Erosional Dissection Research Articles

Identifying the impact of generalization on maps of erosion dissection at different scales

Abstract The issue of building thematic maps of erosion dissection, despite its wide demand in various fields of human activity (construction of hydraulic structures, transport and housing construction, agriculture), still has no clear rules and instructions, which causes different perceptions of the obtained mapping results by specialists. The purpose of the study is to experimentally identify the change in the index of erosive dissection depending on the scale of the initial data, the size of the cell, the method of constructing the thematic map, etc. The methods used in this research are the method of mathematical statistics, GIS mapping and modelling, spatial analysis, and change detection. For each of the selected methods of thematic mapping, we compiled the cartograms that allow the visual tracking of changes in the elements of the erosion network depending on the geometric characteristics of the scale and cell size. The dimensions and characteristics with optimal results were substantiated. The main feature of erosional dissection mapping of any territory is to detect the negative relief or concave upward forms. The result is a visual perception accompanied by the addition of numerical values. Estimation of erosion dissection by these methods was used in the construction of a thematic map of the foothill territory with a relatively homogeneous relief pattern. It should be noted that the change in the morphometric index happens simultaneously with the change in orographic features. Therefore, for areas with different forms of relief, the combination or use of only one of the above methods allows identifying the optimal and most accurate one among them. The use of well-established methods will facilitate the study of foothill plains or mountainous areas and will allow expanding the scope of the use of thematic maps for applied purposes and forecasting.

Современные сейсмотектонические деформации на вулканическом плато Асхатэ и их роль в структуре вулканического поля Дариганга, Юго-Восточная Монголия

From instrumental measurements in southeastern Mongolia and adjacent China, weak seismicity is determined. However, 7.5-kilometer long system of ditches, probably of seismic nature, was detected in the western part of the Dariganga volcanic field, on the edge of the Ashate Plateau that resulted from erosional dissection of the 4.8–4.3 Ma shield edifice. We propose that the modern seismotectonic reactivation of the Askhate volcano is related to tectonic motions in the Late Cenozoic Tamtsag foredeep of the Nukut-Daban range, spatially associated with neotectonic reactivation of the Solonker suture.

ГЕОДИНАМІКА

The article is aimed at conducting the engineering-construction assessment of Irpin town of Kyiv region. It is based on the engineering-geological zoning of the settlement, which provides the allocation of different-level taxonomic units with a set of natural and anthropogenic factors of construction conditions from the largest unit (engineering-geological region) to the smallest (sites and subsites). Engineering and geological surveying and mapping became the main research methods. The main result of the study was a comprehensive comparison of data on the geomorphological, geological-genetic structure, hydrogeological conditions, soils’ composition and properties of Irpin. It ultimately provided an opportunity to build a large-scale synthetic map of engineering-geological zoning and engineering- construction assessment of the town. The study identified eleven engineering-geological sites with appropriate characteristics of natural and anthropogenic factors of construction conditions factors, including have been identified, among which six sitesare unfavorable for construction. The scientific novelty of the above research lies in the application of engineering-geological zoning as a basis for engineering-construction assessment, which is not limited to the selection of planning restrictions of an engineering-geological nature. For the first time the novel method of engineering-geological subsites’ selection is based on the principle of taking into account natural hazards and morphometric characteristics of the relief. They reflect the degree of erosion dissection, potential for the of modern relief-forming processes’ manifestation and soil erosion. The practical aspect of the conducted research consists in creating a high-quality scheme of engineering-construction assessment, supplementing the scheme of existing planning restrictions, selecting optimal and economically justified measures for engineering preparation and territories’ protection against dangerous geological processes. Engineering-geological zoning allows you to determine safe places for the accomodation of engineering structures, their structural features, choose rational types of foundations, reduce the cost of survey and construction work and generally improve the design’s quality.

