Landslide Morphology and Digital Terrain Analysis of the Roughs Landslide Complex Kent UK - Research Proposal Example

LANDSLIDE MORPHOLOGY AND DIGITAL TERRAIN ANALYSIS OF THE ROUGHS LANDSLIDE COMPLEX, KENT, UK Contents 0 Introduction 3 1.1 Background to the Study 3 1.2 Summary of the Problem 3 1.3 Proposed Solution 4 1.4 Research Format 5 1.5 Rationale/Motivation for the Study 5 1.6 Aim of the Study 6 1.7 Research Questions 6 2.0 Background Literature 7 2.1 Landslide Activity in South East England since 1966 7 2.2 Morphology of Landslide in Lympne Site 8 2.3 Linking climate to Landslide Activity 10 3.0 Research Method 11 3.1 Project Site Information 11 3.2 Architecture and Environment 12 3.3 Data Collection Tools 15 3.4 Implementation Issues and Challenges 16 3.5 Deliverables 16 3.6 Timeline 17 3.7 Conclusion 18 References 19 1.0 Introduction 1.1 Background to the Study Research works in applied geology have showed that Lympne in Kent, U.K. has very unique geographical phenomena, one of which is landslides (Buma and Dehn, 2008). Landslides may be noted to be a form of ground movement which occurs in different forms including deep failure of slopes, rockfalls, and shallow debris flows (Hutchinson, 2008). Meanwhile, landslides are not just a geographical phenomenon but ones that demand much attention and studies, especially when it comes to their classification and analysis. This is because an understanding of the nature of landslide that exists in a particular area such as Lympne makes it easier for geographers to adequately react to any accompanying incidences that may come with these landslides. One aspect of study of landslides that have been very important in history is the morphology of landslides and how various systems such as digital terrain analysis can be used to study these landslides to give geographers meaning to the characteristics and nature of the land area in question. Studying the landscape of Lympne, UK, Hungr, Evans, Bovis and Hutchinson (2001) noted that Lympne is made up of abandoned cliffs in an inland form, which is a situation important for the landscape of the area as it is responsible for the extensive clayey strata of the site. This characteristic has been known to present various stability problems and has a morphological classification that is regarded as an accumulation zone. 1.2 Summary of the Problem The classification of the landscape given of Lympne in the background, there is an underlying problem that it presents when it comes to the issue of larger landslide morphology of the site. In the inventory of 8835 landslides in Great Britain, the Geomorphological Services Ltd (GSL) noted that most inland landslides in Great Britain including those in Lympne and specifically the Roughs landslide complex, Kent are relict but generally dormant, having the potential of being re-activated by various activities some of which have been described to include climate change, engineering works and building activities. Meanwhile, the U.K and for that matter Lympne has a predicted climate change, which could directly impact on landslide frequency and the larger magnitude of Lympne (Buma and Dehn, 2008). For example through general circulation models (GCMs), Lympne has been predicted to have increase in rainfall and temperature due to the amassment of greenhouse gases and sulphate aerosols which is largely responsible for global warming. The existing problem can thus be described as a 2-tier situation, the first of which is the fact that Lympne has landslides that are capable of re-activation, and the second is the fact that there are continuing conditions happening in Lympne that naturally provoke the an impact on landslides. 1.3 Proposed Solution Even though the property of the geography of Lympne and the Roughs as being prone to landslides cannot be changed entirely, there is a way that the effect of landslides can be solved, which is through close monitoring. Already, a number of interventions have been attempted at monitoring, including the fact that there has been instrumentation on the Rough, which in 1996 was upgraded to the setting up of an automatic weather station with updated piezometers, tensionmeters and wire extensometers (Hungr, Evans, Bovis and Hutchinson, 2001). Today, it is proposed that much advantage can be taken of the advancement of technology to have better monitoring for the the Roughs landslide complex and the entire site of Lympne. It is thus proposed that the use of technology induced geographic information systems (GIS) be used in connection with classical models such as the topographic index in performing digital elevation model analysis of the selected site. The rationale for this proposed solution is that an in-depth understanding of the landslide morphology and digital terrain analysis of the site will make it possible to make accurate predictions and give accurate precautionary measures on ways of avoiding the impact of these natural phenomena of landslides. 