Malcolm Whitworth

Landslide Laser Scanning: a new look at an old problem

An essential part of the study of any landslide problem is the development of a 3-D conceptual model of the landslide and its surroundings. Traditionally this has been done by pen and paper during a walk-over geomorphological survey (Forster 1989) ideally with pits and boreholes to give subsurface information. More recently aerial photographs and aerial ortho-photographs have aided the surface assessment and geophysical surveys have added to the understanding of the third dimension. A more detailed quantitative model could be achieved by accurate ground surveying by EDM, theodolite and level. However, this is time consuming and a high degree of surveying expertise is necessary for an accurate result where small movements might need to be monitored. More recently ‘total station’ surveying equipment has increased the speed at which this process can be completed. However, the advent of affordable semi-automated laser scanners and accurate differential GPS technology has opened up a new opportunity in rapid landslide modelling. The British Geological Survey is currently using and developing laser scanning for the characterization, modelling and monitoring of landslides, essentially a terrestrial LIDAR technique (Hobbs et al. 2002). A small part of that work has been looking at two landslides in the Cotswolds, in association with the School of Earth and Environmental Sciences of the University of Portsmouth, which has a major research interest in studying the landslides in the Jurassic strata near the village of Broadway in …

Airborne remote sensing for landslide hazard assessment: a case study on the Jurassic escarpment slopes of Worcestershire, UK

This paper describes the application of airborne remote sensing to the study of landslides on the clay-dominated slopes of the Cotswolds Hills between the towns of Broadway, Worcestershire, and Snowshill, Gloucestershire, in the UK. The project involved an initial desk study, airphoto interpretation and field survey in order to provide detailed information about the nature and extent of the landsliding in the area. High-resolution Airborne Thematic Mapper (ATM) imagery was acquired by the NERC Airborne Remote Sensing Facility, which was subsequently processed in order to develop a remote sensing method for landslide identification using airborne multispectral data. A range of image processing methods are described including colour composite enhancement and thermal imaging, while the focus of the paper will be on the development of a semi-automated method of landslide identification using image classification and texture analysis. Results from the first stage of the study have shown that the use of image processing techniques such as colour composites and thermal imaging can provide information on the ground surface not visible in conventional aerial photography. In this case study, this has included more detailed geomorphological information on landsides in the area and the nature of the cambering and gulls at the top of the escarpment. The second part of the study has investigated the use of image texture enhancement as a method of landslide identification, applied in isolation and incorporated into an image classification scheme as a semi-automated method of landslide identification. Results from this investigation indicate that landslides can be identified automatically with a high degree of accuracy (83%) and that by using image texture, the image classification technique is able to successfully differentiate between areas of landslide activity and stable slopes in the airborne imagery. Its is clear from the results of this study that in order to identify landslides in these types of clay-dominated terrains, image texture must be used. Inland landslides, like those on the Cotswolds escarpment, do not have a spectral signature but they do exhibit a distinct spatial signature that allows them to be identified in airborne imagery using textural analysis. The semi-automated method of landslide identification described in this paper represents a rapid method of terrain evaluation and landslide hazard assessment, which can be undertaken prior to more detailed field mapping.

A new technique for the detection of large scale landslides in glacio-lacustrine deposits using image correlation based upon aerial imagery: a case study from the French Alps

Abstract Landslide monitoring has benefited from recent advances in the use of image correlation of high resolution optical imagery. However, this approach has typically involved satellite imagery that may not be available for all landslides depending on their time of movement and location. This study has investigated the application of image correlation techniques applied to a sequence of aerial imagery to an active landslide in the French Alps. We apply an indirect landslide monitoring technique (COSI-Corr) based upon the cross-correlation between aerial photographs, to obtain horizontal displacement rates. Results for the 2001–2003 time interval are presented, providing a spatial model of landslide activity and motion across the landslide, which is consistent with previous studies. The study has identified areas of new landslide activity in addition to known areas and through image decorrelation has identified and mapped two new lateral landslides within the main landslide complex. This new approach for landslide monitoring is likely to be of wide applicability to other areas characterised by complex ground displacements.

Identification of landslides in clay terrains using Airborne Thematic Mapper (ATM) multispectral imagery

The slopes of the Cotswolds Escarpment in the United Kingdom are mantled by extensive landslide deposits, including both relict and active features. These landslides pose a significant threat to engineering projects and have been the focus of research into the use of airborne remote sensing data sets for landslide mapping. Due to the availability of extensive ground investigation data, a test site was chosen on the slopes of the Cotswolds Escarpment above the village of Broadway, Worcestershire, United Kingdom. Daedalus Airborne Thematic Mapper (ATM) imagery was subsequently acquired by the UK Natural Environment Research Council (NERC) to provide high-resolution multispectral imagery of the Broadway site. This paper assesses the textural enhancement of ATM imagery as an image processing technique for landslide mapping at the Broadway site. Results of three kernel based textural measures, variance, mean euclidean distance (MEUC) and grey level co-occurrence matrix (GLCM) entropy are presented. Problems encountered during textural analysis, associated with the presence of dense woodland within the project area, are discussed and a solution using Principal Component Analysis (PCA) is described. Landslide features in clay dominated terrains can be identified through textural enhancement of airborne multispectral imagery. The kernel based textural measures tested in the current study were all able to enhance areas of slope instability within ATM imagery. Additionally, results from supervised classification of the combined texture-principal component dataset show that texture based image classification can accurately classify landslide regions and that by including a Principal Component image, woodland and landslide classes can be differentiated successfully during the classification process.

