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Scaling between volume and runout of rock avalanches explained by a modified Voellmy rheology 用改进的伏尔米流变学解释岩崩体积和冲出量之间的比例关系
IF 3.4 2区 地球科学
Earth Surface Dynamics Pub Date : 2024-01-23 DOI: 10.5194/esurf-12-219-2024
Stefan Hergarten
{"title":"Scaling between volume and runout of rock avalanches explained by a modified Voellmy rheology","authors":"Stefan Hergarten","doi":"10.5194/esurf-12-219-2024","DOIUrl":"https://doi.org/10.5194/esurf-12-219-2024","url":null,"abstract":"Abstract. Rock avalanches reach considerably greater runout lengths than predicted by Coulomb friction. While it has been known for a long time that runout length increases with volume, explaining the increase qualitatively is still a challenge. In this study, the widely used Voellmy rheology is reinterpreted and modified. Instead of adding a Coulomb friction term and a velocity-dependent term, the modified rheology assigns the two terms to different regimes of velocity. While assuming a transition between Coulomb friction and flow at a given velocity is the simplest approach, a reinterpretation of an existing model for the kinetic energy of random particle motion predicts a dependence of the crossover velocity on the thickness of the rock avalanche. Analytical solutions for a lumped mass on a simple 1D topography reveal the existence of a slope-dominated and a height-dominated regime within the regime of flow. In the slope-dominated regime, the kinetic energy at the foot of the slope depends mainly on the slope angle, while the absolute height relative to the valley floor has little effect, and vice versa. Both regimes can be distinguished by the ratio of a length scale derived from the rheology and the length scale of the topography. Long runout occurs in the height-dominated regime. In combination with empirical relations between volume, thickness, and height, the approach based on the random kinetic energy model reproduces the scaling of runout length with volume observed in nature very well.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":"51 2 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139558917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Drainage rearrangement in an intra-continental mountain belt: A case study from the central South Tian Shan, Kyrgyzstan 大陆内部山地带的排水重排:吉尔吉斯斯坦南天山中部案例研究
IF 3.4 2区 地球科学
Earth Surface Dynamics Pub Date : 2024-01-19 DOI: 10.5194/egusphere-2023-2651
Lingxiao Gong, Peter van der Beek, Taylor F. Schildgen, Edward R. Sobel, Simone Racano, Apolline Mariotti
{"title":"Drainage rearrangement in an intra-continental mountain belt: A case study from the central South Tian Shan, Kyrgyzstan","authors":"Lingxiao Gong, Peter van der Beek, Taylor F. Schildgen, Edward R. Sobel, Simone Racano, Apolline Mariotti","doi":"10.5194/egusphere-2023-2651","DOIUrl":"https://doi.org/10.5194/egusphere-2023-2651","url":null,"abstract":"<strong>Abstract.</strong> Fluvial drainage patterns in orogenic belts reflect the interaction between tectonics, climate, and lithology. The central South Tian Shan displays a complex fluvial drainage pattern that shifts from longitudinal (flowing parallel to mountain ranges) in the west to transverse (flowing across ranges) in the east. Whether such drainage patterns reflect underlying patterns of tectonic deformation, lithology, climatic changes, or the influence of surface processes within a drainage basin is often unclear. We focus here on the anomalously large Saryjaz catchment of SE Kyrgyzstan, which marks the transition between longitudinal and transverse drainage. We analyse topographic and fluvial metrics including slope, river steepness (<em>k<sub>sn</sub></em>) and the integral proxy <em>χ</em> along the river profile, and map the spatial distribution and characteristics of knickpoints to discern the possible controls on the observed drainage pattern. We discriminate between knickpoints of different origin: tectonic, lithologic, glacial, and those linked to transient waves of incision. We find a series of transient knickpoints in tributaries downstream of a sharp 180ᵒ bend in the main stem of the Saryjaz River, which also marks a striking increase in channel steepness. Both observations indicate accelerated incision along this lower reach of the catchment. Knickpoint elevations decrease downstream, whereas incision depth, <em>χ</em> values