1.4 Research Format There shall be six major divisions for the research work. The first chapter to be named introduction will give fundamental information about the site in question and the research problem, which is the possible impact of activities such as climate change and engineering activities on the possible re-activation of landslides in the research site. The second chapter to be named literature review shall be committed to secondary data collection, whereby existing works of known researchers in the area of study shall be reviewed. After this, the methodology of the research shall be used to collect specific field based data from the research site to determine the morphology of landslides of the research site. The data collection will be followed with the presentation of data to be collected, which is largely expected to be geographic data on areas such as the landslide classification of Lympne, direct and indirect seismically induce railures at the site, and projected climate situation of the site and its effects. The fifth component of the research shall be made up the analysis of the data, where the intervention made up of the use of GIS shall be used to perform digital elevation model analysis, topographic index analysis and slope stability analysis. The last part of the study shall be the conclusion, where the researcher shall take a position on the research study based on the findings made. 1.5 Rationale/Motivation for the Study Hutchinson (2008) lamented of a situation in existing literature and practical geographic studies where there have been a poor representation of landslides in south-east England in terms of the true distribution of landslides in this area. Once such a situation prevails, the threat is that geographers cannot become effective in making accurate predictions on future trends of landslides. As Lympne and the Roughs are part of south-east England, there is a motivation to conduct this study which uses technology based interventions in critically studying the landslide morphology and digital terrain analysis of the Lympne research site. The problem associated with poor representation of true distribution of landslides has been blamed on not recording landslides equally, leading to the creation of apparent, instead of actual markings of high and low density areas (Hutchinson, 2008). Meanwhile, the computerised GIS has been said to have the advantage of rendering more accurate and uniform recording of geographic data leading to accuracy in landslide data and subsequent analysis. 1.6 Aim of the Study Based on the rationale of the study, the research will approach the study with the aim of critically analysing the landslide morphology and digital terrain of Lympne, Kent, U.K with the use of geographic information systems. To achieve this overall aim, the following specific objectives ought to be performed: 1. To undertake a landslide classification of the research site 2. To analyse how the use of GIS can aid in studying the trend of landslide activity in the research site 3. To undertake a modelling of climate change scenarios for south east England 4. To undertake a digital elevation model analysis of the research site 1.7 Research Questions To ensure that the data collection process is in check and within the confined scope of the research problem, the following research questions will be set as a guide to the study. 1. What is the landslide morphology of Lympne based on its classification? 2. What has been the trend of activities of landslides in Lympne since 1966? 3. How can the GIS based hydrology model to general circulation model (GCM) be used to geerate climate change scenarios of the Lympne site? 4. What implications does the digital elevation model of Lympne have on a long term basis for the site? 2.0 Background Literature This section of the proposal seeks to present some fundamental literature on existing efforts on the problem under study. This is because regardless of the gaps that have been found to exist in literature there have been some efforts to address the research problem from the perspective of different writers. Based on the research questions, three major themes are drawn, from which background literature are collected as a form of secondary data collection to address the issues. 2.1 Landslide Activity in South East England since 1966 The Geomorphorlogical Services Ltd has for a long time been engaged in the activity of accumulating landslide database for the entire Great Britain, based on which a number of geological literatures have been based. Since 1966, Rowntree, Murphy and Mitchell (2003) has held that south-east England where Lympne and the Roughs landslide complex lies is relatively high landslide activity area. This means that the history of landslide activities in the area and the general characteristics of the land in the area make it prone to future events of landslides (Harpe, 2008). When arguing from the point of density of landslides per unit area outcrop, Collison et al (2000) found that the Lower Greensand escarpment which has as many as 288 known landslides makes the south east one of