Author(s): F. Taaffe; S. Gray; A. Sharma; M. Babister

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Keywords: Direct Rainfall Model; Loss Model; Pit Cells; Rainfall Runoff Modelling

Abstract: The direct rainfall approach, a relatively recent method in rainfall runoff models, is commonly combined with traditional loss models that subtract a depth of rainfall from the hyetograph prior to its application. The direct rainfall method removes a second loss value; by applying rainfall to each cell of the DEM, it removes a depth of rainfall via the pit cells in the DEM. The relative effect of this second loss mechanism is examined here, to ascertain whether losses may be being accounted for twice. The effect was measured by determining the depth of rainfall captured by pit cells in several DEM, as well as the effect pit cells may have on the outlet hydrograph. Pit cells in the DEM were found to remove a depth of water that acted as a second loss mechanism when a traditional loss model was also applied, as well as potentially severely attenuating the peak discharge at the catchment outlet. As the effect was found to vary between catchments, as well as with DEM resolution, it was concluded that the behaviour of losses in a direct rainfall model is inherently complex and requires a high degree of user familiarity and expertise.

DOI:

Year: 2011