Analysis Of Digital Elevation Models Research Articles

The importance of the number of points, transect location and interpolation techniques in the analysis of bathymetric measurements

Determining the bathymetric properties of a river, lake or reservoir is important for many reasons because it identifies location of sections with sedimentation or erosion which indicate the key processes and biophysical habitat status. This study used observational data of a 5 km section of the Danube River (transformed into a reservoir after 1972) to determine the best GIS interpolation method and the optimal number of sampling points to get an accurate description of the riverbed. Nine interpolation methods were used to generate bathymetric maps of the Danube course, between km 955 and km 950, in the area of Iron Gates reservoir, using a variable number of points (n = 1943; n = 4328; n = 17139), obtained by single beam echo sounder. Six methods of deterministic interpolation have been used: Inverse Distance Weighting (IDW) – criteria automatically determined (CAD) and manually determined (MD); Local Polynomial Interpolation (LPI) – criteria automatically determined (CAD) and manually determined (MD); Radial Basis Function (RBF) – fully regularized spline CRS; Radial Basis Function RBF – spline with tension SWT, and three geo-statistics methods: Ordinary Kriging – OK, Simple Kriging – SK, Universal Kriging – UK. Cross-validation and bathymetric Digital Elevation Models (DEM s) analysis were used to evaluate the accuracy of the estimated data and maps. The two interpolation methods, Inverse Distance Weighting (IDW-MD) and Simple Kriging (SK), provide satisfactory results, even in the case of a small number of points (n = 1943). If the number of measured points grows and a section grid (perpendicular/longitudinal) is developed, the DEM s bathymetric accuracy improves significantly, especially in the case of complex morphology, even if the positive and negative forms of the bed lead to sudden changes in the measured values. The obtained results revealed differences between the interpolation methods used, particularly in the case of a small number of points measured per perpendicular trajectories, but by the addition of points on longitudinal paths, a significant improvement of the bathymetric maps is obtained.

Curvature derived from LiDAR digital elevation models as simple indicators of debris-flow susceptibility

To mitigate the damage caused by debris flows resulting from heavy precipitation and to aid in evacuation plan preparation, areas at risk should be mapped on a scale appropriate for affected individuals and communities. We tested the effectiveness of simply identifying debris-flow hazards through automated derivation of surface curvatures using LiDAR digital elevation models. We achieved useful correspondence between plan curvatures and areas of existing debris-flow damage in two localities in Japan using the analysis of digital elevation models (DEMs). We found that plan curvatures derived from 10m DEMs may be useful to indicate areas that are susceptible to debris flow in mountainous areas. In residential areas located on gentle sloping debris flow fans, the greatest damage to houses was found to be located in the elongated depressions that are connected to mountain stream valleys. Plan curvature derived from 5m DEM was the most sensitive indicators for susceptibility to debris flows.

The use of digital elevation models for detailed mapping of slope soils

Formulation of the problem. The current stage of agricultural development in Ukraine requires highly informative soil maps. One of the directions for creating such maps is the use of digital elevation models (DEM) as a spatial translator of soil characteristics. The literary review has showed that despite the large volume of publications on this topic, a number of issues of soils digital mapping remain relevant. The purpose of the article is to study the possibilities of using relief-ground indicative models in creation of detailed digital ground maps. Methods. The research was conducted on the territory of the testing ground. During the field study of the landfill, it has been established that the soils are represented by chernozem typical of varying erosion degrees. It is proposed to use a xeromorphism coefficient for the quantitative account of the landforms influence on soil formation, characterizing changes in hydrothermal conditions for a particular section of the topography, compared with the horizontal surface. A detailed DTM was obtained, using the "Phantom 3" UAV.The derivative models of a number of topographic parameters were built on its basis later. A digital model of xeromorphism of the territory was built, transformed into a model of organic carbon (C) content. The specified map shows initial conditions of the soil cover. It can be used as a standard to compare parameters of modern soils for assessment of extent of their degradation. Comparison of this map with the map of actual C content has shown that average loss of C by soils of the studied area owing to anthropogenic degradation can be estimated at 5.1 kg on 1 t of the soil. Results. Investigations have proved that the geoinformation analysis of landforms allows to quantitatively shape hydrothermal conditions of soil formation for a certain territory. The cartographic materials constructed on such a methodical approach characterize landscape potential on soil formations and reflect quasi-virgin land condition of the soil. Scientific novelty and practical significance. The detailed soil maps, based on the results of field and laboratory soil studies, leading to potential soil assessment for DEM analysis in the article, allow to adequately estimate and objectively represent distribution of eroded and xeromorphic soils and their complexes on sloping lands.