of knickpoints (measured from the tributary junctions) and <em>k<sub>sn</sub></em> values and ratios are constant among tributaries. These results suggest that incision is driven “top-down” by a large-magnitude river-capture event rather than “bottom-up” by base-level fall. We estimate an erodibility parameter from <sup>10</sup>Be derived catchment-average denudation rates and use this to estimate the celerity of knickpoints. We find that the knickpoints started retreating at a similar time, between ca. 1.5 and 4.4 Myr ago. Considering the river patterns and the timing constraints, we suggest that this capture event was likely driven by the overfill of Neogene intermontane basins, potentially affected by both tectonic and climate factors.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":"15 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139508548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Statistical characterization of erosion and sediment transport mechanics in shallow tidal environments – Part 2: Suspended sediment dynamics 浅海潮汐环境中侵蚀和沉积物迁移力学的统计特征--第 2 部分:悬浮沉积物动力学
IF 3.4 2区 地球科学
Earth Surface Dynamics Pub Date : 2024-01-18 DOI: 10.5194/esurf-12-201-2024
Davide Tognin, Andrea D'Alpaos, Luigi D'Alpaos, Andrea Rinaldo, Luca Carniello
{"title":"Statistical characterization of erosion and sediment transport mechanics in shallow tidal environments – Part 2: Suspended sediment dynamics","authors":"Davide Tognin, Andrea D'Alpaos, Luigi D'Alpaos, Andrea Rinaldo, Luca Carniello","doi":"10.5194/esurf-12-201-2024","DOIUrl":"https://doi.org/10.5194/esurf-12-201-2024","url":null,"abstract":"Abstract. A proper understanding of sediment resuspension and transport processes is key to the morphodynamics of shallow tidal environments. However, a complete spatial and temporal coverage of suspended sediment concentration (SSC) to describe these processes is hardly available, preventing the effective representation of depositional dynamics in long-term modelling approaches. Through aiming to couple erosion and deposition dynamics in a unique synthetic theoretical framework, we here investigate SSC dynamics, following a similar approach to that adopted for erosion (D'Alpaos et al., 2024). The analysis with the peak-over-threshold theory of SSC time series computed using a fully coupled, bi-dimensional model allows us to identify interarrival times, intensities, and durations of over-threshold events and test the hypothesis of modelling SSC dynamics as a Poisson process. The effects of morphological modifications on spatial and temporal SSC patterns are investigated in the Venice Lagoon, for which several historical configurations in the last 4 centuries are available. Our results show that, similar to erosion events, SSC can be modelled as a marked Poisson process in the intertidal flats for all the analysed morphological lagoon configurations because exponentially distributed random variables describe over-threshold events well. Although erosion and resuspension are intimately intertwined, erosion alone does not suffice to describe also SSC because of the non-local dynamics due to advection and dispersion processes. The statistical characterization of SSC events completes the framework introduced for erosion mechanics, and together, they represent a promising tool to generate synthetic, yet realistic, time series of shear stress and SSC for the long-term modelling of tidal environments.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":"41 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139497341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Past anthropogenic land use change caused a regime shift of the fluvial response to Holocene climate change in the Chinese Loess Plateau 过去人为土地利用变化导致中国黄土高原全新世气候变化的河川响应机制转变
IF 3.4 2区 地球科学
Earth Surface Dynamics Pub Date : 2024-01-18 DOI: 10.5194/esurf-12-163-2024
Hao Chen, Xianyan Wang, Yanyan Yu, Huayu Lu, Ronald Van Balen
