Multi-Sensor Remote Sensing Data and GIS Modeling for Mapping Groundwater Possibilities: A Case Study at the Western Side of Assiut Governorate, Egypt

Groundwater is an essential natural resource and it has a significant role in the development of dry lands. It is the main source of fresh water in arid and semi-arid regions. The present study investigates groundwater potentiality in the western part of Assiut Governorate, Egypt using advanced remote sensing and geospatial techniques along with hydrological data and field validation. The adopted method provides a low-cost and highly effective tool that can be combined with the conventional land-based approach for mapping Groundwater Potentiality. The study aims to determine the groundwater probability and recharging zones based on the contribution of some physiographic variables that influence groundwater storage. Therefore, multi-sensors remote sensing data from ASTER, Landsat-8, MODIS, Shuttle Radar Topography Mission (SRTM), Tropical Rainfall Measuring Mission (TRMM), and Radarsat-1 were accustomed to extract several geospatial thematic layers (variables). These layers include elevation, slope, curvature, drainage density, topographic wetness index, surface roughness, frequency of thermal anomaly, accumulated precipitation, Land Use/Land Cover (LULC), and lineament density. The produced layers are then scaled and weighted based on their contributions to the recharge of near-surface (unconfined) groundwater aquifers through infiltration and percolation processes. The Simple Additive Weight (SAW) method was utilized to aggregate all the weighted layers for creating the Groundwater Potentiality map. This aggregated grouped map was then classified into 5 classes, from very high to very low groundwater potentiality zones. The results show that the high Groundwater Potentiality was associated with low terrain, high surface ruggedness, high drainage and lineament densities, and relatively close to thermal anomalies in wadi deposits, and adjacent sandy areas. The remote sensing results were validated using comprehensive field observations including, pumping tests, water wells data, and vegetation patterns in the study area. The study concluded that a groundwater possibility map based on geospatial techniques and remote sensing data can provide a robust tool in groundwater exploration, and consequently, it can be adopted elsewhere in arid regions

An integrated multiscale approach for characterization of rock masses subjected to tunnel excavation

The design of tunnels must be conducted based on the knowledge of the territory. The longer the structure, the larger the area to be investigated, and the greater the number of surveys and tests to be performed in order to thoroughly examine all the relevant features. Therefore, optimization of the investigation process is strongly required to obtain complete and reliable data for the design of the infrastructure. The fast development of remote sensing technologies and the affordability of their products have contributed to proving their benefits as supports for investigation, encouraging the spreading of automatic or semi-automatic methods for regional scale surveys. Similarly, considering the scale of the rock outcrop, photogrammetric and laser scanner techniques are well-established techniques for representing geometrical features of rock masses, and the benefits of non-contact surveys in terms of safety and time consumption are acknowledged. Unfortunately, in most cases, data obtained at different scales of investigations are only partially integrated or compared, probably due to the missing exchange of knowledge among experts of different fields (e.g. geologists and geotechnical engineers). The authors, after experiencing such a lack of connection among the results of different surveys concerning tunnels, propose a multiscale approach for the optimization of the investigation process, starting from the regional scale, to obtain the data that can be useful not only for planning more detailed surveys in a preliminary phase, but also for making previsions on the discontinuity sets that are present in the rock masses subjected to excavations. A methodological process is proposed and illustrated by means of a case study. Preliminary results are discussed to highlight the potentiality of this method and its limitations. Keywords: Tunnel, Multiscale approach, Geological lineament, Non-contact survey, Discontinuity, Digital terrain model (DTM

A comparison for a multiscale study of structural lineaments in southern Brazil: LANDSAT-7 ETM+ and shaded relief images from SRTM3-DEM

This paper presents a comparison of descriptive statistics obtained for brittle structural lineaments extracted manually from LANDSAT images and shaded relief images from SRTM 3 DEM at 1:100, 000 and 1:500, 000 scales. The selected area is located in the southern of Brazil and comprises Precambrian rocks and stratigraphic units of the Paraná Basin. The application of this methodology shows that the visual interpretation depends on the kind of remote sensing image. The resulting descriptive statistics obtained for lineaments extracted from the images do not follow the same pattern according to the scale adopted. The main direction obtained for Proterozoic rocks using both image types at a 1:500, 000 scale are close to NS±10, whereas at a 1:100, 000 scale N45E was obtained for shaded relief images from SRTM 3 DEM and N10W for LANDSAT images. The Paleozoic sediments yielded the best results for the different images and scales (N50W). On the other hand, the Mesozoic igneous rocks showed greatest differences, the shaded relief images from SRTM 3 DEM images highlighting NE structures and the LANDSAT images highlighting NW structures. The accumulated frequency demonstrated high similarity between products for each image type no matter the scale, indicating that they can be used in multiscale studies. Conversely, major differences were found when comparing data obtained using shaded relief images from SRTM 3 DEM and Landsat images at a 1:100, 000 scale.Este artigo apresenta a comparação, através da estatística descritiva, de lineamentos de estruturas rúpteis obtidas manualmente sobre imagens Landsat e relevo sombreado do SRTM 3 MDE nas escalas 1:100.000 e 1:500.000. A área selecionada localiza-se no sul do Brasil e engloba rochas do pré-Cambriano e unidades estratigráficas da Bacia do Paraná. A aplicação desta metodologia demonstra que a interpretação visual depende do tipo de imagem do sensor remoto. O resultado da estatística descritiva obtido para os lineamentos extraídos das imagens não apresenta o mesmo padrão em função da escala adotada. A principal direção encontrada nas rochas do Proterozoico em ambas as imagens, na escala 1:500.000, é próxima de NS±10, enquanto que na escala 1:100.000 a direção N45E foi obtida nas imagens de relevo sombreado do SRTM 3 MDE e a direção N10W nas imagens Landsat. Rochas sedimentares Paleozóicas monstraram os melhores resultados para ambas as imagens e escalas (N50W). Por outro lado as rochas igneas Mesozóicas monstraram as maiores diferenças, realçando as estruturas NE nas imagens SRTM 3 MDE e as estruturas NW nas imagens Landsat. A frequencia acumulada demonstrou alta similaridade entre os produtos de cada tipo de imagem, independente da escala, indicando que podem ser utilizadas em estudos multiescala. Entretanto as maiores diferenças foram encontradas quando foram comparados os dados obtidos pelas imagens sombreadas do SRTM 3 MDE e imagens Landsat na escala 1:100.000.Brazilian Geological Survey, Companhia de Pesquisa de Recursos Minerais (CPRM); the Post-Graduation Program in Minerals Resources and Hydrogeology of the Geosciences Institute of Universidade de São Paulo; the Universidade Federal Rural do Rio de Janeiro and the Faults and Fluid Flow Project (UFPR/PETROBRAS) for financial support

