Terrain Units Research Articles

Range of Terrain Suitability for the Development of the Aladi Tulabolo Road Network Gorontalo Province

This research aims to identify, analyze and develop a road route development model based on terrain suitability to establish a new road network connecting Aladi with Tulabolo, Bone Bolango Regency in Gorontalo Province. A GIS-based spatial approach is used to describe and measure terrain suitability. Based on the characteristics of the research object, survey methods are used; based on population characteristics, stratified proportional sampling is used as the mapping unit; and based on its relationship to analysis, scoring-based quantitative and qualitative methods are used. The research results show that (1) the characteristics of the distribution of terrain suitability for the development of the road network in the research area are based on the parameters that make up terrain units such as landform units, slope, rock type and soil type, resulting in zoning with 5 (five) levels of suitability. The five levels of suitability are S1 suitability (high suitability), S2 suitability (medium suitability), N1 suitability (temporarily not suitable), and N2 suitability (permanently not eligible). (2) The distribution of terrain suitability classes for developing the dominant road network for the Aladi-Tulabolo area is in suitability class S2 (medium suitability), covering an area of 99.25 km2 . (3) The road route development model based on the suitability of the terrain in the research area is formed with the formulation Terrain Unit (SM) = f (bl, kl, jb, jt), where bl = landform, kl = slope, jb = rock type, and jt = soil type

Exploring the Differences in Tree Species Classification between Typical Forest Regions in Northern and Southern China

Focusing on the trend of continuously seeking high-precision tree species classification results in small areas from the perspectives of sensors and classification algorithms. This study aimed to explore the effects of data sources, classifiers, and seasons on classification accuracy in regions with significant environmental variation, examining patterns of tree species classification to enhance the transferability of classification. Considering two typical forest distribution regions in the north and south of China, this study utilized the revisitation cycle and open-source advantages of Sentinel-2 and Landsat-8. Leveraging the Google Earth Engine (GEE) platform, this study captured spectral features, vegetation indices, and texture features for single seasonal and seasonal combination images. With the assistance of Sentinel-1A and SRTM (Shuttle Radar Topography Mission) DEM (Digital Elevation Model), backscattering coefficient features and topographical features were extracted and input with features captured from Sentinel-2 and Landsat-8 into three types of classifiers: random forest (RF), support vector machine (SVM), and gradient tree boosting (GTB) for major tree species classification. In this research, we discovered that the best classification for single season in the northern study area was spring, whereas, for the southern study area, it was winter. Seasonal combination images effectively improved the classification accuracy of single seasonal images, with Sentinel-2 imagery displaying better classification performance compared to Landsat-8, and the optimal classifier differing between the north and the south. The inclusion of topographical or backscattering coefficient features in the four-season combination imagery contributed to improvements in classification accuracy, with topographical features significantly enhancing the classification performance in the topographically varied southern study area. The evaluation of feature importance indicated that elevation was the most critical feature for classification, while spectral features and vegetation indices were also significant. In the southern study area with large topographical discrepancies, subdividing into different terrain units led to improved tree species classification accuracy in medium-altitude, gentle slope areas. These findings provide insights into the regularity of enhancing tree species classification accuracy in environmentally diverse areas through the use of multi-source remote sensing data and multi-seasonal imagery. Consequently, the results offer a reference for the identification of tree species across large areas and the creation of spatial distribution maps.

Morphostructural influence and neotectonic activity in the geomorphological configuration of southeast Paraíba and northeast Pernambuco, Brazil

