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Abstract In Southwest China (SWC) soil loss is becoming a serious threat to the sustainable development of resources and the health of the environment. A large number of studies have been conducted to investigate the causes (e.g. environmental factors and human activities) and impacts (e.g. karst rocky desertification) of soil loss. However, the following are some important problems related to soil loss in the karst of SWC: 1) although soil loss is caused by chemical weathering, gravity and water interaction in karst, the mechanisms by which soil loss takes place in the SWC and their interaction are still not clear; 2) subsurface soil loss varies under different geological and hydrological conditions, and there is still no consensus on the common the ratio between surface soil erosion and underground soil loss; 3) traditional methods for soil loss risk assessment are difficult to apply over the whole of SWC; and 4) a large number of studies have been published only in Chinese and remain inaccessible to the international science community. Therefore, a review paper is needed to address this gap and introduce the contributions of Chinese researchers to soil loss in karst. This paper proposes a novel modelling approach for the grouped soil loss styles and presents a comprehensive discussion for the mechanism, causes, and risk assessment of the various soil loss styles in SWC karst. Graphical abstract Unlabelled Image Highlights • Soil is eroded not only in the surface but also in the underground rock layer. • Surface/subsurface soil loss and soil leakage are typical soil loss styles in karst. • Novel modelling is proposed to discretize the grouped soil loss styles in karst. [ABSTRACT FROM AUTHOR]

Paleo-altitude reconstructions using oxygen isotopes provide past surface elevation data that can constrain the topographic evolution of mountain belts. This paper presents oxygen and carbon stable isotopic compositions of gastropod fossils, carbonate cements, and shelly sandstones in the Anjihai and Shawan formations located in the Sikeshu drainage basin, northern Tianshan, western China. Correlations between the stable isotopic compositions and lithofacies suggest that the Sikeshu drainage basin was mainly an open hydrological depositional environment. Based on the oxygen isotopic compositions of the gastropod fossils and petrographic examination, the δ13C and δ18O values have not been reset by late-stage diagenesis. Paleo-altitudes were reconstructed using the corrected paleo-surface water δ18O psw values recovered from gastropod fossils, carbonate cements, and shelly sandstones. An empirical formula was developed to calculate the paleo-latitudes when the Anjihai and Shawan formations were deposited. The paleo-altitude of the Sikeshu drainage basin had attained an elevation exceeding 2000 m by 28 Ma, similar to the present-day elevation in this area. This conclusion contributes to our understanding of the extent of surface uplift in the Cenozoic of Tianshan and the climatic differences on either side of Tianshan during the Cenozoic. Unlabelled Image • This study is the first in Tianshan to provide quantitative evidence for uplift and exhumation. • δ18O date of gastropod fossil analyzed in situ by NanoSIMS rule out diagnetic reset. • Paleoelevation of the north of Tianshan have exceeded 2000 m at least before 28 Ma. [ABSTRACT FROM AUTHOR]

The occurrence of earthquakes has the potential to significantly modify river morphology and cause notable effects on the aquatic ecosystem. Prior to the 2008 Wenchuan earthquake with a magnitude of 8.0, the Shiting River located in the upper basin of the Yangtze River was stable. Rapid bed incision or degradation has continued since the earthquake, and weirs and bank revetments were constructed to mitigate degradation. The impacts of channel morphology adjustment and human activities on biodiversity are not clear, which prohibits efficient river restoration. This paper evaluated the morphological quality of the Shiting River by employing the Morphological Quality Index (MQI), an approach recommended in the European Water Framework Directive. Macroinvertebrate diversity was analyzed in relation to the impacts of morphological adjustment and human activities based on field data collected in 2021. The results showed that the channel degraded and deepened after the earthquake, the planform changed from multi-threaded to single-threaded, and swamps on the floodplains disappeared. The quality of channel morphology in 2021 was evaluated using the MQI and was found to be ranging from poor to moderate. The diversity metrics of macroinvertebrates, specifically the Shannon, Simpson, and Evenness indices, exhibited a positive and significant correlation with four MQI sub-indices, which represented channel geomorphological functionality, artificiality, morphological pattern, and substrate, respectively. However, there was no significant correlation observed between the diversity metrics and the overall MQI score. The results imply that channels with superior morphological functionality, slower channel adjustment, and lower levels of anthropogenic disturbances tend to exhibit greater macroinvertebrate diversity. The study found a significant decrease in macroinvertebrate richness downstream of weirs and bridges. The community structures upstream and downstream of weirs and bridges were also significantly different. This study may help inform the ecological response of rivers to dynamic morphological changes and intense anthropogenic disturbances following disastrous earthquakes. • Post-earthquake channel morphological quality was poor to moderate. • Channels with higher morphological quality had higher macroinvertebrate diversity. • Morphology changes and human activities impacted macroinvertebrates. • Higher macroinvertebrate richness upstream of weirs and bridges than downstream. [ABSTRACT FROM AUTHOR]

The coastal mountain system (CMS) of southeastern China has been a natural place to study paleotopographic changes primarily due to its marked topographical contrast since the Late Cretaceous. For a quantitative reconstruction of the paleotopographic evolution of the CMS, this paper provides key information from along the Ningde–Jianyang and Huilai–Longchuan cross-sections using apatite (U-Th)/He (AHe) and zircon (U-Th)/He (ZHe) data combined with thermal history and paleotopographic modeling. For the Ningde–Jianyang section, the AHe dates are in the range of 44.3–70.8 Ma, and the ZHe dates are between 58.5 and 102.9 Ma. For the Huilai–Longchuan section, the resulting AHe dates are in the range of 37.9–73.8 Ma, and ZHe dates are between 65.5 and 119.7 Ma. The modeling results suggest that: 1) the CMS had an asymmetric topography during the Late Cretaceous with the SE segment being significantly higher (peak elevation = 3.8 km) than the NW segment (peak elevation = ~2 km). The marked decreases in elevation and relief of the CMS occurred during 80–40 Ma, followed by relatively minor topographic changes since ~40–30 Ma; 2) The SE segment of the southern CMS experienced significantly faster exhumation (~0.44 km/Myr) than northern CMS (0.16 km/Myr) during 70–60 Ma, which was probably related to thinning of the crust and orogenic collapse linked to the initial-rifting of the South China Sea; 3) The SE segment of southern CMS experienced slower exhumation than northern CMS during 60–40 Ma, likely resulting from the lower elevations in the southern CMS than in the northern CMS during 60–40 Ma. • The coastal mountain system forms a climatic boundary in southeastern China. • Thermochronological data collected along two horizontal transects. • Transect thermochronology results used for topography modeling. • Rapid exhumation from 70-60 Ma along the south 2-D transect linked to rifting. • Rapid exhumation from 60–40 Ma along the north 2-D transect linked to climate change. [ABSTRACT FROM AUTHOR]

Abstract Massive bed degradation (20 m in 7 years) has been observed in the Shi‑ting River, Sichuan Province, China, since the 2008 Wenchuan Ms. 8.0 earthquake. The reason for the massive bed degradation has not been well understood. A hypothesis has been proposed that relates bed degradation to the augmentation of sand supply after the earthquake. The effect of sand on gravel mobility (magic sand effect) has long been observed in laboratory experiments. In this paper, we study whether the augmentation of sand supply and its magic sand effect can lead to the observed massive degradation at decadal scales. A one-dimensional river morphodynamic model is implemented to study the problem in general at field scale and in context of the gravel-bed Shi‑ting River. Sediment transport is calculated with the Wilcock and Crowe (2003) relation, in which the magic sand effect is explicitly embedded in terms of a function relating reference Shields number to the surface sand fraction. We find that the augmentation of gravel supply leads to bed aggradation, whereas the augmentation of sand supply can indeed lead to bed degradation and surface fining. The magnitude and timescale of bed degradation are not sensitive to the sand supply rate but are sensitive to the flood intermittency factor , i.e., the fraction of time the river is in flood. However, an unrealistic flood intermittency factor (≥0.3) would be required in order to match the observed timescale of bed degradation, thus indicating that the magic sand effect might not be the governing reason for massive bed degradation in the Shi‑ting River, and by implication in gravel-bed rivers in general. Our simulation results also indicate that despite the fact that magic sand effects are not explicitly included in most sediment transport relations, they are at least partly built in via the hiding function that is contained in most sediment transport relations for gravel-sand mixtures. While here we use the Shi‑ting River as an example, our results have applicability to gravel-bed rivers subjected to augmentation in sand supply in general. Highlights • Augmentation of gravel supply leads to bed aggradation • Augmentation of sand supply leads to enhanced gravel transport and bed degradation • Magic sand effects alone cannot induce the observed river incision at decadal scale • Magic sand effects can be partly incorporated with a dimensionless hiding function [ABSTRACT FROM AUTHOR]