Morphology of coast and textural characteristics of coastal sediments (NE Gökova Graben, SW Turkey)

This study examines the morphology, lithological characteristic and controlling factors of coastal sediments in the northeast Gokova Graben (southwest Turkey). The northeast Gokova Graben is located in a region with several human settlements and tourism activities, in the summer. The analysis used in the study is field observation, Digital Elevation Model (DEM) analysis, 18 sieve (including statistical evaluations) and 18 X-ray Fluorescence (XRF) analyses. Due to the boundary of normal faults, predominantly faulted-rocky coasts are expected. However, four different coast types were determined in the northeast Gokova Graben. Evolution of these coast types is dependent on orientation of the normal faults and also distribution of different coastal rocks and rivers. The predominant coast type, rocky coasts are formed by faulted, high-resistant Jurassic-limestone. Owing to reworking and short transportation via brooks and the force of gravity, narrow gravely shingle beaches are only observable in front of the Quaternary-conglomerate cliff. Perennial streams form two different coasts. Long stream formed the wide sandy beach in the eastern end of Gulf. While short streams, which obliquely cut the graben, formed the sandy-gravely beach at the western end of the study area. Recent beachrock, coastal rock staining and wave notches are indicators for a stable sea level in the study area. Past sea level indicators are the hanging beachrocks and wave notches located in the western part of the study area. Past activities of the interior faults within the graben are responsible for ancient sea level fluctuations. Moreover, global warming increases the risk of sea level rise. A possible rise in the future sea-level may destroy narrow-gravely beaches. This risk may also threaten the wide sandy beach as well as the settlement in the area.

Morphological Change in the Northern Red River Delta, Vietnam

Coastal erosion has become a worldwide concern, typically in the densely populated Asian mega-river deltas. Severe coastal erosion in the southern Red River Delta (RRD) has been intensively studied. Coastal morphological change in the northern RRD was examined in detail through DEM (Digital Elevation Model) analysis based on time series of bathymetrical maps (1965–2004) and Landsat images (1975–2015) in this study. The results show that the northern RRD is featured by rapid coastal accretion in the past few decades, although suspended sediment flux has dropped by roughly 60% after the completeness of Hoa Binh Dam (HBD) in 1988 and relative sea level rose at 1.9 mm yr−1. However, accretion at the outer part of subtidal shoals and platforms was observed to slow down quickly or even turned into erosion in the last two decades. The resuspended sediments from the erosion zone can be transported landward to replenish the inner coastal zone, keeping the latter accretion in the near future to compensate for the sediment discharge decrease from the river. However, this lag effect should be terminated soon if other adverse effects go worse, e.g., damming rivers, sea-level rising, strengthening storms, land reclamation and other poor-designed coastal engineering. Coastal planners and managers should pay full attention to these changes.