The current study provides critical insights into the field of geomorphology by examining the impact of lithological structures and tectonic activities on the geomorphological configuration of terrain and drainage networks in the southeast of Paraíba and northeast of Pernambuco, Brazil. This geographical region is characterized by phenomena of uplift and fluvial incision at various sites, yet remains inadequately explored with respect to its active deformation and the broader context of its recent geology. Therefore, the primary aim of this research is to elucidate the morphostructural and neotectonic influences on the geomorphological formations in these sectors of Brazil. The methodology encompasses morphostructural analysis, leveraging data derived from altimetry, slope, and geomorphology maps, categorized into taxonomic terrain units. Additionally, this research incorporates the use of morphometric indices, including the Stream Length-Gradient Index (SL), Valley Floor Width (VF), and Asymmetry Factor (AF) to quantify geomorphological anomalies. The analysis of the SL index indicates that a significant portion (87.5 %) of the drainage network exhibits anomalies. Furthermore, the VF index results reveal that 66 % of the profiles analyzed manifest anomalies of various magnitudes. Within the study region, the AF index elucidates the distribution of sub-basins into categories of low (0−30), medium (31−50), and high (>51) asymmetry, comprising 25 %, 31 %, and 44 % of the sub-basins, respectively. The sub-basins demonstrate channel disequilibrium, as evidenced by the SL index, attributed to numerous transient knickpoints along the drainage profiles. This observation is consistent with previous findings in the Koyna-Warna Shallow Seismic Region. The study's outcomes reveal both qualitatively and quantitatively anomalous patterns in the drainage network and terrain forms, which are likely indicative of recent tectonic events affecting the entire eastern edge of Northeast Brazil. Consequently, the findings highlight the significant role of post-Miocene tectonic events in shaping the relief of the study area.

Space-time modeling of landslide size by combining static, dynamic, and unobserved spatiotemporal factors

Landslide spatial prediction using data-driven models has predominantly concentrated on predicting where landslides may occur. Nevertheless, few researchers have turned to jointly modeling how large and when landslides will be for a given terrain unit. This study proposes a data-driven model capable of estimating how large landslides may be, for the entire Taiwan main island in a fourteen-year time window. To address this task, we implement a space–time generalized additive model to fit the complex relationships between environmental factors and landslide size. In addition to incorporating static and dynamic covariates into the modeling process, the model takes into account spatial and temporal interactions to elucidate the spatiotemporal variations affecting landslide size. To test the effectiveness of the model, we employ a comprehensive set of cross-validation (CV) procedures, includes a randomized 10fold-CV, a spatially constrained CV, a temporal leave-one-year-out CV, and a spatio-temporal CV. The experimental results demonstrate that the space–time model delivers acceptable and interpretable prediction outcomes, demonstrating the ability to predict landslide area for a given slope unit within a specified time period. We believe that the space–time landslide modeling will lay the foundation for landslide community to analyze landslide characteristic within a dynamic context. Furthermore, given its inherent spatio-temporal nature, we anticipate that this approach may pave the way for simulation studies exploring diverse climate scenarios.

Mapping SCS hydrological soil groups over South Africa at terrain unit spatial resolution

Given the many users in South Africa of the SCS (Soil Conservation Service) hydrograph-generating technique, which requires key soils information, this paper presents a methodology to develop a detailed map (at the spatial resolution of South Africa's 27 491 terrain units) of the SCS runoff-related soil groups. In order to achieve this objective, background is first provided on the soils context within the SCS technique, as well as on the approaches to defining SCS hydrological soil groups, by assigning SCS soil groups to South African soil series. Steps when mapping SCS soil groups across South Africa at terrain unit spatial resolution are then outlined. This is followed by the presentation and interpretation of the detailed terrain unit level map of SCS soil groups for South Africa. The detailed new map illustrates the finer detail across contributing catchments countrywide now obtained from the terrain unit approach, compared to the previous map of SCS soil groups based only on the coarser soil land types.

Landslide hazard spatiotemporal prediction based on data-driven models: Estimating where, when and how large landslide may be

The geoscientific community primarily focuses on predicting where landslides are likely to occur through data-driven susceptibility models. Recently, few researchers have turned to statistical estimation of landslide planimetric area within a given terrain unit and exploration of the spatiotemporal distribution of landslide occurrence. However, these data-driven approaches cannot fulfill the commonly accepted definition of landslide hazard and cannot predict the location, time/frequency, and magnitude of landslide occurrence simultaneously. This study proposes a unified and data-driven framework for landslide hazard spatiotemporal modeling, enabling dynamic and probabilistic estimation of landslide occurrence within a given slope unit at a specific time period and for a specific landslide magnitude. This framework not only involves static and dynamic factors in modelling, but also considers spatial and temporal interactions to explore the spatiotemporal variation effects of landslide hazard. We test this framework on the main island of Taiwan with a multi-temporal landslide inventory from 2004 to 2018. Specifically, this framework assumes that the occurrence and size of landslides spatiotemporally follows a binomial and a Log-Gaussian distribution, respectively, and then uses generalized additive models to achieve the estimation of landslide hazard probability. Finally, the performance is validated by a spatiotemporal leave-one-out cross-validation scheme. We believe that this framework will lay the foundation for the community to estimate landslide hazard in a unified and probabilistic data-driven prototype. We envision it could lead to studies of dynamic hazard responses to climate change.

