HR: 0800h
AN: H41A-0291    [Abstracts]
TI: Longitudinal Dispersion In Rivers With Floodplains
AU: * Deng, Z
EM: zdeng@lsu.edu
AF: Louisiana State University, Department of Civil and Environmental Engineering, Baton Rouge, LA 70803 United States
AB: A new method is developed for predicting the longitudinal dispersion coefficient in rivers with floodplains. It is found that the longitudinal dispersion in natural rivers with floodplains is significantly enhanced and it displays complicated behavior. When discharge Q is smaller than the bankfull one, the longitudinal dispersion coefficient Kx increases with Q continuously. A discontinuity characterized by a sudden increase in Kx occurs when flow exceeds bankfull level corresponding to the bankfull discharge Qb. The extent of the discontinuity of dispersion coefficients depends on the ratio of the water surface width of the floodplain flows to the top width of the main channel. The dispersion coefficient Kx decreases rapidly and nonlinearly with increase of discharge when Q is greater than Qb and then reach a minimum value Kmin at a discharge Qmin. Kx increases linearly when the discharge increases further. A linear equation of regression for estimating the longitudinal dispersion coefficient is presented for flood flows with Q being greater than Qmin. Moreover, an expression is derived for determining the minimum longitudinal dispersion coefficient Kmin. These findings are of practical significance for the management of floods and river water quality. The predictions of the new method are consistent with field measurements.
DE: 1821 Floods
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting