1. Researcher, National Research Council, Institute for Geo-Hydrological Protection, Via Madonna Alta 126, 06128 Perugia, Italy.
2. Ph.D. Student, National Research Council, Institute for Geo-Hydrological Protection, Via Madonna Alta 126, 06128 Perugia, Italy.
3. Caroline and William N. Lehrer Distinguished Chair in Water Engineering, Professor of Civil and Environmental Engineering, and Professor of Biological and Agricultural Engineering, Dept. of Biological and Agricultural Engineering, Texas A & M Univ., 2117 TAMU, College Station, TX 77842-2117.