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Destruction of the First Nations village of Kwalate by a rock avalanche-generated tsunami

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Destruction of the First Nations village of Kwalate by a rock avalanche-generated tsunami

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Abstract

The First Nations (Da ‘naxda ‘xw) village of Kwalate, Knight Inlet, British Columbia was located along the shore of a funnel‐shaped bay. Archaeological investigations show that this was a major village that stretched 90 m along the shoreline and was home to possibly 100 or more inhabitants. Oral stories indicate that the village was completely swept away by a tsunami that formed when an 840‐m high rock avalanche descended into the water on the opposite side of the fjord. Shipboard geological mapping, combined with empirical tsunami modelling, indicate that the tsunami was likely 2 to 6 m high prior to run‐up into the village. Radiocarbon dates reveal that the village was occupied from the late 1300s CE until the late 1500s CE when it was destroyed by the tsunami.

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... This evidence suggests that the inlet has been prone to landslidegenerated tsunamis over the past 12 000 years. A recent study integrating archaeological and geological observations with oceanographic analysis suggests that the former village of Kwalate, located near the shoreline of Knight Inlet, was destroyed by a slide-induced wave in the late 1500s, with the possible loss of as many as 100 lives (Bornhold et al., 2007). In addition to this event, a slide from Three Finger Peak in November 1999 generated a wave that jostled log booms about 20 km to the north at the head of Knight Inlet. ...
... The submarine debris cone at the base of the slope dips 20-24 • ; it has a surface area of about 0.1 km 2 (Fig. 6) and an estimated volume of 3.5 Mm 3 . Our analysis of images collected by Bornhold et al. (2007) from a remotely operated vehicle indicates that the debris cone comprises openwork, subangular blocks less than 2 m across that are dominantly 0.1-0.4 m in size. ...
... Different methods may produce such a wide range of estimated wave heights that the analysis is unhelpful for hazard evaluation. Bornhold et al. (2007) hindcasted wave amplitudes from a past landslide at Adeane Point, assuming that the 3.5 Mm 3 submarine debris cone at the base of the slope was emplaced by a single landslide. It is possible, however, that a slide of much smaller size was responsible for this event. ...
Article
Rockfalls and rockslides during the past 12 000 years have deposited bouldery debris cones on the seafloor beneath massive rock slopes throughout the inner part of Knight Inlet. The 885 m high rock slope, located across from a former First Nations village destroyed in the late 1500s by a slide-induced wave, exposes the contact between a Late Cretaceous dioritic pluton and metamorphic rocks of the Upper Triassic Karmutsen Formation. The pluton margin is strongly foliated parallel to primary and secondary fabrics in the metamorphic rocks, resulting in highly persistent brittle structures. Other important structures include a set of sheeting joints and highly persistent mafic dykes and faults. Stability analysis indicates that planar and wedge rock slope failures up to about 500 000 m3 in volume could occur. We suspect that failures of this size in this setting would have the potential to generate locally hazardous waves. As several similar rock slopes fronted by large submarine debris cones exist in the inner part of Knight Inlet, it is clear that tsunami hazards should be considered in coastal infrastructure development and land-use planning in this area.
... This evidence suggests that the inlet has been prone to landslidegenerated tsunamis over the past 12 000 years. A recent study integrating archaeological and geological observations with oceanographic analysis suggests that the former village of Kwalate, located near the shoreline of Knight Inlet, was destroyed by a slide-induced wave in the late 1500s, with the possible loss of as many as 100 lives (Bornhold et al., 2007). In addition to this event, a slide from Three Finger Peak in November 1999 generated a wave that jostled log booms about 20 km to the north at the head of Knight Inlet. ...
... The submarine debris cone at the base of the slope dips 20-24 • ; it has a surface area of about 0.1 km 2 (Fig. 6) and an estimated volume of 3.5 Mm 3 . Our analysis of images collected by Bornhold et al. (2007) from a remotely operated vehicle indicates that the debris cone comprises openwork, subangular blocks less than 2 m across that are dominantly 0.1-0.4 m in size. ...
... Different methods may produce such a wide range of estimated wave heights that the analysis is unhelpful for hazard evaluation. Bornhold et al. (2007) hindcasted wave amplitudes from a past landslide at Adeane Point, assuming that the 3.5 Mm 3 submarine debris cone at the base of the slope was emplaced by a single landslide. It is possible, however, that a slide of much smaller size was responsible for this event. ...
Article
Full-text available
Rockfalls and rockslides during the past 12 000 years have deposited bouldery debris cones on the seafloor beneath massive rock slopes throughout the inner part of Knight Inlet. The 885 m high rock slope, located across from a former First Nations village destroyed in the late 1500s by a slide-induced wave, exposes the contact between a Late Cretaceous dioritic pluton and metamorphic rocks of the Upper Triassic Karmutsen Formation. The pluton margin is strongly foliated parallel to primary and secondary fabrics in the metamorphic rocks, resulting in highly persistent brittle structures. Other important structures include a set of sheeting joints and highly persistent mafic dykes and faults. Stability analysis indicates that planar and wedge rock slope failures up to about 500 000 m3 in volume could occur. We suspect that failures of this size in this setting would have the potential to generate locally hazardous waves. As several similar rock slopes fronted by large submarine debris cones exist in the inner part of Knight Inlet, it is clear that tsunami hazards should be considered in coastal infrastructure development and land-use planning in this area.
... The landslide generated a displacement wave of more than 500 m high that stripped the forest from the opposite mountain slope and the lateral shorelines as it travelled down the bay (PararasCarayannis 1999). A large rock slide (4 million m 3 ) entered Knight Inlet sometime in the mid-1500s, dropping more than 800 m vertically (Bornhold et al. 2007). TheModified from Schwab 1999) resulting tsunami destroyed the village of Kwalate, and about 100 (or possibly more) of its First Nations inhabitants. ...
... Some catastrophic landslides are recorded in the oral traditions of First Nations people; however, the dates of the events are uncertain and are usually tested with radiocarbon dating methods. For example, stories of a large rock slide that buried a village near Hazelton some 3000 years ago (Gottesfeld et al. 1991) and of a rockslide–generated tsunami that wiped out a village in Knight Inlet about 500 years ago (Bornhold et al. 2007) are told to this day. ...
... TSF e late AD1500s (1570 ± 70) ( Table 2, Fig. 6) The lines of evidence for this event are primarily from archaeological and anthropological sources. Examination of an archaeological site in Knight Inlet identified a "clean" sand layer overlying a midden (Bornhold et al., 2007). Site abandonment immediately followed emplacement of this sand. ...
... Site abandonment immediately followed emplacement of this sand. This is linked with a Kwakwaka'wakw oral history that talks of a large slope failure on the opposite side of the inlet (Bornhold et al., 2007). This is a remarkable example of the benefits of oral histories for providing valuable data concerning locally catastrophic palaeotsunamis that are at best difficult to identify in the field simply because they may only be found at one site. ...
Article
To fully understand tsunami hazards along Canada’s Pacific coast we must consider all potential sources including local and region-wide earthquakes, volcanic activity, slope failure events and bolide impacts. Furthermore, as climate changes, future extreme meteorological conditions will exacerbate slope failures on steep and over-steepened slopes, and potentially augment the magnitude and frequency of earthquake-generated tsunamis. There have been numerous reviews of the geological records of palaeotsunamis along the Cascadia margin, but as yet there has been no attempt made to pull together all data related to palaeotsunamis along the Pacific coast of Canada. We summarise all geological data related to palaeotsunamis reported in the region, all relevant non-geological data, and other information concerning potential tsunamigenic sources. Evidence for between 10 and 22 palaeotsunamis (prior to European arrival) have been documented, with the Cascadia Subduction Zone Y event (AD1700) being the most widely recognised. Geological, archaeological and anthropological data all indicate a complex, multi-sourced, prehistory of seismic/tsunami activity that is poorly understood. A clustering of potential activity off the SE coast of Vancouver Island suggests that we should also attempt to better understand locally generated events along Canada’s Pacific coast.
... The largest known tsunami height of 524 m occurred in Lituya Bay, Alaska in 1958 (Weiss et al. 2009). In Knight Inlet, British Columbia, the first nations community of Kwalate was devastated by a large tsunami that was generated by a major rockslide, the age of which is unknown (Bornhold et al. 2007). Tsunami models in Douglas Channel have shown that, owing to the long and narrow nature of the channels, the greatest risk of tsunami does not occur from offshore earthquake activity but from local landslides (Thomson et al. 2012;Kirby et al. 2016). ...
... Most of the fjords in British Columbia are uninhabited. There are very few documented occurrences of tsunamis, but nevertheless there are some oral histories, such as a destructive tsunami in Knight Inlet (Bornhold et al. 2007 Most of the fjords in British Columbia are characterized by steep granitic sidewalls with frequent debris flows. Nearly all have a significant river delta (sometimes two) at the head, which is fed in all cases by glacial or snow melt enhanced by precipitation in a coastal rainforest. ...
Article
Douglas Channel is a 140 km-long fjord system on Canada's west coast where steep topography, high annual precipitation and glacially over-deepened bathymetry have resulted in widespread slope failures. A 5 year project involving numerous marine expeditions to the remote area produced a comprehensive assessment of the magnitude and frequency of slope failures in the region. A classification scheme is presented based on morphology and failure mechanism: (1) debris flows are the most common in all parts of the fjord – they are often small with a subaerial component where fjord wall slope is very high or tend to exceed volumes of 10 ⁶ m ³ where fjord wall slope is lower, allowing for accumulation of marine sediments; (2) large failures of oversteepened glacial sediments occurring at transgressive moraines and glaciomarine plateaus following deglaciation – the largest is at Squally Channel with an estimated volume of 10 ⁹ m ³ ; (3) fjord wall failures that involve bedrock slump or rock avalanche; (4) translation of marine sediments; (5) composite/other slides; and (6) two scallop-shaped sackungen, or deep-seated gravitational slope deformations of granodiorite with volumes exceeding 60 × 10 ⁶ m ³ . The postglacial marine sedimentary record shows evidence of large-scale slope failures of all styles that were especially active following deglaciation. The Holocene marks a transition to a lower frequency and change to primarily debris flows and smaller rock slides. Slope failures that may be capable of generating tsunamis and may be damaging to coastal infrastructure have occurred in all parts of Douglas Channel through much of the Holocene. Here we present a morphological analysis with volume estimates and age control using multibeam bathymetry, high-resolution sub-bottom data and sediment cores. The study details an extensive analysis of slope failures in a fjord network that can be extended to other fjord environments.
... 15.18). A 2-to 6-m-high wave in Knight Inlet some 500 years ago destroyed a First Nation's Village; it was generated by a 4 Mm 3 rock slide detached at a distance of 5 km on an 840 m high cliff oversteepened during the Last Glacial Maximum/Fraser Glaciation (Bornhold et al., 2007). A more recent rock-slide-generated wave was triggered in 2015 by the 73 Mm 3 Taan Fiord rock avalanche (see Section 15.3.3.4) that entered the 1.5-km-wide and 90-m-deep recently deglaciated fjord to emerge and deposit debris on the opposite shore, producing a 6-km-long and 2 km 2 subaqueous flow deposit Haeussler et al., 2018). ...
