KURIT HISTORICAL DAM: AN ILLUSTRATING EXAMPLE OF COPING WITH UNCERTAINTIES

The Kurit arch-gravity dam near Tabas, Iran is especially remarkable for its extraordinary height of 60 m. This was to remain a world record for any type of dam from 1350 until early 20th century. Dr. Pircher, the former president of the ICOLD has referred to the Kurit dam as one of the most astounding achievement in dam engineering in the middle ages. Despite the fact that the dam was built 650 years ago, it still serves as an illustrating example of harmony with floods, sustainable development and coping with uncertainties: The overtopping resistance of arch masonry dam was vital to it’s safety, as the dam had no spillway and the dam builders of 650 years ago could not possibly foresee the extreme floods probable during the life of the structure. In this regard, integration of erosion resistance of masonry and geometry of the dam contributed greatly to the safety of the dam during floods. It is estimated that the Kurit dam has been overtopped for more than 1000 times in 650 years. No diversion tunnel was required as the dam was built on a brick arch in the narrow canyon. The lower part the dam was constructed during a dry season. This creative scheme has been used in many historical dams in Iran. The dam was constructed in four stages. In the final stage, the dam was heightened by 4 m around 1850. The stage construction was extremely crucial in increasing the useful life of the dam in view of sedimentation in the reservoir. On the other hand, stage construction was essential in view of structural, geological, hydrological uncertainties and technical limitations. The Kurit dam was built in a very narrow canyon and its crest length reached only 80% of the height. Accordingly selection of arch configuration minimized the thickness and volume of the dam (the crest thickness is only 1.2 m). Otherwise the construction of the dam would have not been feasible due to difficult access to the site. The Kurit dam has experienced the Tabas earthquake with a magnitude of 7.8 (.7g) without even minor damage in 1978. 25000 people were killed in the earthquake in the thinly populated region. The periodic sediment flushing through a 22-meter high intake tower increased the useful life of the dam substantially and ensured sustainable development. In view of uncertainties resulted from climate change and ever-increasing importance of cost effective dams, the construction and operation of Kurit dam could inspire many dam engineers all over the world. This great human heritage has been achieved through creative innovations and teamwork and there was little unnecessary cost in the construction. Consequently the Kurit dam can also be considered as an illustrating example of intuitive Value Engineering.