Pub Date : 2024-04-16DOI: 10.5194/egusphere-2024-792
Janbert Aarnink, Tom Beucler, Marceline Vuaridel, Virginia Ruiz-Villanueva
Abstract. Instream large wood (i.e., downed trees, branches and roots larger than 1 m in length and 10 cm diameter) has essential geopmorphological and ecological functions supporting the health of river ecosystems. Still, even though its transport during floods may pose a risk, it is rarely observed and, therefore, poorly understood. This paper presents a novel approach to detect pieces of instream wood from video. The approach uses a Convolutional Neural Network to detect wood automatically. We sampled data to represent different wood transport conditions, combining 20 datasets to yield thousands of instream wood images. We designed multiple scenarios using different data subsets with and without data augmentation and analyzed the contribution of each one to the effectiveness of the model using k-fold cross-validation. The mean average precision of the model varies between 35 and 93 percent, and is highly influenced by the quality of the data which it detects. When the image resolution is low, the identified components in the labeled pieces, rather than exhibiting distinct characteristics such as bark or branches, appear more akin to amorphous masses or 'blobs'. We found that the model detects wood with a mean average precision of 67 percent when using a 418 pixels input image resolution. Also, improvements of up to 23 percent could be achieved in some instances and increasing the input resolution raised the weighted mean average precision to 74 percent. We show that the detection performance on a specific dataset is not solely determined by the complexity of the network or the training data. Therefore, the findings of this paper can be used when designing a custom wood detection network. With the growing availability of flood-related videos featuring wood uploaded to the internet, this methodology facilitates the quantification of wood transport across a wide variety of data sources.
{"title":"Automatic detection of instream large wood in videos using deep learning","authors":"Janbert Aarnink, Tom Beucler, Marceline Vuaridel, Virginia Ruiz-Villanueva","doi":"10.5194/egusphere-2024-792","DOIUrl":"https://doi.org/10.5194/egusphere-2024-792","url":null,"abstract":"<strong>Abstract.</strong> Instream large wood (i.e., downed trees, branches and roots larger than 1 m in length and 10 cm diameter) has essential geopmorphological and ecological functions supporting the health of river ecosystems. Still, even though its transport during floods may pose a risk, it is rarely observed and, therefore, poorly understood. This paper presents a novel approach to detect pieces of instream wood from video. The approach uses a Convolutional Neural Network to detect wood automatically. We sampled data to represent different wood transport conditions, combining 20 datasets to yield thousands of instream wood images. We designed multiple scenarios using different data subsets with and without data augmentation and analyzed the contribution of each one to the effectiveness of the model using k-fold cross-validation. The mean average precision of the model varies between 35 and 93 percent, and is highly influenced by the quality of the data which it detects. When the image resolution is low, the identified components in the labeled pieces, rather than exhibiting distinct characteristics such as bark or branches, appear more akin to amorphous masses or 'blobs'. We found that the model detects wood with a mean average precision of 67 percent when using a 418 pixels input image resolution. Also, improvements of up to 23 percent could be achieved in some instances and increasing the input resolution raised the weighted mean average precision to 74 percent. We show that the detection performance on a specific dataset is not solely determined by the complexity of the network or the training data. Therefore, the findings of this paper can be used when designing a custom wood detection network. With the growing availability of flood-related videos featuring wood uploaded to the internet, this methodology facilitates the quantification of wood transport across a wide variety of data sources.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560697","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}
Pub Date : 2024-04-15DOI: 10.5194/egusphere-2024-592
Aline Zinelabedin, Joel Mohren, Maria Wierzbicka-Wieczorek, Tibor Janos Dunai, Stefan Heinze, Benedikt Ritter
Abstract. While the formation of periglacial wedges and polygonal patterned grounds has been extensively studied and many of the processes involved have been understood, knowledge on the formation of similar post-sedimentary features found in arid to hyperarid environments remains largely rudimentary. Our contribution to fill this gap is the investigation of a network of vertically laminated calcium sulphate-rich wedges in the subsurface of the Aroma fan in the northern Atacama Desert. The subsurface wedges are characterised by high anhydrite contents and hence differ from the wedge and polygon structures of other study sites in the Atacama Desert, which appear to have been predominantly formed by thermal contraction or desiccation processes. By contrast, haloturbation mechanisms are thought to be a main driver of wedge formation at the Aroma fan site. Haloturbation requires moisture input, and hence Aroma fan wedge formation is likely to be associated with meteoric water received from sporadic rain events and episodes of arid climate characterised by slightly wetter conditions than prevailing at present. The polygonal patterned ground is covered by a stratigraphically younger gypsum-dominated surface crust cover. The presence of the surface crust could indicate an environmental change towards drier conditions, which favoured surface accumulation of calcium sulphate and other salts by means of atmospheric deposition. Such a climatic shift could have caused a deceleration of haloturbation and other wedge formation processes in the subsurface, although modern sediment conveyance from the surface towards its interior still appears to occur along cracks within the crust. In order to gain comprehensive insights into the complex mechanisms involved in wedge formation and formation rates, the establishment of a geochronological framework directly obtained from wedge and crust material remains indispensable. The temporal resolution of wedge growth stored within the succession of vertical laminae promises a high potential for the calcium sulphate wedges to be used as palaeoclimate archives, potentially helping to unravel wedge and polygonal patterned ground formation in other water-limited environments, such as Mars.