Chapter
The present time is a significant stage in the adjustment of mountain slopes to climate change and specifically atmospheric warming. This review examines the state of understanding of the responses of mid-latitude alpine landscapes to recent cryospheric change and summarizes the variety and complexity of documented landscape responses involving glaciers, moraines, rock and debris slopes, and rock glaciers. These indicate how a common general forcing translates into varied site-specific slope responses according to material structures and properties, thermal and hydrological environments, process rates, and prior slope histories. Warming of permafrost in rock and debris slopes has demonstrably increased instability, manifest as rock glacier acceleration, rockfalls, debris flows, and related phenomena. Changes in glacier geometry influence stress fields in rock and debris slopes, and some failures appear to be accelerating toward catastrophic failure. Several sites now require expensive monitoring and modeling to design effective risk-reduction strategies, especially where new lakes form and multiply hazard potential, and new activities and infrastructure are developed.
... Most of the world's high-relief mountain ranges produce catastrophic rock avalanches, which contribute to rapid landscape evolution by instantaneously denuding bedrock slopes, and can dam rivers or cause displacement waves in standing bodies of water (Whitehouse 1983;Evans and Clague 1988;Schuster et al. 1992;Evans and DeGraff 2002;Korup et al. 2007Korup et al. , 2010Hewitt et al. 2008;Evans et al. 2011). From a hazard perspective, these secondary and far reaching effects can be more damaging than the rock avalanche itself (Jørstad 1968;Hendron and Patton 1987;Evans 1989;Braathen et al. 2004;Hermanns et al. 2004;Blikra et al. 2005;Bornhold et al. 2007; Redfield and Osmundsen 2009;Kremer et al. 2014). Furthermore, rock avalanche source areas often produce multiple events ranging from minor rock falls to additional rock avalanches, indicating that their contribution to landscape evolution as well as the hazard they present can persist long after a single event (Plafker and Ericksen 1978;Grimstad and Nesdal 1990;McSaveney 2002;Hermanns et al. 2006;Hewitt et al. 2008). ...
Article
Full-text available
Catastrophic rock avalanches contribute to rapid landscape evolution and can harm humans directly or by secondary effects such as displacement waves. Predicting the volume, timing, and consequences of rock slope failures is therefore essential to managing risk and interpreting landscape response to climatic or tectonic forcing. Here, we synthesize geologic and geodetic observations to document the spatial pattern of movement rates and failure mechanisms at a landslide complex in western Norway, recently identified with systematic interferometric synthetic aperture radar (InSAR) reconnaissance. A differential global navigation satellite system (dGNSS) and global positioning system (dGPS) campaign confirms active slope deformation with horizontal displacement rates of 1.2 to 2.6 mm year−1 at four points distributed across the landslide’s ~1.8-km width. Displacement vectors are consistent with landslide movement occurring on pre-existing discontinuity sets, and a broad synform controls failure mechanisms within the landslide complex. Two ~1.5 million m3 blocks are wedge failures, while flexural toppling and planar sliding of smaller blocks occur throughout the landslide complex. Modern movement rates are comparable to or slower than Holocene-averaged displacement rates, suggesting continued steady deformation or stabilization of parts of the landslide with time. However, a large volume failure with typical run-out for rock avalanches would likely reach the subjacent fjord, causing a displacement wave. We suggest that our collaborative approach of integrating a wide variety of geologic and geodetic methods will be useful for more thoroughly documenting additional landslide sites and for making informed decisions about risk management.
... In Norway, historic records since 1500 C.E. indicate that landslide displacement waves have killed hundreds of people and repeatedly destroyed towns (Blikra et al., 2005). Archaeological investigations suggest that a fiord tsunami occurred in Knight Inlet in the 16th Century and destroyed the First Nations village of Kwalate (Bornhold et al., 2007). ...
Conference Paper
Full-text available
An investigation into evidence of deposits of rapidly moving landslides that may have triggered displacement waves during the post glacial period in Howe Sound, British Columbia, was initiated by the Geological Survey of Canada (GSC) in collaboration with researchers from the Department of Earth Sciences, Simon Fraser University. It consisted of two initiatives: investigation of the present stability of the western slope of Mount Gardner on the west side of Bowen Island and of post glacial sedimentation and rates of sedimentation in Howe Sound. Investigation of sedimentation rates sought to determine the age of the run-out deposits along the sea floor of Collingwood Channel (west of Bowen Island) and to determine the duration of time that rock slide deposits would remain visible to swath multibeam bathymetry (SMB) before they were buried by subsequent sedimentation. A study combining structural geological mapping with geomorphic analysis of the subaerial and submarine portions of Collingwood Channel was carried out below Mount Gardner. More than 800 structural measurements at over 400 outcrops were made. A LiDAR digital elevation model) and orthophotos of Bowen Island were studied along with a digital elevation model of the sea bottom generated from MSB data. The investigation found that deep-seated gravitational deformation appears to have occurred along parts of the western slope of Mt. Gardner (MG) due to its geological structure and topographic factors. Evidence of ongoing deep-seated deformation was not found. Over all, a likelihood of major failure was not found. As a part of the marine geology investigation, three piston cores were collect from the bottom of Collingwood Channel below MG to sample contrasting local depositional environments. Two piston cores were also collected at the same latitude west of Lions Bay in the widest part of HS. One sampled a submarine fan and the other the sea bottom protected from submarine fan sedimentation. Seismic reflection surveys were carried out in the Collingwood Channel and Lions Bay and a remotely operated vehicle (ROV) traversed the sea bottom in both areas and the traverses were recorded by a high definition television system. The seismic reflection profiles determined initial run-out deposits on the sea floor. The cores collected from shallowest depths in Collingwood Channel (62 to 84.5 m) were entirely deposited during deglaciation. They yielded uncalibrated 14C ages of ca. 13.1 to 12.5 years before present (yBP). No Holocene sediments were present. In the Lions Bay area, one of the widest reaches of Howe Sound, a 7 m core taken from a depth of 136 m intersected mud containing scattered plant fragments and invertebrate shells. Carbon-14 ages ranged from 8450 to 5700 yBP with the lowest 4 m of the core yielding statistically indistinguishable ages ca. 8450 yBP. Virtually no sediment postdating 5700 14C yBP was intersected. This indicates that very rapid sedimentation occurred up to the middle Holocene with virtually none after that. This is consistent with enhanced erosion and sediment transport as a result of the paraglacial effect following deglaciation. The other core from Lions Bay core was taken at a depth of 139 m from the submarine fan below debris-flow-prone Lone Tree Creek. The core site is flanked to the north and south by entrenched submarine channels presumably cut by sediment-gravity flows. The core contains sediments at least as old as the oldest 14C dated sample ca. 4250 y BP. The core displays extensively bioturbated sediments containing wood fragments as well as angular clasts of dark Gambier Group volcanic rock which underlies much of the Lone Tree Creek basin. Intertidal invertebrate tests are present in the sediments. The most striking feature of the core is the inversion of stratigraphy with: a wood fragment with a 14C age of ca. 3740 y BP lies 500 cm below a bivalve shell dated at ca. 4250 y BP. This is attributed to the high energy environment expected for a submarine fan where older sediment can be reworked by sediment gravity flows crossing the fan. Only the upper 80 cm of the core was deposited during approximately the last 4000 years. The small amount of sedimentation over the latter half of the Holocene also reflects the waning of the paraglacial effect over this period. The low sedimentation rates over the latter half of the Holocene in Howe Sound make it unlikely that the deposits of any large and rapidly moving rock slide, large enough to generate a destructive displacement wave over the approximately the past 5000 years, would escape detection by the SMB imaging that was carried out in 2007.
... A wave >50 m high resulted in 1946 from a landslide at the cirque wall at Mount Colonel Foster, Vancouver Island (Evans, 1989). A 2-to 6-m-high displacement wave in Knight Inlet some 500 years ago destroyed a First Nation's Village; it was generated by a 4-Mm 3 landslide detached at a distance of 5 km on an 840-m-high cliff oversteepened during the Last Glacial Maximum/ Fraser Glaciation (Bornhold et al., 2007). ...
Chapter
The present time is one significant stage in the adjustment of mountain slopes to climate change, and specifically atmospheric warming. This review examines the state of understanding of the responses of mid-latitude alpine landscapes to recent cryospheric change, and summarizes the variety and complexity of documented landscape responses involving glaciers, moraines, rock and debris slopes, and rock glaciers. These indicate how a common general forcing translates into varied site-specific slope responses according to material structures and properties, thermal and hydrological environments, process rates, and prior slope histories. Warming of permafrost in rock and debris slopes has demonstrably increased instability, manifest as rock glacier acceleration, rock falls, debris flows, and related phenomena. Changes in glacier geometry influence stress fields in rock and debris slopes, and some failures appear to be accelerating toward catastrophic failure. Several sites now require expensive monitoring and modeling to design effective risk-reduction strategies, especially where new lakes as multipliers of hazard potential form, and new activities and infrastructure are developed.
... The displaced material is most simply modeled as a single, solid, rigid body sliding into the water at right angles to the shoreline (Panizzo et al., 2005). Two western Canadian examples are 1) the wave that occurred at Knight Inlet, BC where approximately 500 years ago a large rock fall into the inlet generated a wave that may have engulfed up to a hundred people in the Kwalate Village site several kilometres away (Bornhold et al., 2007), and 2) the 2007 Chehalis Lake rock slide in southwestern BC that triggered a 38 m displacement wave (Brideau et al., 2012). In eastern Canada, a landslide opposite Notre-Dame-de-la-Salette, QU, in 1908, displaced the ice cover of Lievre River. ...
... All but one of the 53 pre-nineteenth century events are from these four areas (44 are from Norway alone). The exception is a rockslide-generated displacement wave mentioned in oral histories on the British Columbia coast that has been confirmed by an archaeological investigation and radiocarbon-dated to the mid-to late sixteenth century (Bornhold et al. 2007). ...
Conference Paper
Full-text available
Displacement waves generated by subaerial landslides can have devastating effects and extend impacts of a landslide tens of kilometres or more. Most research has involved characterization of individual events and, in some cases, comparison of a few events. We have begun to broaden understanding of the phenomenon by compiling a preliminary global catalogue of landslide-generated displacement waves that provides insights into their geographic distribution, size, frequency, and range of mechanisms and impacts. The catalogue is based on a review of published case studies, tsunami catalogues, and the Norwegian national landslide database. It contains 254 events from the fourteenth century AD to 2012. Greater event density in regions with longer written histories, in areas with more settlement, and in the more recent part of the record suggests spatial and temporal biases in documentation and recording. Despite these biases, the spatial pattern of events suggests settings—likely determined by geologic, physiographic and tectonic controls— with elevated hazards that can help focus hazard investigation and mitigation. The diversity of events helps identify differences in displacement wave processes and their resulting impacts, such as wave run-up and travel distance.
... In Norway, historic records since 1500 C.E. indicate that landslide displacement waves have killed hundreds of people and repeatedly destroyed towns (Blikra et al., 2005). Archaeological investigations suggest that a fiord tsunami occurred in Knight Inlet in the 16th Century and destroyed the First Nations village of Kwalate (Bornhold et al., 2007). ...
