The Translatory Wave Model for Landslides

The Saint-Venant equations are usually the basis of numerical models for landslide flows. They are nonstationary and nonlinear. The theory for translatory waves in a prismatic channel and a funneling channel can be used for landslides using the assumption of either turbulent or laminar flow in the slide. The mathematics of translatory waves traveling over dry land or superimposed on another flow are developed. This results in a new slope factor controlling the flow velocity, together with the Chezy coefficient used in previous applications of the translatory wave theory. Flow times for the slide to reach a given destination, slide depth, and velocity can be calculated using the initial magnitude of the flow in the slide. The instabilities of the wave tail are discussed. Three case studies are presented: a submarine slide that started the Tohoku tsunami in Japan, the Morsárjökull rock avalanche in SE Iceland, and the Móafellshyrna slide in central N Iceland

A large rock avalanche onto Morsarjökull glacier, south-east Iceland. Its implications for ice-surface evolution and glacier dynamics

In spring 2007, a large rock avalanche descended onto the Morsárjökull valley glacier in southeast Iceland, leaving one fifth of the glacier buried. The insulating effect of the deposit on the ice was quickly observed as a difference in the ablation between the exposed ice and that under the deposit. After three melt seasons, the ice surface under the deposit was 29 m above the surrounding glacier surface. A reduced rate of ice melting beneath the area of the deposit would likely alter the longitudinal profile of the glacier

Molards as an indicator of permafrost degradation and landslide processes

Molards have been defined in the past as conical mounds of debris that can form part of a landslide's deposits. We present the first conclusive evidence that molards in permafrost terrains are cones of loose debris that result from thawing of frozen blocks of ice-rich sediments mobilised by a landslide, and hence propose a rigorous definition of this landform in permafrost environments. We show that molards can be used as an indicator of permafrost degradation, and that their morphometry and spatial distribution give valuable insights into landslide dynamics in permafrost environments. We demonstrate that molards are readily recognisable not only in the field, but also in remote sensing data; surveys of historic aerial imagery allow the recognition of relict molards, which can be used as an indicator of current and past permafrost conditions. The triggering of landslides as a result of permafrost degradation will arguably occur more often as global atmospheric temperatures increase, so molards should be added to our armoury for tracking climate change, as well as helping us to understand landslide-related hazards. Finally, we have also identified candidate molards on Mars, so molards can inform about landscape evolution on Earth and other planetary bodies

The impact of ground-ice thaw on landslide geomorphology and dynamics: two case studies in northern Iceland

As consequence of ongoing climate change, permafrost degradation is thought to be increasingly affecting slope stability in periglacial environments. This is of growing concern in Iceland, where in the last decade, permafrost degradation has been identified among the triggering factors of landslides. The role of ground ice in conditioning the morphology and dynamics of landslides involving loose deposits is poorly understood. We show the geomorphological impact of the Móafellshyrna and Árnesfjall landslides that recently occurred in ice-cemented talus deposits in northern Iceland. Using field and aerial remote-sensing measurements of the morphological and morphometric characteristics of the landslides, we assess the influence of thawing ground ice on their propagation style and dynamics. The two mass movements are complex and are similar to rock- and debris-ice avalanches, changing trajectory and exhibiting evidence of transitioning their style of motion from a dry granular mass to a debris flow-like movement via multiple pulses. We infer that the thawing of ground ice together with the entrainment of saturated material provided the extra fluid causing this change in dynamics. The hazardous consequences of permafrost degradation will increasingly affect mountain regions in the future, and ground-ice thaw in steep terrain is a particularly hazardous phenomenon, as it may induce unexpected long-runout failures and can cause slope instability to continue even after the landslide event. Our study expands our knowledge of how landslides develop in unstable ice-cemented deposits and will aid assessment and mitigation of the hazard that they pose in Iceland and other mountainous periglacial areas

Reversible glacial-periglacial transition in response to climate changes and paraglacial dynamics: a case study from Héðinsdalsjökull (northern Iceland)