{"title":"Haloturbation in the northern Atacama Desert revealed by a hidden subsurface network of calcium sulphate wedges","authors":"Aline Zinelabedin, Joel Mohren, Maria Wierzbicka-Wieczorek, Tibor Janos Dunai, Stefan Heinze, Benedikt Ritter","doi":"10.5194/egusphere-2024-592","DOIUrl":"https://doi.org/10.5194/egusphere-2024-592","url":null,"abstract":"<strong>Abstract.</strong> While the formation of periglacial wedges and polygonal patterned grounds has been extensively studied and many of the processes involved have been understood, knowledge on the formation of similar post-sedimentary features found in arid to hyperarid environments remains largely rudimentary. Our contribution to fill this gap is the investigation of a network of vertically laminated calcium sulphate-rich wedges in the subsurface of the Aroma fan in the northern Atacama Desert. The subsurface wedges are characterised by high anhydrite contents and hence differ from the wedge and polygon structures of other study sites in the Atacama Desert, which appear to have been predominantly formed by thermal contraction or desiccation processes. By contrast, haloturbation mechanisms are thought to be a main driver of wedge formation at the Aroma fan site. Haloturbation requires moisture input, and hence Aroma fan wedge formation is likely to be associated with meteoric water received from sporadic rain events and episodes of arid climate characterised by slightly wetter conditions than prevailing at present. The polygonal patterned ground is covered by a stratigraphically younger gypsum-dominated surface crust cover. The presence of the surface crust could indicate an environmental change towards drier conditions, which favoured surface accumulation of calcium sulphate and other salts by means of atmospheric deposition. Such a climatic shift could have caused a deceleration of haloturbation and other wedge formation processes in the subsurface, although modern sediment conveyance from the surface towards its interior still appears to occur along cracks within the crust. In order to gain comprehensive insights into the complex mechanisms involved in wedge formation and formation rates, the establishment of a geochronological framework directly obtained from wedge and crust material remains indispensable. The temporal resolution of wedge growth stored within the succession of vertical laminae promises a high potential for the calcium sulphate wedges to be used as palaeoclimate archives, potentially helping to unravel wedge and polygonal patterned ground formation in other water-limited environments, such as Mars.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560524","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}
Pub Date : 2024-04-10DOI: 10.5194/egusphere-2023-2694
Hayden L. Jacobson, Danica L. Roth, Gabriel Walton, Margaret Zimmer, Kerri Johnson
Abstract. Post-fire changes to the transport regime of dry ravel, which describes the transport of individual particles downslope, are poorly constrained on a regional level but critical to understand as ravel may contribute to elevated sediment fluxes and associated debris-flow activity observed post-fire in the western United States. In this study, we evaluated post-fire variability in dry ravel travel distance exceedance probabilities and disentrainment rates through a series of field experiments simulating ravel with particles collected in situ. We conducted experiments between March 2021 and March 2022 on soil-mantled hillslopes in the Diablo Range of central coastal California following the Santa Clara Unit Lightning Complex fire of August 2020 with the goal of identifying a regime of “bounded” (light-tailed) or “runaway” (heavy-tailed or nonlocal) motion for different particle sizes between 3 and 35 mm. We conducted this study on both grassy south-facing slopes and oak woodland north-facing slopes. We tracked the post-fire evolution of particle transport regimes by fitting a probabilistic Lomax distribution model to the empirical travel distance exceedance probabilities of different particle sizes on a range of experimental slopes. Our experimental results indicated that a general transition from more runaway to more bounded transport occurred for our largest experimental particles (median intermediate axis of 28 mm) on south-facing slopes as vegetation recovered within the first year post-fire, while small and medium particles (median intermediate axes of 6 and 13 mm respectively) on south- or north-facing slopes and large particles on north-facing slopes did not experience notable changes in transport behavior. After the first year, seasonal variation in vegetation characteristics, such as grass density, appeared to control particle motion.
