatalities, at least 167 injuries, and 408 damaged homes) underscores the need for improved understanding of debris-flow runout in the built environment, and the need for a comprehensive framework to assess the potential loss from debris flows following wildfire. We present observations of the inundation, debris-flow dynamics, and damage from the event. The data include field measurements of flow depth and deposit characteristics made within the first 12 days after the event (before ephemeral features of the deposits were lost to recovery operations); an inventory of building damage; estimates of flow velocity; information on flow timing; soil-hydrologic properties; and post-event imagery and lidar. Together, these data provide rare spatial and dynamic constraints for testing debris-flow runout models, which are needed for advancing post-fire debris-flow hazard assessments. Our analysis also outlines a framework for translating the results of these models into estimates of economic loss based on an adaptation of the U.S. Federal Emergency Management Agency’s Hazus model for tsunamis.

scholarly journals Basal Water Film, Basal Water Pressure, and Velocity of Traveling Waves on Glaciers

1983 ◽  
Vol 29 (101) ◽  
pp. 20-27 ◽  
Author(s):  
J. Weertman ◽  
G. E. Birchfield
Keyword(s):  
Traveling Waves ◽  
Traveling Wave ◽  
Water Pressure ◽  
Strong Support ◽  
Water Film ◽  
Field Measurements ◽  
Surface Velocity ◽  
Sliding Velocity ◽  
Wave Velocities ◽  
Basal Shear

Abstract The theory of Nye and of Weertman of traveling waves on glaciers is extended to cover the situation where the presence of abundant basal water or increased basal water pressure produces increased sliding of a glacier over its bed. It is found that the ratio of traveling-wave velocity to surface velocity is independent of the amount of water or the basal water pressure. The theoretical value of this ratio, about 4 to 5, agrees with that found in field measurements (the most recent data are from Mer de Glace). It is concluded that field observations of traveling-wave velocities lend strong support to any glacier sliding theory in which the sliding velocity is proportional to the basal shear stress raised to about a second to fifth power and in which the sliding velocity is a function of either or both the amount of water at the bed of a glacier and the pressure within this water.

scholarly journals Mass–Balance and Ice–Flow–Law Parameters for East Antarctica

1985 ◽  
Vol 31 (109) ◽  
pp. 334-339 ◽  
Author(s):  
T.C Hamley ◽  
I.N. Smith ◽  
N.W. Young
Keyword(s):  
Power Flow ◽  
Grid Point ◽  
Ice Sheet ◽  
Field Measurements ◽  
East Antarctica ◽  
Surface Velocity ◽  
Shear Strain Rate ◽  
Polar Research Institute ◽  
Flow Law ◽  
Basal Shear

AbstractA comprehensive set of ice-velocity and thickness data from traverses within the IAGP study area (bounded by long. 90°E. and 135°E., and north of lat. 80°S.) is compared with steady-state mass-flux calculations based on Scott Polar Research Institute (SPRI) map compilations.The results of previous regional mass-budget estimates are reviewed and followed by a description of the new field measurements and the basis upon which a computer “grid–point” program is used to calculate balance fluxes.A comparison of measured and balance fluxes indicates that the ice sheet in this region of East Antarctica is unlikely to be significantly out of balance.The ratio of average column to surface velocity is discussed and calculated to be 0.89.An analysis of the mean shear strain-rate (VS/Z), versus down-slope basal shear stress (τb=ρgᾱZ), suggests that power flow-law parameters ofn= 3.21 andk= 0.023 bar−nm−1are appropriate for the effective basal shear zone in this region of the Antarctic ice sheet.

Comparison of the surface velocity of a debris flow at the Gadria creek using pulse compression radar and digital particle image velocimetry (DPIV).

