Development of consistent design storms

Abstract

Design storms are the basic input for hydrologic assessment and design of the flood control structures. Small and medium sized catchments with shorter concentration times require design storms of shorter, sub-daily, duration, that are defined from the rainfall depth - duration - frequency (DDF) relationships. The DDF relationships are developed by statistical analysis of rainfall depths in intervals of various durations. The development of DDF curves is usually accompanied by many problems that can result in significant uncertainty in the resulting design rainfall depths and intensities. Most problems are related to the measurement errors and data processing; however, due to the customary shortage of this kind of data in Serbia, practicing engineers are forced to develop the DDF curves from a modest amount of the available data, without an insight in the uncertainties inherent in the process. This paper discusses these problems and proposes to Serbian practitioners to apply a robust method described in earlier work of Koutsoyanniset al. (1998) for consistent development of the DDF relationships. The method is illustrated using the short-duration rainfall data from Banja Luka.

Računske kiše su osnovni ulazni podaci za hidrološke proračune i projektovanje objekata za zaštitu od velikih voda. Na malim i srednjim slivovima merodavna trajanja kiše su kraća od 24 sata i računske kiše se definišu zavisnostima visina kiše - trajanje kiše - povratni period (ili zavisnosti HTP), koje se dobijaju statističkom analizom visina kiše u intervalima vremena različitog trajanja. Konstrukciju zavisnosti HTP prate razni problemi koji mogu dovesti do velikih neizvesnosti u vezi sa rezultujućim računskim kišama. Većina ovih problema potiče od grešaka u merenju i obradi podataka merenja padavina, ali poslovični nedostatak ovih merenja dovodi inženjere u praksi do toga da zavisnosti HTP određuju na osnovu skromnih raspoloživih podataka, bez sagledavanja neizvesnosti koje postoje. U ovom radu se razmatraju navedeni problemi i ukazuje se na metode dostupne u literaturi za konsistentno određivanje zavisnosti HTP, a na primeru podataka sa meteorološke stanice Banja Luka.