Firstly, the determining of landslides, or types landslide is very important in detecting any slope movement and identifying its magnitude. This can be done by observation of physical features the landslide has left behind and the extent of movement the process has incurred. There are six different categories of slope movement all differing in the magnitude of movement. Once its features examined, and type of slope movement identified, the magnitude of the slope movement is the next step in monitoring slope movements. Due to landslides often being very dangerous to be around, evidence cannot be gathered by scientists on the ground, thus aerial photographs are taken to scale the movement of the slope and the magnitude of change that the slope has undertaken. “Aerial imagery, such as LiDAR, (light detection and ranging), can be used to map landslides and evaluate their mechanics and material properties” (McKean et al., 2004). An example of this technology being used is that of Salmon Falls Creek in southern Idaho. iDAR perspective view was used here to compare two landslides along the creek. The recent 1999 Salmon Falls landslide ) (Glenn et al., 2006). This shows how simple it is to compare two landslides within a specified area. It also highlights the magnitude of the two landslides.
Furthermore, “A GPS device can determine the size and displacement of a landslide by setting the boundary points on the GPS and determining the distance between the” (Reid and LaHusen, 2004), this would be ideal for scientists to measure the slope movement on steeper or larger landslides. The collection of this data must be made immediately after the event, as landslides reinitiate movement thus the initial slope movement and change cannot be recorded.
Moreover, the physical measuring of landslides is very important, due to the accurate mapping of topographic maps, which allow the evaluation of slope movement. It also allows the collection of data that shows the volume of change within the environment and compares this to older topographic maps, of the same specified area; thus commenting on the deformation of the landscapes. Furthermore, the surveying of topographic features also comments on how the landscape has altered and the extent of deformation the land has experienced. Once this information has been gathered, structural mapping of an area can be created. This is the process of locations being highlighted, due to faults and folds created the landscape and characteristics of that specified area.
Furthermore, Gerald F. Wieczorek states that “reo photography is very important so that the topography can be viewed in three dimensions, making the mapping of landslide more accurate. Colour photography is beneficial for mapping; false-colour infrared photography can emphasise the contrast between landslides and non-landslide topography”, thus allowing a simple judgement to be made of where exactly slope movement occurred and the magnitude of the movement, due to the map allowing the scale of the movement to be analysed.
One way of determining slope movement is that of photographic change detection. This is the method of collecting images which are high in resolution before and after events. These images are then sequenced in order to picture and plot the change in the slope to detect any movement. The images are used to determine the total displacement of the slopes and the rates of change that have occurred within this environment. Sequencing these images will allow the visualisation of slope movement due us being able to detect change and see where activity on the slope has occurred. Furthermore, once collected the images of a before and after of a slope or hill side can easily be compared by the use of overlaying and other computing and photographic techniques making the demonstration of characteristics between the two images simple. This is an efficient way to detect if there is any slope movement and suggests the magnitude of change, i.e. if there is little change detected, magnitude of deformation is low.
Another technique in which slope movement and the magnitude of this movement detected is that of, real time monitoring. This is the process of whereby a number of devices are set up around the specified areas monitoring any signs of movement on the slope. It detects this movement due to the intensity value of each pixel being determined and when this is altered alarms will sound, as slope movement ensues. This is generally used around areas of mining to protect workers from being trapped in the mine due to landslides.
Many instruments implemented by scientists, within landslides and slopes can provide relevant and useful data in slope movement and possible landslides. The magnitude of the slope movement is measured due to the velocity of movement being recorded using an array of equipment. With this equipment it is easy to see the extent of deformation of the slope and the change it has experienced. Using stakes and planting them into the slope’s surface will indicate whether movement within this specified area has taken place thus allowing, geomorphologists to record the data visually in the field.
Another method in determining the magnitude and change of slope movement is that of analysing the geologic materials. When analysing the type of bedrock and other rocks left in the wake of slope movement, geologists are able to recognise the magnitude of the slope movement due to the type of rock left behind and exposed. If there is a large landslide for instance, a lot more bedrock will be uncovered thus this is an obvious indication of a slope movement with high magnitude. If there is little or no bedrock exposed and the rock that is upon the slope is just debri, this therefore means there was a lack of movement thus a slope movement of low magnitude.
Furthermore, the analysis of geomorphic thresholds would allow for information to be collected on slope movement. A Geomorphological threshold is the amount of movement a landform can take before the land faults and leads to incipient failure creating new landforms or moving the already existing landform. It is the point at which the landform becomes unstable. With this identified the movement or scale of movement can be identified using the catastrophe theory and the visualisation of new landforms.
In conclusion, slope movement and magnitude of this movement can be measured and determined in many different ways. Techniques involving technology are the most astute in comparing and contrasting slope movement and the magnitude of this movement. However, the physical measuring of the slope movement highlights and determines ultimately the statue of the slope movement.
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