Landform Evolution Research Articles

Mapping landscape evolution in 3D: Climate change, natural hazard and human settlements across the 1618 Piuro landslide in the Italian Central Alps

AbstractNatural and anthropogenic mountain landscapes coevolve responding on different temporal scales to climate changes and geodynamics by a series of increments that cause the dynamic association of morphological stabilization surfaces, stratigraphic units and landforms. Understanding the incremental history of palimpsest landscapes helps to recognize and forecast the effects of climate change on the sensitive mountain environments, contributes to archaeological and historical reconstruction and supports management strategies for natural risks prevention and mitigation. The Italian Bregaglia Valley provides an excellent site to unravel the recent/historical increments of evolution of landforms and human settlement, permitting to map the paleo‐digital terrain models (DTMs) corresponding to the relevant landscape turning points. After the last de‐glaciation, two large‐scale landslides reshaped the valley floor, both predisposed by deep‐seated gravitational slope deformations and one surely triggered by intense rainfalls. The most recent and impacting event buried in 1618 the rich border town of Piuro, the ancient one occurred in the same area at least 1.5 ka before. Combining stratigraphic, geomorphological, topographic, archaeological and historical data, we drew the paleo‐DTMs of the pre‐ and post‐1618 settings of Piuro, sketching the landscape evolution. Since two millennia, human settlements took advantage of the decadal to secular most stable surfaces, represented by the inactive lobes of debris‐flow fans, the highest trunk river terraces and the top of humps formed by the ancient landslide body in the valley centre. Stratigraphic relationships, archaeological findings and age determinations show that both landslides diverted the trunk river and covered the existing fan lobes. On a secular timescale, fan progradation and trunk river terracing buried and reworked both the landslide bodies. The paleo‐DTMs show their original areal extent and permit to compute their volume and to sketch the setting of the buried Piuro settlements, drawing the changes of the Mera trunk river course and the chronology of activity of the lateral debris‐flow fan lobes.

The first 10 m resolution thermokarst lake and pond dataset for the Lena Basin in the 2020 thawing season

ABSTRACT Climate warming rates in the Arctic are far greater than the global average, exerting stronger impacts on permafrost degradation and thermokarst landform development. Thermokarst lakes and ponds (TLPs), which are widely distributed in the Lena Basin in the Russian Arctic, play a vital role in altering local ecosystem. However, the detailed distribution of TLPs in the Lena Basin still remains poorly known. In this study, we built the first 10 m resolution TLP dataset for the Lena Basin in the 2020 thawing season by utilizing 4902 Sentinel-2 images. A robust mapping workflow was developed and implemented in the Google Earth Engine (GEE) platform. The accuracy assessment demonstrates a satisfactory accuracy (93.63%), and our results exhibit a better consistency with real TLPs than global water body products. A total of 380,477 TLPs (~0.53% of the total surface area of the Lena Basin) were identified, showing an uneven distribution in the five sub-basins. The TLPs were found to be mainly located within plain areas, with an active layer thickness in the range of 80–100 cm. The higher ground ice content and mean annual ground temperature were favorable for TLP development. This dataset will be valuable for investigating the complex interaction between TLPs and permafrost. It will also serve as a baseline product for better incorporating thermokarst processes into permafrost-climate models.

Geospatial Analysis for Tectonic Assessment and Soil Erosion Prioritization: A Case Study of Wadi Al-Lith, Red Sea Coast, Saudi Arabia

An investigation into tectonics and erosion reveals that they play an important role in causing uplifting, valley incision, and soil erosion. The analysis of drainage basins at different scales is irreplaceable in the development of sustainable plans, particularly in arid regions. Morphotectonics and morphometric characterization analyses are very effective methods for defining the evolution of different landforms, current-day tectonic activity, and hydrological and morphological signatures of basins under investigation. The reorganization of critical drainage basins and sub-basin risk priority ranking are essential for effective and accurate sustainable plans for drainage basin management and water resources. In this study, the coupling of geospatial techniques and statistical strategies was used to examine the tectonic activity and priorities in terms of soil erosion for 15 sub-basins of Wadi Al-Lith along the Red Sea coast of Saudi Arabia. Two effective models, namely, the relative tectonic activity model and the weighted sum analysis model, were applied for examining each geomorphological and hydrological characteristic based on an analysis of the morphotectonics and morphometric parameters. Regarding the relative tectonic activity model, the 15 sub-basins were classified into three classes of tectonic activity: low, moderate, and high. Sub-basins 5, 6, 13, and 15 were considered to be in class 1 (high relative tectonic activity). On the other hand, the weighted sum analysis model assigned the sub-basins into three different ranks: low-, moderate-, and high-soil-erosion priorities. The current study’s results suggest that sub-basins 5, 6, 10, 13, and 15 were recorded within the high-soil-erosion zone and highly relative tectonic activity, covering approximately 53.52% of the total sub-basin areas. The relative tectonic activity and weighted sum analysis models proved their validity in the risk studies, which will be very useful for decision makers in various fields, including natural resources and agriculture.