Technical Report
Full-text available
An investigation into evidence of deposits of rapidly moving landslides that may have triggered displacement waves during the post glacial period in Howe Sound, British Columbia, was initiated by the Geological Survey of Canada (GSC) in collaboration with researchers from the Department of Earth Sciences, Simon Fraser University. It consisted of two initiatives: investigation of the present stability of the western slope of Mount Gardner on the west side of Bowen Island and of post glacial sedimentation and rates of sedimentation in Howe Sound. Investigation of sedimentation rates sought to determine 4 the age of the run-out deposits along the sea floor of Collingwood Channel (west of Bowen Island) and to determine the duration of time that rock slide deposits would remain visible to swath multibeam bathymetry (SMB) before they were buried by subsequent sedimentation. A study combining structural geological mapping with geomorphic analysis of the subaerial and submarine portions of Collingwood Channel was carried out below Mount Gardner. More than 800 structural measurements at over 400 outcrops were made. A LiDAR digital elevation model) and orthophotos of Bowen Island were studied along with a digital elevation model of the sea bottom generated from MSB data. The investigation found that deep-seated gravitational deformation appears to have occurred along parts of the western slope of Mt. Gardner (MG) due to its geological structure and topographic factors. Evidence of ongoing deep-seated deformation was not found. Over all, a likelihood of major failure was not found. As a part of the marine geology investigation, three piston cores were collect from the bottom of Collingwood Channel below MG to sample contrasting local depositional environments. Two piston cores were also collected at the same latitude west of Lions Bay in the widest part of HS. One sampled a submarine fan and the other the sea bottom protected from submarine fan sedimentation. Seismic reflection surveys were carried out s Bay and a remotely operated vehicle (ROV) traversed the sea bottom in both areas and the traverses were recorded by a high definition television system. The seismic reflection profiles determined initial relief of run-out deposits on the sea floor. The cores collected from shallowest depths in Collingwood Channel (62 to 84.5 m) were entirely deposited during deglaciation. They yielded uncalibrated 14C ages of ca. 13.1 to 12.5 years before present (yBP). No Holocene sediments were present. In the Lions Bay area, one of the widest reaches of Howe Sound, a 7 m core taken from a depth of 136 m intersected mud containing scattered plant fragments and invertebrate shells. Carbon-14 ages ranged from 8450 to 5700 yBP with the lowest 4 m of the core yielding statistically indistinguishable ages ca. 8450 yBP. Virtually no sediment postdating 5700 14C yBP was intersected. This indicates that very rapid sedimentation occurred up to the middle Holocene with virtually none after that. This is consistent with enhanced erosion and sediment transport as a result of the paraglacial effect following deglaciation. The other core from Lions Bay core was taken at a depth of 139 m from the submarine fan below debris-flow-prone Lone Tree Creek. The core site is flanked to the north and south by entrenched submarine channels presumably cut by sediment-gravity flows. The core contains sediments at least as old as the oldest 14C dated sample ca. 4250 y BP. The core displays extensively bioturbated sediments containing wood fragments as well as angular clasts of dark Gambier Group volcanic rock which underlies much of the Lone Tree Creek basin. Intertidal invertebrate tests are present in the sediments. The most striking feature of the core is the inversion of stratigraphy with: a wood fragment with a 14C age of ca. 3740 y BP lies 500 cm below a bivalve shell dated at ca. 4250 y BP. This 5 is attributed to the high energy environment expected for a submarine fan where older sediment can be reworked by sediment gravity flows crossing the fan. Only the upper 80 cm of the core was deposited during approximately the last 4000 years. The small amount of sedimentation over the latter half of the Holocene also reflects the waning of the paraglacial effect over this period. The low sedimentation rates over the latter half of the Holocene in Howe Sound make it unlikely that the deposits of any large and rapidly moving rock slide, large enough to generate a destructive displacement wave over the approximately the past 5000 years, would escape detection by the SMB imaging that was carried out in 2007.
... Several case studies reveal the relationship of coastal hazards (tsunami) and human adaptation strategies along the pacific coastline of Cascadia (e.g. Hutchinson and McMillan, 1997;Losey, 2005Losey, , 2007Bornhold et al., 2007;Witter et al., 2009;Peterson et al., 2011). Goff and McFadgen (2003), McFadgen and Goff (2007), Hutchinson and Attenbrow (2009) and Goff et al. (2011Goff et al. ( , 2012 provide well documented geo-archaeological evidence for palaeo-tsunami along the shores of New Zealand. ...
... 15.18). A 2-to 6-m-high wave in Knight Inlet some 500 years ago destroyed a First Nation's Village; it was generated by a 4 Mm 3 rock slide detached at a distance of 5 km on an 840 m high cliff oversteepened during the Last Glacial Maximum/Fraser Glaciation (Bornhold et al., 2007). A more recent rock-slide-generated wave was triggered in 2015 by the 73 Mm 3 Taan Fiord rock avalanche (see Section 15.3.3.4) that entered the 1.5-km-wide and 90-m-deep recently deglaciated fjord to emerge and deposit debris on the opposite shore, producing a 6-km-long and 2 km 2 subaqueous flow deposit Haeussler et al., 2018). ...
... Because such events generally take place in relatively shallow and confined inner coastal waterways, they present a serious hazard in terms of tsunami wave generation (Mosher, 2009; Bornhold and Thomson, 2012). Hazards of this form have been well documented for the coastal region of British Columbia and other fjord regions of the world ocean including Alaska and Norway (Bornhold et al., 2007; Bornhold and Thomson 2012). Kitimat Arm and Douglas Channel are integral components of the Confined Channel Assessment area of the Enbridge Northern Gateway Project. ...
Article
Full-text available
Multibeam bathymetric surveys by the Canadi an Hydrographic Service and Natural Resources Canada have revealed the presence of two massive (~65 million cubic meter) submarine landslides along the southeastern side of Douglas Channel in northwestern British Columbia. Although the landslides likely date from the early to mid Holocene, Conway et al. (2012) suggest that these failures could have forced major landslide-generated tsunamis and that the risk of similar events in the channel in the future cannot be ruled out. We characterize this risk using a fully nonlinear, non-hydrostatic numerical mathematical model to simulate the tsunami waves that would have been generated by the two slides were they to occur during present-day marin conditions in southern Douglas Channel. Based on the multibeam data, the slides moved a distance of roughly 300 to 400 m before stopping near the base of the slope in water depths of around 400 m. A reconstruction of the slide regions immediately prior to failure indicates the slides were wedge-shaped. The head of the more northern slide (Slide A) began at a depth of around 60 to 100 m while that of the more southern slide (Slide B) at a depth of 75 to 120 m. Depending on the friction between the slide and the underlying seabed, the slides would have moved downslope with a peak velocity of approximately 25 m/s before coming to rest after a duration of about 30 seconds. The numerical simulations show that submarine landslides with these characteristics would generate tsunami waves with peak amplitudes of 30 to 40 m, current speeds of up to 15 m/s (roughly 30 knots), wavelengths of the order of 1 km, and periods of tens of seconds to several minutes. Highest waves and strongest currents would occur along the shoreline opposite and adjacent to the failure regions. Because of their relatively short wavelengths, the tsunami waves undergo multiple reflections and a high degree of scattering from the complex shoreline and bottom topography in Douglas Channel. These effects combined with the flux of tsunami energy through adjoining waterways and channels, cause rapid attenuation of the waves with distance south and north of the source region. At the estimated propagation speeds of ~65 m/s, it takes roughly 10 to 15 minutes for the simulated waves to propagate the roughly 40 to 45 km to the intersection of Douglas Channel and Kitimat Arm, where peak wave amplitudes would be diminished to less than 1 m. It then takes another 15 minutes for the waves to reach sites near the proposed Enbridge facilities in Kitimat Arm where wave amplitudes would be reduced to a few tens of centimetres and associated currents to speeds less than a few tens of centimetres per second. As with the tsunami generation regions, the highest waves and strongest currents in any particular region of the coastal waterway would occur near the shoreline. Based on the numerical findings, tsunamis generated by submarine landslides of the form identified for the southern end of Douglas Channel would have heights and currents that could have major impacts on the coastline and vessel traffic at the time of the event throughout much of Douglas Channel, but a minor impact on water levels, currents and hence vessel traffic in Kitimat Arm. Hartley Bay, at the southern end of Douglas Channel, would be impacted by high waves and strong currents, whereas Kitimat, at the northern end of Kitimat Arm, would experience negligible wave effects. Additional modeling would be required to assess the characteristics of possible tsunamis originating beyond the area of the two identified slope failure.
... For example, the 1975 submarine slide in Kitimat Arm produced a tsunami with amplitudes up to 8.2 m, resulting in substantial local damage (e.g., Murty 1979; Skvortsov and Bornhold 2007). In Knight Inlet a rock avalanche generated a tsunami that destroyed the First Nations village of Kwalate, probably in the 16th century (Bornhold et al. 2007). The Strait of Georgia, including low-lying parts of greater Vancouver, is potentially at risk from submarine landslide tsunamis (Fig. 1). ...
Conference Paper
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We present a summary of geological tsunami sources with the potential to threaten the coasts of Canada. The study is part of a Geological Survey of Canada project to quantify tsunami hazard with the aim of producing a national tsunami hazard map. The Pacific coast is most at risk. Large tsunamis resulting from M~9 Cascadia megathrust earthquakes have impacted the British Columbia coast on average every 500 years throughout the Holocene, most recently in A.D. 1700. Tsunami potential along the Explorer-North America margin and southern Queen Charlotte fault is not well understood. Far-field earthquake-generated tsunamis are also a significant hazard to the outer coast and inlets; the 1964 Alaska tsunami caused considerable damage in Port Alberni and other western Vancouver Island communities. Landslides can generate locally destructive tsunamis, especially in coastal fjords. A submarine slide in Kitimat Arm in 1975 produced a tsunami with amplitudes up to 8.2 m that caused extensive local damage. The Strait of Georgia (including lower elevations in greater Vancouver) may be at risk from submarine landslide tsunamis, e.g., from the unstable foreslope of the Fraser River Delta. Offshore Vancouver Island, continental slope failures have been mapped along the Cascadia subduction zone deformation front. Future landslides could generate locally destructive tsunamis, or may increase amplitudes of megathrust tsunamis. Canada’s Atlantic coast is far from active plate boundaries, yet was the site of Canada’s most tragic historical earthquake/tsunami. In 1929, an Ms 7.2 earthquake triggered the Grand Banks submarine slide, resulting in 3-8 m tsunami waves that killed 28 people in southern Newfoundland. Locally destructive tsunamis may result from other submarine landslides on the continental shelf edge and in the St. Lawrence Estuary. Far-field sources may include plate-boundary earthquakes in the Caribbean and offshore Gibraltar, and Canary Island volcanic flank failures. Little is known about the tsunami history of the Arctic coastline. Potential sources include submarine slope failures and large thrust earthquakes on the Mackenzie Delta front. Tsunami hazard in the Arctic is reduced by the extensive sea ice.
... Locally destructive waves result from landslides on the Pacific coast, with fjords particularly at risk due to potential failure of their steep walls or submarine delta fronts; relatively small failures can produce high run-up in these long narrow basins. Historical tsunami sources on the coast of BC and Alaska (Fig. 1) include rockfalls in Knight Inlet (*16 century and 1999: Bornhold et al. 2007;van Zeyl 2009) and Lituya Bay (1958: Miller 1960 and submarine slides at Deep Bay (1946: Mosher et al. 2004), Kitimat Arm (1975: Skvortsov and Bornhold 2007), and Skagway (1994: Kulikov et al. 1996. Some were triggered by ground shaking (Lituya Bay and Deep Bay) and others by overloading of sediments at low tide (Kitimat and Skagway); many caused fatalities. ...
