نقش عوامل مورفومتري و اقليمي حوزه در توليد جريان هاي سيلابي (مطالعه موردي حوزه هاي آبخيز ناحيه غربي خزر)

The role of Watershed morphometric and climatic factors In producing of flood flows

Certain ration exist between hydrologic events such as flood flows with watershed physical and climatic factors. Understanding flood generation mechanisms and the influence of morphologic and climatic properties on such mechanisms is very important in hydrologic engineering. In this paper, variation of flood peak discharges of different return periods were studied through multivariate regression models and flood index approach. Physiographic factors such as area and slope were extracted on the basis of digital elevation model (DEM). Annual rainfall raster map was prepared by applying interpolation methods on point rainfall data. The slopes were classified into three classes of 10-25%, 25-35% and 35-45% whereas rainfall was grouped into less than and more than 800 mm. The results showed that flood curves against area in 35-45% slope and rainfall less than 800 mm has a rising and falling portion. The peak on the curve occurs around 400-500 Km2 area. This implies that in large watersheds which receive lower rainfall, the runoff coefficient and specific discharge decreases due to channel transmission losses.