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Spur dikes (SD) are installed along the outer bank of a river to control river bank erosion. The first SD is more susceptible to failure due to toe scouring. A protective spur dike (PSD) is an effective measure to reduce the scouring around the nose of the first SD. In this study, experiments were conducted to determine the optimal location and height of the PSD to minimize scour depth at the nose of the first SD. The results indicate that the maximum scour depth depends on the height and distance of the PSD from the first SD. The best performance was observed when the ratio of PSD height to flow depth (HP/y) was 1.25, and the ratio of the PSD distance from the first SD to flow depth (XP/y) was 1.25. Scour depth at the nose of the first and second SDs was reduced by 54% and 32%, respectively. These findings suggest that PSDs can significantly reduce scour depth, thereby enhancing the effectiveness and stability of SDs. KEYWORDS river engineering scour flow separation permeable spur dike protective spur dike

Interactions between the elastic magma chamber and the variable flow resistance of conduits control volcanic eruptions. Recent geodetic observations have revealed complex conduit deformations, especially in inclined dikes, which traditional models have struggled to capture. In this study, we introduce a simplified coupled model that explicitly accounts for magma flow within a nonuniform, elastically deformable inclined dike conduit under the influence of edifice loading. Dimensional analysis reduces the governing equations to an advection–diffusion type equation, controlled by two key dimensionless parameters representing the relative deformability of the conduit and the contribution of gravitational and pressure gradient forces. Numerical simulations demonstrate that these parameters govern the regime of pressure propagation. Specifically, deformation driven by large overpressure can significantly increase effusion rates and induce response delays between different depths. Applying this model to the 2018 Kilauea eruption, we show that the observed response delays and the spatial pattern of deformation (simultaneous expansion and contraction) are well-reproduced in a regime, where advective effects dominate. Our findings provide a refined theoretical framework for understanding volcanic conduit behavior in complex geometries and could explain observed non-uniform deformation phenomena. Graphical abstract

Seismicity and ground deformation measurements show how a recent segmented dyke intrusion in the Bárðarbunga volcanic system in Iceland grew laterally for 45 kilometres over 14 days; dyke opening and seismicity were focused at the most distal segment, where lateral dyke growth with segment barrier breaking by pressure build-up occurred. Dyke growth in Iceland's largest volcanic system A recent segmented dyke intrusion (a sheet of magma tracing its way through and across the surrounding rocks) is reshaping the landscape in the Bárðarbunga volcanic system in Iceland. Freysteinn Sigmundsson and co-authors have used seismicity and ground deformation mapped by global positioning system (GPS) and satellite radar images to show that the dyke grew laterally for 45 km during a 14-day period in August 2014. Dyke opening and seismicity were focused at the most distal segment, where lateral dyke growth with segment barrier breaking by pressure build-up occurred. Dyke growth was slowed by an effusive fissure eruption near the end of the dyke. Crust at many divergent plate boundaries forms primarily by the injection of vertical sheet-like dykes, some tens of kilometres long 1 . Previous models of rifting events indicate either lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens 2 , 3 , 4 , or magma flowing vertically into dykes from an underlying source 5 , 6 , with the role of topography on the evolution of lateral dykes not clear. Here we show how a recent segmented dyke intrusion in the Bárðarbunga volcanic system grew laterally for more than 45 kilometres at a variable rate, with topography influencing the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred primarily over 14 days, was revealed by propagating seismicity, ground deformation mapped by Global Positioning System (GPS), interferometric analysis of satellite radar images (InSAR), and graben formation. The strike of the dyke segments varies from an initially radial direction away from the Bárðarbunga caldera, towards alignment with that expected from regional stress at the distal end. A model minimizing the combined strain and gravitational potential energy explains the propagation path. Dyke opening and seismicity focused at the most distal segment at any given time, and were simultaneous with magma source deflation and slow collapse at the Bárðarbunga caldera, accompanied by a series of magnitude M  > 5 earthquakes. Dyke growth was slowed down by an effusive fissure eruption near the end of the dyke. Lateral dyke growth with segment barrier breaking by pressure build-up in the dyke distal end explains how focused upwelling of magma under central volcanoes is effectively redistributed over long distances to create new upper crust at divergent plate boundaries.

