1. Professor, Dept. of Biological and Agricultural Engineering and Zachry Dept. of Civil Engineering, Texas A&M Univ., College Station, TX 77843-2117.
2. Professor, Marine and Environmental Sciences Centre, 3030-788 Coimbra, Portugal; Dept. of Civil Engineering, Faculty of Sciences and Technology, Univ. of Coimbra, Rua Luís Reis Santos, Campus II, 3030-788 Coimbra, Portugal (corresponding author).