The Attenuation Rate of Response Intensity in Fluvial Channels

Natural fluvial channels are usually in dynamic equilibrium state, while disturbances caused by human activities such as dam closure tend to destroy the previous equilibrium state and trigger the reformation processes of fluvial channels. Considerable adjustment in downstream reaches of dam site may lead to severe hazards, therefore, how to accurately predict the readjustment processes of lower channels after dam closure has always been a critical issue. Generally, the readjustment process of fluvial channels induced by external changes is called as “response”. Herein, we define the adjustment rate of river characteristic parameter as “response intensity”. Obviously, the change characteristics of “response intensity” is a dominant factor which influences the reformation process of fluvial rivers after external disturbances. In this paper, based on a set of field data recorded after dam closure in the lower reaches downstream of several dams in America, critical hydrological factors related to the temporal attenuation coefficient of “response intensity” are investigated comprehensively. The results show that the attenuation coefficient of “response intensity” is closely associated with the relative change rate of average annual peak discharge and an empirical relationship between the attenuation coefficient of “response intensity” and the relative change rate of representative discharge before and after dam construction is established. In addition, it is discovered that the attenuation coefficient and distance from the disturbance point presents good non-linear negative correlation, and the universal expression of non-linear fitting curves which are obtained through equation transformation can accurately describe the change process of attenuation coefficient with distance to dam site.

Keywords: Fluvial channels; response intensity; attenuation coefficient; dam closure.