{"title":"Past anthropogenic land use change caused a regime shift of the fluvial response to Holocene climate change in the Chinese Loess Plateau","authors":"Hao Chen, Xianyan Wang, Yanyan Yu, Huayu Lu, Ronald Van Balen","doi":"10.5194/esurf-12-163-2024","DOIUrl":"https://doi.org/10.5194/esurf-12-163-2024","url":null,"abstract":"Abstract. The Wei River catchment in the southern part of the Chinese Loess Plateau (CLP) is one of the centers of the agricultural revolution in China. The area has experienced intense land use changes since ∼6000 BCE, which makes it an ideal place to study the response of fluvial systems to past anthropogenic land cover change (ALCC). We apply a numerical landscape evolution model that combines the Landlab landscape evolution model with an evapotranspiration model to investigate the direct and indirect effects of ALCC on hydrological and morphological processes in the Wei River catchment since the mid-Holocene. The results show that ALCC has not only led to changes in discharge and sediment load in the catchment but also affected their sensitivity to climate change. When the proportion of agricultural land area exceeded 50 % (around 1000 BCE), the sensitivity of discharge and sediment yield to climate change increased abruptly indicating a regime change in the fluvial catchment. This was associated with a large sediment pulse in the lower reaches. The model simulation results also show a link between human settlement, ALCC and floodplain development: changes in agricultural land use led to downstream sediment accumulation and floodplain development, which in turn resulted in further spatial expansion of agriculture and human settlement.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":"48 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139497491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Statistical characterization of erosion and sediment transport mechanics in shallow tidal environments – Part 1: Erosion dynamics 浅海潮汐环境中侵蚀和沉积物迁移力学的统计特征 - 第 1 部分:侵蚀动力学
IF 3.4 2区 地球科学
Earth Surface Dynamics Pub Date : 2024-01-18 DOI: 10.5194/esurf-12-181-2024
Andrea D'Alpaos, Davide Tognin, Laura Tommasini, Luigi D'Alpaos, Andrea Rinaldo, Luca Carniello
{"title":"Statistical characterization of erosion and sediment transport mechanics in shallow tidal environments – Part 1: Erosion dynamics","authors":"Andrea D'Alpaos, Davide Tognin, Laura Tommasini, Luigi D'Alpaos, Andrea Rinaldo, Luca Carniello","doi":"10.5194/esurf-12-181-2024","DOIUrl":"https://doi.org/10.5194/esurf-12-181-2024","url":null,"abstract":"Abstract. Reliable descriptions of erosion events are foundational to effective frameworks relevant to the fate of tidal landscape evolution. Besides the rhythmic, predictable action of tidal currents, erosion in shallow tidal environments is strongly influenced by the stochastic wave-induced bottom shear stress (BSS), mainly responsible for sediment resuspension on tidal flats. However, the absence of sufficiently long, measured time series of BSS prevents a direct analysis of the combined tide- and wave-driven erosion dynamics and its proper representation in long-term morphodynamic models. Here we test the hypothesis of describing erosion dynamics in shallow tidal environments as a Poisson process by analysing, with the peak-over-threshold theory, the BSS time series computed using a fully coupled, bi-dimensional numerical model. We perform this analysis on the Venice Lagoon, Italy, taking advantage of several historical surveys done in the last 4 centuries, which allow us to investigate the effects of morphological modifications on spatial and temporal erosion patterns. Our analysis suggests that erosion events on intertidal flats can effectively be modelled as a marked Poisson process in different morphological configurations because the interarrival times, durations, and intensities of the over-threshold exceedances are always well described by exponentially distributed random variables. The resulting statistical characterization allows a straightforward computation of morphological indicators, such as the erosion work, and paves the way for a novel synthetic, yet reliable, approach for the long-term morphodynamic modelling of tidal environments.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":"84 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139497389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Geomorphological and hydrological controls on sediment export in earthquake-affected catchments in the Nepal Himalaya 尼泊尔喜马拉雅山脉受地震影响流域沉积物输出的地貌和水文控制因素
IF 3.4 2区 地球科学
Earth Surface Dynamics Pub Date : 2024-01-16 DOI: 10.5194/esurf-12-135-2024
Emma L. S. Graf, Hugh D. Sinclair, Mikaël Attal, Boris Gailleton, Basanta Raj Adhikari, Bishnu Raj Baral
