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In June 2022, the southern part of Montana and the northern part of Yellowstone National Park experienced flooding along multiple watersheds, including the Yellowstone River. The flooding resulted from heavy snowmelt between June 10-13th, leading to record levels of river water elevation in most of the main tributaries to the Yellowstone River. Substantial damage occurred to residential, commercial, and transport infrastructure, however, no fatalities were reported. Estimated damages accumulate to approximately U.S. $29 million. The GEER reconnaissance effort, conducted between June 30th – July 4th, recorded geotechnical, geo-structural, and geomorphological observations of failures as well as successful mitigation of flood damage. In addition to traditional terrestrial photography and aerial imagery, the team collected (Light Detection Ranging (LIDAR) scanning, Structure for Motion (SfM) imagery, and Multispectral Imagery to establish point cloud models for case history analyses and post-reconnaissance failure analyses. 

Extreme highwater pool elevations in Pactola Reservoir, South Dakota in 2015 and 2019 resulted in massive shoreline erosion along the southern banks. This shoreline erosion occurred despite the geologic material being highly fractured rock with fracture dip angles approximately parallel to that of the subject hillside. The shale and siltstone in the upper 30 meters of the geology had weathered into silt and clay, leaving a matrix of 70% to 90% rock and 10% to 30% fine-grained soil. When highwater occurred, the silty portion of the shore materials eroded, while the remaining small amounts of highly plastic clay were insufficient to bind the weak and thinly bedded rock together, and rock slipped along the 15 to 30-degree fracture dip angle into the water. The shore erosion was arrested by a line of pine trees, and the erosion patterns show the effectiveness of tree roots to resist erosion in highly fractured rock. The erosion case history is presented with descriptions of several individual root systems that were effective in shore stabilization, as well as descriptions of several individual tree root systems that were ineffective in shore stabilization and the trees perished in the highwater evens and toppled. 

The foundation systems of mega-flora (i.e. very tall or large trees), have long been used as an analogy for modern shallow and deep foundations. Terzaghi referenced trees as the model for footings and pilings. However, the topology, form, materials, distribution, and function of the natural foundation system have very little in common with the shallow and deep foundation systems that geotechnical engineers design and construct. These natural foundation systems are resilient, robust, and adaptable; ideal templates for a new generation of anthropogenic foundation systems and new understanding of soil-structure interaction. In an effort to further biomimetic geotechnics, this paper will present a review of the actual topology, form, materials, distribution, and function of mega-flora foundations, highlighting key differences with man-made foundation systems, materials and designs. This paper will dispel common myths about these natural structures, giving engineers insights into their performance under complex and extreme loads. Several key species will be highlighted, with unique aspects of each species’ foundation system highlighted. Field measurements and observations of several natural foundation systems are included in the paper to highlight recent findings about these remarkable systems. 

The 2016 Central Italy earthquake sequence caused numerous landslides over a large area in the Central Apennines. As a result, the Geotechnical Extreme Events Reconnaissance Association (GEER) organized post-earthquake reconnaissance missions to collect perishable data. Given the challenging conditions following the earthquakes, the GEER team implemented a phased reconnaissance approach. This paper illustrates this approach and how it was used to document the largest and most impactful seismically induced landslides. This phased approach relied upon satellite-based interferometric damage proxy maps, preliminary published reports of observed landslides, digital imaging from small unmanned aerial vehicles (UAVs), traditional manual observations, and terrestrial laser scanning. Data collected from the reconnoitered sites were used to develop orthophotos and meshed three-dimensional digital surface models. These products can provide valuable information such as accurate measurements of landslide ground movements in complex topographic geometries or boulder runout distances from rock falls. The paper describes three significant landslide case histories developed and documented with the phased approach: Nera Valley, Village of Pescara del Tronto, and near the villages of Crognaleto and Cervaro. 

The Central Italy earthquake sequence nominally began on 24 August 2016 with a M6.1 event on a normal fault that produced devastating effects in the town of Amatrice and several nearby villages and hamlets. A major international response was undertaken to record the effects of this disaster, including surface faulting, ground motions, landslides, and damage patterns to structures. This work targeted the development of high-value case histories useful to future research. Subsequent events in October 2016 exacerbated the damage in previously affected areas and caused damage to new areas in the north, particularly the relatively large town of Norcia. Additional reconnaissance after a M6.5 event on 30 October 2016 documented and mapped several large landslide features and increased damage states for structures in villages and hamlets throughout the region. This paper provides an overview of the reconnaissance activities undertaken to document and map these and other effects, and highlights valuable lessons learned regarding faulting and ground motions, engineering effects, and emergency response to this disaster.