“…Designing the width of prairie strips requires an estimate of the variation of concentration with distance. Contaminant removal in VFS and urban stormwater treatment systems is frequently estimated using first‐order decay kinetics (Elliott & Trowsdale, 2007; Lerch et al, 2017; Olilo, Muia, et al, 2016; Olilo, Onyando, Moturi, Muia, Ombui, et al, 2016; Olilo, Onyando, Moturi, Muia, Roegner, et al, 2016; Wong et al, 2006) due to its apparent behavior to be weighted to the influent end of the treatment. Inspection of concentration data from Coyne et al (1998), for example, shows that surficial concentration reductions through VFS closely follow a first‐order decay model, written as:where C 0 is the concentration of a contaminant initially entering the prairie strip or VFS, x is the distance from the entrance to the downstream sampling location, C is the concentration at location x , and a is a lumped removal parameter.…”