The Greater Midlands—A Mid-Elevation Centre of Floristic Endemism in Summer-Rainfall Eastern South Africa

The Midlands region of KwaZulu-Natal (KZN) Province in South Africa was hitherto a putative centre of floristic endemism (CFE) based on conjecture. The aim of this study was to empirically explore this concept by delineating unambiguous boundaries for this CFE and documenting the endemic spermatophytes within a conservation framework. The Greater Midlands Centre of Floristic Endemism (GMCFE), a more expanded study area than the parochial Midlands region of KZN, is formally described as southern Africa’s 20th CFE. It is a mid-elevation region occupying the greater Midlands of KZN, with extensions of contiguous grasslands extending northwards into southern Mpumalanga and southwards into north-eastern Eastern Cape. This “foothills” CFE covers ca. 77,000 km2 of predominantly mesic C4 grassland, ranging in elevation from ca. 700–2200 m a.s.l. It is congruent with the “sub-escarpment ecoregion,” essentially a composite of the Sub-escarpment Grassland and Savanna Bioregions and the sub-escarpment grasslands of southern Mpumalanga and northern KZN. The GMCFE hosts at least 220 endemic spermatophytes, of which almost a fifth belong to the family Apocynaceae. Families Asteraceae, Asphodelaceae, Fabaceae, and Iridaceae also contribute significantly. Genera Ceropegia, Aloe, Dierama, Kniphofia, Helichrysum, and Streptocarpus contribute the most endemics. More than half are forbs, and almost three-quarters are confined to the Grassland Biome. Endemic radiations are attributed to geodiversity and geological complexity (especially the strong lithological influence of dolerite); physiographic heterogeneity (particularly elevation gradients and variable terrain units); strategic proximity to hyper-diverse temperate and subtropical “border floras”; and localized pollinator-driven adaptive radiations. Of alarming concern is the high number of threatened plant taxa, with ca. 60% of the endemic flora Red Listed in threat categories (CE, E, and VU) or considered “rare”. Extremely low levels of formal protection and poor ecological connectivity, coupled with high levels of land transformation and intensive utilization, render the GMCFE one of the most imperilled CFE in South Africa. Urgent conservation action is required to safeguard this unique and highly threatened “rangeland flora” and stem the biodiversity crisis gripping the region.

Lacustrine sedimentation by powerful storm waves in Gale crater and its implications for a warming episode on Mars

This investigation documents that the Rugged Terrain Unit, the Stimson formation, and the Greenheugh sandstone were deposited in a 1200 m-deep lake that formed after the emergence of Mt. Sharp in Gale crater, Mars, nearly 4 billion years ago. In fact, the Curiosity rover traversed on a surface that once was the bottom of this lake and systematically examined the strata that were deposited in its deepest waters on the crater floor to layers that formed along its shoreline on Mt. Sharp. This provided a rare opportunity to document the evolution of one aqueous episode from its inception to its desiccation and to determine the warming mechanism that caused it. Deep water lacustrine siltstones directly overlie conglomerates that were deposited by mega floods on the crater floor. This indicates that the inception phase of the lake was sudden and took place when flood waters poured into the crater. The lake expanded quickly and its shoreline moved up the slope of Mt. Sharp during the lake-level rise phase and deposited a layer of sandstone with large cross beds under the influence of powerful storm waves. The lake-level highstand phase was dominated by strong bottom currents that transported sediments downhill and deposited one of the most distinctive sedimentological features in Gale crater: a layer of sandstone with a 3 km-long field of meter-high subaqueous antidunes (the Washboard) on Mt. Sharp. Bottom current continued downhill and deposited sandstone and siltstone on the foothills of Mt. Sharp and on the crater floor, respectively. The lake-level fall phase caused major erosion of lacustrine strata that resulted in their patchy distribution on Mt. Sharp. Eroded sediments were then transported to deep waters by gravity flows and were re-deposited as conglomerate and sandstone in subaqueous channels and in debris flow fans. The desiccation phase took place in calm waters of the lake. The aqueous episode we investigated was vigorous but short-lived. Its characteristics as determined by our sedimentological study matches those predicted by an asteroid impact. This suggests that the heat generated by an impact transformed Mars into a warm, wet, and turbulent planet. It resulted in planet-wide torrential rain, giant floods on land, powerful storms in the atmosphere, and strong waves in lakes. The absence of age dates prevents the determination of how long the lake existed. Speculative rates of lake-level change suggest that the lake could have lasted for a period ranging from 16 to 240 Ky.