{"title":"Post-fire Variability in Sediment Transport by Ravel in the Diablo Range","authors":"Hayden L. Jacobson, Danica L. Roth, Gabriel Walton, Margaret Zimmer, Kerri Johnson","doi":"10.5194/egusphere-2023-2694","DOIUrl":"https://doi.org/10.5194/egusphere-2023-2694","url":null,"abstract":"<strong>Abstract.</strong> Post-fire changes to the transport regime of dry ravel, which describes the transport of individual particles downslope, are poorly constrained on a regional level but critical to understand as ravel may contribute to elevated sediment fluxes and associated debris-flow activity observed post-fire in the western United States. In this study, we evaluated post-fire variability in dry ravel travel distance exceedance probabilities and disentrainment rates through a series of field experiments simulating ravel with particles collected in situ. We conducted experiments between March 2021 and March 2022 on soil-mantled hillslopes in the Diablo Range of central coastal California following the Santa Clara Unit Lightning Complex fire of August 2020 with the goal of identifying a regime of “bounded” (light-tailed) or “runaway” (heavy-tailed or nonlocal) motion for different particle sizes between 3 and 35 mm. We conducted this study on both grassy south-facing slopes and oak woodland north-facing slopes. We tracked the post-fire evolution of particle transport regimes by fitting a probabilistic Lomax distribution model to the empirical travel distance exceedance probabilities of different particle sizes on a range of experimental slopes. Our experimental results indicated that a general transition from more runaway to more bounded transport occurred for our largest experimental particles (median intermediate axis of 28 mm) on south-facing slopes as vegetation recovered within the first year post-fire, while small and medium particles (median intermediate axes of 6 and 13 mm respectively) on south- or north-facing slopes and large particles on north-facing slopes did not experience notable changes in transport behavior. After the first year, seasonal variation in vegetation characteristics, such as grass density, appeared to control particle motion.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560328","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}
Pub Date : 2024-04-04DOI: 10.5194/egusphere-2024-855
Orie Cecil, Nicholas Cohn, Matthew Farthing, Sourav Dutta, Andrew Trautz
Abstract. Existing process-based models for simulating coastal foredune evolution largely use the same analytical approach for estimating wind induced surface shear stress distributions over spatially variable topography. Originally developed for smooth, low-sloping hills, these analytical models face significant limitations when the topography of interest exhibits large height-to-length ratios and/or steep, localized features. In this work, we utilize computational fluid dynamics (CFD) to examine the error trends of a commonly used analytical shear stress model for a series of idealized two-dimensional dune profiles. It is observed that the prediction error of the analytical model increases as compared to the CFD simulations for increasing height-to-length ratio and localized slope values. Furthermore, we explore two data-driven methodologies for generating alternative shear stress prediction models, namely, symbolic regression and linear, projection-based, non-intrusive reduced order modeling. These alternative modeling strategies demonstrate reduced overall error, but still suffer in their generalizability to broader sets of dune profiles outside of the training data. Finally, the impact of these improvements to aeolian sediment transport fluxes is examined to demonstrate that even modest improvements to the shear stress prediction can have significant impacts to dune evolution simulations over engineering-relevant timescales.
{"title":"Examination of Analytical Shear Stress Predictions for Coastal Dune Evolution","authors":"Orie Cecil, Nicholas Cohn, Matthew Farthing, Sourav Dutta, Andrew Trautz","doi":"10.5194/egusphere-2024-855","DOIUrl":"https://doi.org/10.5194/egusphere-2024-855","url":null,"abstract":"<strong>Abstract.</strong> Existing process-based models for simulating coastal foredune evolution largely use the same analytical approach for estimating wind induced surface shear stress distributions over spatially variable topography. Originally developed for smooth, low-sloping hills, these analytical models face significant limitations when the topography of interest exhibits large height-to-length ratios and/or steep, localized features. In this work, we utilize computational fluid dynamics (CFD) to examine the error trends of a commonly used analytical shear stress model for a series of idealized two-dimensional dune profiles. It is observed that the prediction error of the analytical model increases as compared to the CFD simulations for increasing height-to-length ratio and localized slope values. Furthermore, we explore two data-driven methodologies for generating alternative shear stress prediction models, namely, symbolic regression and linear, projection-based, non-intrusive reduced order modeling. These alternative modeling strategies demonstrate reduced overall error, but still suffer in their generalizability to broader sets of dune profiles outside of the training data. Finally, the impact of these improvements to aeolian sediment transport fluxes is examined to demonstrate that even modest improvements to the shear stress prediction can have significant impacts to dune evolution simulations over engineering-relevant timescales.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560415","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}
Pub Date : 2024-04-04DOI: 10.5194/egusphere-2024-784
Elizabeth Orr, Taylor Schildgen, Stefanie Tofelde, Hella Wittmann, Ricardo Alonso
Abstract. Theory suggests that the response time of alluvial channel long-profiles to perturbations in climate is related to the magnitude of the forcing and the length of the system. Shorter systems may record a higher frequency of forcing compared to longer systems. Empirical field evidence that system length plays a role in the climate periodicity preserved within the sedimentary record is, however, sparse. The Toro Basin in the Eastern Cordillera of NW Argentina provides an opportunity to test these theoretical relationships as this single source-to-sink system contains a range of sediment deposits, located at varying distances from the source. A suite of eight alluvial fan deposits is preserved along the western flanks of the Sierra de Pascha. Farther downstream, a flight of cut-and-fill terraces have been linked to eccentricity-driven (100-kyr) climate cycles since ca. 500 ka. We applied cosmogenic radionuclide (10Be) exposure dating to the fan surfaces to explore (1) how channel responses to external perturbations may or may not propagate downstream, and (2) the differences in landscape response to forcing frequency as a function of channel length. We identified two generations of fan surfaces: the first (G1) records surface activity and abandonment between ca. 800 and 500 ka and the second (G2) within the last 100 kyr. G1 fans record a prolonged phase of net incision, which has been recognised throughout the Central Andes, and was likely triggered by enhanced 100-kyr global glacial cycles following the Mid-Pleistocene Transition. Relative fan surface stability followed, while 100-kyr cut-and-fill cycles occurred downstream, suggesting a disconnect in behaviour between the two channel reaches. G2 fans record higher frequency climate forcing, possibly the result of precessional forcing of climate (ca. 21/40-kyr timescales). The lack of a high-frequency signal farther downstream provides field support for theoretical predictions of a filtering of high-frequency climate forcing with increasing channel length. We show that multiple climate periodicities can be preserved within the sedimentary record of a single basin. Differences in the timing of alluvial fan and fluvial terrace development in the Toro Basin appears to be associated with how channel length affects fluvial response times to climate forcing as well as local controls on net incision, such as tectonic deformation.
