Effects of drought on historical bridges. The case of Khaju Bridge on Zayanderood river in Isfahan, Iran

The city of Isfahan located in the middle of Iran and well known for “Zayanderood” which passes through it, is experiencing long periods of drought of the river. It has been observed that subsidence, which is one of the direct consequences of the phenomenon of drought is affecting not only the vicinity of river but also a rather large region. The phenomenon of drought has also other aspects and consequences which should not considered as separate issues. This study after providing a history of the context of Isfahan, tries to study the problem and its cause and effects not only technically but also from other perspectives such as social and economical. The technical part of the study is devoted to proposing techniques or methodology containing monitoring the soil and structure under observation (Khaju bridge). Khaju bridge is one of the 5 bridges on the river of Zayanderood and the technical suggestion could be applied to other bridges as well facing the same problems. The study shows that one of the main reasons that the city is experiencing harsh situations is the human-based activities and as the main cause is the decrease of groundwater level one of the main initial steps is also devising plans to bring back the water to the river. As well, there are some techniuqes that should be used for reinforcing the soil and structure since it takes time to reach a secure level. At the end there are suggestions, considering the historic role of the bridges in the city to enhance their vision inside the city.