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Remote sensing and GIS techniques, with other available different geological data are essential tools in detecting geo-hazards of different types and to check their activities and define their potential areas. Their effect on nearby sites could also be estimated and mitigated by certain precautions.
Landsat 7ETM+, aerial photographs, topographic, geologic and geophysical maps of different scales are used to detect geo-hazard areas caused by karstification in Jazira vicinity, western part of Iraq. Also to detect different karstification phases, trends of abandoned valleys and location of active karst areas. Different combinations of many bands like 7,4,2 and 5,4,2 and GIS extensions are used to achieve the best results.
The Jazirah vicinity, west Iraq is characterized by dense karstification, due to exposure of gypsum beds, which are one of the main lithological constituents with limestone and marl beds forming cyclic deposits of the Fat`ha Formation (Middle Miocene). Different forms of karst with different shapes and sizes are developed, among them are sinkholes and dolines. The latter form large salt marshes, the largest one in the study area is called Ashqar Salt Marsh.
Two main lineaments of NE ? SW trend and length of more than 100 Km form the limits of a densely karstified area in which the Ashqar Salt Marsh, beside many others are located. Along the two lineaments escarpment of height (5 ? 12) m is developed, especially the southeastern lineament. Collapses in different phases, leading to development of large salt marshes and different karst forms, changing the trend of main branches of wadi Tharthar ( the main valley in the study area) and controlling the trend of many valleys are characteristic features , within the study area.
Three main phases of karstification are indicated, in the study area within which is a big site. The latest phase is still active, which may cause a lot of problems to any existing structures or those which will be build. The trends of abandoned valleys are detected and many potential areas for active karstification are detected too.
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