摘要理论表明，冲积河道长剖面对气候扰动的响应时间与强迫的大小和系统的长度有关。与较长的系统相比，较短的系统可能会记录更高频率的强迫。然而，关于系统长度在沉积记录所保留的气候周期性中发挥作用的实地经验证据并不多。阿根廷西北部东科迪勒拉山系的托罗盆地为检验这些理论关系提供了一个机会，因为这个单一的源-汇系统包含一系列沉积物，与源头的距离各不相同。在帕夏山脉的西侧，保存着八组冲积扇沉积。在更远的下游，一连串的切填阶地与自约 500 ka 年以来的偏心驱动（100-kyr）气候周期有关。500ka。我们对扇面进行了宇宙放射性核素（10Be）暴露年代测定，以探索：（1）渠道对外部扰动的响应如何可能或不可能向下游传播；（2）景观对强迫频率的响应差异与渠道长度的函数关系。我们发现了两代扇面：第一代（G1）记录了大约 800 至 500 ka 期间扇面的活动和废弃，第二代（G2）记录了最近 100 kyr 期间扇面的活动和废弃。G1 扇面记录了整个中安第斯山脉长期的净侵蚀阶段，这很可能是中更新世过渡之后 100 千年全球冰川周期增强所引发的。随后，扇面表面相对稳定，而下游则出现了 100 千年的切填循环，这表明两个河道之间的行为脱节。G2 扇面记录了较高频率的气候作用，可能是气候前行作用的结果（时间尺度约为 21/40 千年）。下游缺乏高频信号为理论预测提供了实地支持，即随着河道长度的增加，高频气候作用会被过滤。我们的研究表明，在一个盆地的沉积记录中可以保留多种气候周期。托罗盆地冲积扇和河流阶地发育时间的差异似乎与河道长度如何影响河流对气候作用的响应时间以及当地对净侵蚀的控制（如构造变形）有关。
{"title":"Landscape response to tectonic deformation and cyclic climate change since ca. 800 ka in the southern Central Andes","authors":"Elizabeth Orr, Taylor Schildgen, Stefanie Tofelde, Hella Wittmann, Ricardo Alonso","doi":"10.5194/egusphere-2024-784","DOIUrl":"https://doi.org/10.5194/egusphere-2024-784","url":null,"abstract":"<strong>Abstract.</strong> Theory suggests that the response time of alluvial channel long-profiles to perturbations in climate is related to the magnitude of the forcing and the length of the system. Shorter systems may record a higher frequency of forcing compared to longer systems. Empirical field evidence that system length plays a role in the climate periodicity preserved within the sedimentary record is, however, sparse. The Toro Basin in the Eastern Cordillera of NW Argentina provides an opportunity to test these theoretical relationships as this single source-to-sink system contains a range of sediment deposits, located at varying distances from the source. A suite of eight alluvial fan deposits is preserved along the western flanks of the Sierra de Pascha. Farther downstream, a flight of cut-and-fill terraces have been linked to eccentricity-driven (100-kyr) climate cycles since ca. 500 ka. We applied cosmogenic radionuclide (<sup>10</sup>Be) exposure dating to the fan surfaces to explore (1) how channel responses to external perturbations may or may not propagate downstream, and (2) the differences in landscape response to forcing frequency as a function of channel length. We identified two generations of fan surfaces: the first (G1) records surface activity and abandonment between ca. 800 and 500 ka and the second (G2) within the last 100 kyr. G1 fans record a prolonged phase of net incision, which has been recognised throughout the Central Andes, and was likely triggered by enhanced 100-kyr global glacial cycles following the Mid-Pleistocene Transition. Relative fan surface stability followed, while 100-kyr cut-and-fill cycles occurred downstream, suggesting a disconnect in behaviour between the two channel reaches. G2 fans record higher frequency climate forcing, possibly the result of precessional forcing of climate (ca. 21/40-kyr timescales). The lack of a high-frequency signal farther downstream provides field support for theoretical predictions of a filtering of high-frequency climate forcing with increasing channel length. We show that multiple climate periodicities can be preserved within the sedimentary record of a single basin. Differences in the timing of alluvial fan and fluvial terrace development in the Toro Basin appears to be associated with how channel length affects fluvial response times to climate forcing as well as local controls on net incision, such as tectonic deformation.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560478","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}
Pub Date : 2024-04-02DOI: 10.5194/egusphere-2024-808
Liran Goren, Eitan Shelef
Abstract. The plan-form geometry of branching drainage networks controls the topography of landscapes as well as their geomorphic, hydrologic, and ecologic functionality. The complexity of networks' geometry shows significant variability, from simple, straight channels that flow along the regional topographic gradient to intricate, tortuous flow patterns. This variability in complexity presents an enigma, as models show that it emerges independently of any heterogeneity in the environmental conditions. We propose to quantify networks' complexity based on the distribution of lengthwise asymmetry between paired flow pathways that diverge from a divide and rejoin at a junction. Using the lengthwise asymmetry definition, we show that the channel concavity index, describing downstream changes in channel slope, has a primary control on the plan-form complexity of natural drainage networks. An analytic model based on geomorphic scaling relations and optimal channel network simulations employing an energy minimization principle reveal that landscapes with low concavity channels attain stable plan-form configuration only through simple geometry. In contrast, landscapes with high-concavity channels achieve plan-form stability with various degrees of network complexity, including extremely complex geometries. Landscape evolution simulations demonstrate that the concavity index and its effect on the multiplicity of available geometries control the tendency of networks to preserve the legacy of former environmental conditions. Consistent with previous findings showing that channel concavity correlates with climate aridity, we find a significant empirical correlation between aridity and network complexity, suggesting a climatic signature embedded in the large-scale plan-form geometry of landscapes.