In this paper we present new and review already existing landslide and earthquake data for a large part of the Tien Shan, Central Asia. For the same area, only partial databases for sub-regions have been presented previously. They were compiled and new data were added to fill the gaps between the databases. Major new inputs are products of the Central Asia Seismic Risk Initiative (CASRI): a tentative digital map of active faults (even with indication of characteristic or possible maximum magnitude) and the earthquake catalogue of Central Asia until 2009 that was now updated with USGS data (to May 2014). The new compiled landslide inventory contains existing records of 1600 previously mapped mass movements and more than 1800 new landslide data. Considering presently available seismo-tectonic and landslide data, a target region of 1200 km (E–W) by 600 km (N–S) was defined for the production of more or less continuous geohazards information. This target region includes the entire Kyrgyz Tien Shan, the South-Western Tien Shan in Tajikistan, the Fergana Basin (Kyrgyzstan, Tajikistan and Uzbekistan) as well as the Western part in Uzbekistan, the North-Easternmost part in Kazakhstan and a small part of the Eastern Chinese Tien Shan (for the zones outside Kyrgyzstan and Tajikistan, only limited information was available and compiled). On the basis of the new landslide inventory and the updated earthquake catalogue, the link between landslide and earthquake activity is analysed. First, size–frequency relationships are studied for both types of geohazards, in terms of Gutenberg–Richter Law for the earthquakes and in terms of probability density function for the landslides. For several regions and major earthquake events, case histories are presented to outline further the close connection between earthquake and landslide hazards in the Tien Shan. From this study, we concluded first that a major hazard component is still now insufficiently known for both types of geohazards – and even totally unknown for most giant landslides: the time information. Thus, dating rockslides and any large mass movement is a crucial factor in order to better constrain related hazards. Second, we highlight the role of coupled hazards in the Tien Shan – inside the mountain range the largest disasters were caused by earthquake-triggered landslides and massive earth flows. Therefore, it is of prime importance for these mountain regions to complement single hazard assessment by coupled hazard scenarios. On the basis of these scenarios, risk evaluations may then be completed considering direct impacts on artificial dams, hydropower schemes, mining and road infrastructure as well as remote effects from possible dam breaches and mobilisation of mining and nuclear waste storages. Basic hazard and risk components are partly analysed in this paper and partly in a companion paper ‘Tien Shan geohazards database: Landslide susceptibility and impacts’. [ABSTRACT FROM AUTHOR]

Numerical modeling of landform evolution is the key to understanding the formation of land surfaces. However, landform evolution occurs under certain initial topographic conditions, while existing landform evolution models often use a plane or a randomly produced surface to establish the initial topographic conditions. This misunderstanding of the initial topographic conditions causes the landform evolution results to deviate greatly from the real terrain. Therefore, the initial topographic conditions must be reconstructed and integrated into the current numerical landform evolution model. In this paper, the Loess Plateau of China was selected as a typical sample area. The paleotopography was reconstructed and integrated into the numerical landform evolution model. Based on the evolutionary mechanism of loess landforms, modules of surface erosion, matter diffusion and precipitation were selected to construct a numerical model of loess landform evolution. Moreover, randomly produced terrain was used as the initial conditions during the landform evolution process and compared with the paleotopography-constrained evolution results. In addition, the results of the landform evolution process were evaluated with different terrain factors, and the uncertainty of the model was assessed by comparing different model conditions. The results show that, due to the control of paleotopography, the evolution results can maintain the main morphological structure of valleys in the loess landscape. Without considering the paleotopography, a large difference exists between the evolution results and the true ground terrain. These results show that paleotopography is an important feature of loess landform evolution modeling and is indispensable for reasonably expressing the process of landform evolution. Finally, the numerical modeling of loess landform evolution with the consideration of paleotopography can not only help to achieve a better understanding of the loess landform evolution process but also provide a reference for feature dependent landform evolution modeling in different landform applications. • Paleotopography affects the evolution of loess landform in the Loess Plateau. • We integrate the paleotopography into the numerical loess landform evolution model. • Our results can maintain the main morphological structure of loess landform. • Our research provides a reference for feature-concerned landform evolution modeling. [ABSTRACT FROM AUTHOR]

Ground fissures are a geological hazard with complex formation mechanisms. Increasing amounts of human activity have created more ground fissures, which can destroy buildings and threaten human security. Some ground fissures indicate potentially devastating earthquakes, so we must pay attention to these hazards. This paper documents recently discovered ground fissures in the Hetao basin. These ground fissures are located along the frontal margins of the terraces of the Sertengshan piedmont fault. These fissures are 600–1600 m long, 5–50 cm wide, and at most 1 m deep. These ground fissures emerged after 2010 and ruptured newly constructed roads and field ridges. The deep geodynamic mechanisms within this extensional environment, which is dominated by NE-SW principal compressive shear, involve N-S tensile stress, which has produced continuous subsidence in the Hetao basin and continuous activity along the Sertengshan piedmont fault since the late Quaternary. Trenches across the ground fissures reveal that the fissures are the latest manifestation of the activity of preexisting faults and are the result of creep-slip movement along the faults. The groundwater level in the Hetao basin has been dropping since the 1960s because of overexploitation, resulting in subsidence. When the tensile stress exceeds the ultimate tensile strength of the strata, the strata rupture along preexisting faults, producing ground fissures. Thus, the Sertengshan piedmont fault planes are the structural foundation of the ground fissures, and groundwater extraction induces the development of ground fissures. [ABSTRACT FROM AUTHOR]

Cirques are typical erosional landforms of glaciers and have been used as bases for paleoclimate and paleoenvironment reconstruction and for understanding the interactions between glacial erosion, climate, and topography. The availability of high-resolution digital elevation models (DEMs) provides the opportunity to map large populations of cirques for regional and global scale analysis. However, cirque outlines are still mainly determined based on manual digitization, which is time consuming and labor intensive. This paper introduces an automated method to recognize and delineate cirques using DEMs based on a series of hydrological and morphological analyses, including delineating stream network, filtering streams, determining potential cirque threshold points, and delineating cirque outlines. A semi-automated tool is also developed based on user-specified threshold points or cross sections. The related tools are coded in python and imported into ArcGIS as a toolbox, AutoCirque, with user friendly interfaces. Comparison in a test area of the eastern Tian Shan, China, indicated that the population statistics are relatively consistent between manually digitized and auto-delineated cirques. Detailed comparisons for 11 selected cirques indicated that the AutoCirque-delineated and manually digitized cirque outlines are similar in shape with an average boundary offset of approximately one DEM cell size (30 m) and a 70–90% overlap-fit percentage. The derived cirque metrics are also similar, especially for elevation, slope, and aspect related metrics. This toolbox can significantly speed up the analytical processes, remove the subjectivity in delineating cirque outlines, and allow for the comparison of cirque morphology and metrics at regional and global scales. • This paper presents an automated method to delineate cirque outlines from DEMs. • The developed ArcGIS toolbox incudes both fully automated and semi-automated tools. • Delineated cirques have consistent population statistics with manual-digitized ones. • Manual- and auto-derived cirques are similar in shape with high overlap percentage. • This toolbox allows for large population analyses of cirques at different scales. [ABSTRACT FROM AUTHOR]

Reconstructing three-dimensional palaeoglacier surface, thickness, and volume provides useful information for quantifying palaeo-climate conditions during glacial stages and assessing the impact of glacier change on water resources. A glacial flowline model has been implemented in Excel and ArcGIS to reconstruct palaeoglaciers based on digital elevation models and geomorphic constraints, such as moraines and trimlines that represent the margins and local heights of palaeoglaciers, respectively. However, significant efforts are still needed in using these tools for palaeoglacier reconstruction, such as digitizing flowlines, adjusting shear stress, and deriving shape factors. This paper presents an automated method, PalaeoIce, to reconstruct palaeoglaciers using geomorphic constraints. Coded in python, PalaeoIce is an ArcGIS toolbox with a set of tools to generate glacial flowlines, optimize shear stress, derive shape factors, calculate ice thickness values along flowlines, and interpolate palaeo ice surfaces based on geomorphic constraints. The use of PalaeoIce is demonstrated using extant glaciers with measured thickness values and moraines/trimlines of the Little Ice Age (LIA) and Marine Isotope Stage (MIS) 2 in the eastern Tian Shan, China. The reconstructed ice thickness values of Glacier No. 1 in this area show a reasonable agreement with field measurements with 1.4 % and 5.4 % differences between measured and reconstructed mean ice thickness values using the two methods included in PalaeoIce: a revised ice thickness model for extant glaciers and a palaeoglacier reconstruction method based on glacier outlines, respectively. Two approaches are then illustrated for palaeoglacier reconstructions using two sets of geomorphic constraints: one with the fully reconstructed glacier outlines during the LIA, and the other with just the terminal moraine and limited trimlines during MIS 2. PalaeoIce can significantly improve the efficiency of palaeoglacier reconstructions and the understanding of the impact of glacier change on water resources. • An automated method, PalaeoIce, is presented for palaeoglacier reconstruction. • Tools are developed to create flowlines, modify DEM, and reconstruct palaeoglaciers. • Reconstructed ice thickness data are validated by field measurements in Tian Shan. • Target geomorphic features are of importance for palaeoglacier reconstruction. [ABSTRACT FROM AUTHOR]