2020 ◽  
Author(s):  
Tobias Schöffl ◽  
Georg Nagl ◽  
Johannes Hübl
Keyword(s):  
Particle Image Velocimetry ◽  
Debris Flow ◽  
Debris Flows ◽  
Pulse Compression ◽  
Particle Image ◽  
Video Camera ◽  
Digital Particle Image Velocimetry ◽  
Surface Velocity ◽  
Image Velocimetry ◽  
Pulse Compression Radar

<p><strong>Comparison of the surface velocity of a debris flow at the Gadria creek using pulse compression radar and digital particle image velocimetry (DPIV).</strong></p><p><strong> </strong></p><p>Tobias Schöffl, Georg Nagl, Johannes Hübl</p><p>Institute of Mountain Risk Engineering, University of Natural Resources and Life Sciences, Vienna, Austria</p><p> </p><p>A central aspect of protection against debris flows is the understanding of the process. The flow velocity is an important parameter which is used, for example, in the dimensioning of protective structures, for technical building protection and for early warning systems. The measurement of the surface velocity which is regarded as the maximum velocity occurring within a debris flow, is therefore an essential link in the chain of fundamental process research and applied protection against natural hazards.</p><p>Due to the further development of various technologies such as video technology and high-frequency radar technology, the non-contact measurement of the surface speed of a debris flow has improved significantly in recent years. Radar technology provides a wide aspect of applications in alpine mass movements such as debris flows, avalanches and rockfall and is able to detect such processes up to a range of 2500 meters in distance. An additional beneficial feature is the possibility of non-contact measurement of the surface velocity. In the catchment area of the Gadria basin (South Tyrol, Italy), the measuring station, which has been in operation since 2016, has been extended by a pulse compression radar and a new HD video camera. On July 26, 2019 a debris flow consisting of several surges was recorded with both the radar and the HD video camera. To obtain surface velocity data from the video material, the material was analyzed and evaluated using digital particle image velocimetry by making use of the MATLAB software and its freely accessible ADD-On "PIVlab".</p><p>The results of the compared surface velocity data showed a value of up to 0.74 according to the statistical mean of the coefficient of determination. The results demonstrate the high effectiveness of the pulse compression radar and the DPIV analysis in a wide range of the assessment of surface velocity of natural debris flows. There is great potential in both measuring systems and the chosen comparative analysis provides a blueprint for future recorded debris flows.</p>

Predicting deposition of debris flows in mountain channels

1990 ◽  
Vol 27 (4) ◽  
pp. 409-417 ◽  
Author(s):  
Lee E. Benda ◽  
Terrance W. Cundy
Keyword(s):  
Pacific Northwest ◽  
Debris Flows ◽  
Field Measurements ◽  
Coast Range ◽  
Oregon Coast Range ◽  
Oregon Coast ◽  
Aerial Photos ◽  
The Pacific ◽  
Channel Slope ◽  
Junction Angle

An empirical model for predicting deposition of coarse-textured debris flows in confined mountain channels is developed based on field measurements of 14 debris flows in the Pacific Northwest, U.S.A. The model uses two criteria for deposition: channel slope (less than 3.5°) and tributary junction angle (greater than 70°). The model is tested by predicting travel distances of 15 debris flows in the Oregon Coast Range and six debris flows in the Washington Cascades, U.S.A. The model is further tested on 44 debris flows in two lithological types in the Oregon Coast Range using aerial photos and topographic maps; on these flows only the approximate travel distance is known. The model can be used by resource professionals to identify the potential for impacts from debris flows. Key words: debris flow, deposition, travel, erosion.

scholarly journals The equilibrium flow and mass balance of the Taku Glacier, Alaska 1950–2006

2008 ◽  
Vol 2 (3) ◽  
pp. 275-298 ◽  
Author(s):  
M. S. Pelto ◽  
S. R. McGee ◽  
G. W. Adema ◽  
M. J. Beedle ◽  
M. M. Miller ◽  
...  
Keyword(s):  
Mass Balance ◽  
Field Measurements ◽  
Surface Flux ◽  
Equilibrium Line ◽  
Surface Velocity ◽  
Late Nineteenth Century ◽  
Surface Mass Balance ◽  
Volume Flux ◽  
Surface Mass ◽  
Glacier Velocity

