n Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - The standard design flood : technical paper

Volume 44, Issue 1
  • ISSN : 1021-2019



In this paper it is demonstrated that the unacceptably frequent destruction or severe damage to bridges and other civil engineering structures by floods in South Africa is due to the wide band of uncertainty around all estimates of the flood magnitude-frequency relationship, combined with steep increases in flood magnitude with increase in return periods. These uncertainties cannot be satisfactorily accommodated in current design flood estimation procedures, and there is an urgent need for a new approach to the estimation of the design flood. A new, simple, but robust, standard design flood estimation method is described which, together with the firmly established regional maximum flood method, can be satisfactorily be used for the design of most structures vulnerable to flood damage in South Africa. The designer is relieved of having to evaluate the relative applicability of alternative methods for determining the design flood, and is encouraged to use engineering factors of safety to accommodate uncertainties in the hydrological analyses, rather than investigate, evaluate and apply alternative hydrological procedures.

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