Morphometric analysis for flood flow formation feature identification (on example of Ulaanbaatar agglomeration)

Water flows with significant flow rate feature a high destructive force and can lead to catastrophic consequences. Fluvial processes caused by uneven distribution of rain precipitation over the area pose risks to the developed inland foothill territories. The purpose of this study is to carry out a quantitative morphometric analysis of the territory in order to identify the formation features of flood flows. The analysis and ranking of catchment basins are performed using a basin approach. On the basis of SRTM images and the use of stock cartographic material in the GIS program the authors have built specialized electronic maps that allow to obtain quantitative parameters reflecting the morphometry of the basins under analysis including basin geometry, drainage network and terrain relief. On example of the Ulaanbaatar agglomeration territory it is shown how initial morphometric parameters of basins and watercourses (length, width, area, perimeter, erosion dissection, drainage network density, terrain relief coefficient, Melton coefficient, etc.) form the features of flood flow. For developed territories, the initial data on the catchment basin morphometry constitute the basis for compilation of specialized maps to be used in planning and construction. The combination of morphometric indicators on the territory of the Ulaanbaatar agglomeration indicates that there is possibility of large flood formation and development of dangerous mudstone flows in some catchment basins.

Using geomorphometric approach to investigate spatial pattern and intensity of erosional dissection in a block-faulted topography (Orlickie-Bystrzyckie Mountains, Central Europe)

The paper presents an attempt to recognize areas of enhanced erosional dissection, based on a combined analysis of several geomorphometric variables and using four different approaches (rank-based, cold and hot spot analysis, k-means clustering of ‘raw’ data, and k-means clustering of local measures of spatial autocorrelation). The study area includes the Orlickie-Bystrzyckie Mountains Block (OBMB), which is a block-faulted range within the Sudetes Mountains, Central Europe, typified by fault-generated range fronts, remnant planation surfaces and topographic ramps due to large-scale tilting. Geology is diverse, with basement rocks and sedimentary cover, and the relevant timescale is late Cenozoic. Morphometric variables derived from a LiDAR-based DEM include contour length, standard deviation of elevation, median valley depth and standard deviation of curvature, and are considered to account for various morphometric signatures of erosional dissection. While deriving compound measures of dissection, three grid cell sizes were considered. Within the OBMB several areas were identified as erosionally dissected to a considerable degree. Their spatial pattern is complex and reflects several factors simultaneously. Differential uplift appears as the main trigger, but the erosional response varies, depending mainly on the size of runoff contributing area – itself related to the pattern of uplift, and the distance from the margins of elevated areas. Lithology (bedrock resistance to erosion) seems to play a subordinate role. We also discuss various issues related to the procedures themselves, pointing out their advantages and limitations. Procedural setups proposed in this paper are not site-specific and may be used in various topographic and geological settings.

Использование беспилотных летательных аппаратов для оценки интенсивности проявления опасных береговых процессов водоохраной зоны Цимлянского водохранилища

The water protection zone of the Tsimlyansk reservoir was chosen as the object of research. The subject of the study was the assessment of the intensity of manifestation of dangerous coastal processes of the reservoir: abrasion-latency, erosion activity. A method for monitoring erosion processes in water protection zones of water bodies using a software and hardware complex based on unmanned aerial vehicles and GIS technologies has been developed and tested. The optimal type of digital elevation models has been determined for assessing the density of the erosion net-work, determining the types of banks and the intensity of manifestation of abrasion and landslide processes, measuring the morphometric characteristics of erosional landforms. The types of erosional landforms were determined and the zoning of the territory of the water protection zone of the Tsimlyansk reservoir was carried out according to the density of the erosional dissection of the relief. Studies have shown that the predominant erosional forms of the relief of the water protection zone of the Tsimlyansk reservoir are ravines and gullies. The maximum average value of the density of the erosional network of the relief within the boundaries of the administrative districts of the reservoir coast falls on the Surovikinsky district. In the Kalachevsky district, the maximum value of the density of the erosion network is noted within the water protection zone of the Tsimlyansk reservoir.