Settling the riverscape of Erbil (Kurdistan Region of Iraq): long-term human overprint on landforms and present-day geomorphological hazard

This paper presents a geomorphological reconstruction of the urban landscape of Erbil (Kurdistan Region of Iraq), aimed at explaining how human groups settled the region since the prehistory and contributed modifying natural surface processes. Our reconstruction on landforms evolution is based on satellite and historical aerial images and field control allowing the reconstruction of changes in land use over time. The city of Erbil was established along a fertile alluvial plain during the Chalcolithic period and grew around the pristine citadel, which was likely built on top of fluvial features. Prior to the mid-20th century, Erbil was centred around the citadel and relied on traditional systems for water management such as artificial basins and qanats. The city underwent intense urban expansion since the 1950 s and changed its shape due to the construction of roads and residential and industrial areas, which led to the obliteration of the pristine fluvial network. The analysis of historical and current satellite images highlights the profound modification of the landscape triggered by human actions and a progressive shift of local land use from agricultural to urban. This, coupled with human agency on the natural hydrography led to the increase susceptibility of the city to geomorphological hazard (especially floods). Our investigation suggests that during the Anthropocene the dynamic of urbanization reach a tipping point, when excessive urban growth suffers the effect of geomorphological hazard. For that reason, urbanization in the Anthropocene must consider the existence of natural geomorphological processes.

Polygons with halite-crusted floors and gypsum-raised rims in western Qaidam Basin and implications for polygonal landforms on Mars

Polygons ranging in size from a few meters to kilometers have been observed in playa fields on Earth and Mars. The historically hyperarid climate of the Qaidam Basin has allowed the development of extensive polygonal landforms with diverse geometric and genetic types. Here we report a terrain of polygons with a pan-like structure, raised rims, and a size of about 60 to 120 m, and spatial variation in mineral composition and geometry from the Dalangtan area of the western Qaidam Basin on the Tibetan Plateau. Spatially, the polygons in the northeastern part of the study area have complete rims, while the polygons in the southwest have incomplete rims. These polygons consist of a halite crust in the subsurface and raised rims formed mainly of gypsum. In some areas, the polygonal rims are broadened and form boundary belts that are up to ~30 m wide and about 1.2 m high. We suggest that the formation of the halite crust in the subsurface redirects upward migration of evaporitic pore fluids that accumulate gypsum deposits to form the wide polygonal boundary belts. We argue that the similarly sized polygons with raised rims on Mars have similar lateral and vertical structures caused successively by the strong evaporation of lacustrine brines and subsurface pore fluids.

Karst landform classification considering surface flow characteristics derived from digital elevation models

AbstractKarst landforms are one of the most typical geographical units with a specific physical process on the earth's surface. The classification of karst landforms is an important aspect for understanding their landform processes and mechanisms. However, influenced by various interior and external forces, karst landforms have an extremely complex surface morphology, increasing the difficulty of their automatic classification. In this study, we considered hydrological features as an important factor in characterizing karst landforms and proposed a method that considers surface flow for karst landform classification. In this method, terrain was reversed for hydrological analysis to achieve the landform units. Then, the watershed boundary of the reversed terrain is extracted by hydrological analysis. The boundary of the karst landform unit is determined by erasing the plain area from the watershed boundary. Thereafter, the graph theory segmentation method is employed to merge the landform units belonging to the same karst landform entity. The proposed approach is validated and applied in two sample karst areas, Fenglin and Fengcong, located in Guilin, China, using digital elevation model data with 30 m spatial resolution. In addition, a comparative analysis is conducted to evaluate the accuracy of the proposed method. The results demonstrated that the typical karst landform units of Fenglin and Fengcong can be effectively classified. The overall classification accuracy is 94.44%. The proposed method produced more reasonable and accurate boundaries compared with the contour tree and terrain feature point methods. Furthermore, the classification results indicate various landform development stages of the karst landform process in the study area. The proposed method considering surface flow characteristics can be further extended to other landform types with highly complex landforms.

