TITLE:
Estimation of Ground Vertical Displacement in Landslide Prone Areas Using PS-InSAR. A Case Study of Bududa, Uganda
AUTHORS:
Brian Makabayi, Moses Musinguzi, John Richard Otukei
KEYWORDS:
Bududa, Landslides, PS-InSAR, Vertical Displacement
JOURNAL NAME:
International Journal of Geosciences,
Vol.12 No.4,
April
26,
2021
ABSTRACT: Estimation of ground
displacement in landslide susceptible regions is very critical to understanding
how landslides develop. The knowledge of ground displacement rates and
magnitudes helps plan for the safety of the people and infrastructure. The
early detection of landslides in Bududa is still a challenge due to the limited technology, hard to access, and a need
for an affordable technique that can monitor a wide area continuously. In
recent studies, the use of Persistent Scatterer Interferometry Synthetic
Aperture Radar (PS-InSAR) has provided
vital information on landslide monitoring through the measurement of
ground displacement. In this study, Synthetic Aperture Radar (SAR) band C
series of Sentinel 1-A and 1-B Satellite images were acquired between 2019 and
2020 along ascending and descending orbit paths. The Line of Sight Sight (LOS)
displacement was determined for both satellite tracks, and then the LOS
displacement was projected to the vertical direction. The PS-InSAR derived
vertical displacement was then compared with GPS vertical displacement
magnitudes over three GPS stations in the area. It was observed that vertical
displacement velocity reached 20 cm/yr in Mountain Elgon. This displacement
rate showed that there are points in the region that are highly unstable. The
displacement velocity and magnitude in Bududa reached 6 cm/yr and 13 cm in two
years. This rate and magnitude showed that Bududa is highly unstable compared
with displacement velocities and magnitudes in landslide susceptible areas
globally. The displacement was generally subsidence over the observation
period. The vertical displacement estimated by PS-InSAR was comparable with GPS
based on the estimated RMSE. The vertical displacement was highest at slopes
between 32° and 60° and lowest between 0° and 9°. The vertical ground
displacement was highly correlated with the rainfall
that was received. The soil texture in Bududa has high clay content, with clay
layering hence low drainage rates, field capacity, saturation and bulk density.
It was observed that ground displacement was highly influenced by slope,
rainfall and soil texture. Displacement could be estimated in three dimensions
using PS-InSAR in the future if sufficient SAR images in ascending and
descending tracks are made available with significantly different geometries.
This would add to the knowledge of displacement patterns in the east and north
directions at a large spatial scale.