Tectonic geomorphology and paleoseismology of the northern East Franklin Mountains fault, El Paso, Texas, USA

The 45 km-long, north-trending East Franklin Mountains Fault lies in the southern Rio Grande rift (Texas). Late Quaternary normal fault scarps up to 20 m high traverse the eastern range front, but also bulge up to 2 km out onto the piedmont in lobes as much as 3.5 km wide. In the lobe areas the range-front fault strand displays no fault scarps, as if displacement has shifted to the piedmont strand since ca. 400 ka. We divide the faulted piedmont alluvial fans into seven age classes (from Middle Pleistocene to Holocene), based on erosional dissection and soil profile development. Piedmont scarps in Qf1 deposits (250–400 ka) range from 18 to 20 m high; in Qf2-3 deposits (65–100 ka), 9–10 m high; and in Qf3-4 deposits (20 ka), 2.7–4 m high (the latest displacement event). Scarp heights underestimate true vertical displacement of the footwall surface, which lies buried beneath younger fan deposits of unknown thickness on the hanging wall. Hanging-wall aggradation also causes variable scarp heights along strike on single-age landforms, with burial thickness a second-degree polynomial function (parabolic) of distance to the nearest active stream. Our paleoseismic trench on a 9.8 m-high scarp exposed evidence for five displacement events in the past 44 ka, the latest three of which had vertical displacements of 3–4 m. Such displacements imply surface ruptures longer than the 26.5 km fault length previously mapped in the USA, indicating rupture extended onto adjacent faults. The minimum long-term slip rate (>11.2 m in 44 ka) is 0.25 mm/yr; over last full seismic cycle (ca. 11–29 ka) it is 0.20–0.21 mm/yr. Optically-stimulated luminescence (OSL) dating shows that fine sand-silt grains in colluvial deposits were not all zeroed during deposition. Single-aliquot dating of quartz grains yielded multiple OSL age peaks, the youngest peaks of which yield a chronology compatible with stratigraphy and soil development in the colluvial wedge sequence.

Оценка эрозионной опасности рельефа на основе цифрового моделирования

On the basis of a digital elevation model (DEM) based on generalized data from USGS STRM DEM and ASTER GDEM with a resolution of 3″ with the help of GIS technologies, a morphometric analysis of the territory of the perm Territory at a scale of 1:2.5 million was carried out and a series of morphometric maps was created, as well as an assessment map of the erosion hazard of the relief. According to the results of morphometric analysis, the values of the index of vertical dissection of the relief in the region vary within the range of 0–623 m with an average value of 44 m. The steepness of slopes varies from 0 to 40° with average values of 3°. The horizontal dissection, determined on the basis of the thalweg network of permanent and temporary streams, varies in the range of 0.145–1.202 km/km2. Comparison of morphometric indicators in key areas with the data obtained by traditional methods of morphometric analysis revealed their coincidence at the level of gradations. The following geomorphological factions curtains: wide development of slope surfaces with elevation differences over 50 m and slopes exceeding 3°. According to the results of cartometric analysis, such conditions characterize 35 % of the region’s area. More than half of the region’s area (60 %) has an average density of erosional dissection of 0.5–0.8 km/km2, another 36 % of the area is characterized by moderate values of 0.2–0.5 km/km2. The calculated relief energy index has a value of 3–13 points; on its basis, 4 categories of relief erosion hazard were identified. In accordance with the results obtained, most of the perm Territory (63.0 %) is characterized by a low erosion hazardous relief, 36.6 % by a medium and highly erosion hazardous. The share of land, the relief of which is characterized by zero erosion potential, is 0.4 % of the region’s area.

Hydrographic and erosional dissection pattern as an indicator of landform type of the Malozemelskaya and Bolshezemelskaya Tundra

The paper describes the methodology and presents the results of the calculation of the spectral characteristics of the terrain for the territory of the Bolshezemelskaya and Malozemelskaya Tundra (the north of the European part of Russia). There are nine terrain clusters, differing in the topographic dissection pattern. Their geomorphological interpretation is given. Three clusters characterize mountainous and coarsely hilly terrain with the depth of dissection from 150 m and more. The others are low and elevated terrains with much lower depths of dissection (up to 50 m) and different patterns of interposition of landforms.

