Correction methods for dropping of simulated water level utilising Preissmann and MOUSE slot models

The Preissmann slot model and the MOUSE slot model have been widely used to simulate a pressurized flow in urban drainage sewer pipe systems. In the runoff simulations utilizing theses two models, the slot width is often widened to make the computational time increment large and save the computing time. The resulting simulated water level, however, is likely to decrease to the extent that the simulated water level can not be considered for practical use. The main reason for the tendency mentioned above, in the case of the Preissmann slot model, is that the discharge through the slot, in which the friction loss is not taken into account, increases considerably according to the enlargement of the slot width, and the main reason, in the case of the MOUSE slot model, is that the excess storage of runoff water in the slot increases to a considerable extent according to the enlargement. In this paper, firstly, two correction methods that can improve the accuracy of the runoff simulations are proposed for the Preissmann slot model and the MOUSE slot model respectively. Secondly, the adaptabilities of the methods are examined through numerical runoff experiments.