Geovisualization

Geovisualization involves the depiction of spatial data in an attempt to facilitate the interpretation of observational and simulated datasets through which Earth's surface and solid Earth processes may be understood. Numerous techniques can be applied to imagery, digital elevation models, and other geographic information system data layers to explore for patterns and depict landscape characteristics. Given the rapid proliferation of remotely sensed data and high-resolution digital elevation models, the focus is on the visualization of satellite imagery and terrain morphology, where manual human interpretation plays a fundamental role in the study of geomorphic processes and the mapping of landforms. A treatment of some techniques is provided that can be used to enhance satellite imagery and the visualization of the topography to improve landform identification as part of geomorphological mapping. Visual interaction with spatial data is an important part of exploring and understanding geomorphological datasets, and a variety of methods exist ranging across simple overlay, panning and zooming, 2.5D, 3D, and temporal analyses. Specific visualization outputs are also covered that focus on static and interactive methods of dissemination. Geomorphological mapping legends and the cartographic principles for map design are discussed, followed by details of dynamic web-based mapping systems that allow for greater immersive use by end users and the effective dissemination of data

CoMMa: a GIS geomorphometry toolbox to map and measure confined landforms

The Confined Morphologies Mapping (CoMMa) Toolbox, a novel ArcGIS Pro python toolbox expressly created for semi-automated seabed morphological mapping, is presented here. The toolbox includes a selection of tools for the pre-processing, delineation and description of confined features on a digital elevation model (DEM) that are either negative or positive. The CoMMa Toolbox addresses the need for a flexible and multi-faceted solution applicable to different mapping problems, also encapsulating and re-interpreting existing methodologies. This study also evaluates, qualitatively and quantitatively, the performance of CoMMa delineations performed on a synthetic bathymetry DEM with 150 coral mounds of known characteristics against manual digitisations completed by five expert geomorphologists. The results show that the best CoMMa delineation falls within the range of competence demonstrated by the expert manual mappers. Edge evaluation metrics and attribute error scores are comparable or often superior to four of the five human delineations, although the Toolbox never reaches the performance of the best expert. Nevertheless, the semi-automated techniques can be of assistance to any user, providing rapid, visually unbiased and consistent delineations, thus saving time: they can then be optimised manually where desirable. Moreover, while the toolbox was created for marine geomorphometry, it can be applied to any DEM, either marine, terrestrial or extra-terrestrial. The CoMMa Toolbox is available in a public GitHub repository with a thorough user guide

The drumlin problem : streamlined subglacial bedforms in southern Sweden

This thesis investigates stream-lined subglacial bedforms (often referred to as drumlins) in southern Sweden. The broad aim of this is to contribute to the solution of the ‘drumlin problem’. The term drumlin has come to be applied to a wide range of features whose internal architecture (core) and overall morphology are seen to vary greatly. This range in characteristics is in part responsible for the various competing theories of drumlin formation, each different type of core and morphology generating a new idea for how it came about. Here the new Swedish national height model, a high resolution LiDAR derived digital elevation model, in combination with detailed sedimentological work is used to characterise streamlined terrain in southern Sweden and investigate the formation processes associated with it. The findings of this are that drumlinoids in southern Sweden are predominantly rock cored. Soft cored features tend to be significantly longer than rock cored features. In general, drumlinoids in southern Sweden are located at the lower end of the size spectrum in terms of global streamlined sub-glacial features. Additionally it has been found that drumlinoids can form rapidly at glacial margins as well as within the main body of ice sheets. And finally, the most important contextual geological factor in drumlinoid parameter (morphology) formation appears to be drift depth/properties. The bedrock type beneath a feature and the hydrological system as recorded in eskers do play a role, but the exact nature of this is not certain and the correlations are difficult to analyse. In addition to these findings a generalised conceptual model of drumlinoid formation is proposed and a discussion of the possible ways in which physical processes influence said formation is offered. It is suggested that chaotic behaviour and the role of scale might be useful to consider and that whilst it is something of semantic point, the use of the term drumlinoid is deliberate and important. This is because due to equifinality there are many landforms that researchers can split into different categories, e.g. rock drumlins, clone drumlins, emergent drumlins, downwards emergent drumlins or obstacle drumlins. These are all valid divisions as there are different physical processes involved in their formation. However these processes and the final landforms that result from them are all part of the sub-glacial continuum and so at one level must be considered part of the same family