Article
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We present a preliminary probabilistic tsunami hazard assessment of Canadian coastlines from local and far-field, earthquake, and large submarine landslide sources. Analyses involve published historical, palaeotsunami and palaeoseismic data, modelling, and empirical relations between fault area, earthquake magnitude, and tsunami run-up. The cumulative estimated tsunami hazard for potentially damaging run-up (≥1.5 m) of the outer Pacific coastline is ~40–80 % in 50 years, respectively one and two orders of magnitude greater than the outer Atlantic (~1–15 %) and the Arctic (<1 %). For larger run-up with significant damage potential (≥3 m), Pacific hazard is ~10–30 % in 50 years, again much larger than both the Atlantic (~1–5 %) and Arctic (<1 %). For outer Pacific coastlines, the ≥1.5 m run-up hazard is dominated by far-field subduction zones, but the probability of run-up ≥3 m is highest for local megathrust sources, particularly the Cascadia subduction zone; thrust sources further north are also significant, as illustrated by the 2012 Haida Gwaii event. For Juan de Fuca and Georgia Straits, the Cascadia megathrust dominates the hazard at both levels. Tsunami hazard on the Atlantic coastline is dominated by poorly constrained far-field subduction sources; a lesser hazard is posed by near-field continental slope failures similar to the 1929 Grand Banks event. Tsunami hazard on the Arctic coastline is poorly constrained, but is likely dominated by continental slope failures; a hypothetical earthquake source beneath the Mackenzie delta requires further study. We highlight areas susceptible to locally damaging landslide-generated tsunamis, but do not quantify the hazard.
... Nine landslide-generated tsunami have occurred since reservoir impoundment in 1942, probably reflecting both the impact of the reservoir and monitoring. All of the events shown in Fig. 1, except for that in Knight Inlet (Bornhold et al. 2007), occurred since European colonization in the mid-1800s; an unknown, but undoubtedly large, number of pre-historic events are lacking from the record. ...
Conference Paper
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On 4 December 2007, a 3 Mm3 debris avalanche entered Chehalis Lake, British Columbia, Canada. The resulting tsunami caused extensive shoreline damage as far away as the outlet (7.5 km) and far down lower Chehalis River (>15 km). We documented impacts of the tsunami through a multifaceted investigation that included field surveys and collection and analysis of SONAR data, LiDAR data and high-resolution orthophotographs. Geomorphic impacts included a wide range of erosional and depositional features, many of which provide information on wave energy, direction, run-up and inundation along much of the lakeshore. Our characterization of the geomorphic impacts of the Chehalis Lake event advances understanding of landslide-generated tsunami in several ways: it aids identification of events elsewhere by providing insight into their geomorphic signature; it provides an opportunity to verify hydrodynamic numerical models; and it improves regional understanding of hazard and risk.
... These landslides can be set off by earthquakes, or even by minor tremors. An example of a landslide-generated tsunami in British Columbia is presented by Bornhold et al. (2007). This tsunami wiped out a local village. ...
Article
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This report presents a brief summary of papers describing physical oceanographic research undertaken in Canada in the period 2003 to early 2007. This report is part of the Canadian contribution to the International Association for the Physical Sciences of the Ocean (IAPSO) on the occasion of the meeting of the Interannual Association of Geodesy and Geophysics (IUGG) in Perugia, Italy in July 2007. Previous reports have been prepared at four-year intervals to coincide with quadrennial IUGG meetings.
... Tsunami can also be triggered by rockfalls and rockslides from the walls of British Columbia fiords. Bornhold et al. (2007) proposed that the First Nations village of Kwalate in Knight Inlet was destroyed by a local tsunami triggered by the catastrophic failure of a nearby steep rock wall about 500 years ago. ...
Article
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Canada, the second largest country in the world, is subject to every hazardous natural process on Earth − large earthquakes, tsunami, volcanic eruptions, landslides, snow avalanches, floods, hurricanes, tornados, severe storms, drought, and sea-level rise. Fortunately, much of the country is sparsely populated; hence risk from these hazardous processes is localized to small areas adjacent to the Cana-da−US border, where most Canadians live. The greatest risk comes from earthquakes and landslides on the populated south coast of British Columbia and parts of southern Ontario and Québec; from floods in Vancouver, Calgary, Winnipeg, or Toronto; and from hurricanes in Halifax and St. John's. In the long term, Canada's coastlines are threatened by sea-level rise and Canada's northern indigenous peoples are threatened by permafrost thaw caused by global warming. SOMMAIRE Deuxième plus grand pays de la planète, le Canada est exposé à chacun des risques naturels sur Terre – grands séismes, tsunamis, éruptions vol-caniques, glissements de terrain, avalanches de neige, inondations, oura-gans, tornades, fortes tempêtes, sécher-esses, et hausse du niveau de la mer. Heureusement, le pays est peu peuplé en grande partie, et donc, le risque associé à ces phénomènes naturels est restreint à des bandes étroites le long de la frontière séparant le Canada et les États-Unis, là où la plupart des Canadi-ens vivent. Les risques les plus élevés proviennent des séismes et des glisse-ments de terrain le long de la côte sud peuplée de la Colombie-Britannique et certaines portions du sud de l'Ontario et du Québec; d'inondations dans les villes de Vancouver, Calgary, Winnipeg, et Toronto; et, d'ouragans à Halifax et à Saint-Jean. Au long terme, les côtes canadiennes sont exposées à la hausse du niveau de la mer, et les peuples autochtones du Nord canadien sont menacés par le dégel du pergélisol découlant du réchauffement climatique.
... The most well known event was the seismically triggered rock fall in Lituya Bay, AK in 1958, which generated local runups of up to 525m on the opposing shore (Miller, 1960). Bornhold et al. (2007) have documented a case of the apparent destruction of a sizeable First Nation village of Kwalate, in Knight Inlet, as the result of a rockslide-generated tsunami. Thomson et al. (2012) have investigated the potential for large landslide-generated tsunamis in Douglas Channel, BC using a modeling approach similar to that used in this study. ...
Conference Paper
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Landslide generated tsunamis pose a significant hazard over a wide range of spatial scales. At large scale, tsunamis resulting from failures along the continental shelf margins represent a significant component of coastal tsunami hazard. At smaller scales, tsunamis resulting from subaerial or submarine slope failures represent a significant hazard in many steep-walled fjords. A relatively well known tsunami-genic landslide event occured in Kitimat, British Columbia in 1975 (Prior et al., 1983). Multiple large waves associated with the tsunami caused severe damage to infrastructure. Earlier attempts at slide reconstruction and tsunami modeling have only yielded partial agreement with anecdotal observations of wave heights, draw down and run-up (Murty, 1979; Skvortsov and Bornhold, 2007). In this paper, we consider several models for landslide generation of dispersive tsunami waves. In each case, we model the main water column using the 3-D, nonhydrostatic model NHWAVE, described originally by Ma et al (2012). NHWAVE solves the RANS equations in a surface and terrain following σ coordinate system. In perfect fluid applications, NHWAVE has been shown to provide accurate modeling of dispersive surface wave propagation using as few as three vertical σ levels, making it comparable in cost to high-order Boussinesq models. A recent reformulation of terms representing diffusion mechanisms in the model have led to improved descriptions of wave breaking, turbulence and residual flow generation in periodic and transient wave cases (Derakhti et al, 2015a,b). A variety of tsunami generation approaches are described here. Ma et al (2012) described the generation of a tsunami by a non-deforming slide by specifying a given ground motion in the usual kinematic bottom boundary condition for NHWAVE. Resulting tsunami wave response was validated against laboratory measurements by Enet and Grilli (2007), who studied the motion of a freely sliding mass on a plane slope. Experimental and numerical results clearly demonstrate the importance of frequency dispersion in characterizing the studied event. The resulting model has been used to study landslide tsunami generation in a number of settings, including slope failures along the Great Bahama Bank carbonate platform, flanking the Straits of Florida, and dependencies on terminal outrun velocity, slope inclination and failure volume (Schnyder et al., 2013). At an opposite extreme of model complexity, Ma et al (2013) have described a landslide mass as a suspended sediment load accelerating under its own weight. The resulting model requires an extensive increase in vertical resolution in order to resolve the mechanics of the evolving sediment mass, rendering it computationally expensive in comparison to the 2012 model. The model was extensively validated against detailed laboratory measurements of velocity profiles and sediment concentration in gravity currents (Garcia, 1993), and was further used to examine the dependence of generated tsunami waves on a range of parameters.
... On the west coast of Canada, a 1975 submarine slide in Kitimat Arm not related to an earthquake generated an 8 m tsunami (Murty 1979;Skvortsov and Bornhold 2007). Subaerial rockslides that slide into the ocean can also cause devastating tsunamis ( Bornhold et al., 2007). ...
