. (12)
In the above equations, θ s is the saturated water content, θ i is the initial water content,Δθ =θ s-θ i is the increase in water content, 𝐾s is the saturated permeability coefficient (cm/min), K is the unsaturated permeability coefficient (cm/min), s f is matric suction and H is the height of surface water accumulation (cm).
The model was used to predict the depth of water infiltration through bioretentions in loess. And this is an unsaturated infiltration process; it is difficult to obtain the unsaturated permeability directly. During the test, the cumulative infiltration I at different timest was as shown in Fig. 13. The correlation between t andI based on relevant soil parameters is expressed in Eq. (13). The average infiltration rate S was determined to be 1.698 according to Eq. (13).
[Insert Figure 13]