1. Lecturer in Hydraulic Engineering, School of Civil Engineering and Geosciences, Newcastle Univ., Newcastle upon Tyne NE1 7RU, U.K. (corresponding author).
2. Senior Engineer, Dept. of Planning and Programming, Ministry of Water Resources of China, Beijing 100053, P.R. China.
3. Professor of Earth Systems Engineering, School of Civil Engineering and Geosciences, Newcastle Univ., Newcastle upon Tyne NE1 7RU, U.K.
4. Professor of Engineering Science, Dept. of Engineering Science, Univ. of Oxford, Oxford OX1 3PJ, U.K.