In many estuarine areas around the world, the safety of human societies depends on the functioning of embankments (dikes) that provide protection against river floods and storm tides. Vegetation on land-side slopes protects these embankments from erosion by heavy rains or overtopping waves. We carried out a field experiment to investigate the effect of plant species diversity on soil loss through erosion on a simulated dike. The experiment included four diversity treatments (1, 2, 4, and 8 species). In the third year of the experiment, we measured net annual soil loss by measuring erosion losses every 2 weeks. We show that loss of plant species diversity reduces erosion resistance on these slopes: net annual soil loss increased twofold when diversity declines fourfold. The different plant species had strongly diverging effects on soil erosion, both in the single-species and in the multi-species plots. Analysis of the dynamics of the individual species revealed that the main mechanism explaining the strong effects of plant species diversity on soil erosion is the com pensation or insurance effect, that is, the capacity of diverse communities to supply species to take over the functions of species that went extinct as a consequence of fluctuating environmental conditions. We conclude that the protection and restoration of diverse plant communities on embankments and other vegetated slopes are essential to minimize soil erosion, and can contribute to greater safety in the most densely populated areas of the world.

Lithium is a rare metal widely used in the renewable energy industry. The Altyn region in Xinjiang, China, contains abundant granitic pegmatite-type lithium resources; however, the deeply incised and complex terrain limits the accuracy of conventional two-dimensional remote sensing approaches for dike identification and segmentation. To address this limitation, a remote sensing segmentation method incorporating terrain information was proposed. A digital elevation model (DEM) derived from LiDAR data, together with its associated topographic factors, was integrated into the Spatial–Spectral Mamba framework to enable the joint utilization of spectral and terrain features. Rather than performing explicit three-dimensional geometric modeling, the proposed approach enhances a two-dimensional segmentation framework by introducing elevation-derived information, allowing the model to capture terrain-related spatial variations of pegmatite dikes. This design enables improved representation of both the planar distribution and terrain-influenced morphological characteristics of dikes under deeply incised conditions. The Xichanggou lithium deposit in the Altyn region is a large-scale, economically valuable pegmatite-type lithium deposit, and was therefore selected as the study area for pegmatite dike segmentation. The results demonstrated that, compared with conventional two-dimensional approaches and representative machine learning methods, the proposed method achieved higher segmentation accuracy in complex terrain. Improvements were also observed in the continuity and spatial consistency of the extracted dike patterns. Field verification indicated that the major pegmatite dikes delineated by the model were highly consistent with their actual surface exposures. Sampling analyses further confirmed the validity and reliability of the identification results. Overall, the terrain-integrated remote sensing segmentation approach exhibited good applicability and robustness under deeply incised and complex geomorphological conditions.

In the river system, the deployment of impermeable dikes often leads to significant morphological changes, including scouring due to strong momentum exchanges between the dike field and the main flow. This presents a challenge in managing riverbank erosion effectively. This study aims to analyze the impact of alternative length layouts of dikes on flow dynamics in an open channel, with the focus on minimizing the scour responsible factors around dikes. Employing a Computational Fluid Dynamic approach, this research investigates flow behavior around a series of emerged and a protective dike with varying lengths. The study utilizes the Reynolds Stress Model (RSM) to capture detailed flow characteristics such as velocity, turbulence, and recirculation eye displacement both upstream and downstream of the protective dike. The results showed that employing a protective dike with 0.5 L -0.6 L (where L represents the dike length) can significantly reduce depth averaged velocity and turbulent kinetic energy near the first dike head by 35% and 41%, respectively. The study recommends constructing protective dikes with optimized dimensions to mitigate the adverse impacts of momentum exchanges, thereby enhancing riverbank protection and reducing erosion risks.