{"title":"Channel concavity controls plan-form complexity of branching drainage networks","authors":"Liran Goren, Eitan Shelef","doi":"10.5194/egusphere-2024-808","DOIUrl":"https://doi.org/10.5194/egusphere-2024-808","url":null,"abstract":"<strong>Abstract.</strong> The plan-form geometry of branching drainage networks controls the topography of landscapes as well as their geomorphic, hydrologic, and ecologic functionality. The complexity of networks' geometry shows significant variability, from simple, straight channels that flow along the regional topographic gradient to intricate, tortuous flow patterns. This variability in complexity presents an enigma, as models show that it emerges independently of any heterogeneity in the environmental conditions. We propose to quantify networks' complexity based on the distribution of lengthwise asymmetry between paired flow pathways that diverge from a divide and rejoin at a junction. Using the lengthwise asymmetry definition, we show that the channel concavity index, describing downstream changes in channel slope, has a primary control on the plan-form complexity of natural drainage networks. An analytic model based on geomorphic scaling relations and optimal channel network simulations employing an energy minimization principle reveal that landscapes with low concavity channels attain stable plan-form configuration only through simple geometry. In contrast, landscapes with high-concavity channels achieve plan-form stability with various degrees of network complexity, including extremely complex geometries. Landscape evolution simulations demonstrate that the concavity index and its effect on the multiplicity of available geometries control the tendency of networks to preserve the legacy of former environmental conditions. Consistent with previous findings showing that channel concavity correlates with climate aridity, we find a significant empirical correlation between aridity and network complexity, suggesting a climatic signature embedded in the large-scale plan-form geometry of landscapes.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560473","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}
Pub Date : 2024-03-28DOI: 10.5194/esurf-12-493-2024
Jens Martin Turowski, Aaron Bufe, Stefanie Tofelde
Abstract. The width of fluvial valley floors is a key parameter to quantifying the morphology of mountain regions. Valley floor width is relevant to diverse fields including sedimentology, fluvial geomorphology, and archaeology. The width of valleys has been argued to depend on climatic and tectonic conditions, on the hydraulics and hydrology of the river channel that forms the valley, and on sediment supply from valley walls. Here, we derive a physically based model that can be used to predict valley width and test it against three different datasets. The model applies to valleys that are carved by a river migrating laterally across the valley floor. We conceptualize river migration as a Poisson process, in which the river changes its direction stochastically at a mean rate determined by hydraulic boundary conditions. This approach yields a characteristic timescale for the river to cross the valley floor from one wall to the other. The valley width can then be determined by integrating the speed of migration over this timescale. For a laterally unconfined river that is not uplifting, the model predicts that the channel-belt width scales with river flow depth. Channel-belt width corresponds to the maximum width of a fluvial valley. We expand the model to include the effects of uplift and lateral sediment supply from valley walls. Both of these effects lead to a decrease in valley width in comparison to the maximum width. We identify a dimensionless number, termed the mobility–uplift number, which is the ratio between the lateral mobility of the river channel and uplift rate. The model predicts two limits: at high values of the mobility–uplift number, the valley evolves to the channel-belt width, whereas it corresponds to the channel width at low values. Between these limits, valley width is linked to the mobility–uplift number by a logarithmic function. As a consequence of the model, valley width increases with increasing drainage area, with a scaling exponent that typically has a value between 0.4 and 0.5, but can also be lower or higher. We compare the model to three independent datasets of valleys in experimental and natural uplifting landscapes and show that it closely predicts the first-order relationship between valley width and the mobility–uplift number.