Studi Morfotektonik Daerah Ereunpalay, Kabupaten Tasikmalaya, Jawa Barat

Morphotectonics is a major factor in controlling the development of landforms and has an influence on river systems in the Ereunpalay area and its surroundings. This study uses a quantitative method, starting with a broad perspective and then moving on to a more focused and targeted approach. This tectonic geomorphological analysis uses several morphometric parameters, such as: Drainage Density (Dd), Bifurcation Ratio (Rb), Valley Floor Width to Valley Height Ratio (Vf), Mountain Front Sinousity (Smf), Hypsometric Curve and Hypsometric Integral (HI), and the Tectonic Activity Index (IAT). From the results of IAT calculations, it is found that the Ereunpalay area and its surroundings are in class one to three tectonic activities or commonly called moderate to very high class. The flow pattern of the river that dominates the study area is a parallel flow pattern which is controlled by the geological structure. Based on the results of the morphotectonic analysis, it was found that the Ereunpalay area and its surroundings have a morphological shape that is influenced by tectonic activity in the form of faults and folds.

High resolution mapping shows differences in soil carbon and nitrogen stocks in areas of varying landscape history in Canadian lowland tundra

Soil organic carbon (SOC) in Arctic coastal polygonal tundra is vulnerable to climate change, especially in soils with occurrence of large amounts of ground ice. Pan-arctic studies of mapping SOC exist, yet they fail to describe the high spatial variability of SOC storage in permafrost landscapes. An important factor is the landscape history which determines landform development and consequently the spatial variability of SOC. Our aim was to map SOC stocks, and which environmental variables that determine SOC, in two adjacent coastal areas along Canadian Beaufort Sea coast with different glacial history. We used the machine learning technique random forest and environmental variables to map the spatial distribution of SOC stocks down to 1 m depth at a spatial resolution of 2 m for depth increments of 0–5, 5–15, 15–30, 30–60 and 60–100 cm.The results show that the two study areas had large differences in SOC stocks in the depth 60–100 cm due to high amounts of ground ice in one of the study areas. There are also differences in variable importance of the explanatory variables between the two areas. The area low in ground ice content had with 66.6 kg C/m−2 more stored SOC than the area rich in ground ice content with 40.0 kg C/m−2. However, this SOC stock could be potentially more vulnerable to climate change if ground ice melts and the ground subsides. The average N stock of the area low in ground ice is 3.77 kg m−2 and of the area rich in ground ice is 3.83 kg m−2.These findings support that there is a strong correlation between ground ice and SOC, with less SOC in ice-rich layers on a small scale. In addition to small scale studies of SOC mapping, detailed maps of ground ice content and distribution are needed for a validation of large-scale quantifications of SOC stocks and transferability of models.

Investigating the Tectonic and Structural Controls on the Geomorphic Evolution of Shiriya River Basin, Southern India

Abstract Morphotectonic analysis of a river basin using geomorphic indices helps to identify tectonic deformation. The aim of the present work is to determine geomorphic indices from the digital elevation model and to examine the extent to which structural characteristics of the Shiriya River Basin (SRB) have influenced its drainage morphology. GIS techniques are used to calculate geomorphic indices of the SRB. Morphotectonic and geomorphic analyses were carried out, which included evaluating various geomorphic indices. Hypsometric curve and hypsometric integral (0.46) indicate youth stage of the basin, asymmetry factor (43.23) and transverse topographic symmetry factor (0.37) indicate asymmetry of the basin, basin shape index (2.05) depicts the basin as elongated, sinuosity index (1.47) indicate the sinuous nature of the basin, valley floor width to height ratio is 10.21 and stream length gradient index is 113.75. The entire basin is divided into 18 fourth-order sub-basins for detailed analysis of morphotectonics. Relative active tectonic indices are calculated to identify the subbasin that had undergone pronounced structural disturbance. Out of 18 subbasins 13 subbasin belongs to moderate tectonic active category (class-2) and 5 subbasin belongs to active category (class 2). From the morpho structural analysis following results were arrived, all of which point towards significant structural control: Lower-order streams have an orientation in accordance with significant structural elements of the basin, such as foliations and lineations (E-W). Similarly, the alignment of higher-order streams follows the direction of the major lineaments of the basin (NW-SE). Eight waterfalls/cascades are positioned within the basin, all directed in accordance with the lineament (NW-SE), earthquake recorded near the basin, asymmetry of the basin, acute bending of streams, entrenched meanders, changes in the sinuous river path in several locations where lineament intersect the stream and shrinkage of estuary area indicate neotectonics and structural control over the development of drainage system in the SRB. These findings are essential for understanding the development of river drainage and landform evolution.

