OBTAINING THE ENVELOP CURVE OF PRECIPITATION FOR NORTHERN IRAN

The Probable Maximum Precipitation (P.M.P) and probable maximum flood are among the important issues of designing hydrologic structures. One of the most suitable techniques for predicting probable maximum precipitation is the envelop curve method. According to this method all records of precipitation are plotted in a log-log graph and finally a line which covers all events of precipitation is drawn. The results gained from such method provide higher accuracy as well as reduces the cost of projects which is a very important issue in decision making. Accordingly envelop curve of precipitation was prepared in current research and the results showed that maximum 6-hour precipitation for northern part of Iran is 193 mm while the results for 24 hour, one month and one year data were 384, 949.4 and 2754.4 mm respectively. The results indicated that the values which obtained for northern parts of Iran are about 10% less than the global records.

Envelop curve, probable maximum precipitation, Northern Iran.