Disparate permafrost terrain changes after a large flood observed from space

AbstractThe 2015 spring flood of the Sagavanirktok River inundated large swaths of tundra as well as infrastructure near Prudhoe Bay, Alaska. Its lasting impact on permafrost, vegetation, and hydrology is unknown but compels attention in light of changing Arctic flood regimes. We combined InSAR and optical satellite observations to quantify subdecadal permafrost terrain changes and identify their controls. While the flood locally induced quasi‐instantaneous ice‐wedge melt, much larger areas were characterized by subtle, spatially variable post‐flood changes. Surface deformation from 2015 to 2019 estimated from ALOS‐2 and Sentinel‐1 InSAR varied substantially within and across terrain units, with greater subsidence on average in flooded locations. Subsidence exceeding 5 cm was locally observed in inundated ice‐rich units and also in inactive floodplains. Overall, subsidence increased with deposit age and thus ground ice content, but many flooded ice‐rich units remained stable, indicating variable drivers of deformation. On average, subsiding ice‐rich locations showed increases in observed greenness and wetness. Conversely, many ice‐poor floodplains greened without deforming. Ice wedge degradation in flooded locations with elevated subsidence was mostly of limited intensity, and the observed subsidence largely stopped within 2 years. Based on remote sensing and limited field observations, we propose that the disparate subdecadal changes were influenced by spatially variable drivers (e.g., sediment deposition, organic layer), controls (ground ice and its degree of protection), and feedback processes. Remote sensing helps quantify the heterogeneous interactions between permafrost, vegetation, and hydrology across permafrost‐affected fluvial landscapes. Interdisciplinary monitoring is needed to improve predictions of landscape dynamics and to constrain sediment, nutrient, and carbon budgets.

Stratigraphy, Crater Size–Frequency Distribution, and Chronology of Selected Areas of Ganymede’s Light and Dark Terrains

The stratigraphy of the largest natural satellite of our solar system, Ganymede, is investigated using available global mosaic (basemap) and high-resolution images. We are focusing on the reconstruction of the formation and tectonic evolution of selected areas of dark and light terrain units and investigate their morphological characteristics and relative ages at a local scale using high-resolution images from the sub-Jovian and anti-Jovian hemispheres. For this, geological maps and crater size–frequency distributions for each of the terrain units were prepared, and relative as well as absolute ages were derived by applying the currently available lunar-derived impact chronology model and the Jupiter-family comet chronology model. The relative ages obtained from the cross-cutting relationships of terrain units are not always consistent with the ages derived from the crater size–frequency distributions. Some regions are influenced by secondary and sesquinary craters and tectonic resurfacing activities. Independent of the applied model, the derived crater size–frequency distribution showed that the light terrain started to form soon after the completion of dark terrain formation.

Exploring the initial landing site area of Dragonfly on Titan: Insights into shear failure and strike-slip faulting at Selk crater

Morphologically distinct characteristics of strike-slip deformation have not been well documented on Titan due to limited quality and coverage of observational data. However, optimal shear failure conditions may exist within Titan's shallow subsurface due to the inferred presence of a porous ice layer saturated with liquid hydrocarbons. In this study, we examine the proposed Dragonfly landing site on Titan, the Selk crater region, and investigate the area in context of possible tidal shear deformation and strike-slip faulting. For this, we use established methods of previous studies based on the Coulomb failure criterion and numerical model SatStress to calculate diurnal tidal stresses that may act to deform the region. We extracted stresses along one line of latitude (5°N) from 155°-165° E, crossing various identified geologic terrain units, and found that presently, shear failure initiated through diurnal tidal stresses can only occur if pore fluid pressures are intermediate to high (λ > 0.75) and/or the coefficient of friction of the icy crust is low (μf < 0.3). As it is unlikely for these conditions to be present in this area, we can infer that there is currently no shear deformation occurring in the Selk crater region due to diurnal tidal stresses. The results presented here aim to advance our knowledge of structural crustal properties that promote or limit shear failure on Titan on a local scale, and to better inform the exploration of Titan through the Dragonfly mission. To gain new insights and broaden our understanding of icy worlds, it is imperative that we employ the most precise data in our modeling work. Missions like Dragonfly, Europa Clipper and ESA's JUICE will further constrain our modeling approach and can help pinpoint the most interesting locations for lander exploration and possibly for gaining access to the interior ocean of icy moons.