Holocene landscape evolution of the Brahmaputra River valley in the upper Assam Basin (India): Deduced from the soil-geomorphic studies

The Brahmaputra River basin exhibits a variety of landforms, including alluvial fans, old and active floodplains, and piedmont belts. The surface expression of the subsurface basement ridge, known as the Brahmaputra Arc, is characterized by paleosol exposures aligned along its crestal region. Using Optically Stimulated Luminescence (OSL) chronology and paleopedological studies, four stages of landform development have been identified in this region, influenced by neotectonics and climate change. The soils in the study area have been categorized into four members of the Quaternary Brahmaputra Morphostratigraphic Sequence (QBMS). QBMS-I (<1.77 ka) represents the youngest soil found in the active floodplains, QBMS-II (2–3.65 ka) includes the Mikri hills piedmont and adjacent river plains, QBMS-III (4–6.5 ka) covers most parts of the study area and is formed on alluvium. The oldest unit QBMS-IV (>7 ka) is exposed on the crest of the Brahmaputra Arc. These soils provide insights into the geomorphologic history of the region, with QBMS-II and III recording multiple avulsions during the Holocene. Micromorphological studies indicate that these soils have undergone multi-phase development under varying redox conditions. The Mid-Miocene compression in the foreland basin led to the formation of the Brahmaputra Arch, and subsequent sedimentation covered the crestal part. Presently, erosion and removal of sediment from the crestal region have exposed older soils as paleosols. Two alluvial fans occur in the study area, the older one located in the central part and the younger one in the northeast corner. The Naga hill piedmonts also exhibit a similar distribution, with the older segment in the central part and younger segments in the northern and southern parts. These patterns of piedmonts and alluvial fans suggest distinct tectonic episodes responsible for sediment redistribution in the study area. The proximity of the Brahmaputra Arc and the Naga thrust in the central part further supports this observation. The findings of this study are consistent with the episodes of neotectonic activity in the nearby Ganga plain, highlighting their regional relevance. Overall, the study provides valuable insights into the evolution of landforms in the Brahmaputra River basin, highlighting the role of neotectonics and climate change in shaping the landscape.

Dune movement under climatic changes on the north‐eastern Tibetan Plateau as recorded by long‐term satellite observation versus ERA‐5 reanalysis

AbstractThe movement of active dunes is tightly linked to climatic conditions (e.g., wind regime, temperature and precipitation) as well as human influence (e.g., grazing, dune fixation and greening). Dune migration rates can be studied to draw conclusions of changing wind conditions over time. The Gonghe Basin (GB), located on the north‐eastern Tibetan Plateau (TP), offers a good testing ground for these assumptions. The intramontane basin is highly influenced by two major wind regimes: the mid‐latitude Westerlies and the East Asian summer monsoon. To investigate environmental changes, this study combines optical remote sensing techniques with climatic datasets. High‐resolution satellite images of the last five decades, such as CORONA KH‐4B, are used to map dunes and calculate their respective migration rates. Further, height information was extracted as well. Climatic changes from the ERA‐5 reanalysis dataset and normalized difference vegetation index (NDVI) values were processed alongside. Relating the dunes' surface processes to climate model data shows an accordance between slowing migration, expanding vegetation and a decrease in sand drift potential. From 1968 to present time, an average dune migration rate of 7.3 m a−1 was extracted from the satellite images, with an overall reduction of −1.81 m a−1. The resultant drift potential (RDP) values for the GB are calculated to be below 10 m3 s−3 with a spatial decrease, following a direction from the NW to the SE, fitting well with a corresponding decrease in the migration rates. Our results indicate a good agreement between the development of aeolian landforms and the ERA‐5 climate reanalysis model data, even in a high‐altitude setting with complex topography, which is known to influence such datasets.

