Simulated inundation extent and depth at Whittier, Alaska resulting from the hypothetical rapid motion of landslides into Barry Arm Fjord, Prince William Sound, Alaska
Dates
Publication Date
2021-10-14
Time Period
2021
Citation
Barnhart, K.R., Jones, R.P., George, D.L., Coe, J.A., Staley, D.M., Haeussler, P. J. and Labay, K. 2021, Simulated inundation extent and depth at Whittier, Alaska resulting from the hypothetical rapid motion of landslides into Barry Arm Fjord, Prince William Sound, Alaska: U.S. Geological Survey data release, https://doi.org/10.5066/P9IAPCZ5.
Summary
Summary This data release contains postprocessed model output from simulations of hypothetical rapid motion of landslides, subsequent wave generation, and wave propagation. A modeled tsunami wave was generated by rapid motion of unstable material into Barry Arm Fjord. This wave propagated through Prince William Sound and then into Passage Canal east of Whittier. Here we consider only the largest wave-generating scenario presented by Barnhart and others (2021a, 2021b) and use a simulation setup similar to that work. The results presented here are not identical to those presented in Barnhart and others (2021a, 2021b) because the results in this data release were obtained using an expanded dataset of topography and bathymetry. This [...]
Summary
Summary
This data release contains postprocessed model output from simulations of hypothetical rapid motion of landslides, subsequent wave generation, and wave propagation. A modeled tsunami wave was generated by rapid motion of unstable material into Barry Arm Fjord. This wave propagated through Prince William Sound and then into Passage Canal east of Whittier. Here we consider only the largest wave-generating scenario presented by Barnhart and others (2021a, 2021b) and use a simulation setup similar to that work. The results presented here are not identical to those presented in Barnhart and others (2021a, 2021b) because the results in this data release were obtained using an expanded dataset of topography and bathymetry. This data release presents the extent of simulated inundation and does not include simulation results related to other related phenomena (e.g., current strength).
Model Description
The simulation used the D-Claw model (George and Iverson, 2014; Iverson and George, 2014). D-Claw is a single-layer model that simulates the coupled evolution of fluid and solid material while satisfying mass and momentum conservation. D-Claw conceptualizes landslide material as fully saturated granular material. The model is capable of simulating motion of landslide material, interaction of that material with water, tsunami generation, and wave propagation. Because the mobile material in D-Claw may be water, landslide material, or a mixture between the two, we will use the term "wave height” to refer to the altitude of the mobile material surface, regardless of its composition.
Considered Scenario and Model Implementation
We present results from a single scenario (Table 1). This scenario used the landslide source characteristics of the larger, contractive, more mobile scenario C-689 from Barnhart and others (2021a, 2021b) that generated the largest wave. In this scenario, three landslides on an unstable slope northwest of the northern portion of Barry Arm fjord concurrently move into the fjord, generating a tsunami.
Table 1. Summary of considered scenario including key simulation input parameter values.
Simulation input parameters
Scenario name and description
C-689
Symbol
Units
Description
Larger, contractive, more mobile
α
degrees
Headscarp angle
60
C
-
Logarithmic spiral coefficient (defined in Equation 2 of Barnhart and others, 2021a)
0.5
V
m3
Volume of all three landslides
689,000,000
m0
-
Initial solid volume fraction
0.62
mcrit
-
Critical state solid volume fraction
0.64
φ
degrees
Basal friction angle
36
φΔ
degrees
Basal friction angle offset
0
k0
m2
Hydraulic permeability
10-10
The D-Claw model supports adaptive mesh refinement, and like Barnhart and others (2021a, 2021b), we used a computational grid cell size of 50 m around the landslide and along the wave propagation path. Our implementation differs from this prior work in that we permitted grid refinement to a finer resolution of 1 m as the tsunami approached and inundated Whittier, Alaska (pink region in Figure 1). In the portions of the domain where no wave propagated, the cell size was permitted to remain at a coarse resolution of 1,000 m.
The spatial extent of the simulation domain (shown in Figure 1) is smaller than what was considered by Barnhart and others (2021a, 2021b) and does not cover all of Prince William Sound. Instead, it is limited to the region between Whittier and Barry Arm fjord. Additionally, the duration of simulated time was reduced relative to that presented in Barnhart and others (2021a, 2021b). Simulations ran for 35 minutes of simulated time, reflecting the arrival of the largest wave within the two hours of total simulated time presented by Barnhart and others (2021a, their Figures 7 and 8).
