Studying the Impacts of Land Use Changes on Flood Flows by Using Remote Sensing(RS) and Geographical Information System (GIS) Techniques- a Case Study in Dough River Watershed, Northeast of Iran

Floods are generally categorized as the most important hazard causing enormous social, economic and human loses. Land use changes caused by man's interference resulted to an increase of flood severity and frequency during recent decades. In this research Environmental impacts of land use changes on surface runoff and subsequently flood flows, have been studied in the Dough river watershed. Curve number (CN) method was employed to estimate maximum discharge in two different cases: present land use as well as the proposed land use based on land capability. The study revealed the significant role of land use changes in increasing flood flow as a result of increased surface run off in the basin, particularly in dry soil condition. Changing the present land use to a proper condition based on land capability, may decrease maximum discharge to 70 %, 50% and 20% respectively in moderate, sever and very sever wet soil conditions, also pick discharge will be decreased to 20% in the basin. Here, the important effects of land use policies in severity of heavy floods especially when the soil is dry are apparently clarified. In the case of wet soil condition with high amount of rainfall (with longer return periods), the effect of land cover decreases though still plays its moderating role in diminishing the severity of heavy floods. Obviously, climatic and physical elements like heavy rains, the extent and the size of the watershed are also responsible for causing floods in this region, but anthropocentric activities like degradation of forest and rangelands, incorrect animal husbandry, mismanagement of natural resource, irrational allocation of land to settlements and construction of unsuitable structures and facilities multiplies the impacts and severity of floods. Remote Sensing (RS) and Geographical Information System (GIS) techniques have been extensively used to provide necessary information and maps.