C Cofferdam Qin Qian 1 , Saeid Eslamian 2 , Kaveh Ostad-Ali-Askari 3 , Maryam Marani-Barzani 4 , Farnaz Rafat 5 and Ali Hasantabar- Amiri 6 1 Civil & Environmental Engineering, Lamar University, Texas State University System, Beaumont, TX, USA 2 Department of Water Engineering, Isfahan University of Technology, Isfahan, Iran 3 Department of Civil Engineering, Isfahan Branch, Islamic Azad University, Isfahan, Iran 4 Department of Geography, University of Malaya (UM), Kuala Lumpur, Malaysia 5 Department of Civil Engineering, Khomeinishahr Branch, Islamic Azad University, Isfahan, Iran 6 Department of Civil Engineering, Lenjan Branch, Islamic Azad University, Isfahan, Iran Synonyms Coffer; Temporary dam Definition A temporary watertight enclosure built for specialized con- struction below water level. Introduction Construction in water is a difficult and dangerous job that requires a dry working surface. Cofferdams are one type of temporary structures designed to keep water and/or soil from the execution of construction at a site, so that the permanent facility/structure can be constructed in water (Anderson 2001). A cofferdam should have waterproof walls more than 1 m higher than the maximum water level to ensure that water does not enter the opposite side. Cofferdam design and con- struction involve the consideration of the structure, local soil and water conditions, often construction offshore, and the possibility of severe weather during construction. The hydro- static force of the water and the dynamic force due to currents and waves must be considered in the design. Cofferdams can be classified by their material as earthen, rock-fill, sing-walled, double-walled, braced, and cellular cofferdams https://theconstructor.org/water-resources/types- of-cofferdams-construction-details/13807/: • Earthen cofferdams are used at locations with a water depth less than 3 m and low current velocity. They are built using the locally available soil. The slope is usually 1:1 or 1:2. Rubble stones are pitched on the waterside to protect the embankment. • Rock-fill cofferdams are preferentially built at locations involving rock. The dam height is up to 3 m, and the slopes are at 1:1.5 to 1:1.25. Rubble stones are also pitched on the waterside to protect the dam from wave action. • Single-walled cofferdams are commonly used for at bridge construction sites and can prevent water intrusion for depths more than 6 meters. They are constructed with wooden or timber sheets placed into the river bed along the perimeter of the area of construction. Steel or iron sheets are also driven into the river bed and placed inside the wooden or timber sheets at equal distances. • Double-walled cofferdams are typically used when the construction site area is large and water depth is high. Use of single-walled cofferdams becomes uneconomical due to increasing supports. The difference between single wall and double wall cofferdams is that two walls provide extra stability and can hold water as high as 1 2 m. • Braced cofferdams are used when driving piles into the bed under the water body is difficult. Two piles are driven into the bed and are laterally supported with the help of wooden cribs installed in alternate courses to form pockets. # Springer International Publishing AG 2018 P.T. Bobrowsky, B. Marker (eds.), Encyclopedia of Engineering Geology , https://doi.org/10.1007/978-3-319-12127-7_59-1