Pub Date : 2024-11-13DOI: 10.1016/j.geomorph.2024.109513
Fan Gao , Xibin Tan , Chao Zhou , Shuang Bian , Feng Shi
In the Hengduan Mountains (Southeastern Tibet), the south-draining Nmai Hka (Upper Irrawaddy), Nu (Upper Salween), Lancang (Upper Mekong), and Jinsha (Upper Yangtze) Rivers flow parallel and in proximity to each other, thus forming rather a unique geomorphic configuration (i.e., the Parallel Rivers). It has been suggested that this configuration is an outcome of tectonic shortening that “squeezed” the rivers together. Although the tectonic and surface processes in this region have been extensively studied, the processes that led to this configuration remain controversial. Here, we investigate the potential role of drainage-divide migration in forming the Parallel Rivers. We demonstrate, based on geomorphologic analysis of divide stability between the parallel rivers, that while the two western divides (Nmai-Nu, Nu-Lancang) are likely migrating eastward, the eastern divide (Lancang-Jinsha) is roughly stable. This pattern suggests that the formation of the Parallel Rivers is associated with an abutment of the migrating divides against the fixed one. GPS and precipitation data combined with prior research suggest that the migrations of the two western divides are driven by the spatial variations in precipitation and rock uplift. Concurrently the stability of the eastern divide is influenced by a combination of climatic and tectonic factors, as well as a historical river capture event. This implies that the formation of the Parallel Rivers has not necessarily been an outcome of east-west tectonic shortening but has been influenced by the spatial variations in precipitation and tectonic uplift.
{"title":"Eastward drainage-divide migrations driven by the spatial variations in precipitation and tectonic uplift contribute to the formation of the Parallel Rivers in the Hengduan Mountains, Southeastern Tibet","authors":"Fan Gao , Xibin Tan , Chao Zhou , Shuang Bian , Feng Shi","doi":"10.1016/j.geomorph.2024.109513","DOIUrl":"10.1016/j.geomorph.2024.109513","url":null,"abstract":"<div><div>In the Hengduan Mountains (Southeastern Tibet), the south-draining Nmai Hka (Upper Irrawaddy), Nu (Upper Salween), Lancang (Upper Mekong), and Jinsha (Upper Yangtze) Rivers flow parallel and in proximity to each other, thus forming rather a unique geomorphic configuration (i.e., the Parallel Rivers). It has been suggested that this configuration is an outcome of tectonic shortening that “squeezed” the rivers together. Although the tectonic and surface processes in this region have been extensively studied, the processes that led to this configuration remain controversial. Here, we investigate the potential role of drainage-divide migration in forming the Parallel Rivers. We demonstrate, based on geomorphologic analysis of divide stability between the parallel rivers, that while the two western divides (Nmai-Nu, Nu-Lancang) are likely migrating eastward, the eastern divide (Lancang-Jinsha) is roughly stable. This pattern suggests that the formation of the Parallel Rivers is associated with an abutment of the migrating divides against the fixed one. GPS and precipitation data combined with prior research suggest that the migrations of the two western divides are driven by the spatial variations in precipitation and rock uplift. Concurrently the stability of the eastern divide is influenced by a combination of climatic and tectonic factors, as well as a historical river capture event. This implies that the formation of the Parallel Rivers has not necessarily been an outcome of east-west tectonic shortening but has been influenced by the spatial variations in precipitation and tectonic uplift.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109513"},"PeriodicalIF":3.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661853","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 : 2024-11-12DOI: 10.1016/j.geomorph.2024.109511
Lukman A. Soboyejo, Kathryn L. Russell, Tim D. Fletcher
Urbanisation has resulted in rapid geomorphic changes and ecosystem degradation in many streams worldwide. The question of how channel response to urbanisation can be accurately predicted amid multiple driving factors remains a significant scientific challenge. Numerous efforts have been made to address this issue over the past 80 years. Nevertheless, channel response resulting from urbanisation differs across physiographic regions, making it difficult to predict. The main goal of this study is to investigate the most important factors influencing morphological changes, such as channel area, in streams with urbanised catchments. To accomplish this aim, we reviewed the literature on the application of hydraulic geometry models to urban-impacted rivers worldwide. We set out to investigate two specific questions: (i) to what extent and under what circumstances can urban stream bankfull cross-sectional area be predicted by catchment area and impervious cover metrics? and (ii) is stream bankfull width more susceptible than stream bankfull depth to urban-induced enlargement? However, over 90 % of the urban channels studied in the literature we reviewed showed irregular response patterns to urbanisation, owing to the complex interplay of local factors, such as geology, sediment, hardpoints, and riparian vegetation. Our most important conclusion is that local context is an important controller of stream channel response to urbanisation. While catchment area is a good predictor of channel area in some urban sites, it is a poor predictor of channel area in other urban sites. This contrasts with non-urban sites, where catchment area usually predicts channel area more strongly. In addition, impervious cover alone, which represents the direct hydrological impact of urbanisation, is insufficient to fully explain channel enlargement and incision. Therefore, models of channel response to urbanisation must consider the specific local factors that drive or limit these responses in order to be effective as predictive and explanatory tools.
