Preprint/Prétirage Landslide Risk Assessment with High Spatial Resolution Remote Sensing Satellite Data V.H.Singhroy Canada Centre for Remote Sensing Ottawa, Canada K1A0Y7 vern.singhroy@ccrs.nrcan.gc.ca J.E. Loehr and A.C. Correa Center for Environmental Technology Dept. Civil and Environmental Engineering University of Missouri-Columbia Columbia, MO 65211-2200 USA eloehr@missouri.edu ; CorreaA@missouri.edu ABSTRACT Landslide identification and mapping are essential for landslide risk and hazard assessment. This paper reports on the uses of remote sensing techniques for mapping landslide areas ranging in size from large to small. High-resolution stereo SAR and optical images are providing useful information for detailed mapping of large landslides, however mapping of smaller scale slides still requires extensive use of airphotos and fieldwork. INTRODUCTION Landslides are mass movements of soil or rock down slope and are a major natural hazard, because they are widespread. Globally, landslides cause approximately 1000 deaths a year with property damage of about US $4 billion (ISU, 1993). Landslides pose serious threats to settlements, structures that support transportation, natural resources management and tourism. They do considerable damage to lifelines and especially to highways, railways, waterways and pipelines. They commonly occur with other major natural disasters such as earthquakes and floods caused by heavy rainfall. Damage from landslides and other ground failures have sometimes exceeded damage directly related to earthquakes. In many cases, expanded development and unwise human activity, such as modified slopes and deforestation, can sometimes increase the incidence of landslide disasters. The pressure for continuing development in urban areas many times leads to expansion upon unstable terrain. This has thrown many urban communities into disarray, providing grim examples of the extreme disruption caused by ground failures. Minor landslides, more appropriately referred to as small-scale slope failures, do not cause the catastrophic damage of large-scale landslides. Small slides frequently occur in compacted embankments constructed for highways, levees, and small earth dams and can also occur in shallow cut slopes. They occur both in hilly or mountainous terrain and in areas with rolling or flat topography. While small slides generally pose little direct threat to human well being, maintenance and repair of these slides constitutes a tremendous economic burden due to the extremely high number of small slides encountered. Because of the non-threatening appearance of minor slope failures very little data is available to define how extensive the problem is and the impact they have on our lives. However, the U.S. Transportation Research Board (1996) recently reported that annual maintenance costs incurred for repair of minor slope failures by state departments of transportation that have kept “good maintenance records” was more than $100 million! This amount equaled or exceeded the costs for repair of major slope failures by these agencies. LARGE-SCALE LANDSLIDES Methodology Aerial photography has been used extensively to characterize landslides and to produce landslide inventory maps, particularly because of their stereo viewing capability and high spatial resolution. Airphotos were used to identify steep slopes underlain by weak soils, slopes undercut by rivers and waves, tension cracks, steep hummocky topography, failed surface scarps, anomalous bulges and lumps, terraced slopes, discontinuous bedding planes, drainage vegetation patterns and elongated ponds on hillslopes (Alfoldi, 1973;Mollard, 1977; Nilsen and Brabb, 1977; Cruden and Lu, 1992; Savigny, 1993;).