An analysis of energy expenditure in Goodwin Creek


  • Peter Molnár,

  • Jorge A. Ramírez


The local optimality hypothesis that natural river systems adjust their average channel properties toward an optimal state in which the rate of energy dissipation per unit channel area, Pa, is constant throughout the river network is explored on an analysis of Goodwin Creek, Mississippi. River network parameters describing the variation of channel forming and maintaining discharge, channel downstream hydraulic geometry, bed slope, and sediment concentration as a function of cumulative drainage area are estimated from Goodwin Creek data. Optimal channel characteristics that produce constant Pa are determined and superposed onto the digital elevation model-;extracted river network with reach averaged bed slopes, and the spatial distribution of the energy dissipation rate Pa throughout the network is analyzed. Channel reaches with average energy dissipation rates different from the constant value of the optimal network are identified. We argue that these reaches are potentially unstable relative to the remainder of the network, and that their average channel properties will adjust in the direction of constant Pa. Qualitative statements are made about the direction of this adjustment through differences between the observed and optimal channel widths, and comparisons are made with recent observations of channel change in Goodwin Creek. This energy expenditure analysis suggests that the hypothesis of local optimality can be a useful tool for studying the relative stability and potential channel adjustment of river networks.