The Development of a Simplified Model for Urban Flood Risk Mitigation in Developing Countries

The prevalence of flooding in the world in recent times has arguably been unprecedented. It is particularly challenging for developing countries such as Nigeria, where the hazard is often poorly understood and understudied. With predictions of worse future scenarios, it is important to develop integrated approaches - which include flood modelling and vulnerability assessment - aimed at assisting human populations to cope with the hazard. This paper presents an ongoing research into flood risk mitigation in the Lagos metropolis of Nigeria. Maps of social vulnerability index, and land cover of the area have been produced. The results tend to show that two-thirds of the study area may be classed as highly vulnerable to the hazard, with Ajeromi-Ifeledun local government area, most vulnerable. Rapid urbanization tends to expose a wider population to flood risk as new developments are increasingly being put up in flood-prone areas. While this research is at a relatively early stage, the interim results will inform flood risk mitigation efforts in the study area.

Geomorphological assessment of complex landslide systems using field reconnaissance and terrestrial laser scanning

Digital terrain models (DTMs) generated using ground-based laser scanning provide high-resolution bare earth models of the terrain surface suitable for the geomorphological studies. Using the elevation models, features such as scarps, back-tilted slope units, lobate accumulation zones and irregular topography can be enhanced to allow delineation and classification of landslides. The study identified that a combination of shaded relief models and the application of slope, curvature and topographic roughness filters provided the optimum method for landslide mapping using the terrestrial DTM data. This chapter describes a case study on the application of terrestrial laser scanning to a complex landslide terrain in the United Kingdom and illustrates the use of the topographic filters for landslide identification. The output from the topographic filters has been compared to a field-based geomorphological map; the results show that terrestrial laser scanning can provide for rapid and very detailed geomorphological assessment of landslide terrains that is comparable in accuracy and detail to field-based mapping.

An interactive story map for the Methana volcanic peninsula

The purpose of this research is the identification, recording, mapping and photographic imaging of the special volcanic geoforms as well as the cultural monuments of the volcanic Methana Peninsula. With the use of novel methods the aim is to reveal and study the impressive topographic features of the Methana geotope and discover its unique geodiversity. The proposed hiking trails along with the Methana’s archaeology and history, will be highlighted through the creation of an ‘intelligent’ interactive map (Story Map). Two field trips have been conducted for the collection of further information and the digital mapping of the younger volcanic flows of Kammeni Chora with drones. Through the compiled data, thematic maps were created depicting the lava flows and the most important points of the individual hiking paths. The thematic maps were created using a Geographic Information System (GIS). Finally, those maps were the basis for the creation of the main Story Map. The decision to use Story Maps was based on the numerous advantages on offer such as user-friendly mapping, ease of use and interaction and user customized displays.

Remote Sensing and Geosciences Interpretation of Lineaments for Tectonic and Hydrocarbon Studies in the Bornu Basin

Geological conditions for hydrocarbon potential have been identified in the Bornu Basin in north Eastern Nigeria. The basin is part of the Chad Basin and other tectonically related contiguous basins within the West and Central Africa Rift System (WCARS) formed from the failed extensional rifting at an aulacogen junction during the separation of the South American and the African continents. The Bornu Basin covers about one tenth of the Chad Basin with limited geological mapping campaigns and unsuccessful exploration for oil and gas. Significant gaps still remain particularly in the vast northern areas characterised by flat topography, lack of continuous bedrock outcrops with structures concealed beneath sand cover. Remote sensing and GIS techniques offer potential for improving structural geological mapping in the basin but has not been used for these purposes. This research presents the use of combined remote sensing data including Landsat ETM , ASTER, SRTM and Radar with other existing geosciences data including gravity, seismic, aeromagnetic and well log data to constrain the structure and tectonics of the basin through lineament analysis. The research involved mapping of lineaments, lithology, palaeodrainage and palaeo-shorelines in the basin. Two physiographically distinct study areas are selected in the basin to provide an appropriate comprehensive coverage of the basin attributes. The study sub-area 1 having mostly flat topography and lacking surface outcrops but comprising all the data sets available provides an enabling ground control site while the study sub-area 2 where outcrops are present provides an enabling site for validation of inferred field mapping and new observations of unmapped geology in the basin.

Creation of Landslide Inventory Map for the Toktogul Region of Kyrgyzstan, Central Asia

This project is reliant upon the use of remote sensing for the detection and delineation of landslides. Therefore optical satellite images, such as medium resolution ASTER, and high resolution SPOT 5, will be combined with topographic data to analyse the landslide prone areas. The specific objectives are to generate a landslide inventory distinguishing between different landslide types, and to use this map for GIS based spatial landslide hazard modelling in the Toktogul region of Kyrgyzstan. The project steps include: (1) detection and mapping of landslides at different scales using high resolution imagery and DEM data to generate a GIS landslide inventory database for the area, (2) ground truthing of this landslide inventory using field reconnaissance, (3) integrating morphological, lithological, structural, land use, hydrological and seismic data within a GIS environment (DEM data from SPOT will form an important component of this dataset), and (4) derivation of statistical landslide hazard models through the integration of the landslide inventory with the GIS datasets. The results will be shown in the form of landslide inventory maps including a GIS database at various scales and a landslide hazard model showing landslide prone areas and distinguishing different hazard levels. Consequently, these mapping results will be used to assist in making rational decisions regarding local evacuation plans in areas susceptible to slope failure.