Author(s): Joocheol Kim; Jaehan Kim
Linked Author(s):
Keywords: Lag time; Catchment shape descriptors; Equivalent ellipse; Geomorphologic instantaneous unit hydrograph (GIUH); GIUH velocity
Abstract: One of the most important factors for estimating a flood runoff from streams is the lag time. It is well known as being under the influence of the morphometric properties of basins which could be expressed by catchment shape descriptors. In this paper, the notion of the geometric characteristics of an equivalent ellipse proposed by Moussa (2003) is applied for calculating the lag time of geomorphologic instantaneous unit hydrograph (GIUH) at the basin outlet. The lag time is obtained from the observed data of rainfall and runoff by using the method of moments suggested by Nash (1957), and the procedure based on geomorphology is used for GIUH. The relationships between the basin morphometric properties and the hydrological response are discussed as applied to 3 catchments in Korea. Additionally, the shapes of equivalent ellipse are examined how they are transformed from upstream area to downstream one. As a result, the relationship between the lag time and descriptors is shown to be close, and the shape of ellipse is presented to approach a circle along the river downwards. These results may be expanded to the estimation of hydrological response of ungauged catchment.
Year: 2005