Medium Resolution Digital Elevation Models Research Articles

Assessing gully erosion susceptibility using topographic derived attributes, multi-criteria decision-making, and machine learning classifiers

Gully erosion is an erosive process that contributes considerably to the shape of the earth’s surface and is a major contributor to land degradation and soil loss. This study applied a methodology for mapping gully erosion susceptibility using only topographic related attributes derived from a medium-resolution digital elevation model (DEM) and a hybrid analytical hierarchy process (AHP) and the technique for an order of preference by similarity to ideal solutions (TOPSIS) and compare the results with naïve Bayes (NB) and support vector machine learning (SVM) algorithms. A transboundary sub-basin in an arid area of southern Iraq was selected as a case study. The performance of the developed models was compared using the receiver operating characteristic curve (ROC). Results showed that the areas under the ROC were 0.933, 0.936, and 0.955 for AHP-TOPSIS, NB, and SVM with radial basis function, respectively, which indicated that the performance of simply derived AHP-TOPSIS model is similar to sophisticated NB and SVM models. Findings indicated that a medium resolution DEM and AHP-TOPSIS are a promising tool for mapping of gully erosion susceptibility.

Precision mapping of boundaries of flood plain river basins using high-resolution satellite imagery: A case study of the Varuna river basin in Uttar Pradesh, India

Accurate demarcation of river basin boundaries is an important input for any programme connected with watershed management. In the present study, the boundary of the Varuna river basin is automatically derived using coarse- and medium-resolution digital elevation models (DEMs) of SRTM-30 m, ASTER-30 m, Cartosat-30 m, ALOS Palsar-12.5 m and Cartosat-10 m as well as manually through on-screen digitisation from a very high-resolution 1 m $$\times $$ 1 m remote sensing data available as Google Earth image. The study demonstrated the efficacy of on-screen digitisation from high-resolution Google Earth image supported by detailed field observations in the precision mapping of the place of origin of the Varuna River, its stream network and basin boundary when compared to the maps generated through automatic methods using DEMs of various resolutions. The Varuna river system takes its headwaters from the areas surrounding Umran and Dain ‘tals’ (shallow, large depressions/basins) but not from the west of Mau Aima town as has been previously reported.

Enhancing digital elevation models for hydraulic modelling using flood frequency detection

Medium-resolution DEMs have limited applicability to flood mapping in large river systems within data sparse regions such as Sub-Saharan Africa. We present a novel approach for the enhancement of the SRTM (30 m) Digital Elevation Model (DEM) in The Gambia, West Africa: A time-series analysis of flood frequency and land cover was used to delineate differences in the vertical limits between morphological units within an alluvial floodplain. Combined with supplementary river stage data and vegetation removal techniques, these methods were used to improve the estimation of bare-earth terrain in flood modelling applications for a region with no access to high-resolution alternatives. The results demonstrate an improvement in floodplain topography for the River Gambia. The technique allows the reestablishment of small-scale complex morphology, instrumental in the routing of floodwater within a noise-filled DEM. The technique will be beneficial to flood-risk modelling applications within data sparse regions.

Decadal evolution of tidal flats and channels in the Outer Weser estuary, Germany

This study focuses on the medium scale morphodynamics of the tidal flat and channel system Fedderwarder Priel, located in the Outer Weser estuary (Wadden Sea, Germany). Tidal channels and adjacent flats are highly dynamic systems whose morphologic evolution are driven by tidal, wind, and wave forcings. These coastal environments are an important ecosystem and react to changes in hydrodynamic conditions in various spatial and temporal scales. Based on annual medium-resolution digital elevation models from 1998 to 2016, we describe changes in the surface area over depth with hypsometries and use vertical dynamic trends in order to analyze and visualize the morphologic evolution of the Fedderwarder Priel and adjacent tidal channels. It is shown that several intertidal flats rise in the order of 1.3 to 5.6 cm/year. The findings indicate that the Outer Weser estuary was not in an equilibrium state for the investigated period, and tidal flats accreted with a rate exceeding mean sea level rise.

Scalability Issues for Wind Simulation Using OpenFOAM

AbstractThe use of the OpenFOAM software for wind simulation over rugged terrain is studied in the paper. OpenFOAM requirements for runtime, virtual memory and disk space are considered using small and medium resolution Digital Elevation Models (DEM) models for single-process and multi-process cases when running on local workstation and small parallel systems. Based on obtained data, extrapolation of requirements for relatively high resolution models are made and issues concerning the scalability are discussed.

