Introducing the remote sensing of hazardous terrain

Abstract

With human population and associated environ-mental degradation continuing to increase, it isinevitable that more and more people will be livingin zones of hazardous terrain, and therefore the riskof disaster will increase. Add to this the growingevidence for global warming and the increasedseverityofgeohazardsrelatedtolargerandmorefre-quentstorms(i.e.stormsurges,coastalerosion,land-slides, fluvial flooding, erosion) and both thefrequency and severity of disasters is set to increase(e.g. Kesavan & Swaminathan 2006; Smolka 2006;van Aalst 2006).Remote sensing (measuring and mapping theEarth’s surface from aircraft or satellites) can helpus to rapidly assess, and therefore better manage,geohazards. Remote sensing and hazardous terrainmapping can play key roles in the managementand mitigation of natural disasters (e.g. Cutter2003; Zeil 2003), with applications grouped intothree main stages.(1) Pre-disaster. Maps showing the distri-bution of geohazards and their relative severitiescan be used by key decision makers in government,the insurance industry and the local population, tominimize the danger to people and infrastructure.For this stage, geomorphological mapping basedon stereoscopic aerial photography has beenwidely used for many years (e.g. Verstappen V Doornkamp et al. 1979;Mantovani et al. 1996). A new development ismapping based on spectral responses and digitalelevation models (DEMs), either regionally usingsatellite sensors (e.g. Liu et al. 2004; AndrewsDeller 2006; Theilen-Willige 2006), or in detailusing airborne hyperspectral sensors and laser alti-metry (e.g. Brown 2004; Deronde et al. 2004). Fur-thermore, early warnings of disasters caused byslope instability, seismic activity or volcanic erup-tion should be feasible within a few years, usingconstellations of radar satellites to detect grounddeformation (e.g. Kerle & Oppenheimer 2002;Bruno et al. 2005; Singhroy 2006).(2) Event crisis. With the onset of a disaster,medium-resolution (15–250 m pixel) satelliteimagery (e.g. Landsat or MODIS) is useful forassessing the regional extent and relative severitiesof the various impacts. With rapid-onset disasters,such as earthquakes, explosive volcanic eruptionsor landslides, aerial photography or very high resol-ution(0.5–2 mpixel)satelliteimagery(e.g.Ikonos,Quickbird) is needed to assist rapid search andrescue operations. A useful summary of remotesensing applications in the emergency response toa major disaster, the 2004 Sumatra earthquake andIndian Ocean tsunami, has been given by Kelmeliset al. (2006).(3) Post disaster. Geomorphological and geo-ecological mapping, based on the interpretation ofaerial photography or spectral and DEM data fromsatellites, can assist disaster recovery by highlight-ing locations with essential resources (e.g. water,wood fuel) and materials for reconstruction, suchas timber and sand–gravel or clay deposits. Earthresource maps of Banda Aceh, produced by theBritish Geological Survey in the 1970s, were veryuseful in the reconstruction of that region after the2004 earthquake and tsunami (M. Culshaw, pers.comm. 2005).The hazardous terrains examined in this publi-cation include landslides, flooding, contaminatedland, shrink–swell clays, subsidence, fault zonesand volcanic landforms (Table 1). Featured remotesensing systems include aerial photography,thermal scanning, hyperspectral sensors, laser alti-metry, radar interferometry and multispectral satel-lites, notably Landsat and ASTER. Relatedtechniques, such as the processing of DEMs anddata analysis using geographical informationsystems (GISs), are also discussed.The coverage starts with tectonic geohazards,then moves on to ground instability and flooding,before finishing with linear engineering projectsand disaster management. Kervyn et al. provide acomprehensive review of optical and radarapproaches to the satellite remote sensing of volca-nic terrain, with case studies from Hawaii and theRungwe rift valley of Tanzania. Next, the thermalproperties of Iceland’s Gri´msvo¨tn volcano areexamined by Stewart et al.developments in Newsatellite radar interferometry, which can detectmillimetre-scale ground deformation, are presentedby Reidmann & Haynes, who give examples fromTurkey’s 1999 Izmit earthquake and subsidence inRussia. Dowman & Balan provide a new approachfor correcting errors that occur when linkingtogether DEMs produced by the Shuttle Radar