Technical Report
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1.1 Objectives of the Guide Marine renewable energy (tide, wave and offshore wind) is available in large quantities for integration into the Canadian energy mix (Cornett, 2006), but the ocean is a harsh and unforgiving environment that presents major engineering challenges to industry. The development of standards and best practices for site and submarine transmission corridor characterization and environmental impact assessment are important requirements for moving marine renewable energy development forward. Seabed site characterization is or should be a critical part of the engineering design process required to install turbines as well as to understand environmental impacts. The Geological Survey of Canada (GSC) has conducted a preliminary review of site characterization requirements and methodology at a number of sites with high wave and tidal energy potential. Based on this experience and previous experience related to the offshore oil and gas industry, this document is a first attempt to summarize the range of geological and geophysical information that is required for characterizing the seabed at a marine renewable energy site. The aim of the document is to provide information on methodology and geologic interpretation that will be useful for both proponents evaluating a potential site for development and regulators attempting to identify potential environmental concerns related to the development. The present document will be subject to both peer review and review by industry experts and government regulators. However, given the relative youth of the marine renewable energy industry, it should be regarded as preliminary in nature. As the industry matures, it is anticipated that such a guide would become more finely tuned to the specific needs of both proponents and regulators. 1.2 Scope of the Guide The document aims to be as comprehensive in scope as possible but does not aim to be exhaustive in the level of details provided. References to more detailed work are provided for readers to pursue their own requirements. The most commonly used survey methodologies and equipment are presented but it should be noted that other legitimate tools exist and their exclusion should not be taken as a refutation of their potential value. Many instruments have been developed for specific purposes and may be applicable to specific problems encountered in site characterization. The character of the seabed depends on a large number of factors, but primarily (1) the geological history of the region, which determines the type of underlying bedrock and unconsolidated sedimentary deposits that occur at the seabed; and (2) the present day sedimentary processes that actively move, erode and deposit sediments. Correspondingly, two broad areas of seabed characterization are covered in this guide. First, geospatial mapping of the geological character of the seabed is presented. Modern geologic mapping in the marine environment uses a variety of geophysical remote sensing and sampling techniques to determine the surface morphology and nature of the upper part of the bedrock or sedimentary column immediately below the seabed. This information can be usefully summarized in map form as geological or seascape units with unique or distinguishing characteristics. By inference, these units will also be characterized by particular geotechnical properties. Second, the principles and techniques of determining the dynamics of sediment movement at the seafloor are discussed. Whereas these processes vary spatially and can to some extent be mapped, they also vary temporally and typically require time series data sets to understand the natural variability of the dynamics. As much as possible, the guide uses examples from high energy environments in areas of wave or tidal energy potential. In association with this report, there is a companion GIS-based map product that provides overviews of several of these study areas. 1.3 Geotechnical requirements for offshore structures Knowledge of the geological and geophysical characteristics of the seabed is critical to understanding the geotechnical conditions on which wave and tidal energy conversion systems are founded or anchored. CSA Group’s Code for the design, construction, and installation of offshore structures developed with and for the offshore oil and gas industry comprises several engineering standards for both gravity-based and anchored structures that would be generally applicable to offshore renewable energy structures (CSA Group, 2007; 2008; 2009). Design and placement of offshore structures require detailed regional and site specific information relevant to the seabed and sub-seabed properties to typical depths of tens of metres (CSA Group, 2008; 2009). Geological and geophysical interpretation is necessary for understanding the horizontal and vertical distribution and variability of soil properties. The CSA Group standard for Foundations (CSA Group, 2009) requires site investigations to be performed for all fixed offshore structures with the objective of characterizing “the site conditions and to define relevant bathymetric parameters, morphological features, geological context, and geotechnical design parameters”. These site investigations have to take into account both “near field and far field conditions”. CSA Group (2009) specifically includes determining the effects of bathymetry and geomorphology, surficial geology, bedrock geology, seismicity, slope instability and the sedimentary environment, including erosional processes on the design of structures. Det Norske Veritas (2011) has developed standards for offshore wind turbine structures that include specifications related to soil investigations and geotechnical data. These investigations are “divided into geological studies, geophysical surveys and geotechnical soil investigations”. Further details are provided in a guidance note: “A geological study, based on the geological history, can form a basis for selection of methods and extent of the geotechnical soil investigations. A geophysical survey, based on shallow seismic, can be combined with the results from a geotechnical soil investigation to establish information about soil stratification and seabed topography for an extended area such as the area covered by a wind farm. A geotechnical soil investigation consists of in-situ testing of soil and of soil sampling for laboratory testing.” While anchored structures depend less on the sub-surface conditions, geological maps provide information on seabed and shallow substrate properties (CSA Group 2007). The International Electrotechnical Commission (IEC) Technical Committee 114 (IEC/TC 114) has developed draft standards for the assessment of mooring systems (IEC/TC 114, 2011). Knowledge of sediment transport conditions is of particular importance to anchorages in the high energy sites required for marine energy conversion. 1.4 Geotechnical requirements for submarine cable routing Submarine electricity transmission cables from energy conversion devices to shore are an inevitable component of renewable energy installations. Cable routing and issues related to the laying, burial or trenching of cables are therefore critical aspects of marine renewable energy projects. The International Cable Protection Committee (ICPC), an association of cable industry companies and governments, has developed formal recommendations in a number of technical areas related to these issues (ICPC, 2007; 2010). Geological characterization of the cable corridor, typically “500 m on either side of the engineered route” (ICPC 2010), is a recommended practice either through desktop study using existing data or through subsequent marine surveys (ICPC 2007). Included in the list of geological characteristics that are recommended for evaluation are the following: • tectonic setting and associated seafloor morphology and lithology; • geological history; • seismicity; • surface faulting; • turbidity currents; • sediment transport; • sand waves; • beach and near shore seabed stability; • other geohazards. Submarine pipeline routing involves many similar issues related to seabed conditions and therefore similar principles of information gathering can be applied. Det Norske Veritas (2010) standards require consideration of the following: • seabed characteristics (uneven seabed, unstable seabed, soil properties, hard spots, soft sediment and sediment transport); • subsidence; • seismic activity. Route surveys are required “along the total length of the planned pipeline route to provide sufficient data for design and installation related activities”. Survey results should be presented in map form indicating “location of the pipeline, related facilities together with seabed properties, anomalies and all relevant pipeline attributes”. Features that should be noted include obstructions and topographic features such as rock outcrops, large boulders, pockmarks, potentially unstable slopes, sand waves, valley or channelling and erosion in the form of scour patterns or material deposits.
... Far-field hazards can result from landslide dam breach (Korup, 2002) and, where landslides run out into water, the direct impact and/or subsequent subaqueous slumping of deposits can result in tsunami (Løvholt et al., 2015;Gauthier et al., 2017). The displacement waves generated by rock avalanches that enter water bodies represent a major natural hazard for coastal communities in the fjord regions of New Zealand (Dykstra, 2013), Norway (Olesen et al., 2004;Böhme et al., 2015), British Columbia (Murty, 1979;Bornhold et al., 2007), Alaska (Miller, 1960;Dufresne et al., 2018), Chile (Sepúlveda and Serey, 2009), and, as seen recently, the deglaciated western margin of Greenland (Dahl-Jensen et al., 2004;Gauthier et al., 2017). As well as pre-failure deformation (Jaboyedoff et al., 2011), seismic precursors have also been observed prior to large, tsunamigenic events (for example, at Nuugaatsiaq, Greenland; Poli, 2017). ...
Article
Long run-out rock avalanches are one of the most hazardous geomorphic processes, and risk assessments of the potential threat they pose are often reliant on numerical modelling of their potential run-out distance. The development of such models requires a thorough understanding of past flow behaviour inferred from deposits emplaced by previous events. Despite this, few records exist of multiple rock avalanches that occurred in conditions sufficiently consistent to develop a set of more generalised, and hence transferrable, rules. We conduct field and imagery-based mapping and use numerical modelling to investigate the emplacement of 20 adjacent rock avalanches on the southern flanks of the Nuussuaq peninsula, West Greenland. The rock avalanches run out towards the Vaigat Strait, and are sourced from a range of coastal mountains of relatively uniform geology. We calibrate a three-dimensional continuum dynamic flow code, VolcFlow, with data from a modern, well-constrained event that occurred at Paatuut (AD 2000). The best-fit model assumes a constant retarding stress with a collisional stress coefficient, simulating run-out to within ±0.3% of that observed. This calibration was then used to model the emplacement of deposits from five other neighbouring rock avalanches before simulating the general characteristics of a further 14 rock avalanche deposits on simplified topography. Our findings illustrate that a single calibration of VolcFlow can account for the observed deposit morphology of a uniquely large collection of rock avalanche deposits, emplaced by a series of events spanning a large volume range. Although the prevailing approach of tuning models to a specific case may be useful for detailed back-analysis of that event, we show that more generally applied models, even using a single pair of rheological parameters, can be used to model potential rock avalanches of varied volumes in a region and, therefore, to assess the risks that they pose.
... (Miller, 1960, Slingerland andVoight, 1979). At Knight Inlet, Canada, an impulse wave presumably destroyed an indigenous settlement in the 16 th century (Bornhold et al., 2007). More recent events include Aysén Fjord, Chile, in 2007 (Sepúlveda et al., 2010) and Paatuut, Greenland, in 2000(Dahl-Jensen et al., 2004. ...
Article
Large subaerial mass wasting into water may generate large waves along coast lines and in bays. Hazard assessment of such an events is based on the decay rate of these impulse waves along their propagation path to populated areas and infrastructure along the shoreline. The spatial propagation processes of impulse waves generated by deformable slides was investigated in a wave basin. A videometric measurement approach allowed for a detailed tracking of the free water surface and key wave characteristics during the experimental runs including the wave height. Based on selected tests, the slide width effect on spatial wave propagation is discussed.
... The height of landslide-generated waves primarily depends on the volume, geometry, acceleration, speed, and coherence of the moving mass and water depth (Bornhold et al., 2007;Wang et al., 2017). Thus, the subaerial evolution and the transition from subaerial to subaqueous conditions of a landslide should be simulated continuously to calculate the movement parameters. ...
Article
Subaerial landslides can generate impulse waves in reservoirs, fjords, and other water bodies and cause severe damage to the shipping industry, infrastructure, and human communities along the shorelines. Compared with deterministic hazard models, probabilistic hazard analysis is an important tool for assessing the intensity and exceedance probability of impulse waves generated by multiple landslide sources, which are essential for evidence-based risk mitigation and contingency planning. This paper proposes a methodological procedure for systematic probabilistic hazard analysis of impulse waves generated by subaerial landslides considering all relevant landslide sources and multiple uncertainties (i.e., landslide mechanisms, triggering scenarios, and material parameters). The main steps include: (1) definition of the source parameters by parameterizing the epistemic and aleatory uncertainties. In this respect, the logic tree, event tree, and Monte Carlo models were used to organize the uncertainties of landslide mechanism models, parametric scenarios, and material parameters, respectively; (2) estimation of generated waves based on a landslide dynamic analytical model and previously validated empirical wave models derived from prototype scaled experiments; and (3) aggregation of the hazard analysis results in the form of hazard maps and probability maps under parametric scenarios and a specific scenario. Considering the Wu Gorge in the Three Gorges Reservoir as a case study, soil slides and unstable rock slopes were analyzed to quantify the wave hazard along the reservoir under parametric and specific scenarios while considering rainfall and water level fluctuations. The results show considerable wave hazard in the Wu Gorge. For a 20-year return period, the maximum expected height of propagation waves is 14.41 m. The probability of experiencing propagation waves higher than 2 m in 20 years is over 50% in the river segment with high landslide density. The results of the probabilistic wave hazard analysis could be aggregated and disaggregated to accommodate specific requirements of wave risk management.
... Fjord sediments are also commonly deformed by mass flows originating from onshore mass movements (i.e. debris flows, rockslides and avalanches) propagating into the fjord (e.g., Bornhold et al., 2007;Van Daele et al., 2013). The development of high-resolution imaging technologies in the last decades has allowed mapping such subaquatic features in detail at water depths of tens to thousands of meters (e.g., Dowdeswell et al., 2016). ...
Article
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In recent decades, the land-ocean aquatic continuum, commonly defined as the interface, or transition zone, between terrestrial ecosystems and the open ocean, has undergone dramatic changes. On-going work has stressed the importance of treating Aquatic Critical Zones (ACZs) as a sensitive system needing intensive investigation. Here, we discuss fjords as an ACZ in the context of sedimentological, geochemical, and climatic impacts. These diverse physical features of fjords are key in controlling the sources, transport, and burial of organic matter in the modern era and over the Holocene. High sediment accumulation rates in fjord sediments allow for high-resolution records of past climate and environmental change where multiple proxies can be applied to fjord sediments that focus on either marine or terrestrial-derived components. Humans through land-use change and climatic stressors are having an impact on the larger carbon stores in fjords. Sediment delivery whether from accelerating erosion (e.g. mining, deforestation, road building, agriculture) or from sequestration of fluvial sediment behind dams has been seriously altered in the Anthropocene. Climate change affecting rainfall and river discharge into fjords will impact the thickness and extent of the low-salinity layer in the upper reaches of the fjord, slowing the rate of the overturning circulation and deep-water renewal – thereby impacting bottom water oxygen concentrations.
