1. Visiting Assistant Professor, Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata, West Bengal 700108, India.
2. Professor and Goodrich Chair of Excellence, Dept. of Civil and Environmental Engineering, Director Hydraulics and Sedimentation Lab, Univ. of Tennessee, Knoxville, TN 37996-2313.
3. Professor, Dept. of Civil Engineering, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India; Adjunct Professor, Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata, West Bengal 700108, India (corresponding author).