Canal dikes in low‐lying polders, as well as in other regions worldwide, are critical infrastructure for flood protection and water management. The subsurface water conditions can cause dike failures during excessive rainfall and prolonged periods of drought. There is a lack of multi‐year monitoring of subsurface water conditions in canal dikes and an insufficient understanding of their geohydrological behavior. This study provides and analyses a novel multiyear data set of soil moisture and hydraulic heads (from February 2020 until March 2023) from a monitoring network covering various canal dikes with different characteristics in the western Netherlands. The data, including two extremely dry summers, highlight the impact of meteorological variations on the subsurface water conditions. Non‐hydrostatic hydraulic head levels were observed during droughts that can be detrimental to dike stability and that are often not accounted for in safety assessments for drought situations. The effectiveness of various meteorological drought indicators applied to subsurface water conditions was evaluated: the precipitation deficit is the most reliable measure and outperforms the standardized drought indicators (SPEI and SPI). The drought recovery of dikes was analyzed to understand seasonal transitions and the sequence of different failure mechanisms, during dry and wet situations. This analysis also reveals differences between meteorological, soil moisture, and groundwater droughts, highlighting soil's storage capacity after drought and the limitations of meteorological drought indicators as proxies for soil moisture and groundwater. The insights from this study enhance assessments, inspection procedures and the identification of weak spots of dikes and other earthworks of infrastructure. Key Points Novel multiyear observations of soil moisture and hydraulic heads from various canal dikes reveal geohydrological behavior The precipitation deficit emerges as the most reliable meteorological drought indicator and can be used as an indicator of dike safety The drought recovery lasted 4.5 months in 2022, which is important for the transition between seasons and different failure mechanisms

Natural hazard prediction and efficient crust exploration require dense seismic observations both in time and space. Seismological techniques provide ground-motion data, whose accuracy depends on sensor characteristics and spatial distribution. Here we demonstrate that dynamic strain determination is possible with conventional fibre-optic cables deployed for telecommunication. Extending recently distributed acoustic sensing (DAS) studies, we present high resolution spatially un-aliased broadband strain data. We recorded seismic signals from natural and man-made sources with 4-m spacing along a 15-km-long fibre-optic cable layout on Reykjanes Peninsula, SW-Iceland. We identify with unprecedented resolution structural features such as normal faults and volcanic dykes in the Reykjanes Oblique Rift, allowing us to infer new dynamic fault processes. Conventional seismometer recordings, acquired simultaneously, validate the spectral amplitude DAS response between 0.1 and 100 Hz bandwidth. We suggest that the networks of fibre-optic telecommunication lines worldwide could be used as seismometers opening a new window for Earth hazard assessment and exploration. Imaging the internal structure of faults remains challenging using conventional seismometers. Here, the authors use fibre-optic cables used for telecommunications to obtain strain data and identify faults and volcanic dykes in Iceland and suggest that fibre-optic cables could be used for hazard assessment.

Spur dikes are river protection structures typically used for flow diversion from erodible banks. However, scouring might be a severe problem that compromises their stability and, consequently, their hydraulic function. This paper aims to study the maximum scour depth at permeable and angled spur dikes under hydrographs of different duration. Experiments were carried out in a rectangular channel 10 m long, 0.76 m wide, and 0.6 m deep. The mobile bed was made of nearly uniform sand with a median grain size of 0.8 mm. A total of 36 new experiments were performed with a detailed data collection over the time (i.e., 216 datasets), which could provide a useful contribution to the topic. The impact of the spur dike orientation angle, θ, and the degree of permeability, φ, on the temporal scour evolution were explored. Results were found physically consistent and revealed that the spur dike permeability implies a significant attenuation of the scouring processes in comparison to the impermeable spur dikes and generally its effect is more beneficial than that from a favorable orientation angle. The differences in percentage between the maximum scour depth for impermeable spur dikes and the maximum scour depths for various degrees of spur dike permeability were found ranging from 44% (at φ = 33% and θ = 60°) up to 88% (at φ = 66% and θ = 120°). Other results include the effect of the hydrograph base-time on the scour depth and the comparison between scouring processes under steady and unsteady flow conditions. By quadrupling the hydrograph base-time, keeping constant the peak and base flood discharges, the maximum scour depths increased by about 29%, 42%, and 25% in case of impermeable spur dike, spur dike with 33% degree of permeability, and spur dike with 66% degree of permeability. Furthermore, starting from dimensional analysis a new empirical model (with coefficient of determination R2 equal to 0.94) is introduced to predict the time-dependent scour depth due to the passage of a flood wave. The model suggests that the main independent dimensionless variables which control local scour processes are: the densimetric Froude number, the time t normalized to the hydrograph base-time, the degree of permeability, and the orientation angle. These dimensionless variables would generalize the laboratory results to the real-world scenarios, although caution should always be taken because of possible scale effects.