{"title":"Geomorphological and hydrological controls on sediment export in earthquake-affected catchments in the Nepal Himalaya","authors":"Emma L. S. Graf, Hugh D. Sinclair, Mikaël Attal, Boris Gailleton, Basanta Raj Adhikari, Bishnu Raj Baral","doi":"10.5194/esurf-12-135-2024","DOIUrl":"https://doi.org/10.5194/esurf-12-135-2024","url":null,"abstract":"Abstract. Large earthquakes can contribute to mountain growth by building topography but also contribute to mass removal from mountain ranges through widespread mass wasting. On annual to decadal or centennial timescales, large earthquakes also have the potential to significantly alter fluvial sediment dynamics if a significant volume of the sediment generated reaches the fluvial network. In this contribution, we focus on the Melamchi–Indrawati and Bhote Koshi rivers in central Nepal, which have both experienced widespread landsliding associated with the 2015 Gorkha (Nepal) earthquake. Using a time series of high-resolution satellite imagery, we have mapped exposed sediment along the rivers from 2012–2021 to identify zones of active channel deposition and document changes over time. Counter to expectations, we show negligible increases in coarse-sediment accumulation along both river corridors since the Gorkha earthquake. However, an extremely high-concentration flow event on 15 June 2021 caused an approximately 4-fold increase in exposed sediment along a 30 km reach of the channel with up to 12 m of channel aggradation in the Melamchi–Indrawati rivers; this event was localised and did not impact the neighbouring Bhote Koshi catchment. Based on published reports, new helicopter-based photography, and satellite data, we demonstrate that this event was sourced from a localised rainfall event between 4500 and 4800 m and that a significant fraction of the sediment was supplied from sources that were unrelated to the landslides generated by the Gorkha earthquake.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":"14 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139475424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
River suspended-sand flux computation with uncertainty estimation, using water samples and high-resolution ADCP measurements 利用水样和高分辨率 ADCP 测量,计算河流悬沙通量并进行不确定性估算
IF 3.4 2区 地球科学
Earth Surface Dynamics Pub Date : 2024-01-11 DOI: 10.5194/egusphere-2023-2348
Jessica Laible, Guillaume Dramais, Jérôme Le Coz, Blaise Calmel, Benoît Camenen, David J. Topping, William Santini, Gilles Pierrefeu, François Lauters
{"title":"River suspended-sand flux computation with uncertainty estimation, using water samples and high-resolution ADCP measurements","authors":"Jessica Laible, Guillaume Dramais, Jérôme Le Coz, Blaise Calmel, Benoît Camenen, David J. Topping, William Santini, Gilles Pierrefeu, François Lauters","doi":"10.5194/egusphere-2023-2348","DOIUrl":"https://doi.org/10.5194/egusphere-2023-2348","url":null,"abstract":"<strong>Abstract.</strong> Measuring suspended-sand fluxes in rivers remains a scientific challenge due to their high spatial and temporal variability. To capture the vertical and lateral gradients of concentration in the cross section, measurements with point samples are performed. However, the uncertainty related to these measurements is rarely evaluated, as few studies of the major sources of error exist. Therefore, the aim of this study is to develop a method determining the cross sectional sand flux and estimating its uncertainty. This SDC (for Sand Discharge Computing) method combines suspended-sand concentrations from point samples with ADCP (Acoustic Doppler Current Profiler) high-resolution depth and velocity measurements. The MAP (for Multitransect Averaged Profile) method allows to obtain an average of several ADCP transects on a regular grid, including the unmeasured areas. The suspended-sand concentrations are integrated vertically by fitting a theoretical exponential suspended-sand profile to the data using Bayesian modelling. The lateral integration is based on the water depth as a proxy for the local bed shear stress to evaluate the bed concentration and sediment diffusion along the river cross-section to evaluate the bed concentration and sediment diffusion along the river cross-section. The estimation of uncertainty combines ISO standards and semi-empirical methods with a Bayesian approach to estimate the uncertainty due to the vertical integration. The new method is applied to data collected in four rivers under various hydro-sedimentary conditions: the Colorado, Rhône, Isère and Amazon Rivers, with computed flux uncertainties ranging between 18 and 32 %. The relative difference between the suspended-sand flux in 21 cases calculated with the proposed SDC method compared to the ISO 4363 method ranges between -16 and +3 %. This method, which comes with a flexible, open-source code, is the first proposing an applicable uncertainty estimation, that could be adapted to other flux computation methods.