城市化导致全球许多河流的地貌迅速变化和生态系统退化。在多种驱动因素的作用下,如何准确预测河道对城市化的反应仍然是一个重大的科学挑战。在过去的 80 年中,人们为解决这一问题做出了大量努力。然而,城市化导致的河道响应在不同的地理区域存在差异,因此难以预测。本研究的主要目标是调查影响城市化集水区河道面积等形态变化的最重要因素。为了实现这一目标,我们查阅了有关将水力几何学模型应用于全球受城市影响河流的文献。我们着手研究两个具体问题:(i) 在何种程度上和何种情况下,城市河流的河岸横截面积可以通过集水面积和不透水覆盖率指标进行预测? (ii) 与河岸深度相比,河岸宽度是否更容易受到城市引起的河道扩大的影响?然而,由于地质、沉积物、硬点和河岸植被等当地因素的复杂相互作用,在我们查阅的文献中,超过 90% 的城市河道对城市化的反应模式不规则。我们最重要的结论是,当地环境是河道对城市化反应的重要控制因素。在某些城市地区,集水区可以很好地预测河道面积,但在其他城市地区,集水区却不能很好地预测河道面积。这与非城市地区形成了鲜明对比,在非城市地区,集水面积通常能更准确地预测河道面积。此外,仅仅是不透水覆盖(代表城市化的直接水文影响)还不足以完全解释河道的扩大和内切。因此,河道对城市化反应的模型必须考虑驱动或限制这些反应的当地特定因素,才能有效地作为预测和解释工具。
{"title":"Predicting urban channel morphology amidst multiple complexities","authors":"Lukman A. Soboyejo, Kathryn L. Russell, Tim D. Fletcher","doi":"10.1016/j.geomorph.2024.109511","DOIUrl":"10.1016/j.geomorph.2024.109511","url":null,"abstract":"<div><div>Urbanisation has resulted in rapid geomorphic changes and ecosystem degradation in many streams worldwide. The question of how channel response to urbanisation can be accurately predicted amid multiple driving factors remains a significant scientific challenge. Numerous efforts have been made to address this issue over the past 80 years. Nevertheless, channel response resulting from urbanisation differs across physiographic regions, making it difficult to predict. The main goal of this study is to investigate the most important factors influencing morphological changes, such as channel area, in streams with urbanised catchments. To accomplish this aim, we reviewed the literature on the application of hydraulic geometry models to urban-impacted rivers worldwide. We set out to investigate two specific questions: (i) to what extent and under what circumstances can urban stream bankfull cross-sectional area be predicted by catchment area and impervious cover metrics? and (ii) is stream bankfull width more susceptible than stream bankfull depth to urban-induced enlargement? However, over 90 % of the urban channels studied in the literature we reviewed showed irregular response patterns to urbanisation, owing to the complex interplay of local factors, such as geology, sediment, hardpoints, and riparian vegetation. Our most important conclusion is that local context is an important controller of stream channel response to urbanisation. While catchment area is a good predictor of channel area in some urban sites, it is a poor predictor of channel area in other urban sites. This contrasts with non-urban sites, where catchment area usually predicts channel area more strongly. In addition, impervious cover alone, which represents the direct hydrological impact of urbanisation, is insufficient to fully explain channel enlargement and incision. Therefore, models of channel response to urbanisation must consider the specific local factors that drive or limit these responses in order to be effective as predictive and explanatory tools.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109511"},"PeriodicalIF":3.1,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-08DOI: 10.1016/j.geomorph.2024.109502
S. Pinardi , R.T. Cox , D. Leslie , Md.R. Hasan , N. Adhikari , R.B. Van Arsdale
Northeast-trending linear topographic ridges in Pliocene and Quaternary sediments adjacent to the New Madrid seismic zone (NMSZ), intraplate North America, have been long speculated to be neotectonic landforms related to reactivation of basement faults of the eastern Mississippi Valley Rift margin. Earthquake epicenters and paleoseismological studies show that eastern rift margin faults (ERMF) were active during late Quaternary south of a restraining bend in the Mississippi Valley Rift fault complex, but the ERMF zone north of the restraining bend (ERM-N) and underlying the linear ridges is seismically quiescent. A previous P-wave seismic reflection survey across the most prominent linear ridge (Rives lineament) revealed that it overlies a horst in Eocene sediment. To ascertain whether the Rives lineament could have been produced by surface faulting/folding, we collected electrical resistivity tomography (ERT) and ground penetrating radar (GPR) profiles to image the ridge's shallow subsurface features. We interpret shallow folding and faulting of late Pleistocene sediment in our ERT and GPR images. Additionally, convexity of multiple topographic profiles of scarps along margins of the Rives lineament was quantified and compared to the convexity of profiles of known neotectonic scarps and of fluvial terrace riser profiles within the region. Comparison of these profiles reveals a high degree of similarity between the scarps along the Rives lineament margins and the Holocene Reelfoot thrust scarp. When combined, our results strongly suggest late Pleistocene or Holocene folding and faulting created this ridge despite its current seismic quiescence, and thus they provide useful insight for assessing the seismic hazard potential of quiescent faults in strike-slip systems in general. We conclude that the late Quaternary series of movements documented on the Reelfoot thrust was initiated to accommodate crustal shortening after transpressional fault movements on the ERM-N became inactive in late Pleistocene or early Holocene and that movement along the ERM-N may resume if the Reelfoot thrust has an interval of inactivity in the future. Our results suggest how fault interactions within a strike-slip system can change, making faults with significant amounts of seismic potential appear as though they are inactive.