The objective of this work is to chronologically establish the origin of the different glacial and rock glacier complex landforms deposited by Héðinsdalsjökull glacier (65°39′ N, 18°55′ W), in the Héðinsdalur valley (Skagafjörður fjord, Tröllaskagi peninsula, central northern Iceland). Multiple methods were applied: geomorphological analysis and mapping, glacier reconstruction and equilibrium-line altitude calculation, Cosmic-Ray Exposure dating (in situ cosmogenic 36Cl), and lichenometric dating. The results reveal that a debris-free glacier receded around 6.6 ± 0.6 ka, during the Holocene Thermal Maximum. The retreat of the glacier exposed its headwall and accelerated paraglacial dynamics. As a result, the glacier terminus evolved into a debris-covered glacier and a rock glacier at a slightly higher elevation. The front of this rock glacier stabilized shortly after it formed, although nuclide inheritance is possible, but its sector close the valley head stabilized between 1.5 and 0.6 ka. The lowest part of the debris-covered glacier (between 600 and 820 m altitude) collapsed at ca. 2.4 ka. Since then, periods of glacial advance and retreat have alternated, particularly during the Little Ice Age. The maximum advance during this phase occurred in the 15th to 17th centuries with subsequent re-advances, namely at the beginning of the 19th and 20th centuries. After a significant retreat during the first decades of the 20th century, the glacier advanced in the 1960s to 1990s, and then retreated again, in accordance with the local climatic evolution. The internal ice of both the debris-covered and the rock glacier have survived until the present day, although enhanced subsidence provides evidence of their gradual degradation. A new rock glacier developed from an ice-cored moraine from around 1940–1950 CE. Thus, the Holocene coupling between paraglacial and climatic shifts has resulted in a complex evolution of Héðinsdalsjökull, which is conflicting with previously proposed models: a glacier, which had first evolved into a debris-covered and rock glacier, could later be transformed into a debris-free glacier, with a higher sensitivity to climatic variability.info:eu-repo/semantics/publishedVersio

The triggering factors of the Móafellshyrna debris slide in northern Iceland: Intense precipitation, earthquake activity and thawing of mountain permafrost

On the 20th September 2012, a large debris slide occurred in the Móafellshyrna Mountain in the Tröllaskagi peninsula, central north Iceland. Our work describes and discusses the relative importance of the three factors that may have contributed to the failure of the slope: intense precipitation, earthquake activity and thawing of ground ice. We use data from weather stations, seismometers, witness reports and field observations to examine these factors. The slide initiated after an unusually warm and dry summer followed by a month of heavy precipitation. Furthermore, the slide occurred after three seismic episodes, whose epicentres were located ~60km NNE of Móafellshyrna Mountain. The main source of material for the slide was ice-rich colluvium perched on a topographic bench. Blocks of ice-cemented colluvium slid and then broke off the frontal part of the talus slope, and the landslide also involved a component of debris slide, which mobilized around 312,000-480,000m(3) (as estimated from field data and aerial images of erosional morphologies). From our analysis we infer that intense precipitation and seismic activity prior to the slide are the main preparatory factors for the slide. The presence of ice-cemented blocks in the slide's deposits leads us to infer that deep thawing of ground ice was likely the final triggering factor. Ice-cemented blocks of debris have been observed in the deposits of two other recent landslides in northern Iceland, in the Torfufell Mountain and the Árnesfjall Mountain. This suggests that discontinuous mountain permafrost is degrading in Iceland, consistent with the decadal trend of increasing atmospheric temperature in Iceland. This study highlights a newly identified hazard in Iceland: landslides as a result of ground ice thaw. Knowledge of the detailed distribution of mountain permafrost in colluvium on the island is poorly constrained and should be a priority for future research in order to identify zones at risk from this hazard

Design and Implementation of a Buoy Positioning and Monitoring System Using Differential GNSS and LoRaWAN