{"title":"A physics-based model for fluvial valley width","authors":"Jens Martin Turowski, Aaron Bufe, Stefanie Tofelde","doi":"10.5194/esurf-12-493-2024","DOIUrl":"https://doi.org/10.5194/esurf-12-493-2024","url":null,"abstract":"Abstract. The width of fluvial valley floors is a key parameter to quantifying the morphology of mountain regions. Valley floor width is relevant to diverse fields including sedimentology, fluvial geomorphology, and archaeology. The width of valleys has been argued to depend on climatic and tectonic conditions, on the hydraulics and hydrology of the river channel that forms the valley, and on sediment supply from valley walls. Here, we derive a physically based model that can be used to predict valley width and test it against three different datasets. The model applies to valleys that are carved by a river migrating laterally across the valley floor. We conceptualize river migration as a Poisson process, in which the river changes its direction stochastically at a mean rate determined by hydraulic boundary conditions. This approach yields a characteristic timescale for the river to cross the valley floor from one wall to the other. The valley width can then be determined by integrating the speed of migration over this timescale. For a laterally unconfined river that is not uplifting, the model predicts that the channel-belt width scales with river flow depth. Channel-belt width corresponds to the maximum width of a fluvial valley. We expand the model to include the effects of uplift and lateral sediment supply from valley walls. Both of these effects lead to a decrease in valley width in comparison to the maximum width. We identify a dimensionless number, termed the mobility–uplift number, which is the ratio between the lateral mobility of the river channel and uplift rate. The model predicts two limits: at high values of the mobility–uplift number, the valley evolves to the channel-belt width, whereas it corresponds to the channel width at low values. Between these limits, valley width is linked to the mobility–uplift number by a logarithmic function. As a consequence of the model, valley width increases with increasing drainage area, with a scaling exponent that typically has a value between 0.4 and 0.5, but can also be lower or higher. We compare the model to three independent datasets of valleys in experimental and natural uplifting landscapes and show that it closely predicts the first-order relationship between valley width and the mobility–uplift number.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140313382","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}
Pub Date : 2024-03-26DOI: 10.5194/esurf-12-477-2024
Yuntao Tian, Lili Pan, Guihong Zhang, Xinbo Yao
Abstract. This study implements the least-squares inversion method for solving the exhumation history from the thermochronologic age–elevation relationship (AER) based on the linear equation among exhumation rate, age and total exhumation from the closure depth to the Earth surface. Modeling experiments suggest significant and systematic influence of initial geothermal model, the a priori exhumation rate and the time interval length on the a posteriori exhumation history. Lessons learned from the experiments include that (i) the modern geothermal gradient can be used for constraining the initial geothermal model, (ii) a relatively high a priori exhumation rate would lead to systematically lower a posteriori exhumation and vice versa, (iii) the variance of the a priori exhumation rate controls the variation in the inverted exhumation history, and (iv) the choice of time interval length should be optimized for resolving the potential temporal changes in exhumation. To mitigate the dependence of inverted erosion history on these initial parameters, we implemented a new stepwise inverse modeling method for optimizing the model parameters by comparing the observed and predicted thermochronologic data and modern geothermal gradients. Finally, method demonstration was performed using four synthetic datasets and three natural examples of different exhumation rates and histories. It is shown that the inverted rock exhumation histories from the synthetic datasets match the whole picture of the “truth”, although the temporal changes in the magnitude of exhumation are underestimated. Modeling of the datasets from natural samples produces geologically reasonable exhumation histories. The code and data used in this work are available on Zenodo (https://doi.org/10.5281/zenodo.10839275).