Post-spreading deformation and associated magmatism along the Iberia-Morocco Atlantic margins: Insight from submarine volcanoes of the Tore-Madeira Rise

A new high-resolution bathymetric map combined with a regional Digital Elevation Model (DEM) analysis reveal the modalities of occurrence and emplacement of post-spreading magmatism along the NNE-SSW oriented, 1000 km long Tore-Madeira Rise (TMR) as well as its relationship with the activity of major fault systems including the Estremadura Fault System (ESF) and the Azores-Gibraltar Fracture Zone (AGFZ). Morphological and structural analysis of the bathymetric map were performed to map volcanic features such as eruptive cones, vents and fissures together with faults along the TMR. The new bathymetric map shows that the main NNW-SSE seamount alignment is formed by three structurally distinct volcanic massifs, the Tore, the Josephine and the Southern Volcanic Groups. The majority of the volcanoes of each group emplaced within or along specific portion of pre-existing faults (ESF and AGFZ) including splay fault, releasing bend, fault tips and interaction zones between different segments. Magmas were channelled into sub-vertical pre-existing lithospheric faults that acted as preferential pathways for the vertical magma ascent. Migration and final eruption of magma are controlled by the local stress variation induced by complex fault geometries, change in plate kinematics as well as strong shear zone anisotropy as suggested by the emplacement within localised areas of transtension. We conclude that post-spreading magma emplacement in the southern part of the Iberia margin was related to the development of a transtensional plate boundary between the Iberian and African Plate during the Late Cretaceous. More generally, our findings emphasize that the distribution of volcanism as the expression of the interaction between shallow plate tectonic and mantle processes should be included in plate kinematic reconstruction. This study also demonstrates that the accurate mapping of oceanic seafloor is pivotal to better understand tectono-magmatic evolution of volcanic seamount chains and geological processes in oceanic domains.

Pléiades Tri-Stereo Data for Glacier Investigations—Examples from the European Alps and the Khumbu Himal

In this study, we use Pléiades tri-stereo data to generate a digital elevation model (DEM) from the Pléiades images using a workflow employing semi-global matching (SGM). We examine the DEM accuracy in complex mountain glaciated terrain by comparing the new DEMs with an independent high-quality DEM based on airborne laser scanning (ALS) data for a study area in the Austrian Alps, and with ground control points for a study area in the Khumbu Himal of Nepal. The DEMs derived using the SGM algorithm compare well to the independent high-quality ALS DEM, and the workflow produces models of sufficient quality to resolve ground control points, which are based on Pléiades imagery that are of sufficient quality to perform high spatio-temporal resolution assessments of remote areas for which no field data is available. The relative accuracy is sufficient to investigate glacier surface elevation changes below one meter, and can therefore be applied over relatively short periods of time, such as those required for annual and seasonal assessments of change. The annual geodetic mass balance for the Alpine case derived from our DEM compares well to the glaciological mass balance, and multitemporal DEM analysis is used to resolve the seasonal changes of five glaciers in the Khumbu Himal, revealing that glaciological processes such as accumulation, ablation, and glacier movement mainly take place during the summer season, with the winter season being largely inactive in the year sampled.

Geomorphic Evolution of the Lilas River Fan Delta (Central Evia Island, Greece)

This paper presents the results of geomorphological investigations carried out on the Lilas River fan delta in central Evia Isl., Greece. A geomorphological map has been prepared using Digital Elevation Model analysis, aerial photos and Google Earth image interpretation, a reliable map of 1846, and extensive fieldwork. The Holocene sequence stratigraphy of the fan delta has been studied based on profiles of seven deep cores drilled by the municipal authorities. Two additional shallow boreholes were drilled with a portable drilling set and collected samples were analyzed using micropaleontological and grain size analysis methods while four sediment samples were dated using optically stimulated luminescence (OSL) techniques. During the early Holocene, most of the fan delta plain was a shallow marine environment. Between 4530 ± 220 and 3600 ± 240 years BP the depositional environment at the area of Nea Lampsakos changed from shallow marine to a lower energy lagoonal one. The main distributary changed its course several times leading to the building and subsequent abandonment of five fan delta lobes, through which the fan delta advanced during the late Holocene. The eastern part of the Kampos abandoned lobe is retreating with a maximum mean rate of −0.94 m/year for the period 1945–2009, whereas the presently active mouth of the river and its immediate surrounds are prograding with a mean rate of about +3.2 m/year.