长期以来,人们一直推测毗邻北美板块内部新马德里地震带(NMSZ)的上新世和第四纪沉积物中的东北走向线状地形山脊是与密西西比河谷裂谷东缘基底断层重新活化有关的新构造地貌。地震震中和古地震学研究表明,密西西比河谷裂谷断裂复合体约束弯以南的东部裂谷边缘断层(ERMF)在第四纪晚期十分活跃,但约束弯以北的ERMF区(ERM-N)和线性山脊下层则处于地震静止状态。之前对最突出的线性山脊(里夫线)进行的 P 波地震反射勘测显示,该山脊覆盖在始新世沉积物的一个地角之上。为了确定里夫斯线状构造是否由地表断层/褶皱产生,我们采集了电阻率层析成像(ERT)和地面穿透雷达(GPR)剖面图,对该脊的浅表次表层特征进行成像。我们在 ERT 和 GPR 图像中解释了晚更新世沉积物的浅层褶皱和断层。此外,我们还对里夫斯线边缘疤痕的多个地形剖面的凸度进行了量化,并将其与该地区已知新构造疤痕和河流阶地隆起剖面的凸度进行了比较。对这些剖面进行比较后发现,里夫斯褶皱带边缘的疤痕与全新世的里尔富特推力疤痕具有高度的相似性。综合这些结果,我们强烈认为晚更新世或全新世的褶皱和断层造成了这一山脊,尽管它目前处于地震静止状态,因此它们为评估一般走向滑动系统中静止断层的地震危险潜力提供了有用的见解。我们的结论是,记录在案的第四纪晚期里尔富特推力上的一系列运动是在更新世晚期或全新世早期ERM-N上的转压断层运动不活跃之后为适应地壳缩短而开始的,如果里尔富特推力在未来有一段时间不活跃,ERM-N上的运动可能会恢复。我们的研究结果表明,走向滑动系统中的断层相互作用可能会发生变化,从而使具有巨大地震潜力的断层看起来似乎处于不活跃状态。
{"title":"Topographic ridges express late Quaternary faulting peripheral to the New Madrid seismic zone, intraplate USA: Their tectonic implications","authors":"S. Pinardi , R.T. Cox , D. Leslie , Md.R. Hasan , N. Adhikari , R.B. Van Arsdale","doi":"10.1016/j.geomorph.2024.109502","DOIUrl":"10.1016/j.geomorph.2024.109502","url":null,"abstract":"<div><div>Northeast-trending linear topographic ridges in Pliocene and Quaternary sediments adjacent to the New Madrid seismic zone (NMSZ), intraplate North America, have been long speculated to be neotectonic landforms related to reactivation of basement faults of the eastern Mississippi Valley Rift margin. Earthquake epicenters and paleoseismological studies show that eastern rift margin faults (ERMF) were active during late Quaternary south of a restraining bend in the Mississippi Valley Rift fault complex, but the ERMF zone north of the restraining bend (ERM-N) and underlying the linear ridges is seismically quiescent. A previous P-wave seismic reflection survey across the most prominent linear ridge (Rives lineament) revealed that it overlies a horst in Eocene sediment. To ascertain whether the Rives lineament could have been produced by surface faulting/folding, we collected electrical resistivity tomography (ERT) and ground penetrating radar (GPR) profiles to image the ridge's shallow subsurface features. We interpret shallow folding and faulting of late Pleistocene sediment in our ERT and GPR images. Additionally, convexity of multiple topographic profiles of scarps along margins of the Rives lineament was quantified and compared to the convexity of profiles of known neotectonic scarps and of fluvial terrace riser profiles within the region. Comparison of these profiles reveals a high degree of similarity between the scarps along the Rives lineament margins and the Holocene Reelfoot thrust scarp. When combined, our results strongly suggest late Pleistocene or Holocene folding and faulting created this ridge despite its current seismic quiescence, and thus they provide useful insight for assessing the seismic hazard potential of quiescent faults in strike-slip systems in general. We conclude that the late Quaternary series of movements documented on the Reelfoot thrust was initiated to accommodate crustal shortening after transpressional fault movements on the ERM-N became inactive in late Pleistocene or early Holocene and that movement along the ERM-N may resume if the Reelfoot thrust has an interval of inactivity in the future. Our results suggest how fault interactions within a strike-slip system can change, making faults with significant amounts of seismic potential appear as though they are inactive.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109502"},"PeriodicalIF":3.1,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661885","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 : 2024-11-08DOI: 10.1016/j.geomorph.2024.109494
Piers Larcombe , Peter J. Ross , Chris Fandry
The absence or paucity of known underwater cultural heritage (UCH) sites on the Australian inner shelf stands in stark contrast to the thousands of sites revealed elsewhere in the world. A series of papers have asserted the first in situ (i.e., primary context) UCH sites in the shallow waters of Murujuga (Dampier Archipelago), NW Australia, each arguing the stone artefact scatters are at least 7000 years old and are now submerged because of Post-Glacial sea-level rise. Subsequent papers presented new data and repeated these claims. We present new hydrodynamic modelling and data on coastal erosion and bathymetry, and re-assess each sites' sedimentary setting and archaeological site-formation history.