Description of Inundation
The simulation results show very little inundation at Whittier, Alaska. In the simulations, the parking area to the north of the City of Whittier Campground was inundated by less than 1 m of water. Along the sea wall defining and protecting the harbor, along Camp Road to the west of town and at the airstrip, simulated water levels rose to ~2 m above the MHHW level. At the harbor, the simulated wave did not propagate inland of the sea wall. Similarly, the simulated wave did not reach the elevation of Camp Road or the waiting area at the east portal of the Anton Anderson Memorial Tunnel. Finally, the simulated wave did not inundate the airstrip.
Reference frame
The horizontal reference frame for all files is North American Datum of 1983 (NAD 83) Universal Transverse Mercator (UTM) Zone 6 N (European Petroleum Survey Group Code 26906). The vertical reference frame is mean higher high water (MHHW) at Whittier, Alaska (NOAA Station 9454949). At this station, mean higher high water is defined as 3.395 m above the North American Vertical Datum of 1988. Elevation, altitude, and height, as used in this data release, refer to distance above the MHHW vertical datum.
Topographic and Bathymetric Data Sources
This work relied on integrating multiple topographic and bathymetric data sources. Where original data sources were not provided in the reference frame used in this work, datasets were reprojected to NAD 83 UTM Zone 6 N and translated to MHHW.
In Barry Arm fjord north of Port Wells, we used a digital terrain model derived from subaerial light detection and ranging (lidar) data collected on June 26, 2020, (Daanen and others, 2021) and submarine bathymetric data collected between August 12 and 23, 2020 (NOAA, 2020). These data were combined at 5 m horizontal resolution.
In Passage Canal west of 148.5º W—including at Whittier, Alaska—we use a 1 m topobathymetric dataset described by Haeussler and others (2013). This dataset combines a digital terrain model derived from lidar data collected between October 21 and 25, 2012, (Hubbard and others, 2013) with submarine multibeam data collected in 2011 (Haeussler and others, 2013), and digitized National Ocean Service (NOS) smooth sheet bathymetry for Survey H-10655 (NOAA, 1995).
Elsewhere in the domain, we used the 8/3 arc-second dataset for Prince William Sound (NOAA, 2009a) and the 8/15 arc-second dataset for Whittier and Passage Canal (NOAA, 2009b). These data were projected into UTM coordinates at a resolution of 50 m for the Prince William Sound dataset and 10 m for the Whittier Dataset.
These topographic and bathymetric data sources differ from those used by Barnhart and others (2021a, 2021b) in the addition of the 1 m resolution dataset used near Whittier, Alaska and in Passage Canal (green polygon in Figure 1). All other data sources were used by Barnhart and others (2021a, 2021b).
Results
Herein, we provide two model result files of spatially distributed model output in GeoTiff format and one polyline shapefile for scenario C-689 (Table 1). The shapefile delineates the boundary between model grid cells that were and were not inundated during the simulation. The two GeoTiff files contain the following variables: maximum wave height and the maximum inundation depth for model grid cells, which started dry and were inundated by water or landslide material at some point in the simulation.
These results are presented only in the region surrounding Whittier, Alaska, and at a 1 m spatial resolution. The extent of the region surrounding Whittier, Alaska, where results are provided is given in the east-west direction by eastings 405500—409700 and in the north-south direction by northings 6738600—6740500. The inundation extent is also shown in Figure 2.
In addition, we provide time series from three numerical gages located between the junction of Passage Canal and Port Wells and the Whitter, Alaska, harbor.
Inundation extent
The file “C689_1m_inund_extent.shp” is an ESRI Shapefile containing a polyline demarcating the boundary between areas which were inundated and areas that were not inundated. It was constructed by delineating the boundary between where “inundated_depth_meters.tif” was greater than zero and where it was less than zero.
Inundation depth
The file “inundated_depth_meters.tif” contains the maximum inundation depth for grid cells which were initially dry but became inundated at some point in the simulation. The maximum inundation depth was calculated by analyzing model output at 15 second increments and identifying the maximum inundation depth over all output timesteps. Model grid cells which were never inundated or which originally belonged to the water domain are indicated with “no data.”
Maximum wave height
The file "maximum_wave_height_meters.tif" contains the maximum wave height. The wave height is given in meters relative to the vertical reference frame datum. The maximum wave height was calculated by analyzing model output at 15 second increments and identifying the maximum wave height over all output timesteps. Model grid cells that were never inundated by water or landslide material are indicated with "no data." The maximum wave height reflects the sum of the inundation depth and the grid cell elevation. Note that in grid cells which were initially dry but were inundated later, this value does not reflect the inundation depth.
