Tracking landslide displacements by multi-temporal DTMs: A combined aerial stereophotogrammetric and LIDAR approach in western Belgium
Introduction
The understanding of landslide mechanisms is greatly facilitated when information on their horizontal and vertical displacements is available. Geodetic techniques, recently in particular GPS, are commonly used to monitor ground motion with a high accuracy (Malet et al., 2002, Coe et al., 2003, Squarzoni et al., 2005, Brückl et al., 2006, Demoulin, 2006). However, they require access to the site and may be time-consuming if the information has to be densified, spatially and/or temporally. Moreover such studies generally encompass a time interval of a few years at maximum, thus providing poor information on longer-term landslide kinematics.
According to the scale, accuracy and resolution needed, several techniques of remote sensing are available to build digital terrain models (DTMs) of landslides (Mantovani et al., 1996, Metternicht et al., 2005). In the case of the Flemish Ardennes (Fig. 1), the ground displacements are rather small (in the order of few meters) and slow, and their reliable description requires a final DTM accuracy better than 1 m in the three directions. Several techniques such as GB_InSAR (Tarchi et al., 2003, Antonello et al., 2004), LIDAR (McKean and Roering, 2004, Chen et al., 2006, Glenn et al., 2006), GPS (Higgitt and Warburton, 1999, Nico et al., 2005, Demoulin, 2006), and aerial photogrammetry (Chandler, 1999, Hancock and Willgoose, 2001) are capable of supplying such accurate 3D topographic data. However, only the stereophotogrammetric analysis of aerial photographs can cover several decades of observation (Hapke, 2005).
The main objective of this research is to assess how reliable landslide small displacements can be measured from multi-temporal DTMs produced by aerial stereophotogrammetry. For this purpose, we used classical aerial photographs at scales ranging between 1:18 500 and 25 000 (Table 1), which required careful measurements at each step of the DTM production in order to reach a submeter accuracy (Kraus and Waldhäusl, 1994, Kasser and Egels, 2001). A detailed analysis of the precision, accuracy and reliability associated with each step of the DTM extraction procedure is therefore given. We present first the photogrammetric procedure applied to the photographs. Details on the subsequent DTM construction and on a LIDAR-derived DTM provided by the Flemish Government (DEM of Flanders, 2007) are also given. We then show how vertical and horizontal landslide motions can be inferred from DTM subtraction, focusing on one particular landslide, whose activity is well documented over the last 50 years.
Section snippets
Study area
In West Belgium, Van Den Eeckhaut et al. (2005) mapped more than 150 large deep-seated landslides within the loose Tertiary sediments of the hilly area of the Flemish Ardennes (Fig. 1). All landslides predate 1900 AD and might have been initiated under periglacial conditions, possibly in response to a seismic trigger associated with a period of heavy rainfall (Van Den Eeckhaut, 2006, Van Den Eeckhaut et al., 2007b). According to the Keefer's relation between maximum distance of landslides from
Photogrammetric operations
Aerial photographs are frequently used in digital photogrammetry to extract landslide relief (e.g. Oka, 1998, Weber and Herrmann, 2000, Kääb, 2002, Baldi et al., 2005, Casson et al., 2005, Hapke, 2005, Lantuit and Pollard, 2005). We selected only the aerial covers supplied by the National Geographical Institute (NGI) of Belgium that were taken at the beginning of the spring (when the trees are leaveless) in order to obtain a better restitution of the landslide areas under forest. We thus used
DTM construction
The captured elevation data were interpolated by ordinary kriging with the SURFER 8.0 software. Ordinary kriging is one of the most widely-used method in geostatistics and it has proved very effective in the interpolation of topographic data for the generation of DTMs (e.g. Siska et al., 2005, Chaplot et al., 2006). Through the use of semivariograms, the kriging method considers the spatial autocorrelation in the topographic data (Goovaerts, 1997). This interpolation method also allows the
Results: 1952–2002 evolution of a typical landslide
As an example, we detail the movements recorded for the landslide 1 of the Leupegem hill (Fig. 1). According to size and lithology, this landslide is representative not only of those of the Leupegem and Rotelenberg hills but also of those of the whole Flemish Ardennes (Dewitte and Demoulin, 2005). Moreover, its reactivation in February 1995 caused comparatively large ground displacements, and eye-witness reports of its evolution over the past 50 years are available (Van Den Eeckhaut et al.,
Conclusion
This research aimed at describing and understanding the kinematics of small landslide reactivation in the Flemish Ardennes through the use of multi-temporal DTMs. It demonstrated the effectiveness of multi-temporal DTMs, constructed from aerial stereophotogrammetry using standard photographs and airborne LIDAR data, in retrieving small ground displacements over a period of several decades, and discussing the superficial and inner landslide kinematics.
An example of ground motion analysis has
Acknowledgements
We gratefully thank V. Havart, D. Weverbergh, and T. Steux for their technical support during the photogrammetric analysis. We also thank the editor and two anonymous reviewers for their relevant comments that helped in improving the manuscript.
References (50)
- et al.
Monitoring the morphological evolution of the Sciara del Fuoco during the 2002–2003 Stromboli eruption using multi-temporal photogrammetry
ISPRS Journal of Photogrammetry and Remote Sensing
(2005) - et al.
Surface motion of mountain glaciers derived from satellite optical imagery
Remote Sensing of Environment
(2005) - et al.
Kinematics of a deep-seated landslide derived from photogrammetric, GPS and geophysical data
Engineering Geology
(2006) - et al.
Quality assessment of remote sensing image registration — analysis and testing of control point residuals
ISPRS Journal of Photogrammetry and Remote Sensing
(1997) - et al.
Seventeen years of the “La Clapiere” landslide evolution analysed from ortho-rectified aerial photographs
Engineering Geology
(2003) - et al.
Accuracy of interpolation techniques for the derivation of digital elevation models in relation to landform types and data density
Geomorphology
(2006) - et al.
Topographical changes revealed by high-resolution airborne LiDAR data: the 1999 Tsaoling landslide induced by the Chi-Chi earthquake
Engineering Geology
(2006) - et al.
Seasonal movement of the Slumgullion landslide determined from Global Positioning System surveys and field instrumentation, July 1998–March 2002
Engineering Geology
(2003) - et al.
Analysis of LiDAR-derived topographic information for characterizing and differentiating landslide morphology and activity
Geomorphology
(2006) - et al.
Applications of differential GPS in upland fluvial geomorphology
Geomorphology
(1999)