Evaluation of land-use change and its effect on flood hydrograph in Amameh watershed, Tehran Province

Changes in the land-use pattern has affected hydrological processes in the watersheds and disrupted the natural balance of water flow. In the present study, changes in hydrological components of Amameh watershed as a result of land-use changes from1988 - 2013 were studied. Due to lack of the land-use map in past years, the land-use map was prepared and analyzed by Landsat TM satellite images in the ERDAS Imagine software in 1988. Furthermore, the available ‎information were used to provide land-use map ‎in 2013. Land-use maps of 1988 - 2013 were prepared using ArcGIS software. In existing maps, six land-use classes; class 1, 2, and 3 rangelands, agricultural and ‎garden, arid land, and river-bed were designed. ‎ The results showed that Amameh watershed was affected by severe changes in the land-use‎ during the study period, so that the class 1 rangelands‎ to class 2, class 2 to class 3, and even arid‎ land were changed. In addition, the residential areas (villa) were increased from 2.5% in 1988 to 8.4 in 2013. The HEC-HMS model was used to investigate the effect of land-use changes on the hydrological flood hydrograph of Amameh watershed‎. The results of hydrograph study of 1988 and 2013 showed the volume increase of runoff and peak discharge rates during the 25-year period, and also the watershed runoff coefficient was increased from 0.82 to 0.89.