Abstract: The magnitude of bankfull discharge is an important indicator of the discharging capacity of the Lower Yellow River (LYR), and bankfull discharges at key sections need to be accurately estimated before each experiment of regulating water and sediment in the Yellow River. In this paper, a definition of bankfull stage is first proposed for complicated cross sections in the LYR, including the identification of the main-channel zone and corresponding bankfull elevation, and the geometrical characteristics of typical cross-sectional profiles are investigated during different periods. Four different approaches are listed herein to determine the magnitude of bankfull discharge in the LYR, including a method using the mean daily stage–discharge relation, a method using the instantaneous stage–discharge relation, a method using the stage–velocity relation, and a method using the simulated stage–discharge relation from a one-dimensional hydrodynamic model. The advantages, disadvantages, and applicability of these approaches are pointed out. Finally, the Huayuankou section in the braided reach of the LYR is selected as a study section, and the bankfull discharges at this section during different periods are estimated using these four methods. In addition, the predicted water levels from these approaches are compared with the observed values for the corresponding maximum discharges occurring in the next year. Calculated results show that existing approaches determining the magnitude of bankfull discharge are usually only applicable to specified hydrometric sections with negligible morphological changes during flood seasons, and the fourth method proposed in this paper has higher prediction accuracy than the other methods. [Copyright &y& Elsevier]

Abstract: This paper presents a rational method for estimating the maximum discharge of a landslide-induced debris flow. The method has five basic principles or steps: (a) to identify and measure representative bends and straight zones along a channel through which a debris flow went down; (b) to evaluate peak debris flow velocity in the bends; (c) to assess peak debris flow velocity in the straight channel zones; (d) to use the peak velocities to estimate the distribution of peak discharge along the entire channel; and (e) to find the maximum velocity and discharge of the debris flow. The method is illustrated with a case study of a landslide-induced debris flow at a mountainous region near Chengdu, southwestern China. The results show that the peak debris velocity was between 2.4 and 4.7 m s−1 and the peak debris discharge was between 6.7 and 35.7 m3 s−1. The peak discharge initially increased at the upper portion of the channel, then decreased at the lower portion, indicating that the upper channel experienced erosion but the lower channel experienced deposition. The location with the maximum debris flow discharge corresponds to the point where the volume of the debris flow started to decrease. The method presented in this paper can help to prevent or mitigate debris flow hazards. [Copyright &y& Elsevier]

This paper is the second part of a new geohazards analysis applied to a large part of the Tien Shan, Central Asia, focused on landslide susceptibility computations that are based on recently compiled geographic, geological and geomorphological data. The core data are a digital elevation model, an updated earthquake catalogue, an active fault map as well as a new landslide inventory. The most recently added digital data are a new simplified geological map, an annual precipitation map, as well as river and road network maps that were produced for the Kyrgyz and Tajik parts of the Tien Shan. On the basis of these records we determine landslide densities with respect to morphological (M), geological (G), river distance (R), precipitation (P), earthquake (E) and fault (F) distance factors. Correlations were also established between scarp locations and the slope angle, distance to rivers, curvature. These correlations show that scarps tend to be located on steeper slopes, farther from rivers and on more convex terrain than the entire landslides. On the basis of the landslide density values computed for each class of the aforementioned factors, two landslide susceptibility maps are created according to the Landslide Factor analysis: the first one considers correlations between the landslide occurrences and the first four factors (MGRP); the second one is based on the first map (MGRP) combined with the seismo-tectonic influence (+ E + F) on landslide distributions. From the comparison of these two maps with actual landslide distributions we infer that the distances to rivers as well as to faults and past earthquakes most strongly constrain the susceptibility of slopes to landslides. We highlight several zones where the landslide susceptibilities computed for the MGRP + E + F factors fit better the observed concentration of landslides than those computed for the MGRP factors alone. For a few zones, both maps produce high landslide susceptibilities that do not well reflect the observed low sub-regional landslide activity; for some cases, we consider that some influencing factors must not have been well taken into consideration, for others we show that we simply had missed landslide detections. At the scale of the mountain range, the computed landslide susceptibility maps fit the observed landslide distributions relatively well, but these maps only represent the spatial component of landslide hazards. Temporal aspects are not considered by this analysis. [ABSTRACT FROM AUTHOR]

Although temperature is considered a key factor influencing rock decay, little is known about the quantitative relationship between a rock's decay rate and temperature, which makes it difficult to quantitatively predict the rate of rock decay under varied temperature during wetting–drying cycle conditions. Thus, the aim of the present paper was to observe the decay rate of various purple mudstones and to develop a model with which to calculate their decay rates under varied temperature conditions. Three types of purple mudstone were sampled from the Tuodian group (J 3 t), Matoushan group (K 2 m) and Lufeng group (J 1 l), located in the Chuxiong district of Yunnan province, south-western China. All samples were manually cut into cubes of 50 × 50 × 50 mm, before being subjected to 39 wetting–drying cycles in a 2 mm sieve under artificial constant temperature, natural daily temperature variation and artificial temperature alternation (minimum and maximum) treatments in the laboratory. Decay rates were calculated by weighing the mass remaining in the sieve after each treatment cycle. The results showed that the decay rates of the tested rocks rose with an increase in temperature and temperature difference (maximum–minimum), with the rank order of decay rate being J 3 t > K 2 m > J 1 l. Quantitative analysis revealed rock decay rate to be significantly related to temperature by a power function, and exponentially related to temperature difference. Our results suggested that temperature difference has a stronger effect on purple mudstone decay than that of temperature magnitude during the wetting–drying processes. [ABSTRACT FROM AUTHOR]

River confluences are key nodes in fluvial systems. Past studies on large river confluences were focused on the Paranà, Amazon, and Yangtze rivers, while the Yarlung Zangbo River (YZR), the longest plateau river in China, has not been investigated yet. This paper investigates a large multi-channel confluence between the YZR and one of its major tributaries, the anabranching Niyang River (NR). A remote-sensing study of this area demonstrated that the confluence planform is very stable compared with its upstream and downstream reaches that suffered from sandbar migration, meandering, and the development of a head-cut. A field survey using Acoustic Current Doppler Profiling (ADCP) was conducted at the confluence in June 2019, when the YZR and NR had discharges of about 1393 m3/s and 1299 m3/s in total, respectively. Although the discharge ratio of this confluence attained a value of 0.93, the existence of an estuary delta with a large area of floodplain largely weakened the impact of the NR on the dynamics of the YZR. The inflows of the multiple channels of the NR separated by the delta created an evident and long mixing interface and produced the left-side secondary cells in the YZR. In contrast, the curved riverbank played a more important role in the formation of deep scour holes, generating heterogeneity of the velocity distribution and the fast-mixing of flows. This study leads to an advancement in our current knowledge about multi-channel confluences. • Remote sensing images show that the plateau river confluence planform is very stable. • A field survey on flow and morphological features of the confluence was conducted. • The estuary delta with large floodplain largely weakened the confluence dynamics. • The curved river bank played an important role in river bed scours and flow mixing. [ABSTRACT FROM AUTHOR]

The Yellow River (YR) flows from Northwest China to North China, crossing three topographic steps: the Tibetan Plateau, the Chinese Loess Plateau (CLP), and the North China Plain (NCP). Determining the river's geomorphological evolution is significant for understanding the formation of macro-geomorphic patterns in China. However, the formation age of YR channelization into the Bohai Sea is highly controversial and uncertain, with estimates ranging from the Late Miocene to the Late Pleistocene. This study conducted grain size analysis, whole-rock geochemistry, and detrital zircon U-Pb dating on ~5.2 Ma sediments from borehole G4 drilled in the Bohai Bay. The geochemical results from borehole G4 indicate that chemical weathering was weak during 5.2–1.6 Ma, but showed diverse characteristics since ~1.6 Ma. Moreover, concordant detrital zircons from borehole G4 (~1.6 Ma) yield a major age population of 350–550 Ma, which, however, is scarcely produced by detrital zircons from the nearby Yanshan and Taihang Mountains. Geochemical signals and detrital zircon U-Pb geochronology suggest that the YR reached the NCP after cutting through the Sanmen Gorge and entered the Bohai Bay since ~1.6 Ma. The massive presence of sediments with an age population of 650–1350 Ma in the top of borehole G4 demonstrates that the present topography of the middle and upper reaches of the YR initially formed at ~0.6 Ma. Subsequently, changes in provenance since ~1.6 Ma influenced the records of paleoclimatic signals indicated by elemental geochemistry in the Bohai Bay. Because of detrital inputs from the YR, the (La/Sm) N and (La/Yb) N ratios of borehole G4 abruptly increased after ~1.6 Ma. Other geochemical indicators exhibited no noticeable variation trend, which differs from the decreasing trend of deep-sea δ18O records, the Chemical Index of Alteration (CIA), and the 87Sr/86Sr ratio of the loess from the Chinese Loess Plateau after the YR entered the NCP at ~1.6 Ma. This paper proposes that the YR gradually triggered fluvial erosion up to its upper reaches after entering the NCP, which is primarily in response to climate change. • Detrital zircon U-Pb geochronology and elemental geochemistry of borehole sediments in Bohai Bay indicate the geomorphological evolution of Yellow River • Yellow River cut through the Sanmen Gorge and reached the North China Plain at ~1.6 Ma • The current geomorphic of the middle and upper reaches of Yellow River was initially formed ~0.6 Ma • Changes in provenance since ~1.6 Ma have influenced the records of paleoclimatic signals in Bohai Bay [ABSTRACT FROM AUTHOR]