Geomorphometry-based detection of enhanced erosional signal in polygenetic medium-altitude mountain relief and its tectonic interpretation, the Sudetes (Central Europe)

We explore the assumption that uplift drives erosion and hence, more dissected (eroded) terrains may indicate areas subject to more intense uplift than others, especially if other factors such as elevation and geology can be demonstrated as inconsistent with the spatial pattern of dissection. Geomorphometry and statistics are employed to recognize the enhanced erosional signal within a medium-altitude mountain terrain of the Sudetes in Central Europe, considered as a representative for moderately uplifted areas of complex bedrock diversity. This signal is understood as a meso-scale reflection of relief properties, whereas the recognition of homogeneous terrain units, different in terms of strength of erosional signal, is carried out by means of multi-criteria terrain classification, involving Principal Component Analysis and k-means grouping. Four groups covering 45% of the area have been identified. They were quantitatively compared with independent variables of altitude, lithology, structural units and rock strength, and also assessed in relation to rainfall pattern. It is concluded that their dependence on altitude and geology is only partial. Then, three types of dissected terrain are distinguished and interpreted in terms of uplift intensity, rock strength as a factor modulating erosional response to uplift and timescale. The spatial distribution of these types of terrain indicates several isolated ‘hot spots’ of erosional dissection on predominantly strong rocks, linked by less elevated areas, underlain by rocks of variable strength. The former are considered as having longer history of uplift and dissection, dated back to the late Palaeogene, whereas the latter record more recent history of endo-exogenic interactions, possibly since the late Miocene. The presence of canyon-like valleys incised into planar or gently sloping relief may indicate the most recent pulse of relief rejuvenation. The procedure proposed in the paper is suitable to be used in various settings, given that good quality topographic data are available.

The importance of subsurface lithology in controlling magma storage v. eruption: an example from offshore southern Australia

The volumetric relationship between the intrusive and extrusive components of volcanic fields is difficult to constrain. This is because either the erupted products are commonly eroded or the intrusions are concealed by overburden. Three-dimensional seismic data therefore offer a unique opportunity to study ancient volcanic provinces, as these datasets can image both components without the need for erosional dissection. This study is based on 3D seismic data from the Bight Basin Igneous Complex (BBIC), a volcanic province constructed within a sedimentary basin, offshore southern Australia. We demonstrate that the BBIC contains abundant sills and laccoliths emplaced within deltaic sediments. The intrusions have a total volume of 92–111 km 3 , and the lava flows and volcanoes have a combined volume of 66–76 km 3 (Dense Rock Equivalent). This indicates that the ratio of intrusive:extrusive products for the BBIC is between 1:1 and 2:1. The architecture of the BBIC contrasts markedly with the neighbouring Newer Volcanics Province (NVP), which lacks abundant sills and laccoliths. Because lava flows and volcanoes in the NVP were dominantly fed by dykes hosted in basement rock, we suggest that subsurface lithology plays an important role in causing sill formation and determining the total volume of magma stored in the subsurface.

LOCAL PECULIARITIES OF THE RECENT EXOGEODYNAMIC REGIMES OF THE RUSSIAN PLAIN (THE VOLOGDA, PERM AND SARATOV REGIONS AS AN EXAMPLE)

The paper deals with application of k-means clustering to the analysis of exogeodynamic regimes. Three different regions of Russian Plain were taken for the analysis and the zoning of each one was made on the basis of nine characteristics: precipitation, amount of woodland, amplitude of neotectonic movements, maximal and minimal heights, depth and density of erosion cutting, intensity of landslides and karst processes. Data were obtained by the grid 5'х10'. We consider the area with close mean values of each characteristic, as an area of specific geomorphic regime, the latter defined by the set of values, significantly discrepant from the others. The regions under consideration have different sets of regimes, which nevertheless have some features in common. In every site the regimes of watersheds with low erosion dissection and of deeply dissected slopes are clearly distinguished.

