Modelling of Concentration Time in North Karoon River Basin in Iran

Abstract

Concentration time of river basin is an important factor for control and management of flood and hence, must be determined accurately. In this work, rainfall-runoff data from 6 gauged sub-basins (with drainage areas from 390 to 1000 km2 and mean slopes from 13.6 to 31.27 degrees), located in north Karoon river basin in south-west Iran, were collected and analyzed to calculate the concentration time. 22 events were selected from this analysis. Using field methods, concentration time was measured in two other micro sub-basins. In one such method, carried out in Samsami (drainage area of 0.0271 km2), concentration time was calculated from hydrographs generated by discharge measurement of triangular scaled spillway. In another field method applied in Sureshjan sub-basin, (drainage area of 0.017 km2), methyl orange was used to calculate concentration time. The above 24 events were then used for both making a new empirical equation - called Shahrekord model (SKM) - and its validation. Considering the results from the analysis carried out in work, R2, RMSE and %RE of 0.9, 1.78 and 8.64% respectively, it can be concluded that SKM model in this work estimated concentration time in a satisfactory manner.