Abstract: This paper aims to develop a novel hybrid model for assessing landslide susceptibility at the regional scale using multisource data to produce a landslide susceptibility map of the Zigui–Badong area near the Three Gorges Reservoir, China. This area is subject to anthropogenic influences because the reservoir's water level fluctuates cyclically between 145 and 175m; in addition, the area suffers from extreme rainfall events due to the local climate. The area has experienced significant and widespread landslide events in recent years. In our study, a novel hybrid model is proposed to produce landslide susceptibility maps using geographical information systems (GIS) and remote sensing. The hybrid model is based on rough set (RS) theory and a support vector machine (SVM). RS theory is employed as an attribute reduction tool to identify the significant environmental parameters of a landslide, and an SVM is used to predict landslide susceptibility. Four data domains were considered in this research: geological, geomorphological, hydrology, and land cover. The original group of 20 environmental parameters and 202 landslides were used as the inputs to produce a landslide susceptibility map. According to the map, 19.7% of the study area was identified as medium- and high-susceptibility zones encompassing 89.5% of the historical landslides. The results indicate high levels of landslide hazard in and around the main inhabited areas, such as Badong County and other towns, as well as in rural residential areas and transportation areas along the Yangtze River and its tributaries. The predicted map indicates a good correlation between the classified high hazard areas and slope failures confirmed in the field. Furthermore, the quality of the proposed model was comprehensively evaluated, including the degree of model fit, the robustness of the model, the uncertainty associated with the probabilistic estimate, and the model prediction skill. The proposed model was also compared with the general SVM, which demonstrated that the hybrid model has superior prediction skill and higher reliability and confirmed the usefulness of the proposed model for landslide susceptibility mapping at a regional scale. [Copyright &y& Elsevier]

Debris flow is a major geohazard in mountainous regions and poses a significant threat to life and property. The damage caused by debris flows have increased with the expansion of human settlements and activity into the mountainous regions of China. In regards to risks from debris flows, previously unrecognized low-frequency debris flow catchments constitute an especially significant threat. According to our investigation, only about 500 catchments have debris flow records in >2000 catchments of Bailong River basin. The main purpose of this paper is to introduce a new methodology using Artificial Intelligence (AI) that can simultaneously input parameters related to geomorphological conditions and material conditions to better distinguish low-frequency debris flow catchments (LFD s) from medium-high frequency debris flow catchments (MHFD s). A total of 449 prototypical debris flow catchments, 15 parameters, and 9 commonly used learning machines were used to build identification models. Debris flow catchments are divided into 4 cases (LO1-LO4) based on different sample ratios of LFD s and MHFD s, which are input into each classifier one by one. Based on model evaluation, the CHAID model in the case LO2 performs best, which only uses five parameters (formation lithology index, land use index, vegetation coverage index, drainage density and landslide density index) to predict LFD s. The results indicate that LFD s are mainly distributed in areas with less landslide distribution and better vegetation coverage compared with MHFD s. However, the distribution of LFD s is concentrated on FLI (formation lithology index) =4, which is the weak lithology area. The tree classifier seems to be better at classifying fluvial processes. The model developed in this paper can help us quickly find LFD s in similar areas, and help to assess the risk of debris flows. • A simple decision tree model was built to identify low-frequency debris flows. • Geomorphological and material parameters were used simultaneously for modeling. • Materials seem to be the main influencing factor of low-frequency debris flows. • The tree classifier seems to be better at classifying fluvial processes. [ABSTRACT FROM AUTHOR]

Mons Rümker is a preferred candidate landing region for China's Chang'e-5 (CE-5) mission, from where it is of great significance to select safe landing areas. Lunar terrain factors from Digital Elevation Model (DEM) data, limited by their low resolutions (~10 m/pixel), are inapplicable to evaluating the lunar landing area safety, in spite of the fact that lunar remote sensing imagery has higher resolution (~50 cm/pixel). In this paper, we extracted terrain factors in divided square girds by the aid of the high-resolution Lunar Reconnaissance Orbiter (LRO) Narrow-angle Camera (NAC) images, namely, flat area percentage (Fap), distribution pattern of uneven objects (NNI) based on the double-threshold Otsu method, and roughness based on gray level histogram analysis. Mons Rümker can be divided into four geological units, named as LD, B1, B2, and B3, respectively. Unit B1 has a higher roughness and a lower Fap. Unit B2 and B3 are characterized with the highest Fap and the lowest roughness. NNIs of Unit B1, B2, and B3 are >1 while LD's is <1. Thus, the distribution patterns of uneven objects in Unit LD are clustered but dispersed in all Unit B1, B2, and B3. This paper tends to take Fap and roughness as the main terrain factors to evaluate the safety for CE-5 landing in Mons Rümker with NNI being a supplement to Fap. According to Standard 1–3 mentioned in this paper, we would classify the divided square grids of the Mons Rümker region as the safe or unsafe areas, and then discriminate five potential landing areas for CE-5 probe safe landing. Five potential landing areas (red polygons marked with number 1–5). The blue, purple and red colors are the safe grids classified in line with Standard 1–3, separately. The white solid line indicates the boundary of Mons Rümker. The yellow stars show two candidate landing sites for CE-5 mission mentioned by Zhao et al. (2017). Unlabelled Image • Three terrain factors (Fap, NNI and roughness) were derived from the NAC mosaic image of Mons Rümker; • Mons Rümker can be divided into four geological units, which are named as LD, B1, B2, and B3; • Five potential landing areas for CE-5 probe safe landing were recognized based on Standard 1-3. [ABSTRACT FROM AUTHOR]

Abstract: Knowledge of soil erodibility is an essential requirement for erosion prediction, conservation planning, and the assessment of sediment related environmental effects of watershed agricultural practices. This paper reviews the status of soil erodibility evaluations and determinations based on 80years of upland area erosion research mainly in China and the USA. The review synthesizes the general research progress made by discussing the basic concepts of erodibility and its evaluation, determination, and prediction as well as knowledge of its spatio-temporal variations. The authors found that soil erodibility is often inappropriately or inaccurately applied in describing soil loss caused by different soil erosion component processes and mechanisms. Soil erodibility indicators were related to intrinsic soil properties and exogenic erosional forces, measurements, and calculations. The present review describes major needs including: (1) improved definition of erodibility, (2) modified erodibility determinations in erosion models, especially for specific geographical locations and in the context of different erosion sub-processes, (3) advanced methodologies for quantifying erodibilities of different soil erosion sub-processes, and (4) a better understanding of the mechanism that causes temporal variations in soil erodibility. The review also provides a more rational basis for future research on soil erodibility and supports predictive modeling of soil erosion processes and the development of improved conservation practices. [Copyright &y& Elsevier]

Abstract: Debris flows are typically caused by natural terrain landslides triggered by intense rainfalls. If an incoming mountain torrent collapses a series of landslide dams, large debris flows can form in a very short period. Moreover, the torrent can amplify the scale of the debris flow in the flow direction. The catastrophic debris flows that occurred in Zhouqu, China, on 8 August 2010 were caused by intense rainfall and the upstream cascading failure of landslide dams along the gullies. In the wake of the incident, a field study was conducted to better understand the process of cascading landslide dam failures and the formation of debris flows. This paper looks at the geomorphic properties of the debris-flow gullies, estimates the peak flow discharges at different locations using three different methods, and analyzes the key modes (i.e., different landslide dam types and their combinations) of cascading landslide dam failures and their effect on the scale amplification of debris flows. The results show that five key modes in Luojiayu gully and two modes in Sanyanyu gully accounted for the scale amplification of downstream debris flows in the Zhouqu event. This study illustrates how the hazardous process of natural debris flows can begin several kilometers upstream as a complex cascade of geomorphic events (failure of landslide dams and erosion of the sloping bed) can scale to become catastrophic discharges. Neglecting recognition of these hazardous geomorphic and hydrodynamic processes may result in a high cost. [Copyright &y& Elsevier]