Rock-water interaction processes based on geochemical modeling and remote sensing applications in hyper-arid environment: cases from the southeastern region of Egypt

BackgroundThe interaction between rocks and groundwater can be considered as multi-faceted processes in hydrogeology where the groundwater chemistry can be resulted from leaching and/or minerals dissolution. The scientific approach of this study based on testing the contribution of remote sensing in providing information related to rock-groundwater interaction along with the outputs of the geochemical model. The current research aims to explore the impacts of lithologic nature and structural geology on the groundwater chemistry. The mentioned objective is significant for the future sustainable development of groundwater in hyper-arid regions. Therefore, both geology and geochemistry of water-bearing formations along the flow path to the studied aquifers were identified. The area was chosen as an example from hyper-arid region to carry out this scientific approach.ResultsThe obtained results indicate the existence of three main aquifers: Quaternary alluvial (salinity 1253 mg/l to 18,854 mg/l), Nubian Sandstone (salinity 311 mg/l to 14,388 mg/l), and fractured basement (salinity 320 mg/l to 19,375 mg/l). The results of speciation modeling showed that studied aquifers are supersaturated with gibbsite, goethite, hematite, magnetite, aragonite, calcite, dolomite, and alunite. Nubian aquifer specifically has homogeneity results due to the similarity of water-bearing and geology of watersheds (ferruginous sandstone and ironstone). Remote sensing data and digital elevation model analyses were used for generation of the thematic layers which is affecting the groundwater occurrences and quality such as geology, geomorphology, structural lineaments, slope, flow direction, drainage lines, and elevations.ConclusionsThe current research concluded that the groundwater chemistry can be a signature of the rock-water interaction. The potential implications of the research are represented through a priority map for groundwater exploration for both hydro-geophysical investigation and testing wells in order to evaluate the groundwater capabilities where the data from the recorded wells were used to calibrate this map.

Evaluation of DEM size and grid spacing for fluvial patch-scale roughness parameterisation

Surface roughness is a term used in fluvial research without a unanimous definition. Clarification of the term and improved parameterisation is needed in future research. Improvements to the collection of topographic data, using photogrammetry, have provided accurate digital elevation models (DEMs) of field and laboratory gravel-bed patches of varied sediment size and surface structure. In this study, a moving-window process is used for analysing spatial variability within DEMs. Using this information, and in unison, the effect of DEM size and grid spacing are considered on an extensive range of roughness parameters, in order to provide insights for obtaining grain-roughness statistics. It is shown that DEM size influences the calculated roughness statistics, and the observation of plateaus in statistics for DEM window sizes above 16 × D50A in both directions (where D50A is the median grain size of the bed-surface material) suggests this as a minimum DEM size for grain-scale roughness analysis. Further, the DEM grid spacing should be 1 mm or below, in order to adequately capture grain roughness, as coarser resolutions failed to detect particle imbrication. Finally, variability in roughness parameters was evident due to natural spatial variation in gravel-bed microtopography, suggesting using a single roughness parameter is not appropriate to holistically describe the roughness of a gravel patch. As the importance of topographic information continues to grow in geomorphology, the results of this study will assist researchers in the collection and subsequent analysis of DEMs.

Climatic regionalization of wine grapes in the Hengduan Mountain region of China

The Hengduan Mountain region of China is one of the world's highest altitude and lowest latitude wine grape cultivation areas. This study screened the existing regional indexes; the active accumulated temperature (AAT) for grapes in the growing season was chosen as the heat index, and the dryness index (DI) in the growing season was chosen as the water index for climatic regionalization. An analysis of 90-meter resolution digital elevation model (DEM) data and the corresponding slope degree and direction for the Hengduan Mountain region in the range of 97°E-103°E, 27°N-33°N, as well as daily meteorological data over 30 years (1981-2010) from 53 stations in the study region, were used to establish the AAT and DI models for the northern area of the Hengduan Mountains. According to the multiple stepwise regression method, the interaction terms among different geographical and topographic factors were considered. In addition, the residual errors were interpolated and corrected based on the modeling, and this approach further improved the simulation accuracy of meteorological factors. A regional climatic map of wine grapes was produced according to these results. The model was used to calculate the suitable altitude range for wine grape cultivation in different regions of the Hengduan Mountains. The study shows that the distribution of suitable wine grape cultivation areas in the northern part of the mountain range generally mimics distribution of dry warm and dry hot valleys. The accuracy of the results was confirmed based on the existing locations of vineyards in the Hengduan Mountain region.