Self-organization of channels and hillslopes in models of fluvial landform evolution and its potential for solving scaling issues

Abstract. Including hillslope processes in models of fluvial landform evolution is still challenging. Since applying the respective models for fluvial and hillslope processes to the entire domain causes scaling problems and makes the results dependent on the spatial resolution, the domain is explicitly subdivided into channels and hillslopes in some models. The transition from hillslopes to channels is typically attributed to a given threshold catchment size as a proxy for a minimum required discharge. Here we propose a complementary approach for delineating channels based on the discrete representation of the topography. We assume that sites with only one lower neighbor are channelized. In combination with a suitable model for hillslope processes, this concept initiates the self-organization of channels and hillslopes. A numerical analysis with a simple model for hillslope dynamics reveals no scaling issues, so the results appear to be independent of the spatial resolution. The approach predicts a break in slope in the sense that all channels are distinctly less steep than hillslopes. On a regular lattice, the simple D8 flow-routing scheme (steepest descent among the eight nearest and diagonal neighbors) harmonizes well with the concept proposed here. The D8 scheme works well even when applied to the hillslopes. This property simplifies the numerical implementation and increases its efficiency.

Hillslope and catchment scale landform evolution – Predicting catchment form and surface properties

Computer-based coupled soilscape-landform evolution models provide an avenue for estimating the erosion potential of a landform over geological timescales. They also provide tools to understand soil-landform relationships in the context of both field and modelled pedogenesis processes. In this study, we used the State Space Soil Production and Assessment Model (SSSPAM) and CAESAR-Lisflood landform evolution model to simulate the evolution of a natural catchment where soil erosion rates have been closely monitored over the last 20 years. Both models predict comparable erosion rates to that of field measurements and produce similar catchment scale geomorphological patterns. Rock content data measured in the field along two transects were compared with SSSPAM simulations at the same representative points. The results showed that SSSPAM produced similar rock content variation along the respective transects. The findings demonstrate 'SSSPAM's ability to predict catchment scale erosion and surface soil distribution. The insights demonstrated here provide confidence in the SSSPAM model for Soilscape predictions for natural, agricultural and post-mining landform assessment.

Controls on the regional distribution of landslide dams and implications for fluvial landform evolution in Bhutan and its surrounding area

Controls on the regional distribution of landslide dams and implications for fluvial landform evolution in Bhutan and its surrounding area

Decoding the Late Pleistocene-Holocene Terrace Evolution along the Main Frontal Thrust Zone, Northeastern Himalayas, India: Insights from Tectonic Geomorphology, Sedimentology, and Optical Dating

Abstract Fluvial archives are the best preserved and provide valuable means of obtaining information pertaining to climate and tectonic deformation of an area. The present study is an attempt to reconstruct the landform evolution history in the northeastern Himalayan region of India. Based on field investigation, tectonogeomorphic mapping, and OSL dating, strath and various levels of cut-and-fill terraces were investigated along the mountain front. Optically stimulated luminescence ages of the terrace sequences suggest that the valley incision occurred in three phases, at ~23 ka, ~14 ka and ~9 – 3 ka and one phase of aggradation was also identified at ~ 7 ka. The strath terraces suggest two major episodes of tectonic uplift in the region around ~ 8 ka and ~ 6 ka. This yields an uplift rate of 0.4 and 0.9 mm/yr. The result from the study suggested that the rapid rejuvenation along the mountain front led to the formation of the strath terraces with enhanced incision of the fluvial terrace and influenced the sedimentary architecture of valley fill sequences.

Interactions of soil quality, ages of alluvial fans, and mechanisms controlling total soil organic carbon dynamics

So far, no studies have tested how alluvial fan aging and associated geomorphological differences can affect the mechanisms that control soil organic carbon (SOC) dynamics. In order to understand the SOC dynamics, we quantified the relationship between soil quality (SQ) indicators and alluvial fans aging over area of about 10,000 km2 in north-eastern Iran, using a minimum data set (MDS) and regression analyses. Twenty seven soil attributes and weathering indices were measured at 90 old and young fans. Total SOC and its fractions were found as the key indicators of the MDS. Despite the higher content of SOC in younger fans (6.25 – 7.11 g kg−1), they exhibited a lower value of SQ (0.35 – 0.42). Younger fans had a low content of fine-sized pedogenic oxides, and, thus, a lower sorption potential, giving rise to a lower ability for stabilising SOC. The higher content of SOC in younger fans was due to an accumulation of coarse particulate organic carbon. Long-term exposure of the older surfaces to weathering caused a statistically significant increase in the chemical index of alteration (57.94 – 72.32 %), chemical index of weathering (64.3 – 77.2 %), the carbon size fraction 53 – 250 µm (2.66 – 5.56 g kg−1), the dithionite-extractable Al (48.4 – 59.2 g kg−1) and Fe (21.5 – 25.7 g kg−1) oxalate-extractable Al (25.6 – 32.7 g kg−1) and Fe (9.5 – 13.0 g kg−1). These characteristics promote physical protection of SOC against microbial decomposition. Alluvial fan aging leads to geomorphological differences in terms of the weathering degree, processes of flooding, inundation, and erosion, contributing to high variability of the SOC dynamics. A proper understanding of the relationships between the age evolution of landforms and associated variations in mechanism regulating the preservation and stability of soil C can help to develop new perspectives for geo-conservation and restoration efforts.