THE EVALUATION OF DIFFERENT FACTOR INFLUENCE ON THE INTENSITY OF EXOGENOUS PROCESSES IN THE WEST SIBERIA

Amongst the correlation of exogenous processes with the factors affecting their intensity the highest ones are those with the absolute heights, amplitudes of neotectonic movements, and endurance of warm period. The percent of forest cover, having middle correlation with some processes, itself suffers their influence. The total dependence of exogenous processes on 9 external factors, used in this work, differs from relatively high to low: the determination coefficients for thermokarst and cryogenic processes reach up to 77% and 79%, for the density and the dept of erosion dissection they consist 52% and 32% correspondingly, for swamp development - 41%. The analysis of partial correlation gave some additional interesting results, which proved this type of correlation to be very important while investigating the multifactor processes. In some cases (but not in all) it gives more adequate evaluation of real factor impact on exogenous processes intensity.

ARID KSUR HEIGHTS IN THE NORTH AFRICA: EROSION AND EOLIAN MORPHOSCULPTURE, CLIMATIC AND ANTHROPOGENIC DESERTIFICATION

The Ksur heights are situated between Great Eastern Erg and Gabes bay in the North Africa. The beginning of the tectonic uplift is dated to the Pliocene-Early Pleistocene, upward movements continued during the Pleistocene when erosion dissection took place. In the Holocene the Ksur heights underwent strong deflation. The new data on distribution of the Holocene eolian deposits in the North Africa and in the depression of Tunis shotts (the El'Garsa shott as an example) are discussed. Of seven Holocene layers of the El'Garsa shott five are eolain, which indicates long and intensive deflation within the Great Eastern Erg and western slope of Ksur heights. The questions of anthropogenic relief formation are discussed in details. Two stage of man-induced destruction may be distinguished: the epoch of Rome and the colonial period in the XX and XXI century. The impact of hostility may (in places) overpass the relief destruction during peace periods. The importance of war action for the arid regions destruction is emphasized.

THE INFLUENCE OF THE EROSION DISSECTION DEPTH ON GOLD GRANULOMETRIC COMPOSITION IN AURIFEROUS ALLUVIALS

On the example of Nimansky gold-bearing region it was shown that the gold grains size depends on the depth of erosion dissection in case the original loads and climate conditions being of the same type within the metallogenic province. The largest grains are concentrated in those parts of river valleys, which are about 320-420 m in depth, the smallest ones - in the valleys about 160-240 m in depth. The valleys with the depth less then 120 m and more then 420 m have no commercial deposits.

RECENT GEOMORPHOLOGIC REGIMES OF THE URAL

The territory of the Ural neotectonic structural zone consists of several areas with highly different recent geomor-phologic regimes. For the mountainous regimes of the North and Polar Ural the typical are high values of neotectonic 4* 83 uplift, deep and dense erosion dissection, high gradients of elevations, glacial landforms. The regimes of plain type are characterized by insignificant dissection under condition of low uplift; they occupy Pai-Khoi, the eastern margin of the Ural and Transural plateau. The intermediate regimes have intermediate values of neotectonic uplift, elevations, and erosion dissection, but high intensity of karst and landslides, and large amount of woodland; they are situated on the west slope of the North and Middle Ural and in the NW part of the South Ural. The Ural is usually classified as a single mountain morphostructural type with subtypes. We suppose there should be three or at least two mor-phostructural types: the properly mountain, the transitional, and platform plain types of morphostructure within the Ural neotectonic region (the last two may possibly be merged into one transitional type). These types manifest the different stages or different intensity of the Ural's rejuvenation (or regeneration). The distribution of recent geomor-phologic regimes is governed not only by the Hercynian meridional tectonic structures but by the latitude climatic zones and neotectonic features as well.