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":"44 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139424024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Optimization of passive acoustic bedload monitoring in rivers by signal inversion 通过信号反演优化河流被动声学床载监测
IF 3.4 2区 地球科学
Earth Surface Dynamics Pub Date : 2024-01-11 DOI: 10.5194/esurf-12-117-2024
Mohamad Nasr, Adele Johannot, Thomas Geay, Sebastien Zanker, Jules Le Guern, Alain Recking
{"title":"Optimization of passive acoustic bedload monitoring in rivers by signal inversion","authors":"Mohamad Nasr, Adele Johannot, Thomas Geay, Sebastien Zanker, Jules Le Guern, Alain Recking","doi":"10.5194/esurf-12-117-2024","DOIUrl":"https://doi.org/10.5194/esurf-12-117-2024","url":null,"abstract":"Abstract. Recent studies have shown that hydrophone sensors can monitor bedload flux in rivers by measuring the self-generated noise (SGN) emitted by bedload particles when they impact the riverbed. However, experimental and theoretical studies have shown that the measured SGN depends not only on bedload flux intensity but also the propagation environment, which differs between rivers. Moreover, the SGN can propagate far from the acoustic source and be well measured at distant river positions without bedload transport. It has been shown that this dependency of the measured SGN data on the propagation environment can significantly affect the performance of monitoring bedload flux by hydrophone techniques. In this article, we propose an inversion model to solve the problem of the SGN propagation and integration effect. In this model, we assume that the riverbed acts as SGN source areas with intensity proportional to the local bedload flux. The inversion model locates the SGN sources and calculates their corresponding acoustic power by solving a system of linear algebraic equations, accounting for the actual measured cross-sectional acoustic power (acoustic mapping) and attenuation properties. We tested the model using data from measured bedload SGN profiles (acoustic mapping with a drift boat) and bedload flux profiles (direct sampling with an Elwha sampler) acquired during two field campaigns conducted in 2018 and 2021 on the Giffre river in the French Alps. Results confirm that the bedload flux measured at different verticals on the river cross-section correlates more with the inversed acoustic power than measured acoustic power. Moreover, it was possible to fit data from the two field campaigns with a common curve after inversion, which was not possible with the measured acoustic data. The results of the inversion model, compared to measured data, show the importance of considering the propagation effect when using the hydrophone technique and offer new perspectives for the calibration of bedload flux with SGN in rivers.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":"29 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139462321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Stochastic properties of coastal flooding events – Part 2: Probabilistic analysis 沿海洪水事件的随机特性--第 2 部分:概率分析
IF 3.4 2区 地球科学
Earth Surface Dynamics Pub Date : 2024-01-10 DOI: 10.5194/esurf-12-105-2024
Byungho Kang, Rusty A. Feagin, Thomas Huff, Orencio Durán Vinent
{"title":"Stochastic properties of coastal flooding events – Part 2: Probabilistic analysis","authors":"Byungho Kang, Rusty A. Feagin, Thomas Huff, Orencio Durán Vinent","doi":"10.5194/esurf-12-105-2024","DOIUrl":"https://doi.org/10.5194/esurf-12-105-2024","url":null,"abstract":"Abstract. Low-intensity but high-frequency coastal flooding, also known as nuisance flooding, can negatively affect low-lying coastal communities with potentially large socioeconomic effects. Partially driven by wave runup, this type of flooding is difficult to predict due to the complexity of the processes involved. Here, we present the results of a probabilistic analysis of flooding events