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Conclusions: The mechanism of plate tectonics is affected by many factors which are changing with time. This essay highlights recent discoveries that axial spin has an effect. We ask the geological community to consider the place of planet Earth in the Solar System, and how the orbital forces have changed over the past 4.5 billion years, and if we can find ways to test whether or not these forces are significant, and preserved in the rock record. The final publication is available at Springer via https://doi.org/10.1007/s12583-022-1748-4. [ABSTRACT FROM AUTHOR]

A new, fundamental catchment attribute called the hydrologic time scale τ governs the rate of delivery of runoff to a particular site, and is equal to ∫Qdt/∫∣dQ∣, where Q is discharge and t is time. The value of τ for any gauged site is readily calculated from tabulated discharge data by replacing the integrals with sums. This quantity, coupled with the square root of catchment area, A , form a coordinate pair that embodies the characteristic time and length scales for any catchment, which govern its flow dynamics. The fitting constants used in several unit hydrograph models are simple multiples of τ, so knowledge of τ allows rapid calibration of these models for the particular site, facilitating flow prediction from rainfall data. Values of τ reflect many different landscape attributes, but for multiple sub-basins in watersheds with homogeneous land use and lithologic conditions, they correlate linearly with A . The ratio A / τ provides a characteristic velocity that is high for channelized, flood-prone rivers, for flashy urban streams with high impervious cover, and for sites downstream of hydro-power dams. Sites with low velocities are resistant to flooding, as their landscapes have a greater ability to delay the delivery of runoff by retention, detention, and infiltration into the groundwater system. [ABSTRACT FROM AUTHOR]

Variations of reservoir water level and seasonal precipitation have reactivated or accelerated many reservoir landslides in the Three Gorges Reservoir area since impoundment in 2003. Updated daily monitoring data since 2017 reveals details about the step-like pattern of annual movement of the Baijiabao landslide, a large creeping landslide with a maximal cumulative surface displacement of 0.2 m over this 2-year period. The spatiotemporal deformation characteristics show that mass movement was greatest in 2017 and boundary cracks exhibit more frequent steps and are more sensitive to hydraulic factors than surface displacement. Acceleration periods are triggered when the reservoir water level falls below 153 m above mean sea level, with most annual movement occurring before the reservoir rises back to that critical level. The rate of daily surface movement is controlled by the daily variation of reservoir water level and by cumulative rainfall during the previous 1 to 7 days. The movement responses vary from different years and movement periods, but the one-factor critical-level model can effectively predict surface movement. The correlation between surface displacement rate and reservoir water level also comprehensively indicates the association between landslide movement and hydraulic factors including rainfall and variation of reservoir water level. Low reservoir level and its drawdown, and heavy or continuous rainfall, increase hydraulic gradients and change stress conditions, which destabilize the Baijiabao landslide and accelerate its surface movement. [ABSTRACT FROM AUTHOR]

New methods allow the direct computation of flood inundation maps from lidar data, independently of discharge estimates, hydraulic analysis, or defined cross sections. One method projects the interpolated profile of measured flood levels onto surrounding topography, creating a smooth inundation surface that is entirely based on data and geometrical relationships. A second method computes inundation maps for any simple function that relates the water surface to the elevation of the channel bottom, exploiting their known, sub-parallel character. A final method theoretically combines the elevation of the channel bottom and the upstream catchment area for points along the thalweg, all defined by lidar data. Historical data from stream gauges can be incorporated to generate inundation maps for floods having different return periods. The conceptual simplicity and realism of these maps facilitate data-based planning. [ABSTRACT FROM AUTHOR]

Monitoring data show that many landslides in the Three Gorges region, China, undergo step-like displacements in response to the managed, quasi-sinusoidal annual variations in reservoir level. This behavior is consistent with motion initiating when the reservoir water level falls below a critical level that is intrinsic to each landslide, with the subsequent displacement rate of the landslide being proportional to the water depth below that critical level. Most motion terminates when the water level rises back above the critical level, so the annual step size is the time integral of the instantaneous displacement rate. These responses are incorporated into a differential equation that is easily calibrated with monitoring data, allowing prediction of landslide movement from actual or anticipated reservoir level changes. Model successes include (1) initiation and termination of the annual sliding steps at the critical reservoir level, producing a series of steps; (2) prediction of variable step size, year to year; and (3) approximate prediction of the shape and size of each annual step. Annual rainfall correlates poorly with step size, probably because its effect on groundwater levels is dwarfed by the 30 m annual variations in the level of the Three Gorges Reservoir. Viscous landslide behavior is suggested. [ABSTRACT FROM AUTHOR]

Extensive USGS data tables and detailed, 1 m2 LiDAR surveys are used to determine the optimal power n that relates discharge (Q) to stage (h*) above channel bottom (ho) at 39 gauging stations on small streams in the St. Louis, Missouri area, all of which have catchments of 0.6 to 220 km2. Four different methodologies are employed to determine both n and ho: (1) optimizing linearity in a plot of Q1/nvs. local stage (hL) using USGS field measurements at each site; (2) optimizing linearity in a plot of Q1/nvs. hL using USGS rating tables at each site; (3) a mathematical inverse method applied to the same USGS rating tables; (4) use of LiDAR data on channel geometry to determine the power dependences of channel area A and hydraulic radius H on h*, combined with the Manning and rational equations to predict n. Of these methods, only methods 2 and 3 compare favorably, and these values compare poorly with Method 1 based on field data, and with method 4 based on theoretical and empirical relationships. Because Method 4 is predictive, it provides a useful alternative to methods 1–3 that are based on USGS field measurements, which are heavily weighted toward low discharges. We conclude that the apparent values of n in the USGS rating tables are systematically too low for small streams. [ABSTRACT FROM AUTHOR]

Natural rock often suffers from cyclic wetting–drying involving different water types, and the resulting deterioration may differ from laboratory tests using distilled water or salt solutions. An inappropriate estimation of this deterioration effect may lead to fatal geological hazards and engineering failures. A multiscale study is conducted to investigate the physical and mechanical features of sandstone in Three Gorges Reservoir region (TGR sandstone) subjected to cyclic wetting–drying of Yangtze River water. During this study, three types of water, i.e., Yangtze River water, ionized water having similar ion compositions as the Yangtze River water, and distilled water, are used for comparison. The results show that the multiscale physical properties including mineral compositions (especially calcite and albite), micro-pore parameters, computed tomography values, and macro-mechanical parameters (i.e., Young's modulus, uniaxial compression strength and tensile strength) are remarkably altered during the cyclic wetting–drying process. Significant correlations are found between these numerous multiscale properties. The results indicate that changes of mineral compositions and microstructure are the primary reasons for the deterioration of sandstone strength. The deterioration effect of distilled water on TGR sandstone is the least, while the effect of ionized water is the greatest, and that of river water being intermediate. These differences are ascribed to different chemical interactions, together with possible microorganism effects for river water, as microorganisms in river water potentially weaken the deterioration of cyclic wetting–drying of river water. In situ water is recommended for studying how rock properties are affected by water–rock interactions in real settings. [ABSTRACT FROM AUTHOR]