The arguments for these sites being of primary context and reflecting Early Holocene land surfaces are unfounded, and at best untested. All artefacts are of unknown age, and many or all are likely to have been reworked, including the subtidal artefacts in Flying Foam Passage. Such sites of secondary context, if treated appropriately, can inform our understanding of site-formation processes, and may support more powerful contributions to submerged archaeology than attempts to seek the first or the oldest.
{"title":"Applying geoarchaeological principles to marine archaeology: A new reappraisal of the “first marine” and “in-situ” lithic scatters, Murujuga (Dampier Archipelago), NW Australia","authors":"Piers Larcombe , Peter J. Ross , Chris Fandry","doi":"10.1016/j.geomorph.2024.109494","DOIUrl":"10.1016/j.geomorph.2024.109494","url":null,"abstract":"<div><div>The absence or paucity of known underwater cultural heritage (UCH) sites on the Australian inner shelf stands in stark contrast to the thousands of sites revealed elsewhere in the world. A series of papers have asserted the first <em>in situ</em> (i.e., primary context) UCH sites in the shallow waters of Murujuga (Dampier Archipelago), NW Australia, each arguing the stone artefact scatters are at least 7000 years old and are now submerged because of Post-Glacial sea-level rise. Subsequent papers presented new data and repeated these claims. We present new hydrodynamic modelling and data on coastal erosion and bathymetry, and re-assess each sites' sedimentary setting and archaeological site-formation history.</div><div>The arguments for these sites being of primary context and reflecting Early Holocene land surfaces are unfounded, and at best untested. All artefacts are of unknown age, and many or all are likely to have been reworked, including the subtidal artefacts in Flying Foam Passage. Such sites of secondary context, if treated appropriately, can inform our understanding of site-formation processes, and may support more powerful contributions to submerged archaeology than attempts to seek the first or the oldest.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109494"},"PeriodicalIF":3.1,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661881","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 : 2024-11-07DOI: 10.1016/j.geomorph.2024.109501
B.P. Graves , T.J. Ralph , A.M. Morgan
Improved knowledge regarding dryland river character and behaviour is important as the increasing threats of climate change and anthropogenic activities exacerbate water security issues in channels prone to discontinuity and termination. Dryland river character and behaviour is determined by a complex and dynamic interplay between extrinsic controls and intrinsic processes. Polacca and Oraibi Wash are two discontinuous dryland rivers, tributaries of the Little Colorado River in semi-arid, north-eastern Arizona, USA. Valley-scale morphometrics and downstream longitudinal trends were derived from remote sensing and geospatial analyses, hydraulic modelling, and field measurements, to assess the key controls, patterns, and processes driving channel diminution and discontinuity. Both rivers are entrenched along most of their valleys and experience downstream hydro-geomorphic changes as valley confinement eases in their low gradient floodplains. The rivers exhibit non-equilibrium responses to a concomitant decline in calculated discharge (from ∼82 to <4 m3 s−1), stream power (from ∼334 to <5 W m−2), and channel cross-sectional area (from ∼82 to <3 m2), which are the principal factors contributing to channel breakdown and the development of broad floodouts. Small distributary channels and avulsions are evident in the lowland reaches where channel discontinuity occurs, with a dominance of knickpoints in distal floodout reaches as they attempt to re-establish channel continuity. Using historical aerial imagery we show that knickpoint headcut retreat rates have ranged from ∼1.7 to 53 m a−1. Channel breakdown patterns and processes in the Polacca and Oraibi Washes are similar to other dryland rivers around the world, and reveal common underlying factors that are central to river termination and reformation. This study reveals a combination of intrinsic erosion and sedimentation processes and avulsion threshold responses that trigger channel adjustment resulting from downstream fluvial decline. However, key extrinsic controls, such as valley confinement and hydroclimate, influence and limit the rate and nature of these adjustments. Early recognition of these geomorphic changes can inform river, land, and water management strategies across the American southwest.
