Qanat hazard in Iranian urban areas: explanation and remedies

This article explains the qanat hazard in Iranian urban areas. Each qanat consists of an underground gallery (tunnel) which conveys groundwater to the surface, and several to tens of vertical wells (shafts) which provide access to the gallery. It is estimated that about 10,000 km qanats with 300,000 wells lie under Iranian urban areas. Their number under urban areas of the other countries containing it seems to be significant as well. In Iran, subsidence and other problems related to shafts and galleries of hidden qanats impose millions of dollars damage annually. Despite the importance of the qanat hazard, it has not yet received enough attention from scholars. In this article, qanat hazard as a special kind of geological hazard is explained from such aspects as the causes, the extents, the impacts and the various remedies to combat this hazard. Remedies to abate this hazard should include hazard assessment, risk assessment and risk reduction phases. Generally, the most efficient strategy is to detect qanats using aerial photos, maps or inquiring local people and construct the buildings in hazard-prone areas with spread footing foundations. However, this is not applicable in all occasions. So, depending on conditions, some other strategies which are provided in the text may be more effective.