Actually the valley of Swat starts from the foothill of Malakand but we are concerned with portion from Landakay to Gabral (Gulabad), the area within the administrative boundaries of Swat. Two narrow strips of plains run along the banks of Swat River from Landakay to Madyan. So for as the width concerns, it is not similar, it varies from place to place. We can say that the average width is 5 miles
. The widest portion of the valley is between Barikot and khwaza khela. The widest view point and the charming sight where a major portion of the valley is seen is at Gulibagh on main road, which leads to Madyan. There are some subsidiary valleys, which help to increase the width of the main valley. These subsidiary valleys are called "Daras". A Dara a narrow passage between mountains, and sometimes, the upper course of a river is also called Dara. If we imagine the main valley as a stem of a tree the subsidiary valleys form its branches. Swat River and its tributaries drain Swat. There fore, the whole valley is the outcome of running water. This flowing water cuts the upper courses deeply, and flows the load of washed away materials. As the gradient is greater in the upper course so the erosion is on large scale, particularly in the summer rains, when all the rivers are in flood. The big boulders and stones are rolled, which causes more destruction in the upper courses. When the loaded water reaches to the areas of low gradient, the heavier materials are deposited. The deposition takes place according to the slope, generally, we observe, that the upper course is made up of big boulders, the middle course is of relatively small stones, pebbles, and debris, while the lower course is made of fine clay. Anyhow, the whole plain of Swat valley is strewn by the running water, and is made up of fine alluvial soil.