ON SOME FLUVIAL LANDFORMS IN SOUTHERN AFRICA AND THEIR DEVELOPMENT UNDER CHANGING NATURAL ENVIRONMENT

Natural climatic and tectonic factors had a strong impact on the Mz-Kz development of fluvial relief of the region. During the dry seasons the chemical and physical weathering, different types of denudation, gravitational and aeolean processes are predominant, while fluvial processes play subsidiary role. Phased uprise of the Large Escarpment along the periphery of Southern Africa coming along with its axis displacement into the interior of the continent caused the formation of the deep incisions in the river valleys and strong erosion dissection of the neighbouring parts of the planation surface. The faults of the ancient and recent rifts have a significant impact on the morphology of the fluvial relief.

Comparison of volumetric and remote sensing methods (TLS) for assessing the development of a permanent forested loess gully

The gully systems develop a compact network dissecting the loess cover of the NW part of the Lublin Upland. They are overgrown by dense and multi-storey forest assemblages. It is very difficult to apply teledetection techniques, GPS positioning, and geodesic tools, such as a laser rangefinder or total station, for monitoring of gully development. The detailed research, involving the comparison of traditional and modern methods, was conducted in a gully with a secondary erosional dissection, developing in the gully bottom with varied intensity for the last 15 years. In the period of comparative research (2012/2013), the rate of development of the erosional dissection was measured by means of traditional methods as well as a Leica HDS 7000 laser scanner. 3D laser scanning permitted precise terrain modelling and the assessment of qualitative and quantitative spatial changes. This paper compares the results of three measurement campaigns. The analysis showed intensive development of the dissection, manifested in an increase in its volume (37 %), retreat of the erosion scarp (32 m), deep erosion (19 %), and lateral erosion (27 %). Registered moderate snowmelt in 2013 caused the volume dissection to increase by 57 m3, mainly as a result of the gully bottom scouring. During heavy rainfalls in June, the landforms were widened by a further 217 m3 and observed deepening and widening of erosive potholes. The prevalence of deep erosion resulted in the transformation back into a V-shaped cross section. A total of 37.3 Mg km−2 of material was discharged from the gully catchment during snowmelt runoffs in 2013. A precipitation event in June 2013 caused the discharge of 856.9 Mg km−2 of material from the catchment. The obtained results confirm that snowmelt erosion determines the spatial development of perennial gullies, but the volume of material discharged from the catchment depends on the occurrence of extreme precipitation during the warm season.

LATE PLEISTOCENE CYCLE OF EROSION DISSECTION AND INFILLING OF THE DRAINAGE NETWORK IN THE NORTH-EASTERN STAVROPOL'E (PAPER 2. RECENT BALKAS. HISTORY OF THE DRAINAGE NETWORK)

In the northeastern Stavropol Highland erosion network depth and density were much higher at the Middle/Late Pleistocene (MP/LP) boundary than at present. During the Valdai (Vistulian) cold epoch of the LP, erosion network was filled with slope and alluvial deposits. Probable incision in the Late Glacial interrupted the infilling tendency, but the erosion network rejuvenation had much smaller scales compared to the preceding erosion dissection. Therefore, the upper reaches of the erosion network at the MP/LP boundary were almost buried and transformed into hollow systems by the beginning of the Holocene, while in lower reaches thick LP deposits make wide valley bottoms. In the Holocene, sedimentation processes proceeded both in hollows and in small valleys, but their rates decreased considerably. Land cultivation started in the region in the middle XIXth century. During the last 150 years, sedimentation in valley and hollow bottoms continued to prevail over erosion. This shows that artificial lowering of landscape sustainability by land cultivation has not led to incision along the modern and ancient erosion network. The probable explanation is that modern climate is not so favorable for erosion as it was at the MP/ LP boundary and in the Late Glacial.

GEOMORPHOLOGY AND NEOTECTONICS OF THE SOUTHERN LEVANT

Relief of Israel and Jordan is very young one; it was formed in the Late Cenozoic in the result of folding and block movements on the Cr-Pg shelf plain and its erosion dissection. Neotectonic activation of the territory began in the second half of the Late Cretaceous (in the post-Turonian time). Folding preceded block movements. Neotectonic activation of the Levant is but weak refl ection of the colossal collision events at the boundary of the Eurasian and African plates.