Vegetation cover changes impacts on flood increasing and acceleration. Case study Soofi Chai sub basin,Iran

The present work aims to assess the effects that land use changes as well as climate fluctuations have induced on the flood frequency regime. Study area is located on the upper part of Alavian Dam with 250 km2 in the Sofi Chi basin (western-north part of IRAN). The analysis has been carried out by applying 2years return period flood as base flood which derived from maximum daily discharge data. Then by comparing each daily discharge time series with calculated base flood, the flood event frequency and duration have been investigated. Here, climate changes investigated by considering deviations of climatic parameters from their long term averages. The land use change detection have been assessed by digital interpreting land use maps which refer to the years 1989,2000 and 2005 of Land sat and Spot satellite images respectively. Relationship between land use and climate change with flood frequency and its magnitude has been investigated by counting each flood event with their related duration. Land use changes effects on flood frequency were investigated by HEC-HMS model.The results indicate that flood events as well as their duration tended to decreasing specially throughout the last decade. Based on obtained results from digital satellite images interpretations, it can be concluded that changing of crop patterns (overdeveloping of orchards as well as dry farms increasing), executing some watershed management operations such as mechanical conducting (gabion and masonry dams) for storage of surpluses runoff, can be mentioned as important flood reduction factors on the study area, climate changes in form of precipitation decreasing seem to be noteworthy roles on flood event reduction trend in form of drought events.

کلیدواژه ها:

flood ، climate fluctuation ، land cover change