{"title":"Channel breakdown and avulsion in arroyos feeding the Little Colorado River, Arizona, USA","authors":"B.P. Graves , T.J. Ralph , A.M. Morgan","doi":"10.1016/j.geomorph.2024.109501","DOIUrl":"10.1016/j.geomorph.2024.109501","url":null,"abstract":"<div><div>Improved knowledge regarding dryland river character and behaviour is important as the increasing threats of climate change and anthropogenic activities exacerbate water security issues in channels prone to discontinuity and termination. Dryland river character and behaviour is determined by a complex and dynamic interplay between extrinsic controls and intrinsic processes. Polacca and Oraibi Wash are two discontinuous dryland rivers, tributaries of the Little Colorado River in semi-arid, north-eastern Arizona, USA. Valley-scale morphometrics and downstream longitudinal trends were derived from remote sensing and geospatial analyses, hydraulic modelling, and field measurements, to assess the key controls, patterns, and processes driving channel diminution and discontinuity. Both rivers are entrenched along most of their valleys and experience downstream hydro-geomorphic changes as valley confinement eases in their low gradient floodplains. The rivers exhibit non-equilibrium responses to a concomitant decline in calculated discharge (from ∼82 to <4 m<sup>3</sup> s<sup>−1</sup>), stream power (from ∼334 to <5 W m<sup>−2</sup>), and channel cross-sectional area (from ∼82 to <3 m<sup>2</sup>), which are the principal factors contributing to channel breakdown and the development of broad floodouts. Small distributary channels and avulsions are evident in the lowland reaches where channel discontinuity occurs, with a dominance of knickpoints in distal floodout reaches as they attempt to re-establish channel continuity. Using historical aerial imagery we show that knickpoint headcut retreat rates have ranged from ∼1.7 to 53 m a<sup>−1</sup>. Channel breakdown patterns and processes in the Polacca and Oraibi Washes are similar to other dryland rivers around the world, and reveal common underlying factors that are central to river termination and reformation. This study reveals a combination of intrinsic erosion and sedimentation processes and avulsion threshold responses that trigger channel adjustment resulting from downstream fluvial decline. However, key extrinsic controls, such as valley confinement and hydroclimate, influence and limit the rate and nature of these adjustments. Early recognition of these geomorphic changes can inform river, land, and water management strategies across the American southwest.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109501"},"PeriodicalIF":3.1,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-06DOI: 10.1016/j.geomorph.2024.109499
Chenhe Zhu , Fei Guo , Zhigang Zhang , Mingyuan Xu , Hong Zhang , Yiman Li , Shilong Li
Recognition of landforms associated with past glaciation is crucial for understanding past ice dynamics and their relationship to climate. With the development of artificial intelligence technology, deep learning techniques have assisted in the automatic extraction of glacial landforms, but these methods still face problems of low precision and weak transferability. This study proposes a new method named geomorphology-attention DeeplabV3+ (GA-DeeplabV3+) model. This method adds spatial attention and channel attention modules based on the DeeplabV3+ network and utilizes a combination of multi-modal geographic data. Verification shows that the model proposed in this paper significantly enhances the recognition precision of glacial troughs with cirques compared to existing models, reaching a Mean Intersection over Union (MIoU) of 86.2% and a mean Pixel Accuracy (mPA) of 90.64% in the area of the Palaeo-Daocheng ice cap. In addition, validation experiments were conducted in the Peiku Gangri region and the Tenasserim mountains, achieving MIoU scores of 70.09% and 73.28% respectively. This accomplishment represents a vital stride towards automating the extraction of palaeo-glacial landforms, which holds great significance for analyzing the scale and evolution of ancient glaciers.