Geodynamic ‘Hotspots’ in a Periglacial Landscape: Natural Hazards and Impacts on Productive Activities in Chilean Fjordlands, Northern Patagonia

In this paper, we study natural hazards and their potential impacts on productive activities in the Comau Fjord in Chilean Northern Patagonia. We carried out hazard mapping to identify areas with evidence of geomorphological activity on slopes in terms of landslides, river/tsunami flooding, and glacial retreat. The assessment of different geomorphic processes was carried out by both detailed fieldwork and analysis of satellite remote sensing and aerial photography information. We identified terrain units that are subject to multi-hazards overlapping different spatially distributed hazard maps. This information was overlaid with spatial data of economic activities in the area in order to establish the impacts of the natural hazards on the local salmon and mussel farming infrastructure (risk). The results suggest significant exposure levels for these productive activities and potential damage due to the occurrence of natural hazards. The extension of a major highway (CH-7 Austral Highway) on the east coast of the Comau Fjord will be a new incentive for economic development in the area. However, the highway construction sites show a high level of exposure to natural hazards, especially floodings and landslides. Our study highlights that the geohazard potential might have a high negative impact on future productive activity in the fjord as well as on the new highway infrastructure.

Delineation of terrain features in Demini’s Watershed – Setentrional Amazonia using regional geomorphometry

The mapping of terrain features relies on the necessity of an object-based approach, which can be related to the constitution of terrain units. The regionalization of land surface parameters enables the assessment of characteristics inside terrain unities and enhances heterogeneity outside these patches. This study presents a classification methodology for hierarchical geomorphometric delineation, using visual and Random Forest (RF) classification in a regionalized dataset of terrain variables, applied in Demini’s watershed, north of Amazonia. These variables, calculated by segments derived from multiresolution segmentation, were evaluated in order to identify which had major contributions to RF’s classifications. The characterization of features had great correspondence with Environmental Informations Database (BDIA) data of geomorphological mapping, used as a reference in this work. The Overall Accuracy for RF taxon 1 was 96%, while Taxon 2 Highland and Lowland RF models reached 84% and 87%, respectively. Identification of subdomain classes was possible mostly using the digital elevation model (DEM) and variables directly derived from the DEM. The delineation of floodplain presented significant differences between visual and RF results, including BDIA’s data.

Insights into spatial differential characteristics of landslide susceptibility from sub-region to whole-region cased by northeast Chongqing, China

Landslides have differential characteristics in different regions. This study explores landslide susceptibility mapping (LSM) based on different evaluation units and proposes a strategy for landslides’ differential characteristics in different sub-regions. Based on data of lithology, elevation, and historical landslides, terrain units (TUs) and slope units (SUs) were obtained. LSM was developed using the Random Forest (RF) model and Light Gradient Boosting Machine (LGBM) model. The LGBM-TUs showed the highest performance and were therefore, selected to obtain LSM. The study area was divided into four sub-regions using the geographically weighted regression (GWR) model, along with spatial differential characteristics of topography conditions. The distribution and characteristics of landslides within each sub-region were assessed using GeoDetector. The results illustrated the reliability of the LGBM-TUs model. Lithology, elevation, and average annual rainfall were the dominant factors, while the influence of other factors on the occurrence of landslides was strengthened only when these factors interacted. This study proposed a new method for LSM research to insight the spatial differential characteristics of landslides in various sub-regions. Our results provide novel insights into landslide mitigation.

