Arab J Sci Eng DOI 10.1007/s13369-017-2599-7 RESEARCH ARTICLE - CIVIL ENGINEERING Experimental Analysis of the Scour Pattern Modeling of Scour Depth Around Bridge Piers Mujahid Khan 1 · Muhammad Tufail 2 · Muhammad Ajmal 3 · Zia Ul Haq 3 · Tae-Woong Kim 4 Received: 1 July 2016 / Accepted: 7 May 2017 © King Fahd University of Petroleum & Minerals 2017 Abstract Bridge pier scouring measurement in the field, especially during flood season, is very difficult. This study experimentally investigated the pier scour pattern to find better alternatives to represent the actual field conditions. For this purpose, piers of different shapes (circular and square) and different sizes were modeled in the labora- tory. The contour maps were drawn to check the extent of possible damage caused by scouring. Under the same laboratory flow conditions and sediment properties, scour depth resulted from square-shaped piers was more evident compared to circular piers and pier geometry. It was also evident that the scour depth increases with an increase in pier size. The contour maps could reflect different flow conditions, sediment, and pier geometry. The scouring pro- cess could identify the extent of remedial measures needed. The models developed were regression, artificial neural B Muhammad Ajmal engr_ajmal@uetpeshawar.edu.pk Mujahid Khan mujahidkhan@uetpeshawar.edu.pk Muhammad Tufail tufail1@msn.com Zia Ul Haq ziahaq72@gmail.com Tae-Woong Kim twkim72@hanyang.ac.kr 1 Department of Civil Engineering, University of Engineering and Technology, Peshawar 25120, Pakistan 2 Dubai, United Arab Emirates 3 Department of Agricultural Engineering, University of Engineering and Technology, Peshawar 25120, Pakistan 4 Department of Civil and Environmental Engineering, Hanyang University, Ansan 15588, Republic of Korea network (ANN), and genetic function (GF) based, and the results obtained from these models were compared with the experimental data. From the models comparison based on coefficient of determination ( R 2 ), the dimensional variables- based regression, ANN, and GF models depicted R 2 values as 0.38, 0.64, and 0.67, respectively, which were inferior to the corresponding R 2 values of 0.80, 0.95, and 0.97 for models developed using non-dimensional input variables. Overall, GF-based model performed better than the rest of the models not only because it gave higher R 2 values and less measured error but also because it resulted in more simple, compact, and explicit expression for bridge pier scour. Keywords Bridge pier scour modeling · Pier scour depth · Scour hole dimensions · Artificial neural network · Genetic function List of symbols d 50 Median size of bed material (mm) b Pier width y Flow depth V Flow velocity d s Scour depth 1 Introduction Bridge scour is the lowering of the stream bed at around the bridge pier and abutment and is considered as the biggest cause of bridge failure resulting in very high reconstruction cost. Its underprediction can result in bridge failures and pos- sibly loss of human lives, while overprediction may result in 123