Geo-structural map of the Laguna Blanca basin (Southern Central Andes, Catamarca, Argentina)

The Laguna Blanca basin is a rhomb-shaped basin located at the SE margin of the Puna plateau in the southern Central Andes (Catamarca, Argentina). An interactive analysis using remote sensing and field mapping enabled us to produce a geo-structural map at a 1:350,000 scale. Satellite images from multispectral sensors (ASTER and Landsat 7 ETM+) and medium resolution Digital Elevation Models (SRTM and ASTER GDEM) were used in order to recognize the structures and main lithologies, which were validated in the field and through laboratory tests (e.g. spectral analysis). The final result is a geo-structural map of the Laguna Blanca basin with a new geological unit subdivision, highlighting its tectonic origin, which appears to be related to a releasing stepover along N-S sinistral strike-slip master faults.

Active Tectonics Revealed by River Profiles along the Puqu Fault

The Puqu Fault is situated in Southern Tibet. It is influenced by the eastward extrusion of Northern Tibet and carries the clockwise rotation followed by the southward extrusion. Thus, the Puqu Fault is bounded by the principal dynamic zones and the tectonic evolution remains active alongside. This study intends to understand the tectonic activity in the Puqu Fault Region from the river profiles obtained from the remotely sensed satellite imagery. A medium resolution Digital Elevation Model (DEM, 20 m) was generated from an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) stereo pair of images and the stream network in this region was extracted from this DEM. The indices of slope and drainage area were subsequently calculated from this ASTER DEM. Based on the stream power law, the area-slope plots of the streams were delineated to derive the indices of channel concavity and steepness, which are closely related to tectonic activity. The results show the active tectonics varying significantly along the Puqu Fault, although the potential influence of glaciations may exist. These results are expected to be useful for a better understanding of tectonic evolution in Southeastern Tibet.

Analysis of a complex tectonic scenario based on 2D discrete wavelet analysis

Processing of digital elevation models is a hot issue for identifying tectonics features of an area. Medium resolution digital elevation models are interesting for analyzing topographic anomalies that may be related to regional phenomena, like ongoing or past tectonic processes. In order to perform this, the identification of these features from elevation models is the key issue. An effective approach is 2D discrete wavelet transforms. These perform a multi-scale decomposition, capable of giving numerically based evidence to details from digital elevation models, which sometimes may be concealed or unclear. These details can be associated to anomalies or singularities of the topography, possibly related to regional tectonic processes or, more in general, to landscape evolution phenomena, i.e. big landslides, erosion, etc.. Thus this can be an effective approach to territorial analysis.

Hillslope and catchment scale soil organic carbon concentration: An assessment of the role of geomorphology and soil erosion in an undisturbed environment

The role of geomorphology in relation to the spatial and temporal distribution of soil carbon is of considerable interest in terms of landscape management and carbon sequestration. Soil carbon plays an important role in soil water holding capacity, soil structure and overall soil health. Soil is also a significant store of terrestrial carbon. This study examines total soil carbon (SC) concentration at the hillslope and catchment scale in the Tin Camp Creek catchment, Arnhem Land, Northern Territory, Australia. The catchment is largely undisturbed by European agriculture or management practices and is located in the monsoonal tropics. Results show that SC concentration along hillslope transects has remained consistent over a number of years and it is strongly related to hillslope position and topographic factors derived from precision surveying and provides a baseline assessment. Poor relationships were found when using a good quality medium resolution digital elevation model to derive topographic factors. This finding demonstrates the need for high resolution survey data for the prediction of total C at the hillslope and catchment scale. There was little difference in SC concentration between years and overall, SC down the hillslope profile varies little temporally suggesting that concentrations are relatively stable in this environment. An assessment of the relationship between SC and soil erosion using 137Cs and erosion pins demonstrates that sediment transport and deposition play little role in the distribution of SC in this environment. Vegetative biomass appears to be the major contributor to SC concentration with vegetative biomass being strongly controlled by topographic factors. While the SC concentration is constant over the study period further sampling is required to assess decadal trends.