Geomorphological Mapping and Spatial Analyses of an Upper Weichselian Glacitectonic Complex Based on LiDAR Data, Jasmund Peninsula (NE Rügen), Germany

Glacitectonic deformation in the Upper Weichselian led to the tectonic framework of large-scale folds and displaced thrust sheets of Maastrichtian (Upper Cretaceous) chalk and Pleistocene glacial deposits in the southwestern Baltic Sea region. They form surface expressions of sub-parallel ridges and elongated valleys in between and on the Jasmund Peninsula. Geomorphological mapping and detailed landform analyses give another insight into the arrangement and the formation history of these proglacial surface structures. Light detection and ranging (LiDAR) digital elevation models (DEM) analysis techniques were applied to a proglacial rather than a subglacial environment. Results suggest a division into a northern part with morphological ridges striking NW–SE and a southern part with SW–NE trending ridges. The observation of partly truncated northerly ridges and their superimposition by the southern sub-complex suggest that the northern part was generated earlier than the southern part. The applied spatial analyses tools were used to develop a new, self-consistent genetic model integrating all parts of the 100 km2 large Jasmund Glacitectonic Complex. Results suggest a more consistent terminology for the tectonic setting and a revised genetic model for Jasmund, including three evolutional stages that are characterized by different ice flow patterns.

An Experimental Analysis of Digital Elevation Models Generated with Lidar Data and UAV Photogrammetry

A digital elevation model (DEM) is a very important product that represents the topography digitally. It is an essential requirement of many engineering applications. From past to present, the methodology of DEM generation process is changed with respect to technology. Today, the laser scanner and aerial imagery are two widely used technologies to get DEM. Especially, the computer vision aided the use of unmanned aerial vehicles (UAV) opened new horizons in this regard. This study investigates the airborne LiDAR and UAV based DEM comparisons in terms of correlation and vertical accuracy. For this purpose four different LiDAR data are provided. Moreover, a photogrammetric flight is carried out with UAV and images of the study area are captured after field surveys. Then, five different DEMs are generated from five different point clouds. Finally, the statistical analyses are performed to calculate the correlations and accuracies of DEMS. According to the analysis, the UAV based models are as accurate as LiDAR based models along with some other advantages.

An integrated approach to investigate slope instability affecting infrastructures

This article focuses on an area located at the northern border of the Monte Poro plateau along the Tyrrhenian coast of Calabria (southern Italy). The area is characterized by weathered gneissic rocks involved in widespread landslides. This research employed an integrated approach concerning the relationships between the geological and geomorphological setting and landslides triggered during the construction of a road. The data were obtained by geological, geomorphological, structural, and geomechanical field surveys, coupled with a geomorphological analysis carried out through a combination of aerial photographs, satellite images, and digital elevation models (DEMs). Rock mass classifications of the weathered gneissic materials were applied to evaluate the quality of the rock masses and to define the potential stability conditions of the slopes. Furthermore, a DEMs analysis of pre- and post-road construction was also performed to define a detailed evolution of the instability conditions affecting the studied escarpment. A total of 32 landslides were recognized before the road construction, while 27 landslides were collected after the road construction. Rotations are the most frequent type of mass movements and involved the more weathered rocks or eluvial/colluvial deposits. Complex landslides are less widespread than the previous ones involving different weathering grades. The results showed that the roadworks had a great impact on the geomorphological scenario in terms of landslide trigger in an area already characterized by a high landslide susceptibility. The approach used can provide a reliable tool to evaluate the hazard conditions in other regions with similar geological features.