the prone geological formations in the U.K. Based on the above revelation, Buma and Dehn (2008) undertook more studies in to the specific features of the landscape that makes it posses such an activity of landslide. The study showed that the major factor that underlines the activities of landslide is the structure of permeable and brittle sandstones found in areas of south east including Hythe, Lympne and Sandgate beds. On the other hand of the landscape to is the impermeable and plastic clay layers found in areas such as Atherfield and Weald clays, creating exposed wet periods of water accumulation on the lines of the lithological boundary (Collison et al, 2000). Meanwhile, the creation of such water accumulation along the lithological boundary gives rise to the generation of large pore pressures. Already, Keefer (1984) had mentioned that the possible reactivation of relict landslides in areas such as Lympne is no longer a threat but reality because in post-glacial times, such reactivation took place. 2.2 Morphology of Landslide in Lympne Site The classification of landslides is something that Hutchinson (2008) has argued to be a collective process made up of several systematic tasks and practices. This means that to have the ideal classification of landslides based on which the form and structure are drawn, there are several factors that need to be taken into consideration. On the whole, six categorisation of factors are given that come under the collective mapping of landslides. These are type, sub-type, activity, depth, vegetation and body (Rowntree, Murphy and Mitchell, 2003). For a particular landslide, all these six variables have to be considered in order to make substantial claim of the morphology of a landslide. For the Lympne site, a photo-interpretation used produced the following pattern of classification according to the six main variables. Adopted from Rowntree, Murphy and Mitchell (2003) Adding up to the above information, Corominas and Moya (1999) noted that the type of material that the slide type of translational landslides as found in the Lympne site are made of comprise of rock block slides at the bedrock and also possessing earth block slide as part of its engeering soils, which also produces debris block slide. According to Varnes (1996), in translational slides there is a characteristic whereby the mass displaces along a planar or any available undulating surface of rupture, leading to a sliding out over the original ground surface. Such translational landslides occur in speed from anything extremely slow to extremely rapid (Harpe, 2008) and may slope in angles of 45-90°. Below is a picture of a typical translational slide and its major labels. Source: U.S Geological Survey (2004) In the type of translational slide that is found in Lympne, the U.S Geological Survey explains that they are characterised by mass movement along a roughly planar surface, made up of little rotational or backwards tilting. It is this tilting that creates deep depth of the slide movement. 2.3 Linking climate to Landslide Activity There are several studies directed at finding the relationship between climate and landslide, all of which virtually conclude that there is a positive correlation between climate and landslide. Cruden and Varnes (2006) maintained that climate will not directly be the reason there will be a landslide but that climate actually affect landslide activity, which subsequently provoke the occurrence of landslide. Collison et al (2000) noted that until now, even though there is a consensus on the impact of climate on landslide activity, the issue of resolution and extent of linkage actually depends on approach used in the models used in the assessment. For the best of results however, the use of an intermediate approach that involves the development of layered one-dimensional hydrology model, digital terrain modelling, application of infinite slope model and GIS analysis are recommended (Collison et al, 2000). Using such an intermediate approach makes it possible to gain the advantage of having a more in-depth understanding of the impact of climate and weather on slope stability, which is a crucial landslide activity, leading to the actual occurrence of landslides. Corominas and Moya (1999) advised that to have a perfect linkage between climate and landslide activity, variables such as the estimate of mean water table depth of the site, average water table across the escarpment, and digital elevation model to be used in determining slope angles must all be considered. Once all these factors are fulfilled, Cruden and Varnes (2006) said that it would be noted that climate will be linked to landslide for three major reasons. The first is that landslides react to changes in pore pressure, which is determined by groundwater level, which is also influenced by activities such as rainfall. Secondly, landslides are highly localised and so the nature of a site, if it is upland with complex rainfall patterns, could provoke local landslide activity. Lastly, precipitation controls a lot of activity in most landslide prone sites such as the Roughs landslide complex and so climate change trends that affect precipitation could impact on landslide (Harpe, 2008). 