Commonly applied in Poland, the Błaszczyk equation of 1954 for design rainfall is based on not quite reliable data and the approach presented therein raises serious doubts concerning the correctness of the method. Of course, not only the scarcity of the then data bases should be taken into account, but also computational difficulties existing in those years. However, independently of these problems, there was no rationale for accepting 67 years as the length of the observation series when the actual number of observation years was 37. As a consequence, the resulting design rainfall intensities for given exceedance probabilities were lower than the values that would be obtained if the correct length of the observation series had been adopted. There is also second critical point of the discussed method: the estimation procedure of the model parameter is incompatible with that presented in the paper and, moreover, is clearly erroneous. ...
The Chomicz model of 1953 for DDF curves, used in Poland mainly as a comparative model, is based on not quite adequate data and the approach presented by Chomicz was not substantiated enough, which raises serious doubts on the correctness of the method. Of course, the scarcity and relevance of the then data bases should be taken into account. However, independently of that problem, there are substantial reservations about the correctness of the design rainfalls developed by Chomicz for exceedance probabilities 10%, 20%, 50% and 100%. The most significant reservation concerns the correctness of the method of extending measured rainfall depth over its measured duration. The method can hardly be accepted, because it assumes that that the greatest rainfall interval intensity occurs in the end of the rainfall event, which is not supported by observations. Moreover, the number of extended rainfall depths, i.e., the number of semi-empirical values, used to develop the model of design rainfall, increases strongly with rainfall duration doubling the number of original data in the extreme case of the longest duration of 180 minutes. Also, no rationale is given for adopted criterion for the time limit of rainfall extension over the measured duration. ...
