Work presented here consists of two parts: the first part, presented before as a separate paper (Niemczynowicz 1984b), described studies performed on conceptual catchment, the second part presented here describes studies made on real catchments in the city of Lund.

The scope of the paper is to use previously calculated statistical characteristics of rainfall movement in Lund for quantitative description of the influence of storm movement on runoff modeled on real catchments in Lund. The relations between rainfall characteristics and the magnitude of directional bias are shown. The special interest in this study is to locate the combination of factors which maximize the effect of directional bias. Finally, by combination of rainfall movement statistics with modeled runoff, the probability distribution of directional bias for differently oriented catchments in Lund is given.

The most important conclusion is that the maximal directional bias observed for real catchments is much smaller than for the conceptual catchment, but still can reach significant values. The maximal bias occurs when the rainfall movement is parallel to direction to conduits and when rain velocity is close to average flow velocity. The highest values of directional bias occur for storms with short durations which give low peak flow discharge without practical importance. Still, the phenomenon of the directional bias can be one of the reasons why frequency of the rainfall does not follow frequency of runoff.

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