Geomorphic impact and assessment of flexible barriers using multi-temporal LiDAR data: The Portainé mountain catchment (Pyrenees)

Multi-temporal digital elevation models (DEMs) obtained from airborne LiDAR surveys are widely used to detect geomorphic changes in time and quantify sediment budgets. However, they have been rarely applied to study the geomorphic impact of engineering structures in mountain settings. In this study, we assessed the influence and behavior of flexible sediment retention barriers in the Portainé catchment (Spanish Pyrenees), using three LiDAR data sets (2009, 2011 and 2016) that covered a 7-year period. Densely forested mountainous areas present some limitations for reliable DEM analysis due to spatial variabilities in data precision, accuracy and point density. A new methodological approach for robust uncertainty analysis along channels, based on changes in cross-sectional elevations, was used to discriminate noise from real geomorphic changes. The obtained results indicated that erosion occurs along most reaches covering a large area, whereas deposition is localized in specific areas such as those upstream of sediment retention barriers and in the debris cone. Despite the presence of 15 flexible sediment retention barriers, the channels presented net degradation during both 2009–2011 and 2011–2016, with 2838 and 147 m3 of material exported from the basin, respectively. For the same periods, the barriers retained 33% and 25% of the total deposition (up to 1300 m3 per barrier), respectively, but also induced lateral and downstream incision, the latter reaching 703 m3 for a single barrier. We detected a horizontal displacement of the net of up to 1.2 m in filled barriers, resulting from net flexion. The interference of the natural river evolution by defense measures has resulted in a complex erosion-deposition pattern. The presented methods show high potential for the hydrogeomorphic study of mountain catchments, especially for a high-resolution assessment of flexible barriers or other engineering structures in remote areas.

An approach to DEM analysis for landform classification based on local gradients

In this paper we propose an exploratory methodology, devoted to classify the pixels of a Digital Elevation Model (DEM), to be used as a morphometric basis for studies in other frameworks. The aim is to classify the terrain units according to eight topographical local gradients, computed as differences between each pixel and the eight surrounding ones. A partition of the pixels into homogeneous classes is carried out, emphasizing different details of the terrain units characteristics. Each class is described by a complete set of statistics of terrain attributes, including elevation, slope, and aspect, and graphical tools are used to ease the understanding of the partition. In addition, appropriate colours are attributed to each class, in order to build a thematic map that may simulate a three-dimensional effect. They are defined by computing their hue and saturation according to each class mean slope and aspect, respectively. Applications to Mount Soratte (Italy) and Cephalonia island (Greece) show how the results may be successfully used to describe in different ways the morphometric structure of the terrain under study and provide appropriate graphical representations.

Terrestrial CDOM in Lakes of Yamal Peninsula: Connection to Lake and Lake Catchment Properties

In this study, we analyze interactions in lake and lake catchment systems of a continuous permafrost area. We assessed colored dissolved organic matter (CDOM) absorption at 440 nm (a(440)CDOM) and absorption slope (S300–500) in lakes using field sampling and optical remote sensing data for an area of 350 km2 in Central Yamal, Siberia. Applying a CDOM algorithm (ratio of green and red band reflectance) for two high spatial resolution multispectral GeoEye-1 and Worldview-2 satellite images, we were able to extrapolate the a(λ)CDOM data from 18 lakes sampled in the field to 356 lakes in the study area (model R2 = 0.79). Values of a(440)CDOM in 356 lakes varied from 0.48 to 8.35 m−1 with a median of 1.43 m−1. This a(λ)CDOM dataset was used to relate lake CDOM to 17 lake and lake catchment parameters derived from optical and radar remote sensing data and from digital elevation model analysis in order to establish the parameters controlling CDOM in lakes on the Yamal Peninsula. Regression tree model and boosted regression tree analysis showed that the activity of cryogenic processes (thermocirques) in the lake shores and lake water level were the two most important controls, explaining 48.4% and 28.4% of lake CDOM, respectively (R2 = 0.61). Activation of thermocirques led to a large input of terrestrial organic matter and sediments from catchments and thawed permafrost to lakes (n = 15, mean a(440)CDOM = 5.3 m−1). Large lakes on the floodplain with a connection to Mordy-Yakha River received more CDOM (n = 7, mean a(440)CDOM = 3.8 m−1) compared to lakes located on higher terraces.

