Effect of Water Withdrawal on Hydraulics and Morphology of Pumduang River, Thailand
Abstract The HEC-6 river morphological mathematical model is applied to predict the effect of water withdrawal from the Pumduang River on its water surface and bed profiles. The river is situated in the Surat Thani province in the south of Thailand. The HEC-6 model is calibrated and verified based on field data. After the model calibration and verification, the HEC-6 is applied to predict the effect of water withdrawal on changes in water level and bed level of the river. The predicted changes are compared with the results of a physical movable bed hydraulic model of scale 1:60. The agreement is found to be satisfactory. The equilibrium river bed and water surface profiles are determined for the annual average flow and the 2-, 10-, 25- and 100-year return period floods for the cases with and without water withdrawal. The water withdrawal of 16 percent of the average annual discharge of the Pumduang river is found to have no endangering effect on the flow and morphological condition of the river
Effects of Dam Removal: An Approach to Sedimentation.
Abstract : In recent years hydraulic structures such as dams have been removed due to deterioration, increased maintenance cost or obsolescence. Investigation of the hydraulic, hydrologic, and sediment transport consequences of the removal of these structures have been very limited, thus necessitating the establishment of analytical techniques and procedures to adequately predict these effects. To properly evaluate the development of techniques and procedures, a model must be selected that closely simulates the actual behavior of the phenomenon being modeled. A mathematical (HEC-6) was selected because of its success in the prediction of sediment transport when applied to a wide variety of cases. The removal of the Washington Water Power Dam on the Clearwater River near Lewiston, Idaho, was selected for study. Procedures and techniques of calibration and verification developed, comparison of actual and predicted volume of sediment transported, where the sediment scoured or deposited, and their rates are presented. There is discussion of the applicability of the model to this type of problem, limitations of a one-dimensional model, and interpretation of the results. (Author)
Annual floods and the partial‐duration flood series
Flood data are ordinarily listed either in annual-flood series or in a partial-duration series. If the expectancy of a flood in the duration series ϵ is known, then the probability of that flood being an annual flood is shown to be e−ϵ. From this relationship it is possible to transform recurrence intervals in the partial duration series to those in the annual-flood series. It is shown that for equivalent floods, the recurrence intervals in the partial-duration series are smaller than in the annual-flood series, but that the difference becomes inconsequential for floods greater than about five-year recurrence interval.