... Poerua River, located on the South Island of New Zealand, was dammed for six days after 10-15 million m 3 of rock fell into the river (Hancox et al., 2005), before overtopping, which caused flooding and considerable gravel deposition downstream. Around the world, in addition to the Lituya Bay event of 1958 (Fritz et al., 2009) and the 1963 Vajont Dam Tsunami (Bosa and Petti, 2012) referred to earlier, landslidegenerated tsunamis have been reported in a number of locations, including Canada (Bornhold et al., 2007;Roberts et al., 2013) Norway (Harbitz et al., 1993;Blikra et al., 2005), Greenland (Dahl-Jensen et al., 2004) and Chile (Watt et al., 2009;Sepúlveda et al., 2010). One example of how widespread landslides can be after a seismic event is the 2008 Wenchuan earthquake, where 60,000 individual landslide scarps were identified throughout China (Gorum et al., 2011). ...
Article
The Waikari River tsunami was caused by a landslide triggered by the 1931 Hawke's Bay earthquake, New Zealand's deadliest natural disaster to date. Although it was reported in newspapers and personal diaries at the time, this is the first study to examine the tsunami using a multi-proxy approach aimed at investigating the physical evidence of this event. Sedimentological, geochemical, chronological and microfossil analyses were carried out on an anomalous gravel layer within the sedimentary sequence of Waikari Station located in a meander bend close to the river mouth. The chronology was established by extrapolation from ¹³⁷ Cs data coupled with historical artefacts found within the gravel layer. Diatoms within the deposit were brackish, and most probably sourced from the adjacent tidally-influenced Waikari River. Principal component analysis performed on geochemical data showed that the anomalous gravel layer at all sites is associated with a cluster of elements not related to detrital input nor organic matter, but indicative of an estuarine source. A second, older, gravel layer was also identified. It is considered to have been deposited by an earlier tsunami, quite likely caused by a landslide generated by the 1863 Hawke's Bay earthquake. The deposit has similar sedimentological, geochemical and microfossil characteristics to the gravel layer deposited by the 1931 event. This study adds valuable insights into the poorly understood topic of landslide generated tsunamis by investigating the largest historical event of its kind to occur in New Zealand.
... A wave >50 m high resulted in 1946 from a landslide at the cirque wall at Mount Colonel Foster, Vancouver Island (Evans, 1989). A 2-to 6-m-high displacement wave in Knight Inlet some 500 years ago destroyed a First Nation's Village; it was generated by a 4-Mm 3 landslide detached at a distance of 5 km on an 840-m-high cliff oversteepened during the Last Glacial Maximum/ Fraser Glaciation (Bornhold et al., 2007). ...
... Guesmia et al., 1996;Baptista et al., 1998;Bondevik, 2005 on tsunami features or their triggering source such as slides or faults are also carried out by seismic and/or multibeam bathymetry investigations (e.g. Bøe et al., 2007;Bornhold et al., 2007;Goto et al., 2011b;Haraguchi et al., 2013;Kremer et al., 2014). ...
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The number of tsunami-related scientific publications increased within the last years due to numerous extensive and destructive tsunami events worldwide. The research on tsunami deposits is needed to improve hazard assessment in coastal areas worldwide. While the state of knowledge is rising, the discipline is still relatively young and there are presently a high number of unsolved questions and processes. In the field of palaeotsunami research new insights gained from the most recent events, such as sedimentary characteristics, morphologic features, as well as the recently used methods or so called proxy toolkit, are not yet widely tested on historical events. In this thesis I try to shed light on diverse problems by means of three case studies carried out in coastal regions of the western Peloponnese (Greece), the Sultanate of Oman and along the eastern Gulf of Cádiz (Spain). There are open questions as to how the clear identification of tsunami deposits can be carried out and how the preservation of historical event deposits varies in specific archives. Furthermore, the proxy toolkit on palaeotsunami deposits differs from recent deposit investigations. The deposit characteristics, the way of detecting and proving them, the several types of archives, the deposit preservation potential and the challenges of the proxy toolkit are all discussed. The first case study from Greece uses an approach to detect palaeotsunami deposits by different classical investigation methods, such as sedimentological, palaeontological and geochemical investigations, in different environments/archives. Sedimentary evidence includes the existence of rip-up clasts in multiple sandy fining upward sequences with an erosive base as well as a mixture of foraminifera species from different habitats. Radiocarbon dating proves a minimum of one tsunami landfall in the study area between AD 540 and minimum AD 1274. The second case study from Oman demonstrates the extensive use of ground penetrating radar (GPR) as well as its potential and limitations concerning tsunami deposit investigations. This investigation method is tested on an inferred tsunami deposit which was identified in previous studies by huge blocks and boulders, most probably transported by tsunami wave action along the coast close to Fins (Oman). The investigated GPR facies reveals wedging out structures, channels, scours and erosion mounds, as well as landward directed foresets. Sedimentary evidence by trenching and age calibration is also presented. The third case study carried out along the south-eastern Gulf of Cádiz shows an integrative multi-method approach on palaeotsunami deposits. In this study several classical and new investigation tools/techniques were tested and compared to the most recently discovered tsunami characteristics. Furthermore, new tsunami features were found within the sedimentary record of high-energy event deposits. In the presented study a combination of different dating techniques (radiocarbon and optically stimulated luminescence) was also tested to yield possible event ages of the palaeotsunami. Based on the conclusions achieved from the presented studies I try to answer some of the main questions which arose at the start of this research, regarding the incomplete state of knowledge on tsunami features and characteristics. This thesis also comprises a summary of event ages in the different study areas. The event ages yielded by different dating results are compared to the recent tsunami catalogue of each region, and recurrence intervals which are necessary for an improved hazard assessment are discussed.
... Large catastrophic rock-slope failures can also trigger destructive tsunami when they enter lakes or the sea. Landslide-triggered tsunami have been documented in several mountainous areas, including the fjords of Norway ( Blikra et al., 2005), Alaska ( Coombs et al., 2007), British Columbia ( Bornhold et al., 2007;Skvortsov and Bornhold, 2007), Chile, and Greenland ( Dahl-Jensen et al., 2004). The steep and high fjord walls in these areas consist of strong rocks with discontinuities on which large masses of rock may suddenly fail. ...
Article
The hazard of any natural process can be expressed as a function of its magnitude and the annual probability of its occurrence in a particular region. Here we expand on the hypothesis that natural hazards have size–frequency relationships that in parts resemble inverse power laws. We illustrate that these trends apply to extremely large events, such as mega-landslides, huge volcanic debris avalanches, and outburst flows from failures of natural dams. We review quantitative evidence that supports the important contribution of extreme events to landscape development in mountains throughout the world, and propose that their common underreporting in the Quaternary record may lead to substantial underestimates of mean process rates. We find that magnitude–frequency relationships provide a link between Quaternary science and natural hazard research, with a degree of synergism and societal importance that neither discipline alone can deliver. Quaternary geomorphology, stratigraphy, and geochronology allow the reconstruction of times, magnitudes, and frequencies of extreme events, whereas natural hazard research raises public awareness of the importance of reconstructing events that have not happened historically, but have the potential to cause extreme destruction and loss of life in the future.
... Several case studies reveal the relationship of coastal hazards (tsunami) and human adaptation strategies along the pacific coastline of Cascadia (e.g. Hutchinson and McMillan, 1997;Losey, 2005Losey, , 2007Bornhold et al., 2007;Witter et al., 2009;Peterson et al., 2011). Goff and McFadgen (2003), McFadgen and Goff (2007), Hutchinson and Attenbrow (2009) and Goff et al. (2011Goff et al. ( , 2012 provide well documented geo-archaeological evidence for palaeo-tsunami along the shores of New Zealand. ...
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Bending moment normal faults (BMF) form during outer-arc extension of a folding layer. These faults, observed in contractional and extensional tectonic environments, can represent the only tectonic features potentially available for paleoseismological investigations (i.e., trenching) in order to date the movement of deeper structures. Yet, the reliability of BMF as a paleoseismological feature is debated in terms of its potential to continuously record coseismic deformation and their relationship with progressive flexure. We made use of analogue modeling in order to explore a simple model of progressive orthogonal flexure and the development of BMF. We collected data on mode of BMF inception and growth by analyzing time-series of cross section deformation, measuring dip-parallel BMF displacement profiles, and constructing a three-dimensional model of fault architecture by slicing of the experiment. Our results point to a model of BMF development typical of mechanically constrained faults, where limits on self-similar growth of faults is imposed once a maturity stage of displacement accumulation is attained. The BMF can accumulate displacement until the structure reaches a maturity stage when further slip is inhibited. This could result in an incomplete paleoseismological record of further fold movements. However, this fault stage can be recognized by the D-shaped displacement profile, typical of mature BMF. A simple two-dimensional constant-area balancing model is proposed, allowing us to derive incremental changes in flexuring, given the area of the collapsed sector with BMF and the thickness of the faulted layer. These results support the use of BMF as a paleoseismological proxy for deeper structures.
... For example, a 524 m tsunami wave developed from a landslide in Lituya Bay in SE Alaska in 1958 (Weiss et al. 2009). The potential for large rock slides and sackungen to trigger tsunamis in coastal BC is therefore of concern as large events causing significant casualties have marked the past in this region (Bornhold et al. 2007). The British Columbia coast is earmarked by steep slopes, seasonal extremes of soil moisture, macrotidal conditions, and the highest seismicity in Canada, all of which increase the potential for slope failures in the form of slides and sackungen. ...
Article
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Very large (>60×10⁶ m³) sackungen or deep-seated gravitational slope deformations occur below sea level along a steep fjord wall in central Douglas Channel, British Columbia. The massive bedrock blocks were mobile between 13 and 11.5 thousand radiocarbon years BP (15,800 and 13,400 BP) immediately following deglaciation. Deformation of fjord sediments is apparent in sedimentary units overlying and adjacent to the blocks. Faults bound the edges of each block, cutting the glacial section but not the Holocene sediments. Retrogressive slides, small inset landslides as well as incipient and older slides are found on and around the large failure blocks. Lineations, fractures and faults parallel the coastline of Douglas Channel along the shoreline of the study area. Topographic data onshore indicate that faults and joints demarcate discrete rhomboid-shaped blocks which controlled the form, size and location of the sackungen. The described submarine sackungen share characteristic geomorphic features with many montane occurrences, such as uphill-facing scarps, foliated bedrock composition, largely vertical dislocation and a deglacial timing of development.
... Landslide-generated tsunamis can be classified as subaerial, partially submerged or submarine, depending on the initial landslide position. Major subaerial and partially submerged landslide impact-generated tsunamis occurred at Knight Inlet in British Columbia, Canada (1500s) [3], Tafjord (1934) and Lake Loen (1936) in Norway [4,5], Lituya Bay, AK, USA, in 1958 [6][7][8][9], Vajont Dam in Italy in 1963 [10,11], Yanahuin Lake, Peru, in 1971 [12], Fatu Hiva (Marquesas Islands; French Polynesia) in 1999 [13], Aisén Fjord, Chile, in 2007 [14,15], Chehalis Lake in British Columbia, Canada, in 2007 [16][17][18] and in Haiti in 2010 [19]. Tsunamis generated by submarine landslides were associated with the ancient Storegga slides [20,21], and were observed in Puerto Rico in 1918 [22], Grand Banks, Newfoundland, in 1929 [23] and Papua New Guinea in 1998 [24,25]. ...