{"title":"An efficient approach for inverting rock exhumation from thermochronologic age–elevation relationship","authors":"Yuntao Tian, Lili Pan, Guihong Zhang, Xinbo Yao","doi":"10.5194/esurf-12-477-2024","DOIUrl":"https://doi.org/10.5194/esurf-12-477-2024","url":null,"abstract":"Abstract. This study implements the least-squares inversion method for solving the exhumation history from the thermochronologic age–elevation relationship (AER) based on the linear equation among exhumation rate, age and total exhumation from the closure depth to the Earth surface. Modeling experiments suggest significant and systematic influence of initial geothermal model, the a priori exhumation rate and the time interval length on the a posteriori exhumation history. Lessons learned from the experiments include that (i) the modern geothermal gradient can be used for constraining the initial geothermal model, (ii) a relatively high a priori exhumation rate would lead to systematically lower a posteriori exhumation and vice versa, (iii) the variance of the a priori exhumation rate controls the variation in the inverted exhumation history, and (iv) the choice of time interval length should be optimized for resolving the potential temporal changes in exhumation. To mitigate the dependence of inverted erosion history on these initial parameters, we implemented a new stepwise inverse modeling method for optimizing the model parameters by comparing the observed and predicted thermochronologic data and modern geothermal gradients. Finally, method demonstration was performed using four synthetic datasets and three natural examples of different exhumation rates and histories. It is shown that the inverted rock exhumation histories from the synthetic datasets match the whole picture of the “truth”, although the temporal changes in the magnitude of exhumation are underestimated. Modeling of the datasets from natural samples produces geologically reasonable exhumation histories. The code and data used in this work are available on Zenodo (https://doi.org/10.5281/zenodo.10839275).","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140313182","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}
Pub Date : 2024-03-25DOI: 10.5194/egusphere-2024-172
Dominik Amschwand, Jonas Wicky, Martin Scherler, Martin Hoelzle, Bernhard Krummenacher, Anna Haberkorn, Christian Kienholz, Hansueli Gubler
Abstract. We estimate the sub-surface energy budget and heat fluxes in the coarse-blocky active layer (AL) of the Murtèl rock glacier, a seasonally snow-covered permafrost landform located in the eastern Swiss Alps. In the highly permeable AL, conductive/diffusive heat transfer including thermal radiation, non-conductive heat transfer by air circulation (convection), and heat storage changes from seasonal accretion and melting of ground ice shape the ground thermal regime. We quantify individual heat fluxes based on a novel in-situ sensor array in the AL and direct observations of the ground ice melt in the years 2020–2022. Two thaw-season mechanisms render Murtèl rock glacier comparatively climate-resilient. First, the AL intercepts ~70 % (55–85 MJ m−2) of the thaw-season ground heat flux by melting ground ice that runs off as meltwater, ~20 % (10–20 MJ m−2) is spent on heating the blocks, and only ~10 % (7–13 MJ m−2) is transferred into the permafrost body beneath and causes slow permafrost degradation. Second, the effective thermal conductivity in the ventilated AL increases from 1.2 W m−1 K−1 under strongly stable temperature gradients to episodically over 10 W m−1 K−1 under unstable temperature gradients, favouring convective cooling by buoyancy-driven Rayleigh ventilation (thermal semiconductor effect). In winter, radiatively cooled air infiltrating through a discontinuous, semi-closed snowcover leads to strong AL cooling. The two characteristic parameters (effective thermal conductivity and intrinsic permeability) are sensitive to debris texture, hence these convective undercooling processes are specific to highly permeable coarse-blocky material.
摘要我们估算了位于瑞士阿尔卑斯山东部的穆尔泰尔岩石冰川（一种季节性积雪覆盖的永久冻土地貌）粗块状活动层（AL）的次表层能量预算和热通量。在高渗透性的活动层中，包括热辐射在内的传导性/扩散性热传递、空气循环（对流）产生的非传导性热传递以及地冰季节性增厚和融化产生的热储量变化决定了地热状态。我们根据 AL 中的新型原位传感器阵列和 2020-2022 年对地冰融化的直接观测，对各个热通量进行了量化。两种解冻季节机制使穆尔泰勒岩石冰川具有相对较强的气候适应能力。首先，融化季的地面热通量中，约 70% （55-85 兆焦耳/平方米-2）由融化的地冰截取，以融水形式流走，约 20% （10-20 兆焦耳/平方米-2）用于加热块体，只有约 10% （7-13 兆焦耳/平方米-2）转移到下面的永久冻土体中，导致永久冻土缓慢降解。其次，在温度梯度非常稳定的情况下，通风冻土层的有效热传导率从 1.2 W m-1 K-1 增加到温度梯度不稳定时的 10 W m-1 K-1 以上，有利于通过浮力驱动的雷利通风进行对流冷却（热半导体效应）。在冬季，辐射冷却空气通过不连续的半封闭雪盖渗入，导致强烈的 AL 冷却。这两个特征参数（有效热导率和固有渗透率）对碎屑质地非常敏感，因此这些对流过冷过程是高渗透性粗块状物质所特有的。