Abstract: This paper investigates the fractal properties of landforms in the Ordos Block and surrounding areas within China and discusses their geological and geomorphological implications. The Ordos Block is tectonically stable, but the surrounding areas are much more active and are affected by shear-extensional structures. We utilized the variogram method and the cellular fractal model to estimate parameters such as the fractal dimension (D), ordinate intercept (γ), and range (R) from the SRTM3 DEM using a moving window operation. We suggest that the fractal dimension reflects the frequency of variation in elevation, while the ordinate intercept reflects the amplitude of relief. The fractal properties range from 90m to 30km. Geomorphological zones can be delineated using the fractal dimension and ordinate intercept. These zones are consistent with known qualitative types of topography. Some basins are characterized by high fractal dimensions and low ordinate intercepts, in contrast to mountainous areas with low fractal dimensions and high ordinate intercepts. Other areas such as the Loess Plateau and deserts also have unique values of fractal properties. The effects of geological and geomorphological processes on the fractal properties are also discussed. [Copyright &y& Elsevier]

Abstract: Support vector machine (SVM) modeling is based on statistical learning theory. It involves a training phase with associated input and target output values. In recent years, the method has become increasingly popular. The main purpose of this study is to evaluate the mapping power of SVM modeling in earthquake triggered landslide-susceptibility mapping for a section of the Jianjiang River watershed using a Geographic Information System (GIS) software. The river was affected by the Wenchuan earthquake of May 12, 2008. Visual interpretation of colored aerial photographs of 1-m resolution and extensive field surveys provided a detailed landslide inventory map containing 3147 landslides related to the 2008 Wenchuan earthquake. Elevation, slope angle, slope aspect, distance from seismogenic faults, distance from drainages, and lithology were used as the controlling parameters. For modeling, three groups of positive and negative training samples were used in concert with four different kernel functions. Positive training samples include the centroids of 500 large landslides, those of all 3147 landslides, and 5000 randomly selected points in landslide polygons. Negative training samples include 500, 3147, and 5000 randomly selected points on slopes that remained stable during the Wenchuan earthquake. The four kernel functions are linear, polynomial, radial basis, and sigmoid. In total, 12 cases of landslide susceptibility were mapped. Comparative analyses of landslide-susceptibility probability and area relation curves show that both the polynomial and radial basis functions suitably classified the input data as either landslide positive or negative though the radial basis function was more successful. The 12 generated landslide-susceptibility maps were compared with known landslide centroid locations and landslide polygons to verify the success rate and predictive accuracy of each model. The 12 results were further validated using area-under-curve analysis. Group 3 with 5000 randomly selected points on the landslide polygons, and 5000 randomly selected points along stable slopes gave the best results with a success rate of 79.20% and predictive accuracy of 79.13% under the radial basis function. Of all the results, the sigmoid kernel function was the least skillful when used in concert with the centroid data of all 3147 landslides as positive training samples, and the negative training samples of 3147 randomly selected points in regions of stable slope (success rate=54.95%; predictive accuracy=61.85%). This paper also provides suggestions and reference data for selecting appropriate training samples and kernel function types for earthquake triggered landslide-susceptibility mapping using SVM modeling. Predictive landslide-susceptibility maps could be useful in hazard mitigation by helping planners understand the probability of landslides in different regions. [Copyright &y& Elsevier]

Abstract: In the Wenchuan area in SW China, an abundance of loose co-seismic landslide debris was present on the slopes after the Wenchuan earthquake, which in later years served as source material for rainfall-induced debris flows or shallow landslides. Slopes composed of Cambrian sandstones and siltstones intercalated with slates appeared to be most susceptible to co-seismic landsliding. A total of 20 debris flows are described in this paper; all were triggered by heavy rainfall on 13th of August 2010. Field reconnaissance and measurements, supported by aerial photo interpretation, were conducted to identify the locations and morphological characteristics of the debris flow gullies in order to obtain information about surface area and volume of landslides and the debris flows. The debris flows in the study area were initiated by two processes: a) run-off erosion on co-seismic landslide material, and concentrated erosion of landslide debris in steep channels; b) new landslides that transform into debris flows. The volume of debris flow deposits on individual fans varies by many orders of magnitude. The smallest deposit has a volume of from 5760 to 3.1millionm3. A comparison of the measured volumes, deposited on the fan with the volumes of debris stored in the catchment shows the huge potential for future debris flow activity. Whilst there is a weakly significant positive correlation between these two volumes, no significant statistical correlation could be established between volumes of debris flow deposits and other morphometric parameters of the catchment. A catastrophic debris flow catchment (the Wenjia catchment) was selected as an extreme case to show in detail the mechanism of debris flow formation as a result of intensive erosion in loose material, which was deposited by a rock avalanche during the 2008 Earthquake event. Analyses of the meteorological conditions that triggered these debris flows show one day antecedent precipitation varying between 67.7 and 137.6mm, with a mean rainfall intensity of about 7.3 to 22.5mm/h. A rainfall event with peak intensity of 38.7mm/h triggered the largest debris flow event. Rainfall data related to five debris flow events in the Wenjia torrent was used to establish a primary rainfall intensity–duration relationship for the triggering of debris flows, which was compared to other rainfall duration thresholds from other parts of the world. In the discussion emphasis is laid on the need to unravel the process mechanisms which initiated the debris flows for a better understanding and assessment of meteorological thresholds. [Copyright &y& Elsevier]

Abstract: The devastating earthquake that occurred in Wenchuan County, Sichuan Province, China, on the 12th May 2008, caused widespread damage and devastation to rural communities and economy. The terrain of the entire region has been weakened and is now highly susceptible to long-term slope instability that will trouble this region for many years to come. Before the earthquake, the maximum seismic intensity expected in the region was VI–VIII in the 12-degree Liedu scale (the intensity measure adopted in China). However, the actual intensity caused by the earthquake ranged between VIII and XI. The seismic intensity map is practical for regional guidance but lacks the detail to provide an adequate representation of the true damage level, in terms of current status and future potential in such a seismically active and populated region, especially when the hazards and risks are likely to be multiple and cascading in high relief areas. This paper presents a GIS based novel approach to earthquake damage zone modelling using satellite remote sensing and DEM data. The novelty is to take into account the co-seismic ground deformation (measured using differential SAR interferometry) as an important modulating factor in modelling the susceptibility of earthquake related geohazards, together with conventional multi-criteria factors which draw on geological and topographical variables such as rock competence, slope, proximity to drainage, and fracture density. The modulating effect of the earthquake greatly enhances the susceptibility in the areas where the majority of the ensuing landslides and debris-flows actually took place. When this susceptibility model is further modulated by the mapped surface disruption caused by the earthquake (which encompasses all forms of mass movement and urban destruction), it is directly linked to seismic intensity and we call it “earthquake damage”. The output earthquake damage map represents both the current damage status as well as the future damage (hazard) potential. The resulting earthquake damage map for the Beichuan region clearly defines a series of zones of increasing seismic intensity, approximately corresponding to Liedu values VIII–XI but with great details. [Copyright &y& Elsevier]

Abstract: To improve navigability of the major access channel into Shanghai Harbor, a large-scale Deep Waterway Project was carried out in the North Passage (NP) of the Yangtze Estuary. In this paper, we investigate how the navigational works affected morphological changes of this channel, as well as those of the adjacent North Channel (NC), Hengsha East Shoal (HES), Jiuduansha Shoal (JDS), and the South Passage (SP). Morphological changes were assessed by analyzing digitized bathymetric data of this area prior to and after execution of the engineering works. The qualitative relations between these changes, along with the hydrodynamic changes as a result of the construction of engineering works, were subsequently investigated. The results reveal that the construction of training walls, groins and jetties resulted in decreased ebb transport in the upper reach of the NP and increased ebb transport in the upper reach of the SP. In turn, this led to intensive upstream erosion with large amounts of sediment transported seaward in the SP and associated sedimentation in the downstream area. At the same time, intense siltation occurred in the upper reach of the NP, while the main channel of the NP mainly experienced erosion caused by the construction of training walls and groins that concentrated ebb flow in the main channel. The waterway deepened significantly in previously shallow areas. Small tidal channels in the HES, which used to connect the NP and the NC, were cut off by the northern training wall. Consequently, residual flow in the middle reach of the NC flowed directly toward the northern bank of the HES, leading to local erosion. Flow obstruction by the southern training wall reduced the upstream propagation of the flood tide in the SP. As a result, a collection of small flood channels evolved under the flushing action of flood currents in the JDS, preventing the natural trend of horizontal extension of the JDS. However, the flow obstruction enhanced the vertical accretion of the JDS. [Copyright &y& Elsevier]

Abstract: Yardangs are typical wind-eroded landforms that are found in most of the world''s major deserts. This paper describes the morphology of yardangs in the Kumtagh Desert, analyzes their control factors, and discusses their development processes, age, and rates of formation. Yardangs in the Kumtagh Desert lack the ideal streamlined morphology and the length-to-width ratio close to 4:1 that have been previously described as being due to their unique controlling factors, which include a combination of stratigraphic structures, wind erosion and fluvial erosion. Fluvial erosion plays a particularly important role in the development of the yardangs, though wind continuously sculpts their morphology. The development of yardangs can be divided into four stages: an embryonic stage, adolescence, maturation, and recession. Most yardangs in the Kumtagh Desert are in the mature to receding stages. We determined an approximate age for the yardangs based on the erosion rates estimated by several researchers: on this basis, the yardangs in the Kumtagh Desert appear to have formed during the Holocene. [Copyright &y& Elsevier]