Article
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Tsunamis generated by landslides and volcanic island collapses account for some of the most catastrophic events recorded, yet critically important field data related to the landslide motion and tsunami evolution remain lacking. Landslide-generated tsunami source and propagation scenarios are physically modelled in a three-dimensional tsunami wave basin. A unique pneumatic landslide tsunami generator was deployed to simulate landslides with varying geometry and kinematics. The landslides were generated on a planar hill slope and divergent convex conical hill slope to study lateral hill slope effects on the wave characteristics. The leading wave crest amplitude generated on a planar hill slope is larger on average than the leading wave crest generated on a convex conical hill slope, whereas the leading wave trough and second wave crest amplitudes are smaller. Between 1% and 24% of the landslide kinetic energy is transferred into the wave train. Cobble landslides transfer on average 43% more kinetic energy into the wave train than corresponding gravel landslides. Predictive equations for the offshore propagating wave amplitudes, periods, celerities and lengths generated by landslides on planar and divergent convex conical hill slopes are derived, which allow an initial rapid tsunami hazard assessment. © 2016 The Author(s) Published by the Royal Society. All rights reserved.
... The most well known event was the seismically triggered rockfall in Lituya Bay, AK, in 1958, which generated local runups of up to 525 m on the opposing shore (Miller 1960). Bornhold et al. (2007) have documented a case of the apparent destruction of the sizeable First Nation village of Kwalate, in Knight Inlet, as the result of a rockslide-generated tsunami. Thomson et al. (2012) have investigated the potential for large landslide-generated tsunamis in Douglas Channel, BC, using a modeling approach similar to that used in this study. ...
Article
We present numerical simulations of the April 27, 1975, landslide event in the northern extreme of Kitimat Arm, British Columbia. The event caused a tsunami with an estimated wave height of 8.2 m at Kitimat First Nations Settlement and 6.1 m at Clio Bay, at the northern and southern ends of Kitimat Arm, respectively. We use the nonhydrostatic model NHWAVE to perform a series of numerical experiments with different slide configurations and with two approaches to modeling the slide motion: a solid slide with motion controlled by a basal Coulomb friction and a depth-integrated numerical slide based on Newtonian viscous flow. Numerical tests show that both models are capable of reproducing observations of the event if an adequate representation of slide geometry is used. We further show that comparable results are obtained using estimates of either Coulomb friction angle or slide viscosity that are within reasonable ranges of values found in previous literature.
Article
Impulse waves generated by rapid subaerial landslides into water bodies may pose a threat to riparian settlements and infrastructure. Empirically derived prediction equations based on experiments at laboratory scale provide information on key wave characteristics for preliminary hazard assessment. This research discusses existing prediction methods for spatial wave propagation features and compares their results with own impulse wave height decay experiments. While some prediction methods are based on simplified approaches for wave generation such as rigid body slides, others take only limited sets of slide parameters into account, narrowing their range of applicability considerably. The prediction methods are intentionally applied outside their ranges of applicability with the aim to assess their characteristics on an extended parameter range. It is found that a combination of separate terms for wave generation and wave propagation from two different existing prediction methods provides the best representation of the experimental data.
Article
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The Canadian coastline is the longest of any country in the world, and is at risk from tsunamis generated in three oceans. The current state of knowledge precludes a complete probabilistic tsunami hazard assessment, which would require quantification of a wide range of possible scenarios for each tsunami source, coupled with modelling that incorporates fine-resolution bathymetry and onland topography to adequately assess potential runup at the coast. This preliminary assessment presents a first attempt to quantify the tsunami hazard on the Canadian Pacific, Atlantic and Arctic coastlines from local and far-field, earthquake and large landslide sources. For each source considered, we calculate the probability that tsunami runup at the coast will exceed 1.5 m (threshold for potential damage) and 3 m (significant damage potential), in a 50-year period. For each coastal region, we then combine the relative hazard from each source to calculate the overall probability that the coastline in question will experience tsunami runup exceeding 1.5 m (and 3 m) within a 50-year period, from any geological source. We also consider the maximum runup levels expected to occur within time periods of 100, 500, 1000, and 2500 years. Our assessment indicates that the overall tsunami hazard (runup ≥ 1.5 m) of the outer Pacific coastline (~40-80% probability of exceedance in 50 y) is an order of magnitude greater than that of the outer Atlantic coastline (~1-15%), which in turn is an order of magnitude greater than the Arctic coastline (< 1%). These probabilities are equivalent to an expected recurrence of runup exceeding 1.5 m of ~30-100 years for the outer Pacific coast, ~300-1700 for the Atlantic, and ~6500-17,000 years for the Arctic. For larger runup (≥ 3 m), the estimated Pacific hazard (~10-30% probability of exceedance in 50 y) is significantly larger than both the Atlantic (~1-5%) and the Arctic (< 1%). Equivalent recurrence intervals are ~150-500 years for the Pacific, ~650-4000 years for the Atlantic, and ~7000-20,000 years for the Arctic. On the outer Pacific coastline, the 1.5 m runup hazard is dominated by far-field subduction zone sources, whereas the more severe 3 m runup hazard is almost entirely contributed by local subduction zone sources. The Cascadia subduction zone presents the highest tsunami hazard to the Pacific coast, with the most extreme potential runup; potential thrust sources along the Explorer and Queen Charlotte margins contribute a significant proportion of the estimated tsunami hazard for the northern BC coastline. For the more sheltered inner Pacific coasts of Juan de Fuca and Georgia Straits, the hazard at both levels is contributed mostly by Cascadia subduction zone events. Tsunami hazard on the Atlantic coastline is dominated by far-field subduction zone sources, but this hazard is poorly constrained. Significant tsunami hazard is also provided by near-field continental slope failures similar to the 1929 Grand Banks event. Tsunami hazard on the Arctic coastline remains poorly constrained, but these regions are assumed to be sheltered from far-field tsunamis, so the hazard is provided by local sources. A hypothetical earthquake source beneath the Mackenzie delta requires further study. We discuss briefly but do not quantify the hazard of locally-damaging waves triggered by subaerial or submarine landslides, but we highlight susceptible areas. A probabilistic analysis of local landslide tsunamis would require (1) the identification of potential sources; (2) evidence for past tsunamigenic events to establish frequency-size relationships and/or slope stability analyses that incorporate expected earthquake shaking levels; (3) probabilistic tsunami modelling of a wide range of possible failures.
Article
Reservoir landslides pose a great threat to shipping safety, human lives and properties, and the operation of the hydropower station. In this paper, the 24 June 2015 Hongyanzi landslide at the Three Gorges Reservoir is considered as an example to study the initiation mechanism and landslide-generated wave process of a reservoir landslide. The finite difference method and limit equilibrium analysis are used to analyze the deformation and failure characteristics of the Hongyanzi slope. Simulation results show that a large deformation (about 358 mm) happens in the shallow deposits under intermittent rainfall condition, and the slope is in a limit state. At the same time, continuous rapid drawdown of the water level (about −0.55 m/day during 8–24 June 2015) reduced the support and accelerated the drainage of the water for the bank slope. A coupling effect of intermittent rainfall and rapid drawdown of the water level was the triggering factor of the 24 June Hongyanzi landslide. Landslide-generated wave process was simulated using a fluid–solid coupling method by integrating the general moving object collision model. Simulation results show that the landslide-generated wave is dominated by the impulse wave, which is generated by sliding masses entering the river with high speed. The maximum wave height is about 5.90 m, and the wave would decay gradually as it spreads because of friction and energy dissipation. To prevent reservoir landslides, the speed for the rising or drawdown of the water level should be controlled, and most importantly, rapid drawdown should be avoided.
Article
The west coast of Canada is one of the major fjord coastlines of the world, hosting about 150 fjords which are locally known as inlets. Much of the coastline remains remote without extensive research, and this paper summarizes what is known of the Canadian west coast fjord environments. Two fjord regimes are recognized along the British Columbia coastline. Mainland fjords drain high mountains and ice fields with sediment input from snowmelt and glacier runoff in spring and summer. By contrast, the inlets on Vancouver Island are in a milder marine climate, and sediment input occurs mostly during heavy rains of autumn and winter. Due to unique oceanographic conditions and shallow sills at the mouth of some Vancouver Island inlets, anoxic bottom waters exist which allow the preservation of annually laminated sediments. Studies of these annually laminated sediment archives over the past decade, including two international drill ship investigations, have characterized the deglacial, sea-level and palaeoenvironmental history of the British Columbia coastal area. These coastal depositional archives have also advanced our knowledge of the cyclical nature of the NE Pacific ocean and climate system, as well as given evidence of infrequent, yet significant abrupt changes that characterize it.
Article
Canada has the longest coastline and largest continental margin of any nation in the World. As a result, it is more likely than other nations to experience marine geohazards such as submarine landslides and consequent tsunamis. Coastal landslides represent a specific threat because of their possible proximity, to societal infrastructure and high tsunami potential; they occur without warning and with little time lag between failure and tsunami impact. Continental margin landslides are common in the geologic record but rare on human timescales. Some ancient submarine landslides are massive but more recent events indicate that even relatively small slides on continental margins can generate devastating tsunamis. Tsunami impact can occur hundreds of km away from the source event, and with less than 2 hours warning. Identification of high-potential submarine landslide regions, combined with an understanding of landslide and tsunami processes and sophisticated tsunami propagation models, are required to identify areas at high risk of impact.
Article
In the last 15 years there have been 16 tsunami events recorded at tide stations on the Pacific Coast of Canada. Eleven of these events were from distant sources covering almost all regions of the Pacific, as well as the December 26, 2004 Sumatra tsunami in the Indian Ocean. Three tsunamis were generated by local or regional earthquakes and two were meteorological tsunamis. The earliest four events, which occurred in the period 1994-1996, were recorded on analogue recorders; these tsunami records were recently re-examined, digitized and thoroughly analysed. The other 12 tsunami events were recorded using digital high-quality instruments, with 1-min sampling interval, installed on the coast of British Columbia (B.C.) in 1998. All 16 tsunami events were recorded at Tofino on the outer B.C. coast, and some of the tsunamis were recorded at eight or more stations. The tide station at Tofino has been in operation for 100 years and these recent observations add to the dataset of tsunami events compiled previously by S.O. W igen (1983) for the period 1906-1980. For each of the tsunami records statistical analysis was carried out to determine essential tsunami characteristics for all events (arrival times, maximum amplitudes, frequencies and wave-train structure). The analysis of the records indicated that significant background noise at Langara, a key northern B.C. Tsunami Warning station located near the northern end of the Queen Charlotte Islands, creates serious problems in detecting tsunami waves. That station has now been moved to a new location with better tsunami response. The number of tsunami events observed in the past 15 years also justified re-establishing a tide gauge at Port Alberni, where large tsunami wave amplitudes were measured in March 1964. The two meteorological events are the first ever recorded on the B.C. coast. Also, there have been landslide generated tsunami events which, although not recorded on any coastal tide gauges, demonstrate, along with the recent investigation of a historical catastrophic event, the significant risk that landslide generated tsunami pose to coastal and inland regions of B.C.
