Abstract
Landslides are a frequent phenomenon on mountain Elgon, particularly in Bududa district on the SW side of this extinct shield volcano. Landslides have led to the destruction of property and loss of life we, therefore, need to monitor them. Monitoring how landslides build-up makes it possible to timely evacuate people and build barriers to protect property against damage by landslides. Residents in Bududa have reported cracks developing in the ground and houses. These cracks continue to grow, suggesting a future catastrophic event. Such an event may resemble the 2010 landslide in Bududa, which killed approximately 450 people and destroyed much property. In order to mitigate the consequences of a new landslide as much as possible, we monitored ground motion in Bududa in eleven stations from June 2018 to June 2019. Six-hour session GPS observations were made, and deformation was determined over the observation period, June to September 2018, September to November 2018, November 2018 to February 2019 and February to June 2019. A congruency test was performed to determine how significant the deformation was. It appeared that the ground deformation differed largely at various monitored stations, ranging from 0.004 to 0.076 m, 0.001 to 0.067 m and 0 to 0.078 m in the East, North and vertical directions respectively. The values indicate that most slopes in the district are unstable, particularly in the wet seasons, which implies that future landslides pose a high risk for society.
Highlights
Deformation was determined from June 2018 to June 2019 as is shown in Tables 2-4 and Figure 5 and between the five consecutive observations June 2018, September 2018, November 2018, February 2019 and June 2019 as is shown in Figure 6 and Table 4
Campaign Global Positioning Systems (GPS) measurements are normally done at an annual scale, probably due to cost or thought that deformation variation within a year is not significant to necessitate observations within a year [26] [27]
This study investigated the effect of shortening the time between campaign observations to a monthly level in characterizing ground deformation magnitudes [11]
Summary
Ground deformation has been measured using Global Positioning Systems (GPS) over the past 15 years to detect areas at risk of landslides [13] [14]. In measuring ground deformation using GPS, the change in distances, height, angles and coordinates can be determined. The GPS measurements can either be continuous or be restricted to temporary campaigns and there are several reasons why campaign measurements are still applied according to [11]. These are cheaper, and there is the flexibility to where to install the GPS equipment. It is difficult to have a dense network when CORs are used due to the expenses involved
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