Abstract: Following construction of the Three Gorges Dam, many farmers resettled in surrounding mountain areas and cultivated marginal lands, which are mostly on steep slopes with soil of poor structure. In general, high soil loss rates occur during intense storms. Therefore, soil erosion is a major environmental problem in the Three Gorges area (TGA) of China. Understanding and quantifying sediment load is important for sustainable agriculture and the environment in this region. This paper analyzes the relationships between rainfall, runoff, and sediment transport in the Wangjiaqiao watershed. Strong seasonal and monthly variability in sediment load was found. Sediment was strongly transported during summer months, a period when frequent flood events of high magnitude and intensity occurred. Analysis of the relationships between precipitation, discharge and sediment transport at an individual event scale showed significant correlations between total precipitation, peak discharge, total water yield, maximum 30min rainfall intensity, and sediment-related variables. Stepwise multiple regression analysis revealed that rainfall amount is the major cause of runoff, while events producing a large discharge in a short time play an important role in inducing severe soil erosion. During 40 flood events, three different types of hysteretic loops were observed: clockwise (28 events, 70%), figure-eight (5 events, 12.5%), and complex (7 events, 17.5%). The results of this study confirm the complex and heterogeneous nature of sediment response in the Wangjiaqiao watershed. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to investigate the morphological implications of the interplay between tectonic movements at different rates, timescales, and spatial extent in a catchment of intermediate size, the Huang Shui River (a main tributary of the Yellow River in the NE Tibet Plateau). River incision started from a peneplain-like surface that developed in post-Miocene–Pliocene times. At the end of the Tertiary, a general tectonic uplift of the Tibetan Plateau initiated river incision. This general uplift also caused local fragmentation of the Huang Shui catchment into blocks (kilometers or maximally, a few tens of kilometers) of local extent that have subsided and/or uplifted relative to one another. Fluvial deposition of >30m in the subsiding blocks contrasts with erosion and formation of gorges in the uplifted blocks. Incision into the former peneplain was not continuous but a staircase of terraces developed under climatic influences. Terrace deposits are sometimes capped by interglacial soils or soil-derived material. Apparently, terrace incision occurred at the transition to the next cold period. The different rates of uplift and subsidence of the individual blocks resulted in the simultaneous development of erosion and accumulation terraces of different sizes within the same catchment, even within the same tectonic block. This makes it impossible to connect the terraces of the different blocks, except for the three youngest terraces (representing the last 300,000years), thus illustrating the uniform tectonic history of the catchment since that time. [Copyright &y& Elsevier]

Abstract: The 12 May 2008 Wenchuan earthquake (Ms 8.0) triggered over 56,000 landslides over a broad area, including shallow, disrupted landslides, rock falls, deep-seated landslides, and rock avalanches. Among these landslides, rock avalanches are of great concern because of the large volume of displaced material, the long runout distance and the resulting fatalities. In this paper, some rock avalanches (including the Woqian, the Tangjiawan, the Hongyancun, the Xiejiadianzi, and the Shuimogou rock avalanches) were selected for detailed study. Mapping of coseismic surface rupture has been carried out at regional and site scales. The minor scarps or stepped topographic features observed at the source areas of the rock avalanches correspond spatially to the surface rupture, indicating that they should be created by thrusting of a fault that ruptured during the 2008 Wenchuan earthquake. Avalanche deposits of some rock avalanches are shifted northeastward, the same direction with the strike–slip of the fault rupture, compared with the sources of the rock avalanches, indicating that the component of strike–slip of the fault rupture exerted a horizontal initial velocity on the failed mass. For the Woqian rock avalanche, the source rock on the hanging wall was pushed northeastward, creating a hummocky topographic feature because of the right-lateral slip of the fault rupture. These rock avalanches are, therefore, triggered by oblique-thrust faulting. In addition, the source rock mass was of poor quality resulting from the shearing and brecciation associated with fault movement in history, rendering the rock slopes prone to failure and contributing to the high degree of disintegration of the failed rock mass. [Copyright &y& Elsevier]

Abstract: This paper examines the spatial variation of sediment yield in the Yangtze basin in China, a large basin with complex geology, climate, land-use history, and extensive sediment monitoring. 287 stations with drainage area less than 10,000km2 were used to study the scale effects of sediment yield. In order to develop scale relations for regional sediment yield, the whole study area was divided into eight sub-basins. Relation between specific sediment yield and drainage basin area was built for each sub-basin. Regional scaling relation was analyzed based on landforms, geology, lithology and land-use of each sub-basin. Three regional trends were identified in relation to the drainage area: (1) a declining trend, due to soil erosion on heavily cultivated steep land and the storage of sediment in floodplains; (2) a flat trend, due to mass movement on the upper reach and heavy agricultural disturbance on the middle and lower reaches; and (3) an increasing trend, due to downstream recruitment of sediment from land downstream where slope farming and deforestation occurred. Using these developed relations, areally adjusted sediment yield maps were created over the entire Yangtze basin. [Copyright &y& Elsevier]

Abstract: Based on samples taken from four large sand seas of northern China, this paper first provides basic data about the concentrations and chemistries of soluble salts in deserts of northern China and then discusses the origins and parameters triggering geographical variations. The total concentration of soluble salts in the aeolian sands of four large sand seas in northern China ranges between 0.14‰ and 1.32‰, with the pH of the soluble salts solution (mixing ratio of sand and water 1:5) changing between 8.4 and 9.6, confirming alkaline soil conditions in these regions. Sodium chloride and bicarbonate are the dominant salts occurring as soluble salts in the aeolian deposits of these sand seas. The geographical changes of soluble salts'' concentration display a clear correlation with regional climatic parameters, i.e., precipitation and temperature. The domination of sedimentation of soluble salts in the aeolian sands deposited via atmospheric processes is discussed, which are heavily associated with dry deposition. The mean percentages of Na and Cl, derived from dry depositions, are estimated to be >90% in both Badain Jaran and Taklamakan deserts. [Copyright &y& Elsevier]

Abstract: This paper summarizes process-oriented field and numerical studies undertaken on the river plume in the partially-mixed Changjiang River estuary. Both estuarine circulation and tidal asymmetry are of great importance to the fine sediment processes. Mean suspended sediment concentration (C̄) and bottom shear stress are the dominant physical parameters controlling the flocculation and settling velocities (w s ) of mud flocs in suspension. Two important physical processes are revealed by acoustic imaging, i.e. (i) the near-bed impulsive resuspension and (ii) the transport processes driven by fine sediment-induced plumes during a spring tide. A turbidity maximum, associated with a suspended sediment front, is observed. Its formation is caused mainly by tidal asymmetry, near-bed periodic tidal resuspension and turbulence suppression by suspension/salinity stratifications. A conceptual sketch of the turbidity maximum is cautiously proposed for the Changjiang River estuary. Four different settling velocity equations, taking flocculation into account, have different effects on the modeled concentration profiles of fine sediment: apparently, Cao and Wang (1994, pp. 252–253) would be the best for spring tide and Thorn (1982, Fig. 3/page 66) for neap tide. Both tidal acceleration and tidal deceleration have strong effects on the concentration profiles of fine sediment within the Changjiang River estuary. [Copyright &y& Elsevier]

Abstract: This paper focuses on identifying changes in the tidal range and the duration of the flood tide in the Pearl River Delta region, China. Mann–Kendall test and regression methods are employed to verify the existence of trends in the annual tidal range and duration series (from the 1950s to 2005) at 17 stations in the 3 major tributaries of the delta. The research results indicate that generally there is an increasing trend in the tidal range and flood tide duration at most of the stations in the channel network. Moreover, the more upstream the location of the station, the more obvious the change in trend is, and these increasing trends are all significant at the stations in the upper part of the delta. Specifically, the tidal range at Shilong station in the East River has increased abruptly since the middle of the 1980s such that the mean level of post-1990 data is approximately three times that for pre-1985. Most stations near the mouth of the estuary show significant downward trends in the tidal range and flood tide duration. Results of the intersection point of the Mann–Kendall test curves for these Pearl River Delta stations appear mostly in 1980s–1990s, indicating that a noticeable change point occurs during this period. Human activities in the Pearl River Delta reached their peak during the 1980s. Among these, large-scale and long-term sand excavation modified the hydrodynamic regime dramatically in a way that increased the water depth and lowered the level of the riverbed, leading to an increased tidal prism and upstream movement of the tidal limit. Land reclamation is also likely to have had a relatively large effect on the tidal range and flood tide duration at stations near to the estuary mouth. Changes in other factors, such as freshwater flow and sea-level rise, seem to be of relatively minor importance. It is noteworthy that in a dry season the tidal dynamics are greatly enhanced and has resulted in strong saltwater intrusion into the estuary in recent years. [Copyright &y& Elsevier]

