Modelling Effects of Land Use Type and Spatial Pattern on Flow Hydrograph Variations

Assessing effects of land use spatial pattern on hydrologic characteristics and variation of flow hydrograph can provide new information leading more effective decision-making and integrated watershed management. However, less attention has been relatively paid to this subject. The emphasis of this research is to quantify the contribution and effects of different land use types and spatial pattern on flood hydrographs in Galaz Watershed (103 km2 area), located in West-Azarbaijan Province, Iran. In the present study, the Clark's Time-Area model has been employed for simulation of hydrograph. The Time Area Histogram (TAH) of the study watershed has been derived based on a spatially distributed travel time approach, and the flow hydrograph was simulated in incorporating with the different land use types and design rainfall. The hydrograph has been routed to the watershed outlet. Then, the distribution of flow hydrograph and the peak discharge were analysed considering different land uses between isochrones. According to the results, the effect of land use types and patterns led to variations of time area histograms and the resulted hydrograph. Based on the results, the higher peak discharge were determined for rangeland, agriculture and forest land use types, respectively. The generated runoff volume of the rangeland, agriculture, and forest land use types were 84, 12, and 4%, respectively. The implemented method can be used to simulate the effects of land use changes in storm basis to study the temporal flow variations and also to quantify the components of flow hydrograph