Abstract. The Taku Glacier, Alaska has advanced 7.5 km since the late nineteenth century, while all other primary outlet glaciers of the Juneau Icefield are in retreat. The Juneau Icefield Research Program has completed field work on the Taku Glacier annually since 1946. The collected observations of surface mass balance, glacier velocity and glacier thickness at Profile IV 29 km above the terminus and 4 km above the equilibrium line provide a means to assess the equilibrium nature of the Taku Glacier. Velocity measured over a twelve month span and annual summer velocity measurements completed at a Profile IV from 1950–2006 indicate insignificant variations in velocity seasonally or from year to year. The consistency of velocity over the 56-year period indicates that in the vicinity of the equilibrium line, the flow of the Taku Glacier has been in an equilibrium state. Surface mass balance was positive from 1946–1988 averaging +0.42 m a−1. This led to glacier thickening. From 1988–2006 an important change has occurred and annual balance has been −0.14 m a−1, and the glacier thickness has ceased increasing along Profile IV. Field measurements of ice depth and surface velocity allow calculation of the volume flux at Profile IV. Volume flux is then compared with the surface balance flux from the region of the glacier above Profile IV, determined annually in the field. Above Profile IV the observed mean surface flux is 5.50×108 m3/a (±5%), while the calculated volume flux range flowing through profile IV is 5.00–5.47×108 m3/a. The mean surface flux has been greater than the volume flux, which has led to slow thickening of the Taku Glacier up to 1988. The thickening has not led to a change in the flow of Taku Glacier at Profile IV.

scholarly journals The Kalmag Model as a Candidate for IGRF-13

2020 ◽  
Author(s):  
Julien Baerenzung ◽  
Matthias Holschneider ◽  
Johannes Wicht ◽  
Vincent Lesur ◽  
Sabrina Sanchez
Keyword(s):  
Inverse Problem ◽  
Kalman Filter ◽  
Vector Field ◽  
Geomagnetic Field ◽  
Time Window ◽  
Field Measurements ◽  
Covariance Matrices ◽  
Smoothing Algorithm ◽  
Mean Fields ◽  
Observable Field

Abstract We present a new model of the Geomagnetic field spanning the last 20 years and called Kalmag. Deriving from the assimilation of CHAMP and SWARM vector field measurements, it separates the different contributions to the observable field through parameterized prior covariance matrices. To make the inverse problem numerically feasible it has been sequentialized in time though the combination of a Kalman filter and a smoothing algorithm. The model provides reliable estimates of past, present and future mean fields and associated uncertainties. The version presented here is an update of our IGRF candidates, the amount of assimilated data has been doubled and the considered time window has been extended from [2000.5,2019.74] to [2000.5,2020.33].

scholarly journals Delineation of a catchment boundary using velocity and elevation measurements

1998 ◽  
Vol 27 ◽  
pp. 140-144 ◽  
Author(s):  
S. F. Price ◽  
I. M. Whillans
Keyword(s):  
Field Measurements ◽  
Surface Velocity ◽  
Data Sampling ◽  
West Antarctica ◽  
Ice Surface ◽  
Ice Stream ◽  
Elevation Data ◽  
Boundary Location ◽  
Ice Stream B

The determination of catchment boundaries is a major source of uncertainty in net balance studies on large ice sheets. Here, a method for defining a catchment boundary is developed using new measurements of ice-surface velocity and elevation near the Ice Stream B/C boundary in West Antarctica. An objective method for estimating confidence in the catchment boundary is proposed. Using elevation data, the resulting mean standard deviation in boundary location is 13 km in position or 6000 km2 in area. Applying a similar uncertainty to both sides of the Ice Stream Β catchment results in a catchment-area uncertainty of 9%. Much larger uncertainties arise when the method is applied to velocity data. The uncertainty in both cases is primarily determined by the density of field measurements and is proportionally similar for larger catchment basins. Differences in the position of the velocity-determined boundary and the elevation-determined boundary probably result from data sampling. The boundary positions determined here do not support the hypothesis that Ice Stream Β captured parts of the Ice Stream C catchment.

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