Based on the simplified model for estimating the clogging time which was made by Rowe and Fleming

the assumptions and derivations are developed reasonably due to the time-space distribution of clogging in drainage layers; and a simplified model is obtained which can reflect the development of clogging and the variation of hydraulic conductivity of the drainage layers. Using the cell analysis of water balance

a method for calculating maximum liquid depth in drainage layers which is based on the maximum liquid depth clogging model is proposed. Comparing with the steady and transient results

it is shown that no clogging results are in accordance with the transient results

which all tend to the steady results. And the clogging must be considered when clogging is serious which may affect the liquid depth markedly. Parameter analysis shows that the greater previously (the smaller later) the hydraulic conductivity

the longer the drainage distance

the faster the infiltration rate

the higher the concentration

the more serious the impact of clogging on liquid depth. At the same time design suggestions are proposed for improving the drainage system.