When vessels at sea currently install sea marks, such as floating buoys, they use their own Global Navigation Satellite Systems (GNSS) receivers to acquire a position and use that as an estimate for the buoys’ position, but the buoys are typically installed from the rear of the vessel while the GNSS receiver is closer to the middle of the vessel. These vessels are quite large and there are several meters between the GNSS receiver and the where the buoy is actually installed. Errors in the GNSS signals, which are mainly caused by Earth’s ionosphere, further add to the inaccuracy of the buoys’ position. The inaccuracy caused by the errors can be drastically mitigated by using GNSS correction data. The purpose of this thesis is to develop a system that includes a device that could be placed on a buoy in order to acquire a highly accurate position using GNSS and real-time GNSS correction data while also using low amounts of power. To achieve this a LoRa Wide Area Network (LoRaWAN) was set up which includes a LoRaWAN gateway that transmits corrections to the buoy device which uses them to acquire a position with a positioning error of less than a meter. The corrections are provided by a Continuously Operating Refer- ence Station (CORS) network operating in Iceland called IceCORS which streams the corrections over the internet. The corrections are fetched by a Raspberry Pi computer which relays them to the LoRaWAN gateway via Ethernet. The buoy device is an ESP32-based microcontroller equipped with a LoRa transceiver module and a GNSS receiver. The Raspberry Pi and gateway can be placed on the vessel installing the buoy (assuming the vessel has Internet connectivity) or on shore with a good view over the areas where buoys would be installed as LoRa communication requires a line of sight when communicating over distances of multiple kilometers. In-field testing revealed that the corrections transmitted via LoRa provided a signif- icant increase in the position accuracy and well within 1 m. They also revealed that corrections could be transmitted up to 15.5 km while achieving such an accurate position.Þegar skip á sjó leggja sjómerki, til dæmis baujur, nota þau sinn innbyggða GNSS staðsetningarbúnað til að fá staðsetningu sína og skrá þá staðsetningu sem staðset- ning baujannar. En baujur eru yfirleitt lagðar frá aftari enda skipsins og staðset- ningarbúnaðurinn er nær miðju þess. Þessi skip eru nokkuð stór og er staðsetningar- búnaðurinn mörgum metrum frá þeim stað þar sem baujan er lögð í raun og veru. Skekkjur í merkjum GNSS, sem verða til einkum af völdum jónhvolfs jarðar, auka enn skekkjuna á staðsetningu baujunnar. Tilgangur þessa verkefnis er að þróa tæki sem er sett á baujuna þegar hún er lögð. Tækið mælir mjög nákvæma staðsetningu með GNSS og GNSS leiðréttingargögnum og á sama tíma notar lítið afl. Til þess var LoRaWAN netkerfi sett upp þar sem leiðréttingargögn eru send frá LoRaWAN gátt til tækisins á baujunni sem notar þau til að öðlast staðsetningu sína með skekkju innan við einn metra. Leiðréttingargögnin eru sótt frá kerfi viðmiðunarstöðva sem er rekið af Landmælingum Íslands og heitir IceCORS. IceCORS streymir gögnunum á internetið gjaldfrjálst og eru þau sótt af Raspberry Pi tölvu sem sendir þau til gáttarinnar yfir Ethernet. Tækið á baujunni er ESP32 örtölva vædd LoRa sendi- viðtæki og GNSS viðtæki. Raspberry Pi tölvan og gáttin gætu ýmist verið sett á skipið sem leggur baujuna eða sett upp á landi þar sem góð yfirsýn er yfir þau svæði þar sem baujur verða lagðar. Prófanir á kerfinu leiddu í ljós að nákvæmni staðsetningar tækisins batnar verulega þegar leiðréttingar eru sendar til þess með LoRa og var skekkjan vel innan eins metra. Mælingar sýndu að hægt var að senda leiðréttingar allt að 15,5 km vegalengd meðan tækið náði slíkri nákvæmni.Vegagerði

Physics and Modeling of Various Hazardous Landslides

In 2014, the Varnes classification system for landslides was updated. Complex landslides can still be a problem to classify as the classification does not include the flow type in the hydrodynamical sense. Three examples of Icelandic landslides are presented and later used as case studies in order to demonstrate the methods suggested to analyze the flow. The methods are based on the different physical properties of the flow types of the slides. Three different flow types are presented, named type (i), (ii), and (iii). Types (i) and (ii) do not include turbulent flows and their flow paths are sometimes independent of the velocity. Type (iii) include high velocity flows; they are treated with the translator wave theory, where a new type of a slope factor is used. It allows the slide to stop when the slope has flattened out to the value that corresponds to the stable slope property of the flowing material. The type studies are for a fast slide of this type, also a large slip circle slide that turns into a fast-flowing slide farther down the path and finally a large slide running so fast that it can run for a kilometer on flat land where it stops with a steep front

Meteorological conditions during slush-flow release and their geomorphologic impact in Northwestern Iceland - the case-study from the Bíldudalur valley

International audienc

Distribution and frequency of snow-avalanche debris transfer in the distal part of colluvial cones in Central North Iceland

International audienc