Abstract: This paper examines the characteristics of historical floods and associated monsoon precipitation in the Yangtze Catchment, with specific attention given to the middle and lower Yangtze basin. Based on in situ field observations and historical discharge, flood duration, and land-use information, etc, we propose a number of flood characteristics of the basin: 1) floods have occurred more frequently after 1950s, however, changes in discharge can only partially explain the occurrence of the floods; 2) spectral analysis on the annual mean water discharge during 1860–1985 in Hankou hydrological gauging station of the middle Yangtze River reveals 16.4-year and 2.5-year flood recurrences, which become shortened from what has been recorded in the Chinese historical literature on millennial time scale; 3) floods after 1950s tend to have higher water levels (both mean and peak) and longer duration than before, but with remarkably limited inundation area; and 4) a series of flood waves generated by monsoon precipitation in 1998, initiated from the middle Yangtze, highlights the basin-wide climate hazards with a recurrence of around 60 years. Intensifying anthropogenic activity in the last century, including deforestation, dyking, and lake–coast reclamation etc. that results directly in riverbeds aggradation and shrinkage of lake water area in the middle Yangtze basin, are the key causes for recently human-induced floods in the basin. Threatened land property in the basin reminds us to harmonize with the river and provide more space for flooding. [Copyright &y& Elsevier]

Abstract: The problem of historical desertification of the Mu Us desert, northern China has been paid considerable attention during the past several decades. Through the analysis of stratigraphic evidence, historical records and archaeological discoveries, this paper studied the problem using a multidisciplinary approach. The results show that two phases of serious desertification occurred during the last two millennia, one is during the mid-to-late Tang dynasty (about A.D. 800) and the other during the late Ming dynasty (about A.D. 1500–1600). Further investigation of the cause of each phase of desertification demonstrates that the former phase of desertification is closely related to abrupt climate change occurring in the mid-eighth century, but the latter, which started during the Ming dynasty and stopped at late 1980s, is not consistent with climatic causation. Therefore, we suggest that human activities contributed to the development of the latter phase of desertification. [Copyright &y& Elsevier]

Abstract: Investigations of river terraces are often seriously hindered by difficulties in dating the formation of terraces using conventional and well-established methods such as 14C dating. In this paper, recently developed optical dating techniques were applied to a Yellow River terrace sequence in the Hequ area, Shanxi Province, China. Based on field investigations, four terraces were identified. Systematic sampling for optical dating was carried out on these terrace deposits. The single-aliquot regenerative-dose method was used to determine equivalent dose. By analyzing the degree of bleaching of fluvial samples, maximum and minimum optical ages were obtained for these samples. The minimum optical dates obtained are geomorphologically and stratigraphically consistent with each other, suggesting that the dates are reliable. The formation ages of the four terraces are 3.4∼10, 20∼25,∼30 and ∼90 ka, respectively. On the basis of these optical dates, the geomorphological evolution of the terrace sequence was established, and the factors affecting the terrace development discussed. [Copyright &y& Elsevier]

Abstract: This paper describes 20th century climate and human impacts on terrestrial and fluvial systems in the Dabie Mountains, Anhui Province, China, based on analyses of four types of information. Analyses of particle size, mineral magnetism, organic carbon, nitrogen and phosphorus in a sediment core taken from the Longhekou reservoir, built in 1958 AD in the upper reaches of Hangbu River, provide an ∼45 year record of fluvial responses, while monitored meteorological and hydrological data provide records of climate and river discharge. Census data compiled for the local Shucheng County provide records of population and land use, complemented with analyses of satellite images. The Xiaotian river delivers over 65% of the total water and silt to the reservoir. Analyses indicate that the fluvial regime tracks the monsoon climate over seasonal timescales, but human activities have a strongly mediating effect on sediment supply, sediment delivery and, to a lesser extent, runoff over longer timescales. Notable periods of human impact on erosion include the Great Leap Forward (1958–1960) and Great Cultural Revolution (1966–1976). A rising trend in precipitation and new land use changes at the present time may be leading to an enhanced flood risk. [Copyright &y& Elsevier]

Coastal morphodynamics and environmental changes have been obviously altered by global warming, sea-level fluctuations, and human activities. Palynological analysis is one of the most important tools for providing information on vegetation, climate, and environmental change, which can be relatively sensitive indicators of human activity during the Holocene. However, Holocene coastal morphodynamics and palynological evidence from the Pearl River Delta and coastal areas has not been sufficiently studied. In this paper, we carry out analyses using detailed grain-size and palynological records of pollen, spores, freshwater algae, and marine dinoflagellate cysts from Borehole QZK13 in the Pearl River Estuary (PRE), southern China. The results show information relating coastal morphodynamics, vegetation evolution, climate changes, and anthropogenic activities during the Holocene based on radiocarbon chronology. In general, the PRE experienced marine transgressive processes; sea-level and the coastline tended to migrate landward between 10,700 and 4250 cal yr BP. Meanwhile, abundant arboreal pollen (mainly Castanopsis , Quercus -evergreen, Oleaceae, and Castanea) and small amounts of non-arboreal pollen (mainly Poaceae, Cyperaceae, and Artemisia) were observed in Borehole QZK13, which suggests that subtropical evergreen broadleaved forests were distributed throughout the PRE and adjacent areas, and relatively warm and moist climatic conditions were present during the early-middle Holocene. After that, there were relatively cool and wet climatic conditions, and marine regressive processes occurred in the PRE during the Late Holocene (ca. 4250–960 cal yr BP) indicated by an abrupt increase in aquatic herbs and Dicranopteris. Moreover, we hypothesize that the Neolithic "cultural fault" in the PRE is likely related to frequent storm surges induced by extreme typhoon events that occurred ca. 3000–2700 yr BP. • Grain size, pollen, spores, freshwater algae and dinoflagellate cysts from the Pearl River Estuary were investigated. • Three major phases shown by palynological results were corresponding to the changes in vegetation and climate. • We hypothesized that the Neolithic "cultural fault" is probably related to the storm surges induced by extreme typhoon events. • Natural vegetation cover has suffered large-scale destruction by ancient humans during the Late Holocene. [ABSTRACT FROM AUTHOR]

Seasonal or interannual precipitation differences lead to changes in the water level of a tufa lake, while the underwater topography affects its local depth. Therefore, topo-bathymetry is important to study and protect the aquatic environment of tufa lakes. However, traditional field-based topo-bathymetric surveying methods (e.g., sounding rod or sonar) inevitably disturb the fragile lake ecosystem. In recent years, the emerging remote sensing technology of unmanned aerial vehicles (UAV) has provided a cost-effective solution for measuring topo-bathymetry without disturbance. In this paper, taking Spark Lake in Jiuzhaigou, China, as an example, we captured red-green-blue (RGB) images using a fixed-wing UAV and produced a digital elevation model (DEM) prior to the Jiuzhaigou Earthquake using Structure-from-Motion (SfM) photogrammetry. The underwater topography of Spark Lake was obtained by refraction correction and water color inversion based on the DEM and orthophoto, respectively. For refraction correction, a water depth correction model based on Snell's Law was used. For water color inversion, general band ratio models were replaced by a band difference model (blue band - green band). The qualities of the resulting DEMs produced by the two methods were evaluated against the topography of the drained Spark Lake after the earthquake, and the corresponding DEMs of difference (DoD) were also analyzed. The coefficient of determination (R2) and root mean square error (RMSE) are 0.88 and 1.32 m for refraction correction, and 0.86 and 1.37 m for water color inversion, respectively. The results demonstrated the feasibility and effectiveness of applying UAV-acquired RGB imagery and the two optical remote sensing methods to topo-bathymetric mapping of transparent tufa lakes. • UAV-acquired RGB images were applicable for testifying topo-bathymetry of tufa lake. • Refraction correction demonstrated a good performance for water depths up to 12 m. • The difference between blue and green bands was the optimal spectral combination. • Water color inversion exhibited a fine performance across the entire lake depth range. [ABSTRACT FROM AUTHOR]

Abstract: In the previous studies, a method was developed to assess soil erosion based on land use information. In this paper, we present another approach that uses environmental data to assess soil erosion. A soil erosion characteristic index EI is proposed, and its value is derived using the Analytic Hierarchy Process (AHP) technique based on standardized environmental information stored in minimum polygons that tile the erodible area under consideration. The approach is applied to a case study of the Yellow River basin, north China, where serious erosion is occurring. To represent different grades of soil erosion, the range of EI is divided into six levels according to standard grades of soil erosion intensity. The application indicates that the method deals properly with data scarcity, with the results giving a satisfactory representation of the characteristics of soil erosion in the Yellow River basin. The spatial–temporal distribution of EI in the Yellow River basin is predicted, and the results interpreted to give the long-term trend and state of soil depletion. Comparisons are given between EI and surveyed soil erosion zoning maps for the Yellow River basin at the end of the 1980s and 1990s. The output reliability and the approach applicability in smaller spatial scales are investigated in a case study of Zhifanggou basin. [Copyright &y& Elsevier]