3.0 Research Method 3.1 Project Site Information The project aims to analysing the landslide morphology and digital terrain of Lympne in general and the Roughs landslide complex to be specific. The selection of the research site was influenced by a number of factors. First, the Lympne site has been described as being significant to the larger international Earth Science community (Keefer, 1984). This is because of the rich geographical history of the site, which makes it a useful academic and professional point of studies and discussion. Secondly, the presence of an automatic weather station, which is well equipped with modern technology tools including different forms of GIS, makes the site ideal for enhanced data collection and analysis. What is more, the site continues to have very exceptional geographical and geomorphological features that makes the discussion of the landslide morphology of the site highly evidence based. Again, the fact that Lympne is situated on former sea cliffs makes the place exposed to new lines of geographic studies that are focused mainly on what the bearing that past geographic characteristic such as sea cliffs can have on landslide situation of the region. 3.2 Architecture and Environment Bromhead (1997) identified the soil properties for the Rough landslide complex and this was later related to the larger Lympne region by Cruden and Varnes (2006). The findings of these researchers showed that the mean saturated conductivity in ms-1 of the root zone 0-30cm is given as 1.3x10-5. The landslide debris 30-200cm for the same variable stands at 8.7x10-7, whereas the weald clad >200cm is pegged at 7.8x10-9. This data is further expanded in the table below. Knowing the importance of winter and summer temperatures to the landslide morphology of Lympne, Collison et al (2000) investigated the winter and summer temperatures of the site and produced the results given below. Fig 1: Winter and Summer Temperatures for Lympne from 1930 to 2080. Source: Collison et al. (2000, p. 207). On his part, Cooper (2007) measured the average dimensions of landslide in the Lympne region and produced the result in fig 2 below, which shows the width of the displaced mass, Wd, width of the rupture surface, Wr, total length, L, length of the displaced mass, Ld, length of the rupture surface, Lr, depth of the displaced mass, Dd, and depth of the rupture surface, Dr. Based on the dimensions, the dominant type of landslide at the site was identified to be Fig 2: Average Landslide dimensions for Lympne Source: Cooper (2007) Based on the dimensions given above, Corominas and Moya (1999) described the architecture of the landslide as a rotational slump with the Lympne block undermined by slippage within the concentrated Atherfield clay with several shallow translational slides that do not go beyond 2 to 3m. A typical diagram of a slide is thus given in fig 3 below Fig 3: A translational slide Source: Cooper (2007) 3.3 Data Collection Tools One of the major research tool that will be used in this study include GIS based hydrology model to GCM. This will be used primarily to generate the possible impact of major climatic changes on the frequency and magnitude of landslide activity. It would be noted that the GIS based hydrology model to GCM is fundamentally a GIS data model that has been combined with two major variables, which are hydrology and downscaled GCM data. The combined approach will be used in order to attain a more authenticated scope of data collection and analysis on the multi-variant nature of the research problem. Earlier, it was stated that the research problem is a 2-tier problem that has components of the natural landslide morphology of Lympne and the possible impact of climate change on the site. This means that the study will end will with the combined tool accommodating the provisions of all two aspects of the study. As part of the digital terrain analysis also, the research shall make use of remote sensing tools to get remote sensing images based on morphological conditions of the site. Other possible tools that may be employed include Terrain Analysis Programmes for the Environmental Sciences (TAPES) software, which can be used to give biophysical processing of landscapes. 3.4 Implementation Issues and Challenges The research will be conducted as a mixed research method which makes use of both primary data collection and secondary data collection approaches. Much of the emphasis will however go to the primary data collection. This means that the researcher shall collect first hand data from the research site. One challenge that is perceived as part of the primary data collection has to do with the guarantee for permission to use targeted weather stations and equipment in these stations for data collection. Once permission is granted, there are challenges perceived at the data collection stage. For example Keefer (1984) reported on how particular types of landscapes including that within the Roughs landslide complex is prone to slope failure, which is seldom directly recognised. The implication of this is that there may be slope failures that may actually be interpreted as part of the analysis on the number of elements pertaining to the slop instability feature (Westen, 2008). Due to the advanced GIS, such slope failures are expected to be read using various spatial analyses with GIS mechanisms. 