Hazard mapping of karst along the coast of the Algarve, Portugal

The engineering geology of the West Algarve coastline between Cape St Vince nt in the west and Fare in the east varies considerably, from the high lime stone cliffs between Salema and Burgau to the lower but more problematic ka rstic cliffs around Lagos and east of Portimao. Geotechnical problems vary from toppling failure and rockfalls in the higher, more heavily jointed lim estone and sandstone cliffs between Salema and Burgau, to sinkhole collapse , subsidence and gullying within the Miocene calcarenites and Pleistocene s ands east of Portimao. This latter area is the subject of this paper. Field mapping was completed on scales of 1:2000 and 1:5000 to encompass geomorph ology, geology and vegetation cover. Both sinkhole and sea cliff formation controlling factors are discussed and subsequently nine factors affecting p otential hazard location are identified. The relative importance of these t en factors is determined and then each cell, 100 m(2) in size, is assessed for its individual score relative to the presence of, or degree of influenc e of each of the hazard forming processes. The resulting composite hazard m ap is aimed at planners and developers as a multipurpose map for general us e. (C) 1999 Elsevier Science B.V. All rights reserved.