The Effects of Surface Soil Characteristics on Length Expansion Gullies in Different Climates of Fars Province

One of the most significant water erosion is gully erosion that leads to creating problems and losses. This kind of erosion has special importance because of sediment production and major damages to lands، highways and civil projects. Fars province has gully erosion in six regions. In this study، 30 active gullies were recognized in selecting one region in each climate. Gully progress by means of historical documents such as aerial images and topographic maps and field studies was determined. In watershed located on headcut gully، surface soil specification، slope and cover plant was measured. In order to determine effective factors on gully length progress، the relationship between gully length as a dependent variable and surface soil Characteristics as independent variables by means of step by step regression method in SPSS software were analyzed. The result of this study showed that four factors including; slope، EC، pH، cover plant have significant correlation in one percent level with gully length progress. The slope gradient of above gully headcut was the most important factor. The factors such as; slope، EC and pH had positive relationship and cover vegetation had negative relationship with length expansion gullies rate. The significant influence of slope is due to production of surface flow speed in headcut. Decreasing slope and increasing cover plant around gullies can have main influence on decreasing gullies and sediment production.