3.5 Deliverables Based on the research objectives, there are four major phases that the proposed study will cover. Each phase of the study reflects one particular research objective and will thus be made up of data collection that aims to achieve the said specific objective. This means that there shall be four major project deliverables at the end of the research. The table below shows the various phases, tasks to take place, and the deliverables that will be produced at the end of the phases. Phase Deliverable Objective Achieved Preliminary secondary data collection Landslide classification document for the research site To undertake a landslide classification of the research site Pre-Intervention Field based data collection Report on trend of landslide activity in the research site To undertake a modelling of climate change scenarios for south east England Intervention Field based data collection GIS based hydrology model To analyse how the use of GIS can aid in studying the trend of landslide activity in the research site Post-Intervention field based data collection Digital elevation model analysis report To undertake a digital elevation model analysis of the research site 3.6 Timeline The project is estimated to be carried out in 9 weeks with each week having a particular milestone to achieve. The milestones are given as follows. Milestone/Week 1 2 3 4 5 6 7 8 9 Identification of research problem Collection of secondary sources and materials Designing consent form for primary data collection Seeking approval from research site Pre-intervention data collection Intervention phase data collection Post-intervention phase data collection Analysis of available data 3.7 Conclusion The proposed research study seeks to focus on the problem of the possible re-activation of landslides in the Lympne region, which is a case that has been worsened by other variables and factors such as predicted climate change and engineering activities. The researcher hypothesises that until such a time when a more accurate approach to analysing the landslide morphology and digital terrain of the site is done, geographers will not be in a position of offering accurate predictions and warning of possible landslide activities at the site. The motivation in undertaking the study is therefore to come up with a research study that bridges the gap in literature on how technology can be taken advantage of through the use of advanced geographic information systems in setting the record straight on the true state of the landslide situation at the Lympne region. The proposed solution is a combined intervention that uses combination of GIS data model and downscaled GCM data. References Bromhead, E.N., (1997). Unpublished technical report presented at NEWTECH Workshop, London, 1997. Buma, J., Dehn, M. (2008). A Method for predicting the impact of climate change on slope stability. Environ. Geol. 35(4), 190-196 Collison et al (2000). Modelling the impact of predicted climate change on landslide frequency and magnitude in SE England. Engineering Geology 55(3): 205–218. Cooper, R.G. (2007) Mass Movements in Great Britain. Geological Conservation Review Series, 33(1): 1-348 Corominas, J. and Moya, J. (1999). Reconstructing recent landslide activity in relation to rainfall in the Llobregat River basin, Eastern Pyrenees, Spain. Geomorphology, 30, 79-93. Cruden D.M., Varnes D. J. (2006) - Landslide types and processes. Transp Res Board, Spec Rep 247, pp 36–75. Harpe C. F. S. (2008). Landslides and related phenomena. A Study of Mass Movements of Soil and Rock. New York: Columbia Univo Press Hungr O, Evans SG, Bovis M, and Hutchinson JN (2001) Review of the classification of landslides of the flow type. Environmental and Engineering Geoscience, VII, 221-238. Hutchinson J. N. (2008). Mass Movement. In: The Encyclopedia of Geomorphology (Fairbridge, R.W., ed.), New York: Reinhold Book Corp. Keefer, D.K. (1984) Landslides caused by earthquakes. Bulletin of the Geological Society of America , (34) 4, 406-421. Rowntree P.R, Murphy J.M. and Mitchell J.F.B (2003). Climate Change and Future Rainfall Predictions. J. Inst. Water Environ. Manag. 7(3). 464-470. U.S Geological Survey (2004). Landslide Types and Processes. Accessed March 1, 2014 from http://pubs.usgs.gov/fs/2004/3072/fs-2004-3072.html Varnes D. J. (2004). Slope movement types and processes. Transportation Research Board Sp. Rep. 43( 176), 11–33. Westen C. (2008). Introduction to Landslides. Enscheda: International Institute for Aerospace Survey and Earth Sciences Read More