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

摘要

The engineering geology of the West Algarvecoastline between Cape St Vincent in the west and Faro in theeast varies considerably, from the high limestone cliffs betweenSalema and Burgau to the lower but more problematic karsticcliffs around Lagos and east of Portimao. Geotechnical problemsvary from toppling failure and rockfalls in the higher, moreheavily jointed limestone and sandstone cliffs between Salemaand Burgau, to sinkhole collapse, subsidence and gullying withinthe Miocene calcarenites and Pleistocene sands east of Portimao.This latter area is the subject of this paper. Field mapping wascompleted on scales of 1:2000 and 1:5000 to encompassgeomorphology, geology and vegetation cover. Both sinkhole andsea cliff formation controlling factors are discussed andsubsequently nine factors affecting potential hazard location areidentified. The relative importance of these ten factors isdetermined and then each cell, 100 m2 in size, is assessed for itsindividual score relative to the presence of , or degree ofinfluence of each of the hazard forming processes. The resultingcomposite hazard map is aimed at planners and developers as amultipurpose map for general use.