measured on an eroded beach at the Texas coast. A high-resolution time series of the flooded area was obtained from pictures using convolutional neural network (CNN)-based semantic segmentation methods, as described in the first part of this contribution. After defining flooding events using a peak-over-threshold method, we found that their size follows an exponential distribution. Furthermore, consecutive flooding events were uncorrelated at daily timescales but correlated at hourly timescales, as expected from tidal and day–night cycles. Our measurements confirm the broader findings of a recent multi-site investigation of the probabilistic structure of high-water events that used a semi-empirical formulation for wave runup. Indeed, we found a relatively good statistical agreement between our CNN-based empirical flooding data and predictions using total-water-level estimations. As a consequence, our work supports the validity of a relatively simple probabilistic model of high-frequency coastal flooding driven by wave runup that can be used in coastal risk management and landscape evolution models.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":"66 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139420806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Field monitoring of pore water pressure in fully and partly saturated debris flows at Ohya landslide scar, Japan 日本大谷滑坡疤痕完全和部分饱和泥石流孔隙水压力的实地监测
IF 3.4 2区 地球科学
Earth Surface Dynamics Pub Date : 2024-01-09 DOI: 10.5194/esurf-12-67-2024
Shunsuke Oya, Fumitoshi Imaizumi, Shoki Takayama
{"title":"Field monitoring of pore water pressure in fully and partly saturated debris flows at Ohya landslide scar, Japan","authors":"Shunsuke Oya, Fumitoshi Imaizumi, Shoki Takayama","doi":"10.5194/esurf-12-67-2024","DOIUrl":"https://doi.org/10.5194/esurf-12-67-2024","url":null,"abstract":"Abstract. The characteristics of debris flows (e.g., mobility, sediment concentration, erosion, and deposition of sediment) are dependent on the pore water pressure in the flows. Therefore, understanding the magnitude of pore water pressure in debris flows is essential for improving debris flow mitigation measures. Notably, the pore water pressure in a partly saturated flow, which contains an unsaturated layer in its upper part, has not been previously understood due to a lack of data. The monitoring performed in Ohya landslide scar, central Japan, allowed us to obtain the data on the pore water pressure in fully and partly saturated flows during four debris flow events. In some partly and fully saturated debris flows, the pore water pressure at the channel bed exceeded the hydrostatic pressure of clean water. The depth gradient of the pore water pressure in the lower part of the flow, monitored using water pressure sensors at multiple depths, was generally higher than the depth-averaged gradient of the pore water pressure from the channel bed to the surface of the flow. The low gradient of the pore water pressure in the upper part of partly saturated debris flows may be affected by the low hydrostatic pressure due to unsaturation of the flow. Bagnold number, Savage number, and friction number indicated that frictional force dominated in the partly saturated debris flows. Excess pore water pressure was observed in the lower part of partly saturated surges. The excess pore water pressure may have been generated by the contraction of interstitial water and have been maintained due to low hydraulic diffusivity in debris flows. The pore water pressure at the channel bed of fully saturated flow was generally similar to the hydrostatic pressure of clean water, while some saturated surges portrayed higher pore water pressure than the hydrostatic pressure. The travel distance of debris flows, investigated by the structure-from-motion technique using uncrewed aerial vehicle (UAV-SfM) and the monitoring of time-lapse cameras, was long during a rainfall event with high intensity even though the pore water pressure in the flow was not significantly high. We conclude that the excess pore water pressure is present in many debris flow surges and an important mechanism in debris flow surge behaviors.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":"15 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139411580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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