{"title":"Recognition of palaeo-glacial troughs with cirques on parts of Tibetan Plateau using multi-modal datasets with deep learning models","authors":"Chenhe Zhu , Fei Guo , Zhigang Zhang , Mingyuan Xu , Hong Zhang , Yiman Li , Shilong Li","doi":"10.1016/j.geomorph.2024.109499","DOIUrl":"10.1016/j.geomorph.2024.109499","url":null,"abstract":"<div><div>Recognition of landforms associated with past glaciation is crucial for understanding past ice dynamics and their relationship to climate. With the development of artificial intelligence technology, deep learning techniques have assisted in the automatic extraction of glacial landforms, but these methods still face problems of low precision and weak transferability. This study proposes a new method named geomorphology-attention DeeplabV3+ (GA-DeeplabV3+) model. This method adds spatial attention and channel attention modules based on the DeeplabV3+ network and utilizes a combination of multi-modal geographic data. Verification shows that the model proposed in this paper significantly enhances the recognition precision of glacial troughs with cirques compared to existing models, reaching a Mean Intersection over Union (MIoU) of 86.2% and a mean Pixel Accuracy (mPA) of 90.64% in the area of the Palaeo-Daocheng ice cap. In addition, validation experiments were conducted in the Peiku Gangri region and the Tenasserim mountains, achieving MIoU scores of 70.09% and 73.28% respectively. This accomplishment represents a vital stride towards automating the extraction of palaeo-glacial landforms, which holds great significance for analyzing the scale and evolution of ancient glaciers.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109499"},"PeriodicalIF":3.1,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661880","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 : 2024-11-06DOI: 10.1016/j.geomorph.2024.109498
Monte Fleming , Cornelis Bootsman , Norman Moll , Leonard Brand
In areas of the Colorado Plateau, rock basins, or potholes, occur in abundance. Because of their impressive size and often enigmatic location, their presence begs an explanation. Our goal in undertaking this research is to suggest a model for the origin of Rock Window Mesa's potholes, by which we might better interpret the geomorphological history of the mesa and Chinle Valley. Data collection consisted of both field work and analysis of a high-resolution 3D point cloud of the mesa. The southern and western edges of the mesa, closest to the Chinle Wash, and close to where knickpoints may have been, are the areas of highest pothole density. The pothole-forming processes disrupted drainage systems, and pothole sizes do not correlate with the catchment areas of the potholes. There are abundant, fluvially deposited erratic pebbles and cobbles on the mesa, and the joints and cracks that are present in the bedrock exert little to no control over pothole morphology. These data suggest that the potholes were formed subaqueously. A proposal that may point us to a possible mechanism is that similar potholes, in the Navajo Sandstone exposed in the Henry Mountains, appear to have been formed via fluvial processes in over-steepened tributary junctions. At our research location, the water that carved out the potholes appears to have come from ENE, and the point at which this water met the Chinle Wash may have been over-steepened as a result of rapid incision of the Chinle Wash through the poorly lithified Navajo Sandstone.
{"title":"Pothole formation on Rock Window Mesa, Chinle valley, AZ","authors":"Monte Fleming , Cornelis Bootsman , Norman Moll , Leonard Brand","doi":"10.1016/j.geomorph.2024.109498","DOIUrl":"10.1016/j.geomorph.2024.109498","url":null,"abstract":"<div><div>In areas of the Colorado Plateau, rock basins, or potholes, occur in abundance. Because of their impressive size and often enigmatic location, their presence begs an explanation. Our goal in undertaking this research is to suggest a model for the origin of Rock Window Mesa's potholes, by which we might better interpret the geomorphological history of the mesa and Chinle Valley. Data collection consisted of both field work and analysis of a high-resolution 3D point cloud of the mesa. The southern and western edges of the mesa, closest to the Chinle Wash, and close to where knickpoints may have been, are the areas of highest pothole density. The pothole-forming processes disrupted drainage systems, and pothole sizes do not correlate with the catchment areas of the potholes. There are abundant, fluvially deposited erratic pebbles and cobbles on the mesa, and the joints and cracks that are present in the bedrock exert little to no control over pothole morphology. These data suggest that the potholes were formed subaqueously. A proposal that may point us to a possible mechanism is that similar potholes, in the Navajo Sandstone exposed in the Henry Mountains, appear to have been formed via fluvial processes in over-steepened tributary junctions. At our research location, the water that carved out the potholes appears to have come from ENE, and the point at which this water met the Chinle Wash may have been over-steepened as a result of rapid incision of the Chinle Wash through the poorly lithified Navajo Sandstone.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109498"},"PeriodicalIF":3.1,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661886","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 : 2024-11-06DOI: 10.1016/j.geomorph.2024.109500
Cuiping Kuang , Xin Cong , Lixin Gong , Jiantao Liu , Xuejian Han , Wei Xing
Pressures from anthropogenic activities and climate change in lagoon ecosystems have increased rapidly in recent years. Coastal vegetation serves as a natural sea defense mechanism and is pivotal in maintaining a robust ecological balance. However, our understanding of how vegetation influences the evolution of typical sandbar-lagoon coasts is limited. To address this gap, a series of mobile-bed flume experiments were conducted within a typical sandbar-lagoon cross-section to investigate the impact of sparse Phragmites spp. planted on the sandbar on wave propagation and the evolution of the cross-shore profile under varying water depths and irregular wave conditions. These findings revealed that vegetation attenuates infragravity and sea-swell waves. Notably, infragravity waves are associated with the formation of a right- or obtuse-angled foredune scarp, whereas sea-swell waves tend to create an acute-angled scarp. Vegetation-induced changes in the local amplitudes of short waves within wave groups and the local mean water level are instrumental in reshaping foredune scarps. Additionally, the cross-shore width of the vegetation had a more pronounced influence on sediment transport within the lagoon than that of the solid volume fraction. Sparse vegetation not only reduces sediment deposition in the lagoon but also enhances offshore sediment transport. These insights significantly advance our understanding of wave-vegetation-sediment dynamics and provide essential scientific support for the implementation of coastal ecological restoration initiatives, particularly in the context of sandbar-lagoon coasts.
