the methods of flow estimation for the design of urban storm drainage in iran.

the economic growth and development programs in iran call for particular attention for environmental quality control and protection through designing proper sewage treatment and disposal. to design such system, 'the frequency analysis of rainfall is required for the estimation of quantities of flows. there are few places in iran, with adequate rainfall data to permit frequency analysis, and no effort has been yet made to make such .analysis for areas with rainfall data. the methods of flow estimation for the design of urban storm-drainage system are discussed here and recommendation is made to adopt the method best suited to iran conditions. at the end, the frequency analysis of rainfall data for tehran, bojnurd and birjand is made and their rainfall duration frequency curves are ploted .to estimate rainfall intensity for these cities, relation as function of duration are presented.