The most frequent disasters in Saudi Arabia are flash floods, earthquakes, volcanism, especially submarine volcanism causing tsunamis in the Red Sea and submarine mass movements, dust storms and droughts. As the consequences and effects of the climate change will have an increasing impact on the intensity and occurrence of geohazards as flash floods, length of drought periods, or dust storms, the surveillance and systematic, continuous monitoring of these hazards and affected areas using satellite data and integration of the results into a GIS data base is an important issue for hazard preparedness. Over the last 30 years (1981–2011), floods have been the most recurrent disasters recorded in EM-DAT, with at least 300 events, indicating a strong need for early warning systems. The increase of the built environment and the enlargement of urban areas has lead to a great impact on the landscape in Western Saudi Arabia.
Visual interpretation and digital image processing of different satellite images, including radar images, combined with ASTER, SRTM (30 m resolution), and ALOS PALSAR DEM data (12 m) are used for the mapping and inventory of traces of past hazards. Causal or critical environmental factors influencing the disposition to be affected by hazards and the potential damage intensity are analyzed interactively, then, in a GIS database. The interactions and dependencies between different causal and preparatory factors can be visualized and weighted step by step in the GIS environment. Examples are presented how remote sensing and GIS methods contribute to the detection of the following geohazards in Western Saudi Arabia:
- Detection of areas prone to hydrological hazards such as flash floods causing flooding of roads and settlements
- Mapping of dust storms
- Mapping of coastal areas of the Red Sea prone to tsunami flooding and storm surge.
- Mapping of traces of volcanic activity
- Mapping of fault and fracture zones and structural features
- Mapping of local site conditions influencing earthquake shock in case of stronger earthquakes and of areas susceptible to earthquake related secondary effects such as compaction or rock fall.