Abstract

• This research is carried out along Yangon-Naypyidaw Highway between Mile Post 10 and 40 to explore the degradation of soil especially caused by gully erosion. The study area covers along the road with Irrawaddy Formation, Older Alluvium (Lateritic soil) and Younger Alluvium. The top soil layer of study road segment is mainly composed of sand, silt, clay and little gravel of Older Alluvium. This layer consists of loosely consolidated, fine to medium grained silty sand with clay which possess 5-10 numbers of blow count as Standard Penetration Test. Moisture contents of top soil layer comprising cohesionless soil is mainly controlled to land degradation. There are many erosion processes along the study road because of the highly rainfall as well as deforestation. Land degradation is high potential during rainy season. The main causes of human-induced land degradation in this area are expansion of cropland and cutting for fire woods. Soil salinization caused by sodium and potassium elements composing in soil is also one of the main controlling factors for soil degradation in rainy season. Vegetation covered on gully floor is very important to protect soil degradation which can reduce surface erosion. Reforestation should also be made for soil stabilization. In some places, temporary physical structures such as gully reshaping, brushwood, sandbag, loose stone, gabion and arc-weir check-dams should be built to minimize gully erosion.