{"title":"Sub-surface processes and heat fluxes at coarse-blocky Murtèl rock glacier (Engadine, eastern Swiss Alps)","authors":"Dominik Amschwand, Jonas Wicky, Martin Scherler, Martin Hoelzle, Bernhard Krummenacher, Anna Haberkorn, Christian Kienholz, Hansueli Gubler","doi":"10.5194/egusphere-2024-172","DOIUrl":"https://doi.org/10.5194/egusphere-2024-172","url":null,"abstract":"<strong>Abstract.</strong> We estimate the sub-surface energy budget and heat fluxes in the coarse-blocky active layer (AL) of the Murtèl rock glacier, a seasonally snow-covered permafrost landform located in the eastern Swiss Alps. In the highly permeable AL, conductive/diffusive heat transfer including thermal radiation, non-conductive heat transfer by air circulation (convection), and heat storage changes from seasonal accretion and melting of ground ice shape the ground thermal regime. We quantify individual heat fluxes based on a novel in-situ sensor array in the AL and direct observations of the ground ice melt in the years 2020–2022. Two thaw-season mechanisms render Murtèl rock glacier comparatively climate-resilient. First, the AL intercepts ~70 % (55–85 MJ m<sup>−2</sup>) of the thaw-season ground heat flux by melting ground ice that runs off as meltwater, ~20 % (10–20 MJ m<sup>−</sup><sup>2</sup>) is spent on heating the blocks, and only ~10 % (7–13 MJ m<sup>−</sup><sup>2</sup>) is transferred into the permafrost body beneath and causes slow permafrost degradation. Second, the effective thermal conductivity in the ventilated AL increases from 1.2 W m<sup>−</sup><sup>1</sup> K<sup>−</sup><sup>1</sup> under strongly stable temperature gradients to episodically over 10 W m<sup>−</sup><sup>1</sup> K<sup>−</sup><sup>1</sup> under unstable temperature gradients, favouring convective cooling by buoyancy-driven Rayleigh ventilation (thermal semiconductor effect). In winter, radiatively cooled air infiltrating through a discontinuous, semi-closed snowcover leads to strong AL cooling. The two characteristic parameters (effective thermal conductivity and intrinsic permeability) are sensitive to debris texture, hence these convective undercooling processes are specific to highly permeable coarse-blocky material.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140299230","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}
Pub Date : 2024-03-19DOI: 10.5194/egusphere-2024-656
Rachele Dominguez, Michael Fenster, John McManus
Abstract. This study extracted historical water level data from 12 National Oceanographic and Atmospheric Administration tide gauge stations, spanning the period from the early 20th century to 2022 from central Maine to southern Florida, in order to determine if temporal and spatial trends existed in frequency and magnitude of storms along the U.S. Atlantic Ocean coast. We used the Storm Erosion Potential Index (SEPI) to identify and quantify storms. We then use the timing and magnitude of those storms to determine the cumulative effect of storm clustering and large magnitude storms on sandy beaches using the cumulative storm impact index (CSII) empirical model. The results from this study showed (1) no appreciable increase in storm frequency at any of the stations (except for sheltered stations susceptible to storm tide augmentation); (2) statistically significant, but modest increases in storm magnitudes over time for eight of the 12 tidal stations; (3) regional differences in storm magnitudes (SEPI) and cumulative storm impacts (CSII) characteristic of more frequent extratropical storms (temporal clustering) in the north and less frequent tropical storms in the south; and (4) a four to 10 year recovery period for regional beach recovery.
{"title":"Storm surge frequency, magnitude, and cumulative storm beach impact along the U.S. east coast","authors":"Rachele Dominguez, Michael Fenster, John McManus","doi":"10.5194/egusphere-2024-656","DOIUrl":"https://doi.org/10.5194/egusphere-2024-656","url":null,"abstract":"<strong>Abstract.</strong> This study extracted historical water level data from 12 National Oceanographic and Atmospheric Administration tide gauge stations, spanning the period from the early 20th century to 2022 from central Maine to southern Florida, in order to determine if temporal and spatial trends existed in frequency and magnitude of storms along the U.S. Atlantic Ocean coast. We used the Storm Erosion Potential Index (SEPI) to identify and quantify storms. We then use the timing and magnitude of those storms to determine the cumulative effect of storm clustering and large magnitude storms on sandy beaches using the cumulative storm impact index (CSII) empirical model. The results from this study showed (1) no appreciable increase in storm frequency at any of the stations (except for sheltered stations susceptible to storm tide augmentation); (2) statistically significant, but modest increases in storm magnitudes over time for eight of the 12 tidal stations; (3) regional differences in storm magnitudes (SEPI) and cumulative storm impacts (CSII) characteristic of more frequent extratropical storms (temporal clustering) in the north and less frequent tropical storms in the south; and (4) a four to 10 year recovery period for regional beach recovery.","PeriodicalId":48749,"journal":{"name":"Earth Surface Dynamics","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140170762","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：