A statistical approach for sea cliff hazard and setback lines mapping in the northeast of Peniche, Portugal

The considerable increase in the occupation of coastal areas requires strategies to conceive and apply hazard prevention and mitigation measures, especially in coastlines with sea cliffs where mass movements are more likely to occur. To predict the potential of sea cliff failures and identify the more unstable cliff sections, analytical, physical and/or statistical tools can enable the assessment of cliff failure susceptibility, which is a progress towards a better understanding of sea cliff failure hazard assessment and mapping.In this study, statistical approaches for the assessment of sea cliff failure susceptibility and definition of safety set-back lines located landwards of the cliff top crest were adopted, in the coast located to northeast of Peniche, between Baleal and the Óbidos lagoon, in the western coast of Portugal. For the susceptibility assessment, the logistic regression was used to correlate a set of predictive factors, obtained from thematic maps of geology (lithology, structure, faults), geomorphology (cliff height, slope angle, exposure, curvature, toe protection) and wave action, with an inventory of cliff failures that caused cliff top retreat, compiled from aerial photographs from 1947 to 2010. This method enabled the production of cliff failure susceptibility models using terrain units with different sizes, encompassing cliff crest length segments of 50 m, 20 m, and 10 m. The ordinal logistic regression was applied for the setback lines definition.The modeling results were analyzed using diagnostic measures and external validation, with each model being validated against the cliff instability inventory which indicated very good statistical performance and allowed the production of reliable susceptibility maps.The application of such statistical techniques enables estimation of the degree of susceptibility for cliff failures at regional scales of analysis, and assists the definition of cliff setback lines, which provide answers to planning and hazard prevention problems of coastal areas with sea cliffs.

Spatial Assessment of Soil Erosion Risk Using RUSLE Embedded in GIS Environment: A Case Study of Jhelum River Watershed

The watershed area of the Mangla Reservoir spans across the Himalayan region of India and Pakistan, primarily consisting of the Jhelum River basin. The area is rugged with highly elevated, hilly terrain and relatively thin vegetation cover, which significantly increases the river’s sediment output, especially during the monsoon season, leading to a decline in the reservoir’s storage capacity. This work assesses the soil erosion risk in the Jhelum River watershed (Azad Jammu and Kashmir (AJ&amp;K), Pakistan) using the Revised Universal Soil Loss Equation of (RUSLE). The RUSLE components, including the conservation support or erosion control practice factor (P), soil erodibility factor (K), slope length and slope steepness factor (LS), rainfall erosivity factor (R), and crop cover factor (C), were integrated to compute soil erosion. Soil erosion risk and intensity maps were generated by computing the RUSLE parameters, which were then integrated with physical factors such as terrain units, elevation, slope, and land uses/cover to examine how these factors affect the spatial patterns of soil erosion loss. The 2021 rainfall data were utilized to compute the rainfall erosivity factor (R), and the soil erodibility (K) map was created using the world surface soil map prepared by the Food and Agriculture Organization (FAO). The slope length and slope steepness factor (LS) were generated in the highly rough terrain using Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM). The analysis revealed that the primary land use in the watershed was cultivated land, accounting for 27% of the area, and slopes of 30% or higher were present across two-thirds of the watershed. By multiplying the five variables, the study determined that the annual average soil loss was 23.47 t ha−1 yr−1. In areas with dense mixed forest cover, soil erosion rates ranged from 0.23 t ha−1 yr−1 to 25 t ha−1 yr−1. The findings indicated that 55.18% of the research area has a low erosion risk, 18.62% has a medium erosion risk, 13.66% has a high risk, and 11.6% has a very high erosion risk. The study’s findings will provide guidelines to policy/decision makers for better management of the Mangla watershed.

Erosion Hazard Levels in Padang Batung Sub-district, Hulu Sungai Selatan Regency, South Kalimantan Province, Indonesia

Erosion is a form of damage to the soil caused by changes in land function on certain plains without management. The Padang Batung Sub-district area experienced land damage which was characterized by the distribution of critical land area reaching half of the area. The purpose of this study is to analyze the level of erosion hazards that occur in Padang Batung Sub-district. This study used a terrain unit map as the basis for the sample analysis unit. The number of samples in this study was 20 samples using the purposive random sampling method. The data analysis used is in the form of the Universal Soil Loss Equation (USLE) equation which can predict the level of erosion hazard through several parameters in the study area. The results showed that the erosion hazard level in Padang Batung Sub-district was dominated by severe criteria with an affected area of 74 km2 with an average erosion rate of 345.27 tons/ha/yr. One of the dominating factors causing the high erosion in Padang Batung Sub-district to be included in the medium and high classification is rain intensity, high erodibility, unstable topography and land cover vegetation.