{"title":"Cross-shore profile evolution induced by real emergent vegetation in a sandbar-lagoon coast: Laboratory experiments","authors":"Cuiping Kuang , Xin Cong , Lixin Gong , Jiantao Liu , Xuejian Han , Wei Xing","doi":"10.1016/j.geomorph.2024.109500","DOIUrl":"10.1016/j.geomorph.2024.109500","url":null,"abstract":"<div><div>Pressures from anthropogenic activities and climate change in lagoon ecosystems have increased rapidly in recent years. Coastal vegetation serves as a natural sea defense mechanism and is pivotal in maintaining a robust ecological balance. However, our understanding of how vegetation influences the evolution of typical sandbar-lagoon coasts is limited. To address this gap, a series of mobile-bed flume experiments were conducted within a typical sandbar-lagoon cross-section to investigate the impact of sparse <em>Phragmites</em> spp. planted on the sandbar on wave propagation and the evolution of the cross-shore profile under varying water depths and irregular wave conditions. These findings revealed that vegetation attenuates infragravity and sea-swell waves. Notably, infragravity waves are associated with the formation of a right- or obtuse-angled foredune scarp, whereas sea-swell waves tend to create an acute-angled scarp. Vegetation-induced changes in the local amplitudes of short waves within wave groups and the local mean water level are instrumental in reshaping foredune scarps. Additionally, the cross-shore width of the vegetation had a more pronounced influence on sediment transport within the lagoon than that of the solid volume fraction. Sparse vegetation not only reduces sediment deposition in the lagoon but also enhances offshore sediment transport. These insights significantly advance our understanding of wave-vegetation-sediment dynamics and provide essential scientific support for the implementation of coastal ecological restoration initiatives, particularly in the context of sandbar-lagoon coasts.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109500"},"PeriodicalIF":3.1,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661854","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}
To estimate long-term rates of coastal uplift along the northern Pacific coast of Northeast Japan, we determined the surface exposure ages of marine and fluvial terraces based on terrestrial in situ cosmogenic radionuclide dating of exposed bedrock surfaces. Based on reinterpretation of marine and fluvial terraces, we collected samples from the northern and southern Sanriku coast. The surface exposure ages from 10Be concentrations in quartz calculated from the measured 10Be/9Be ratios commonly suggest MIS 5 and MIS 7 for the marine and fluvial terraces and averaged coastal uplift rates of ca. 0.25 ± 0.15 and 0.4 mm/yr along the northern and southern Sanriku coast at intermediate timescales. The results may demonstrate different styles of crustal strain accommodation in the northern Northeast Japan arc above the subducting Pacific plate.