Identifying mountain permafrost degradation by repeating historical electrical resistivity tomography (ERT) measurements

Abstract. Ongoing global warming intensifies the degradation of permafrost. Permafrost thawing impacts landform evolution, reduces freshwater resources, enhances the potential of natural hazards and thus has significant socio-economic impacts. Electrical resistivity tomography (ERT) has been widely used to map the ice-containing permafrost by its resistivity contrast compared to the surrounding unfrozen medium. This study aims to reveal the effects of ongoing climate warming on mountain permafrost by repeating historical ERT and analyzing the temporal changes in the resistivity distribution. In order to facilitate the measurements, we introduce and discuss the employment of textile electrodes. These newly developed electrodes significantly reduce working effort, are easy to deploy on blocky surfaces and yield sufficiently low contact resistances. We analyze permafrost evolution on three periglacial landforms (two rock glaciers and one talus slope) in the Swiss and Austrian Alps by repeating historical surveys after 10, 12 and 16 years, respectively. The resistivity values have been significantly reduced in ice-poor permafrost landforms at all study sites. Interestingly, resistivity values related to ice-rich permafrost in the studied active rock glacier partly increased during the studied time period. To explain this apparently counterintuitive (in view of increased resistivity) observation, geomorphological circumstances, such as the relief and increased creep velocity of the active rock glacier, are discussed by using additional remote sensing data. The present study highlights ice-poor permafrost degradation in the Alps resulting from ever-accelerating global warming.

Modelling of a Post-Mining Catchment for Future Simulations

Landform evolution modelling (LEM) provides an avenue for simulating how a landscape may evolve over extended time periods of thousands of years. CAESAR-Lisflood LEM which includes a hydrologic model (TOPMODEL) and a hydraulic model (Lisflood) can be used to assess the proposed final landform morphology of a mine site by simulating how the mine landform and the landscape would evolve over a 1000-year period. The accuracy of future simulations depends on the calibration and validation of the model to past and present events. Calibration and validation of the model involve finding a combination of parameters of the model which when applied and simulated gives model outputs similar to those observed for the real site scenario for corresponding input data. Calibrating the sediment output of the CAESAR-Lisflood model at the catchment level and using it for studying the equilibrium conditions of the landform is an area that has yet to be explored. Therefore, the aim of this study was to calibrate the CAESAR-Lisflood model and then validate it. To achieve this, the model was run for a rainfall event with a set of parameters, plus discharge and sediment data for the input point of the catchment, to analyse how similar the model output would behave when compared with the discharge and sediment data for the output point of the catchment. The model parameters were then adjusted until the model closely approximated the real site values of the catchment. The model was then validated by running it for a different set of events and checking that the model gave similar results to the real site values. The outcomes demonstrated that while the model can be calibrated to a greater extent for hydrology (discharge output) throughout the year, sediment output calibration may be slightly improved via the ability to change parameters to take into account the seasonal vegetation growth during the start and end of the wet season. This study is important for designing and testing post-mining rehabilitated landscape systems that assess hydrology and sediment movement in seasonal biomes.

Control of Structural Landform Evolution on Karst Groundwater Cycle in a Large-Scale Anticlinorium.