Wave height time series
The file "whittier_passage_canal_gages.csv" contains simulated wave height time series for three locations where numerical gages were placed in the simulation (Figure 3). Latitude, longitude, easting, and northing coordinates for each of the three numerical gage locations are provided in Table 2.
Table 2. Gage locations for file “whittier_passage_canal_gages.csv.csv”.
Gage number
Easting
Northing
Latitude
Longitude
Description
1
425353
6739687
60.7856
-148.3710
Junction of Passage Canal and Port Wells (between Point Pigot and Blackstone Point)
2
415561
6743131
60.8146
-148.5523
Passage Canal between Port Wells and Whittier, Alaska (between Gradual Point and Trinity Point)
3
407506
6739559
60.7807
-148.6986
Whittier, Alaska harbor (240 m north of the Port of Whittier Deep Water Dock)
The file "gages.csv" contains four columns:
The first column "scenario" contains a string representing the scenario. In this case only one scenario was considered: "C689.”
The second column "gage_id" contains an integer referring to the gage ID number (1, 2, or 3)
The third column "time_seconds" contains an integer indicating the simulation time in seconds.
The fourth column "waveheight_meters" contains a floating-point number indicating the simulated wave height in meters above a reference datum.
Figure Captions
Figure 1. Extent of simulation domain and data sources used. White diamonds show the location of the three numerical gages. Pink region indicates where the model grid was permitted to refine to 1 meter resolution.
Figure 2. Extent of inundation at Whittier, Alaska.
Figure 3. Time series of wave height at the three numerical gages (Table 2).
References Cited
Barnhart, K.R., Jones, R.P., George, D.L., Coe, J.A., and Staley, D.M., 2021a, Preliminary assessment of the wave generating potential from landslides at Barry Arm, Prince William Sound, Alaska: U.S. Geological Survey Open-File Report 2021–1071, 28 p., accessed July 22, 2021, at https://doi.org/10.3133/ ofr20211071.
Barnhart, K.R., Jones, R.P., George, D.L., Coe, J.A., Staley, D.A., 2021b, Select model results from simulations of hypothetical rapid failures of landslides into Barry Arm Fjord, Prince William Sound, Alaska: U.S. Geological Survey data release, accessed July 22, 2021, at https://doi.org/10.5066/P9XVJDNP.
Daanen, R.P., Wolken, G.J., Wikstrom Jones, K., and Herbst, A.M., 2021, High resolution lidar-derived elevation data for Barry Arm landslide, southcentral Alaska, June 26, 2020: Alaska Division of Geological & Geophysical Surveys Raw Data File 2021–3, 9 p., accessed June 17, 2021, at https://doi.org/10.14509/30593.
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Iverson, R.M., and George, D.L., 2014, A depth-averaged debris-flow model that includes the effects of evolving dilatancy—I. Physical basis: Proceedings of the Royal Society of London. Series A, v. 470, no. 2170, p. 20130819, accessed June 17, 2021, at https://doi.org/ 10.1098/rspa.2013.0819.
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Hubbard, T.D., Wolken, G.J., Stevens, D.S.P., and Combellick, R.A., 2013, High-resolution lidar data for the Whittier area, Passage Canal, and Portage Lake, Alaska: Alaska Division of Geological & Geophysical Surveys Raw Data File 2013-3, 5 p., accessed July 22, 2021 at https://doi.org/10.14509/24976.
National Oceanic and Atmospheric Administration [NOAA], 1995, Report for H10655: National Oceanic and Atmospheric Administration [NOAA] web page, accessed July 22, 2021, at https://www.ngdc.noaa.gov/nos/H10001-H12000/H10655.html.
National Oceanic and Atmospheric Administration [NOAA], 2020, Report for H13396: National Oceanic and Atmospheric Administration [NOAA] web page, accessed April 5, 2021, at https://www.ngdc.noaa.gov/ nos/ H12001- H14000/ H13396.html.
National Oceanic and Atmospheric Administration [NOAA] National Geophysical Data Center, 2009a, Prince William Sound, Alaska 8/3 arc-second MHHW coastal digital elevation model: National Oceanic and Atmospheric Administration [NOAA], National Centers for Environmental Information web page, accessed April 5, 2021, at https://data.noaa.gov/metaview/page?xml=NOAA/NESDIS/NGDC/MGG/DEM//iso/xml/638.xml&view= getDataView&header= none.
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