为了估算日本东北部北太平洋沿岸的长期海岸隆升速率,我们根据暴露基岩表面的陆地原位宇宙放射性核素测年法,确定了海洋和河流阶地的地表暴露年龄。根据对海洋和河流阶地的重新解释,我们在三陆海岸北部和南部采集了样本。根据测得的 10Be/9Be 比率计算出的石英中 10Be 浓度所得出的地表暴露年龄通常表明,海洋阶地和河川阶地的年代为 MIS 5 和 MIS 7,三陆海岸北部和南部的平均海岸隆升速率为大约 0.25 ± 0.15 和 0.4 毫米/年(中时间尺度)。这些结果可能表明,俯冲太平洋板块之上的日本东北弧北部地壳应变容纳方式不同。
{"title":"Surface exposure ages of middle–late Pleistocene marine and fluvial terraces along the northern and southern Sanriku coasts, Northeast Japan","authors":"Sachi Wakasa , Tatsuya Ishiyama , Daisuke Hirouchi , Nobuhisa Matta , Natsuko Fujita , Tomoo Echigo","doi":"10.1016/j.geomorph.2024.109497","DOIUrl":"10.1016/j.geomorph.2024.109497","url":null,"abstract":"<div><div>To estimate long-term rates of coastal uplift along the northern Pacific coast of Northeast Japan, we determined the surface exposure ages of marine and fluvial terraces based on terrestrial in situ cosmogenic radionuclide dating of exposed bedrock surfaces. Based on reinterpretation of marine and fluvial terraces, we collected samples from the northern and southern Sanriku coast. The surface exposure ages from <sup>10</sup>Be concentrations in quartz calculated from the measured <sup>10</sup>Be/<sup>9</sup>Be ratios commonly suggest MIS 5 and MIS 7 for the marine and fluvial terraces and averaged coastal uplift rates of ca. 0.25 ± 0.15 and 0.4 mm/yr along the northern and southern Sanriku coast at intermediate timescales. The results may demonstrate different styles of crustal strain accommodation in the northern Northeast Japan arc above the subducting Pacific plate.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109497"},"PeriodicalIF":3.1,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-03DOI: 10.1016/j.geomorph.2024.109496
Katja Laute, Achim A. Beylich
Most existing studies on rockwall frost regimes and frost weathering at rockwalls focus on permafrost-affected rockwalls. However, a high share of rockwall surface areas in Norway and in many other cold-climate environments is actually free of permafrost. It is therefore of interest how these permafrost-free rockwall systems will respond to future changes in air and rock temperatures. In this study, we report field measurements conducted at rockwalls beneath the current permafrost limit and investigate thermal regimes at rockwalls that include both rockwall areas with and without permafrost. We present a unique dataset of up to ten years of rockwall temperature measurements from ten temperatures sensors installed in two mountain valleys in western Norway. An analysis of the different rockwall thermal regimes with respect to rock weathering and associated rockfall supply for both, permafrost-affected and permafrost-free rockwalls is provided. The highest intensity of recent rockwall weathering including determined rockwall retreat rates and associated rockfall supply is detected for northeast-facing rockwalls followed by south-facing rockwalls in our study area. Frost cracking activity, probably in the form of segregation ice growth, seems to be an important factor particularly for the high weathering intensity on northeast-facing rockwalls whereas solar radiation-induced thermal stresses, which favour incremental subcritical crack growth, is assumed to play a relevant role in the moderate weathering intensity on south- and southwest-facing rockwalls. A mean annual and study area-wide rockwall retreat rate of 0.24 mm yr−1 is estimated for our ten-year investigation period (2010−2020) which is comparable to other published rates in similar lithologies and climates. As it can be assumed that seasonal frost regimes and permafrost will react differently to ongoing and future climate changes, more attention should be paid to analyse these two different thermal regimes with respect to possible varied implications for mechanical rockwall weathering and associated rockfall supply.
{"title":"Relating ten years of rock temperature monitoring to rockwall weathering processes in steep mountain valleys in western Norway","authors":"Katja Laute, Achim A. Beylich","doi":"10.1016/j.geomorph.2024.109496","DOIUrl":"10.1016/j.geomorph.2024.109496","url":null,"abstract":"<div><div>Most existing studies on rockwall frost regimes and frost weathering at rockwalls focus on permafrost-affected rockwalls. However, a high share of rockwall surface areas in Norway and in many other cold-climate environments is actually free of permafrost. It is therefore of interest how these permafrost-free rockwall systems will respond to future changes in air and rock temperatures. In this study, we report field measurements conducted at rockwalls beneath the current permafrost limit and investigate thermal regimes at rockwalls that include both rockwall areas with and without permafrost. We present a unique dataset of up to ten years of rockwall temperature measurements from ten temperatures sensors installed in two mountain valleys in western Norway. An analysis of the different rockwall thermal regimes with respect to rock weathering and associated rockfall supply for both, permafrost-affected and permafrost-free rockwalls is provided. The highest intensity of recent rockwall weathering including determined rockwall retreat rates and associated rockfall supply is detected for northeast-facing rockwalls followed by south-facing rockwalls in our study area. Frost cracking activity, probably in the form of segregation ice growth, seems to be an important factor particularly for the high weathering intensity on northeast-facing rockwalls whereas solar radiation-induced thermal stresses, which favour incremental subcritical crack growth, is assumed to play a relevant role in the moderate weathering intensity on south- and southwest-facing rockwalls. A mean annual and study area-wide rockwall retreat rate of 0.24 mm yr<sup>−1</sup> is estimated for our ten-year investigation period (2010−2020) which is comparable to other published rates in similar lithologies and climates. As it can be assumed that seasonal frost regimes and permafrost will react differently to ongoing and future climate changes, more attention should be paid to analyse these two different thermal regimes with respect to possible varied implications for mechanical rockwall weathering and associated rockfall supply.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109496"},"PeriodicalIF":3.1,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661882","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}