Structural landform evolution and hydrogeochemical analyses are crucial for understanding the characteristics of karst groundwater systems and the development of deep karst formed by complex aquifers in a tectonic collision zone. Detailed structural landform evolution analysis was carried out along the large-scale anticlinorium to investigate the temporal evolution of karst aquifer systems and karstification. Results showed that the tectonic activity included weak horizontal compression and slow vertical uplift during the Triassic to Middle Jurassic, forming a denuded clastic platform. This period was mainly preserved in the geological record as burial karst. From the Late Jurassic to the Early Cretaceous, the study area was strongly compressed by S-N-trending stress, and developed E-W-trending high-angle imbricate thrust structures, which controlled the formation of folded and fault-blocked mountains. Vertical multilayered strata underwent a strong horizontal extrusion, forming a large-scale anticlinorium with secondary folds and faults. With the exposure of carbonate rocks due to rapid crustal uplift, karst began to develop, forming a vertical multilayer karst aquifer system and controlling the distribution of karst groundwater. The Fangxian faulted basin was formed from the Late Cretaceous to the Paleogene, whereby landforms were dominated by intermountain basins. Slow crustal uplift caused the retreat of the denudation line to the east, leading to an increase in hydrodynamic conditions and karstification, and the initiation of early karst groundwater systems. Since the Neogene, intermittent and rapid crustal uplift has led to the deepening of rivers, resulting in the formation of peak clusters and canyons, the development of deep karst, and the complete formation of karst groundwater systems. Combined with hydrogeochemical and borehole data, local, intermediate, and regional karst groundwater systems were identified. It has vital significance to the geological route selection or construction of deep-buried tunnels and the utilization of karst groundwater.

Energy efficiency in transient surface runoff and sediment fluxes on hillslopes – a concept to quantify the effectiveness of extreme events

Abstract. Surface runoff over time shapes the morphology of the landscape. The resulting forms and patterns have been shown to follow distinct rules, which hold throughout almost all terrestrial catchments. Given the complexity and variety of the Earth's runoff processes, those findings have inspired researchers for over a century, and they resulted in many principles and sometimes proclaimed laws to explain the physics that govern the evolution of landforms and river networks. Most of those point to the first and second law of thermodynamics, which describe conservation and dissipation of free energy through fluxes depleting their driving gradients. Here we start with both laws but expand the related principles to explain the co-evolution of surface runoff and hillslope morphology by using measurable hydraulic and hydrological variables. We argue that a release of the frequent assumption of steady states is key, as the maximum work that surface runoff can perform on the sediments relates not only to the surface structure but also to “refueling” of the system with potential energy by rainfall events. To account for both factors, we introduce the concept of relative dissipation, relating frictional energy dissipation to the energy influx, which essentially characterizes energy efficiency of the hillslope when treated as an open, dissipative power engine. Generally, we find that such a hillslope engine is energetically rather inefficient, although the well-known Carnot limit does not apply here, as surface runoff is not driven by temperature differences. Given the transient and intermittent behavior of rainfall runoff, we explore the transient free energy balance with respect to energy efficiency, comparing typical hillslope forms that represent a sequence of morphological stages and dominant erosion processes. In a first part, we simulate three rainfall runoff scenarios by numerically solving the shallow water equations, and we analyze those in terms of relative dissipation. The results suggest that older hillslope forms, where advective soil wash erosion dominates, are less efficient than younger forms which relate to diffusive erosion regimes. In the second part of this study, we use the concept of relative dissipation to analyze two observed rainfall runoff extremes in the small rural Weiherbach catchment. Both flood events are extreme, with estimated return periods of 10 000 years, and produced considerable erosion. Using a previously calibrated, distributed physics-based model, we analyze the free energy balance of surface runoff simulated for the 169 model hillslopes and determine the work that was performed on the eroded sediments. This reveals that relative dissipation is largest on hillslope forms which relate to diffusive soil creep erosion and lowest for hillslope profiles relating to advective soil wash erosion. We also find that power in surface runoff and power in the complementary infiltration flux are during both events almost identical. Moreover, there is a clear hierarchy of work, which surface runoff expended on the sediments and relative dissipation between characteristic hillslope clusters. For hillslope forms that are more energy efficient in producing surface runoff, on average, a larger share of the free energy of surface runoff performs work on the sediments (detachment and transport) and vice versa. We thus conclude that the energy efficiency of overland flow during events does indeed constrain erosional work and the degree of freedom for morphological changes. We conjecture that hillslope forms and overland dynamics co-evolve, triggered by an overshoot in power during intermittent rainfall runoff events, towards a decreasing energy efficiency in overland flow. This implies a faster depletion of energy gradients during events and a stepwise downregulation of the available power to trigger further morphological development.