Abstract: This paper contributes to a better understanding of the source of dust storms in northern China and the relationship between these sources and other aeolian sediments in this region. Sediment samples in potential source areas were collected from the Hunshandake Sandy Land, Heaven Desert, the loess deposits of the Bashang area, the mountainous basins and valleys north of Beijing and from the Badain Jaran Desert and Hulunbaier Sandy Land (). Dust samples were collected in Beijing during two dust storms in March 2002 and April 2006. The laboratory methods used in this study included measurements of abundance of trace elements, in particular the rare earth elements (REEs), mineral assemblages and grain size. The REE contents, Eu and Ce anomalies show clear differences between various deposits. Provenance is considered to be the key factor influencing REE patterns in the study areas. The REE abundances and patterns indicate that the aeolian sand north of Beijing, such as in the Heaven Desert, is mainly of local origin rather than from desert encroachment from the north. The mineral grains carried in dust storms, however, are highly mixed, and may come partly from local sources but mainly from distant desert regions in western China. [Copyright &y& Elsevier]

Abstract: To understand the evolution and stability of beaches, prediction of the equilibrium beach profile (EBP) is theoretically and practically important. In the present paper, a new equation, h = Ae Bx + C is developed to predict the change in beach profile for sections above the water level and the adjacent nearshore portions. Moreover, fractal analysis is applied to predict types of EBP for the first time using the field data collected from Liao Zuikou and Nanwan beaches, South China. Three types of EBP termed Upward-concave EBP (U-EBP), Downward-concave EBP (D-EBP) and Medium-characteristic EBP (M-EBP), are given for the studied region of South China. [Copyright &y& Elsevier]

Abstract: River deltas grow in response to sediment discharge from the land. It is not clear, however, whether or not there is a limit for such growth. Conceptual geometric models are used in this paper, in association with the principle of mass conservation, in an attempt to answer this question. Preliminary analyses of the Changjiang Delta indicate that delta growth is constrained by a number of factors: the original topography/bathymetry, sediment supply, sediment retention in the estuary, sea-level rise, ground subsidence. The quantity of sediment supply per unit area and the Sediment Retention Index for the subaqueous delta decrease as the delta progrades towards deeper water, resulting in a decreasing rate of growth. The limit of growth is reached when the index approaches zero, i.e. the shoreline reaches the shelf edge. If the combined effect of sea-level rise and ground subsidence is considered together with decrease in the sediment discharge from land, the limit is reached at an earlier stage. For the Changjiang Delta, the model output (using hypothesized Sediment Retention Index estimates) implies that the delta growth will reach its limit in the near future. This will occur sooner if the sediment output of the river is reduced to 60% of its original level, in response to the upstream basin changes. Further knowledge, however, is required of the Retention Index, together with the information on future changes in river input and the character of the sediments in order to improve the accuracy of the simulations. [Copyright &y& Elsevier]

Abstract: A sharp decrease in total suspended solids (TSS) concentration has occurred in the Mekong River after the closure of the Manwan Dam in China in 1993, the first of a planned cascade of eight dams. This paper describes the upstream developments on the Mekong River, concentrating on the effects of hydropower dams and reservoirs. The reservoir-related changes in total suspended solids, suspended sediment concentration (SSC), and hydrology have been analyzed, and the impacts of such possible changes on the Lower Mekong Basin discussed. The theoretical trapping efficiency of the proposed dams has been computed and the amount of sediment to be trapped in the reservoirs estimated. The reservoir trapping of sediments and the changing of natural flow patterns will impact the countries downstream in this international river basin. Both positive and negative possible effects of such impacts have been reviewed, based on the available data from the Mekong and studies on other basins. [Copyright &y& Elsevier]

Abstract: Intensive anthropogenic disturbances have affected the channel of the middle Yangtze River since the 1950s. This paper selects the Jianli reach as an example to examine human impact on channel change in the middle Yangtze River. 1:100,000 channel distribution maps from 1951, 1961 and 1975 and 1:25,000 navigation charts from 1981 and 1997 were employed to reconstruct channel change in the study reach. The result indicates that the channel, under the constraint of levees along the riverbanks, underwent a minor widening but frequent bank failure due to susceptible bank structure and increase in water discharge. The bank failure promoted bar growth in the channel. Cross-section changes and quantitative calculations of erosion and deposition based on the DEM derived from navigation charts present a pattern of over-bank sedimentation and riverbed incision. The stage and duration of floods have increased following levee construction and bank revetment. [Copyright &y& Elsevier]

Abstract: Debris flows, landslides and rock falls are severe abrupt mass movement hazards, whose recorded occurrence in China has increased markedly in the past two decades. With the county- and city-based data, the debris flow hazard zonation for China was accomplished using the Rapid Zonation of Abrupt Mass-movement Hazard (RZAMH) approach, whose principles are described in the Part I companion paper. The entire area of China was classified into five regions with different degrees of hazard. Landslide and rock-fall hazard zonations for China were also presented. A sensitivity analysis demonstrated the robustness of the RZAMH approach. Direct validation was made with comparison of the zonation results and historical recordings on occurrence distribution of debris flows. The zonations produced by the RZAMH approach and other methods were compared by similarity analysis and paired-sample t-tests for the indirect validation of the accuracy of the RZAMH approach. [Copyright &y& Elsevier]

Abstract: This paper addresses the recent (1970s–1990s) processes of river mouth bar formation, riverbed aggradation and distributary migration in the Huanghe River mouth area, in the light of station-based monitoring, field measurements and remote sensing interpretation. The results show that the morphological changes of the river mouth bar have been closely associated with the largely reduced fluvial discharge and sediment load. Landform development such as bar progradation occurred in two phases, i.e. before and after 1989, which correspond to faster and lower bar growth rates, respectively. Fast riverbed aggradation in the mouth channel was strongly related to river mouth bar progradation. During 1976–1996, about 2.8% of the total sediment loads were deposited in the river channel on the upper to middle delta. Therefore, the river water level rose by a few meters from 1984 to 1996. The frequent distributary channel migration, which switched the radial channel pattern into the SE-directed pattern in the mid-1980s, was linked with mouth bar formation. Marine conditions also constrain seaward bar progradation. Furthermore, the history of river mouth bar formation reflects human impacts, such as dredging and dyking in order to stabilize the coastal area. [Copyright &y& Elsevier]

Abstract: The Kunlun fault is one of the largest strike-slip faults in northern Tibet, China. In this paper, we focus upon the Kusai Lake–Kunlun Pass segment of the fault to understand the geomorphic development of offset streams caused by repeated large seismic events, based on tectono-geomorphic analysis of high-resolution satellite remote sensing images combined with field studies. The results indicate that systematic left-lateral stream offsets appear at various scales across the fault zone: Lateral offsets of small gullies caused by the 2001 M w 7.8 Kunlun earthquake vary typically from 3 m to 6 m, meanwhile streams with cumulative offsets of 10 m, 25–30 m, 50–70 m, 250–300 m and 750–1400 m have resulted from repeated large seismic events during the late Quaternary. An average slip rate of 10±1 mm/year has been estimated from the lateral stream offsets and 14C ages of alluvial fan surfaces incised by the streams. A three-dimensional model showing tectono-geomorphic features along a left-lateral strike-slip fault is also presented. The Kusai Lake–Kunlun Pass segment provides an opportunity to understand the relationship between geomorphic features produced by individual large seismic events and long-term geomorphic development caused by repeated large seismic events along a major strike-slip fault. [Copyright &y& Elsevier]

Abstract: Chinese historic documents recorded that on June 1, 1786, a strong M=7.75 earthquake occurred in the Kangding-Luding area, Sichuan, southwestern China, resulting in a large landslide that fell into the Dadu River. As a result, a landslide dam blocked the river. Ten days later, the sudden breaching of the dam resulted in catastrophic downstream flooding. Historic records document over 100,000 deaths by the flood. This may be the most disastrous event ever caused by landslide dam failures in the world. Although a lot of work has been carried out to determine the location, magnitude and intensity of the 1786 earthquake, relatively little is known about the occurrence and nature of the landslide dam. In this paper, the dam was reconstructed using historic documents and geomorphic evidence. It was found that the landslide dam was about 70 m high, and it created a lake with a water volume of about 50×106 m3 and an area of about 1.7 km2. The landslide dam breached suddenly due to a major aftershock on June 10, 1786. The peak discharge at the dam breach was estimated using regression equations and a physically based predictive equation. The possibility of a future failure of the landslide seems high, particularly due to inherent seismic risk, and detailed geotechnical investigations are strongly recommended for evaluating the current stability of the landslide. [Copyright &y& Elsevier]