Geomorphological Classification of Western Western Doon of Dehra, Uttarakhand (India)

Morphological units are those sections of landforms, which have uniform morphological property. The identification of morphological or terrain units is an exercise of regional classification of terrain with similar properties on varying scales. Morpho units enable the planners to determine land use planning, infrastructure development and natural resource management. Such type of terrain classification also highlights the hazardous unit, particularly in mountainous areas. Doon of Dehra is an important geomorphic unit in terms of both natural and cultural point of view. Dehradun, which is the capital city of Uttarakhand is also situated in this geomorphic unit. So, it becomes important to delineate the unit in smaller geomorphic units for proper land use planning and infrastructural development and to mitigate the hazards as well. Topographical sheets published by the government of India are the database of study. In the present study ‘principle component analysis’ based on the centroid method of Holziger and Herman (1941) has been adopted as this is manageable manually. The components, like - relief, drainage derivatives and slope has been taken for meso and micro level division of area into morpho units. The study area consists of 4 major morpho units and 28 micro units.

Landslide susceptibility assessment in the rocky coast subsystem of Essaouira, Morocco

Abstract. In recent decades, multiple researchers have produced landslide susceptibility maps using different techniques and models, including the information value method, which is a statistical model that is widely applied to various coastal environments. This study aimed to evaluate susceptibility to landslides in the Essaouira coastal area using bivariate statistical methods. In this study, 588 distinct landslides were identified, inventoried, and mapped. Landslides are performed by means of observation and interpretation of different data sources, namely high-resolution satellite images, aerial photographs, topographic maps, and extensive field surveys. The rocky coastal system of Essaouira is located in the middle of the Atlantic coast of Morocco. The study area was split into 1534 cliff terrain units that were 50 m in width. For training and validation purposes, the landslide inventory was divided into two independent groups: 70 % for training and 30 % for validation. Twenty-two layers of landslide conditioning factors were prepared – namely, elevation, slope angle, slope aspect, plan curvature, profile curvature, cliff height, topographic wetness index, topographic position index, slope over area ratio, solar radiation, presence of faulting, lithological units, toe lithology, presence and type of cliff toe protection, layer tilt, rainfall, streams, land-use patterns, normalised difference vegetation index, lithological material grain size, and presence of springs. The statistical relationship between the conditioning factors and the different landslide types was calculated using the bivariate information value method in a pixel-based model and in the elementary terrain units-based model. Coastal landside susceptibility maps were validated using landslide training group partitions. The receiver operating characteristic curve and area under the curve were used to assess the accuracy and prediction capacity of the different coastal landslide susceptibility models. Two methodologies, considering a pixel-based approach and using coastal terrain units, were adopted to evaluate coastal landslide susceptibility. The results allowed for the classification of 38 % of the rocky coast subsystem as having high susceptibility to landslides, which were mostly located in the southern part of the Essaouira coastal area. These susceptibility maps will be useful for future planned development activities as well as for environmental protection.

Regional dissection volume in central Amazonia sedimentary plateau mapped from SRTM-DEM

Fluvial incisions are the prevailing source of short-range topographic variations in central Amazonia plateau, organized in patterns of varying degrees of dissection. Dissection was estimated from a DEM (digital elevation model) and computed as the volume of sediment removed by fluvial erosion relative to the area of terrain units. The elementary input for regional integration was the local depth, calculated by regional-residual relief separation techniques. The top sedimentary surface, used as the regional reference for subtracting the original DEM, was reconstructed by filling the fluvial incisions with the use of maximum filter followed by smoothening. Terrain units were established with segmentation of elevation data from the reconstructed top sedimentary surface, to delineate extensions of sedimentary deposits over the plateau without the influence of the modern fluvial incisions. The size of the terrain units was constrained by the extent of a repeated downstream variation pattern of local dissection data within the individual drainage systems. Numerical and spatial distribution of dissection volume intervals in the study area were consistently grouped in at least four descriptive patterns, sketched into contiguous regions subordinate to the sedimentary plateau. Results were generally consistent with published geological information, despite providing elements for occasional revision and further detailing.