The study and determination of depth - area - duration (DAD)of rainfall in Hamedan, Zanjan and Qazvin Provinces.

Estimation of design flood is the first step in hydraulic structures and flood control projects designing. On the other hand، estimation of runoff and flood، need to precipitation and design rainfall informations. Therefore، with respect to the spatially variations of rainfall and providing Depth–Area–Duration relationship، we can obtain suitable patterns of rainfall for estimation of design rainfall values in various locations. In this study، after gathering all storms in Hamedan، Qazvin and Zanjan provinces، 9 maximun and overall storms from 50 storms were selected. The results showed that between all of storms،the November 5،1994 storm is maximum and overall than others. The number of stations varies from 116 – 125 of 169 total stations in different storms. After drawing rainfall accumulation curves for climatology raingage stations، the hytograph curves were drived for noun recorded stations. After that the rainfall maps provided for 9 storms. Finally Depth–Area–Duration curves provided using rainfall maps. Using this curves were derived rainfall amount in any region and duration.