Article
The devastating impacts of tsunamis have received increased focus since the Indian Ocean tsunami of 2004, the most devastating tsunami in over 400 years of recorded history. This professional reference is the first of its kind: it provides a globally inclusive review of the current state of tsunami detection technology and will be a much-needed resource for oceanographers and marine engineers working to upgrade and integrate their tsunami warning systems. It focuses on the two main tsunami warning systems (TWS): International and Regional. Featured are comparative assessments of detection, monitoring, and real-time reporting technologies. The challenges of detection through remote measuring stations are also addressed, as well as the historical and scientific aspects of tsunamis. Offers readers the only source of practical content on the technological details of the subject Written by a tsunami detection and monitoring expert who has 32 years of experience in the field Companion web site featuring multi-media components, timely updates on fast-paced technological developments, and an online forum where scientists can exchange ideas, discuss technological updates and provide the author with valuable feedback.
Chapter
In the last 15 years there have been 16 tsunami events recorded at tide stations on the Pacific Coast of Canada. Eleven of these events were from distant sources covering almost all regions of the Pacific, as well as the December 26, 2004 Sumatra tsunami in the Indian Ocean. Three tsunamis were generated by local or regional earthquakes and two were meteorological tsunamis. The earliest four events, which occurred in the period 1994–1996, were recorded on analogue recorders; these tsunami records were recently re-examined, digitized and thoroughly analysed. The other 12 tsunami events were recorded using digital high-quality instruments, with 1-min sampling interval, installed on the coast of British Columbia (B.C.) in 1998. All 16 tsunami events were recorded at Tofino on the outer B.C. coast, and some of the tsunamis were recorded at eight or more stations. The tide station at Tofino has been in operation for 100 years and these recent observations add to the dataset of tsunami events compiled previously by S.O. Wigen (1983) for the period 1906–1980. For each of the tsunami records statistical analysis was carried out to determine essential tsunami characteristics for all events (arrival times, maximum amplitudes, frequencies and wave-train structure). The analysis of the records indicated that significant background noise at Langara, a key northern B.C. Tsunami Warning station located near the northern end of the Queen Charlotte Islands, creates serious problems in detecting tsunami waves. That station has now been moved to a new location with better tsunami response. The number of tsunami events observed in the past 15 years also justified re-establishing a tide gauge at Port Alberni, where large tsunami wave amplitudes were measured in March 1964. The two meteorological events are the first ever recorded on the B.C. coast. Also, there have been landslide generated tsunami events which, although not recorded on any coastal tide gauges, demonstrate, along with the recent investigation of a historical catastrophic event, the significant risk that landslide generated tsunami pose to coastal and inland regions of B.C.
Conference Paper
Recent tsunami events in Indonesia, Chile and Japan highlight the importance of understanding the near-source impacts of devastating tsunamis. These events have also raised awareness of the need for risk assessment for local (e.g. submarine and subaerial landslide-generated) and near-field tsunamis (those that can impact a coastal community less than an hour after generation). Although existing tsunami warning systems such as DART (Deep-ocean Assessment and Reporting of Tsunamis) are highly effective at providing an assessment and warning of far-field tsunami events, comparable systems do not currently exist for local and near-field events. Tsunami inundation models can predict coastal run-up yet the lack of wave amplitude, direction, and shape data within a few minutes of a near-field tsunami event limits the information needed for warning populations at risk. The Ocean Networks Canada (ONC) Observatory, combining the VENUS and NEPTUNE Canada cabled networks, is the world's largest regional ocean observation system with over 900 km of electro-optic cable. The ONC Observatory, located off the east and west coasts of Vancouver Island spans the Juan de Fuca tectonic plate and edge of the overriding North American plate, a region known to produce mega-thrust earthquakes. The ONC Observatory has an extensive tsunami monitoring system of bottom pressure recorders used to provide high resolution tsunami data for modeling far-field tsunamis in coastal regions [1]. Since the start-up of operations of the NEPTUNE Canada network in 2009, the capability of the system has already been proven by the high precision of the bottom pressure recorders that monitored the passage of the tsunami waves generated by the Samoan, Chilean, and Japanese earthquake events. The Observatory has an extensive sensor network covering a broad range of research themes and provides standardized connection ports for guest instruments. The system is supported by a sophisticated Data Management and Arc- iving System, which provides data acquisition, archiving, processing and visualization from sources across the Observatory. With the base core technologies and infrastructure for tsunami warning system research, the ONC Observatory is an ideal site for the test and evaluation of near-field tsunami detection technologies. This paper discusses how this unique infrastructure can be used to facilitate international collaboration, combining new technologies, concepts and algorithms to create an international near-field tsunami research facility to develop, evaluate, and test warning technologies and solutions for at-risk populations.
Article
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We show that the tsunami of November 3, 1994 in Skagway, Alaska was generated by an underwater landslide formed during the collapse of a cruise ship wharf undergoing construction at the head of Taiya Inlet. This event occurred at a time of extreme low tide and was not associated with a regional seismic event or incoming oceanic tsunami. Persistent wave motions with an amplitude of 1 m and a period of 3 min recorded by a tide gauge in Skagway Harbor following the landslide are linked to the formation of a cross-inlet seiche and quarter-wave resonance within the harbor. The high Q factor for the harbor (Q ≈ 20) indicates weak dissipation and strong resonance within the harbor.
Article
Lituya Bay, a ⊺-shaped tidal inlet on the northeast shore of the Gulf of Alaska, heads in the trench along the Fairweather fault. Displacement along this fault at the time of the earthquake of July 9, 1958 (local time), triggered a rockslide into deep water in Gilbert Inlet, one of the two arms at the head of Lituya Bay. The rockslide, with a volume of 40 million cubic yards, caused water to surge to an altitude of 1,740 feet on a spur opposite the point of impact, and generated a gravity wave that swept 7 miles to the mouth of the bay at a speed probably between 97 and 130 miles per hour. The surge and wave of water destroyed the forest on the shores over an area of 4 square miles, sank two of three fishing boats in the outer part of the bay, and took two lives.
Article
A digitally acquired, scale-corrected side-scan sonar survey yielded high-resolution imagery of a submarine landslide in British Columbia. The landslide, in a fjord-head setting at Kitimat, was last active in 1975 and created a wide area of deformed sea floor. The sediment failure involved shallow rotational movements on the slopes of a fjord-head delta, marginal tearing, translational sliding, compressional folding, and block gliding of fjord-bottom marine clays. The slide is shallow and elongate and appears to have been produced by failure in mobile, low-strength sediments.
Article
A major submarine slide occurred on April 27, 1975, in Kitimat Inlet in the Douglas Channel system on the west coast of Canada. Following this slide at least two water waves were observed, and it was estimated that the range (crest plus trough) of the first wave could have been 8.2 m. Two simple theories have been used here to estimate the wave height. By considering the uncertainties both in the observed data as well as in the calculated wave height, there is reasonable agreement.
Article
The 1996 Finneidfjord slide was a combined submarine/subaerial, retrogressive flow/quick clay slide that mobilized 1 mill. m^3 of sediments and killed four people. The submarine part of the slide has been surveyed through several cruises utilising methods like swath bathymetry, high-resolution seismic, side-scan sonar and coring. Interpretation of the morphology of the submarine slide scar and the slide deposits, combined with eyewitness observations, suggest that the initial failure occurred on the steepest slope of the foreshore platform. Detachment along a weak layer within silty clay caused, unloading, oversteepening and erosion and triggered retrogressive sliding. Outrunner blocks, as large as 10 000 m^3, from the slide occur up to 1.6 km outside the main debris lobe. Excess hydrostatic pressure related to meteorological and anthropogenic influence is thought to have triggered the slide.
Article
A large landslide occurred November 21, 2000 at Paatuut, facing the Vaigat Strait onthe west coast of Greenland. 90 million m3 (260 million tons) of mainly basalticmaterial slid very rapidly (average velocity 140 km/h) down from 1,000–1,400 maltitude. Approximately 30 million m3 (87 million tons) entered the sea, creatinga tsunami with an run-up height of 50 m close to the landslide and 28 m at Qullissat,an abandoned mining town opposite Paatuut across the 20 km wide Vaigat strait. Theevent was recorded seismically, allowing the duration of the slide to be estimated tocirca 80 s and also allowing an estimate of the surface-wave magnitude of the slideof 2.3. Terrain models based on stereographic photographs before and after the slidemade it possible to determine the amount of material removed, and the manner ofre-deposition. Simple calculations of the tsunami travel times are in good correspondencewith the reports from the closest populated village, Saqqaq, 40 km from Paatuut, whererefracted energy from the tsunami destroyed a number of boats. Landslides are notuncommon in the area, due to the geology with dense basaltic rocks overlying poorlyconsolidated sedimentary rocks, but the size of the Paatuut slide is unusual. Based onthe observations it is likely at least 500 years since an event with a tsunami of similarproportions occurred. The triggering of the Paatuut slide is interpreted to be caused byweather conditions in the days prior to the slide, where re-freezing melt water inpre-existing cracks could have caused failure of the steep mountain side.
Article
We investigate the generation, propagation, and probabilistic hazard of tsunami spawned by oceanic asteroid impacts. The process first links the depth and diameter of parabolic impact cavities to asteroid density, radius, and impact velocity by means of elementary energy arguments and crater scaling rules. Then, linear tsunami theory illustrates how these transient cavities evolve into vertical sea surface waveforms at distant positions and times. By measuring maximum wave amplitude at many distances for a variety of impactor sizes, we derive simplified attenuation relations that account both for geometrical spreading and frequency dispersion of tsunami on uniform depth oceans. In general, the tsunami wavelengths contributing to the peak amplitude coincide closely with the diameter of the transient impact cavity. For the moderate size impactors of interest here (those smaller than a few hundred meters radius), cavity widths are less than or comparable to mid-ocean depths. As a consequence, dispersion increases the 1/□r long-wave decay rate to nearly 1/r for tsunami from these sources. In the final step, linear shoaling theory applied at the frequency associated with peak tsunami amplitude corrects for amplifications as the waves near land. By coupling this tsunami amplitude/distance information with the statistics of asteroid falls, the probabilistic hazard of impact tsunami is assessed in much the same way as probabilistic seismic hazard, by integrating contributions over all admissible impactor sizes and impact locations. In particular, tsunami hazard, expressed as the Poissonian probability of being inundated by waves from 2 to 50 m in height in a 1000-year interval, is computed at both generic (generalized geography) and specific (real geography) sites. For example, a typical generic site with 180° of ocean exposure and a reach of 6000 km, admits a 1-in-14 chance of an impact tsunami exceeding 2-m in height in 1000 years. The likelihood drops to 1-in-35 for a 5-m wave, and to 1-in-345 for a 25-m wave. Specific sites of Tokyo and New York have 1-in-24 and 1-in-47 chances, respectively, of suffering an impact tsunami greater than 5 m in the next millennium.
Repatriation of T'sadzis'nukame – A Vision Becomes Reality. Da'naxda'xw Nation, Alert Bay, British Columbia Canada, 24 pp. Downloaded by
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Archeological and oral history evidence of an ancient tsunami event at Kwalate, Knight Inlet. Report to the Archeological Branch, British Columbia The Alaska earthquake of
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Rock avalanches, gravitational bedrock fractures and neotectonic faults onshore northern West Norway: examples, regional distribution and triggering mechanism Norwegian Geotechnical Institute, 53 pp. BOAS, F. 1910. Kwakiutl Tales, Volume II
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Waves in the Ocean The 1996 Finneidfjord slide; seafloor failure and slide dynamics. In: Submarine Mass Movements and their Consequences
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Full Moon Tide: Bill Proctor's Raincoast Asteroid impact tsunami: a probabilistic hazard assessment
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