Can Satellite Remote Sensing be Applied in Geological Mapping in Tropics?

Remote sensing (RS) techniques are based on spectral data registered by RS scanners as energy reflected from the Earth’s surface or emitted by it. In “geological” RS the reflectance (or emittence) should come from rock or sediment. The problem in tropical and subtropical areas is a dense vegetation. Spectral response from the rocks and sediments is gathered only from the gaps among the trees and shrubs. Images of high resolution are appreciated here, therefore. New generation of satellites and scanners (Digital Globe WV2, WV3 and WV4) yield imagery of spatial resolution of 2 m and up to 16 spectral bands (WV3). Images acquired by Landsat (TM, ETM+, OLI) and Sentinel 2 have good spectral resolution too (6–12 bands in visible and infrared) and, despite lower spatial resolution (10–60 m of pixel size) are useful in extracting lithological information too. Lithological RS map may reveal good precision (down to a single rock or outcrop of a meter size). Supplemented with the analysis of Digital Elevation Model and high resolution ortophotomaps (Google Maps, Bing etc.) allows for quick and cheap mapping of unsurveyed areas.

Variations of Lateral Bedrock Erosion Rates Control Planation of Uplifting Folds in the Foreland of the Tian Shan, NW China

AbstractFluvial planation surfaces, such as straths, commonly serve as recorders of climatic and tectonic changes and are formed by the lateral erosion of rivers, a process that remains poorly understood. Here we present a study of kilometer‐wide, fluvially eroded, low‐relief surfaces on rapidly uplifting folds in the foreland of the southwestern Tian Shan. A combination of field work, digital elevation model analysis, and dating of fluvial deposits reveals that despite an arid climate and rapid average rock‐uplift rates of 1–3 mm/yr, rivers cut extensive (>1–2 km wide) surfaces with typical height variations of <6 m over periods of >2–6 kyr. The extent of this “beveling” varies in space and time, such that different beveling episodes affect individual structures. Between times of planation, beveled surfaces are abandoned, incised, and deformed across the folds. In a challenge to models that link strath cutting and abandonment primarily to changes in river incision rates, we demonstrate that lateral erosion rates of antecedent streams crossing the folds have to vary by more than 1 order of magnitude to explain the creation of beveled platforms in the past and their incision at the present day. These variations do not appear to covary with climate variability and might be caused by relatively small (much less than an order of magnitude) changes in sediment or water fluxes. It remains uncertain in which settings variations in lateral bedrock erosion rates predominate over changes in vertical erosion rates. Therefore, when studying fluvial planation and strath terraces, variability of both lateral and vertical erosion rates should be considered.

Quantifying and Predicting the Contribution of Sea-Level Rise to Shoreline Change in Ghana: Information for Coastal Adaptation Strategies

ABSTRACT Evadzi, P.I.K.; Zorita, E., and Hunicke, B., 2017. Quantifying and predicting the contribution of sea-level rise to shoreline change in Ghana: Information for coastal adaptation strategies. The purpose of this study is to estimate the contribution of sea-level rise (SLR) in Ghana over the last decades and provide an estimation of shoreline retreat due to the projections of regional SLR. This study first analyzes historical shoreline change in Ghana from 1974 to 2015 using satellite images and orthophotos. Second, this study quantifies the SLR contribution to historical shoreline change using sea-level trend estimates from satellite observations, results from digital elevation model analysis, and shoreline change rates. This study finally makes predictions of shoreline in Ghana on the basis of modified Intergovernmental Panel on Climate Change Fifth Assessment Report representative concentration pathways (RCPs) scenarios for Ghana. On average, sea level has risen by about 5.3 cm over the last 21 y...