Pm. Davis et Tc. Atkinson, Longitudinal dispersion in natural channels: 3. An aggregated dead zone model applied to the River Severn, UK, HYDROL E S, 4(3), 2000, pp. 373-381
An Aggregated Dead Zone (ADZ) model is presented for longitudinal dispersio
n of tracer in river channels, in which the channel cross-section is divide
d into two parallel regions: the bulk flow and dead zone storage. Tracer pa
rticles in the bulk flow are assumed to obey plug-flow advection at the dis
charge velocity U without any mixing effects. The dispersive properties of
the model are completely embodied in the residence time for tracer storage
in the dead zone. The model provides an excellent description and predictio
n of empirical concentration-time distributions, for times t > x/U. Its phy
sical realism is demonstrated by using it to describe the evolution of a tr
acer cloud in the River Severn, U.K., and by comparing it with a more compl
ex model which incorporates the additional effects of shear flow dispersion
within the bulk flow. The ADZ model is a potentially useful tool for pract
ical prediction of dispersion in natural channels.