LANDSLIDE DETECTION USING INSAR TECHNIQUES ALONG THE COASTAL BLUFF OF LAKE MICHIGAN

Over the years landslide-related losses in residential, commercial and governmental properties were reported along the coastal bluff of Lake Michigan. These have been attributed to one or more of these factors: wave action, fluctuation in groundwater levels, and storm events. In this project, we compare findings from radar interferometric studies with reported historical landslides along the bluff of Allegan County in Michigan. The adopted procedure entails five main steps. Firstly, detecting and measuring the slope subsidence velocity rates along the line of sight using radar persistent scatter interferometric techniques (PSI) and Persistent Scatters Small Baseline Subset Technique (StaMPS-SBAS) applied to ESA's European Remote Sensing (ERS) satellites, ERS 2 (spatial resolution: 25 m) that were acquired in 1995 to 1998. Secondly scenes were selected taking in account a spatial baseline threshold of less than 1300 m and temporal baseline threshold of less than 560 days. Thirdly, topographic and orbital phase contributions were removed using 1-arcsecond SRTM DEM and precise orbital records from Delft precise orbits and radar coordinates were geocoded to the WGS84 using the same DEM that used earlier. Fourthly, the study area (965 km²) was delineated using a buffer zone that defines areas with steep slopes (> 60 degrees) that are either proximal (< 80 m) to the Lake shoreline of Allegan, or proximal (< 100 m) to rivers draining into the Lake. The final step involves spatial correlations within a GIS environment, between the radar-based land deformation results and other relevant datasets (e.g., distribution of streams, lakes, and sand dunes, lithology, and topography). Findings include: (1) high subsidence rates (up to -5 mm/yr) were found in several locations (e.g., Miami park south, northern Miami park, Fabun roads, the 116^th avenue along the western Allegan county shorelines) (2) the radar-based subsidence locations coincided with the historical landslide locations within the strip of western Allegan County shoreline (~ 10-16 miles between the cities of South Heaven, near the 104^th avenue, Miami park, Fabun road, southern 114^th avenue, and the 116 avenue).