Two rivers are passing over Troyan and its surrounding area - Cherni Osam river and Beli Osam river which spring from Troyan mountain. Immediately in the north part of the town the two rivers merges in one river called Osam. Main river is Cherni Osam because of its longer length and bigger capacity in comparison with Beli Osam. Soils
The soil cover in Troyan region consists of grey forest soils. They have developed in the area of deep serrated relief in the Balkan. The ledges in the valleys are covered with fruitful alluvial soils. The higher we go in the mountain the bigger area is covered by brown forest soils which at 1000 m above sea-level occupies wide territory. Potatos, oats and raspberry are sowed here. On the ridge in the presence of a grass there are developed mountain-meadow soils. Here occurs also delluvial and alluvial soils. Fruit trees grows well here. This vertical change of soil cover is connected with development of the relief at high and with vertical climate zoning.