Water flows from high to low latitudes. When there is a slope, the water moves in the shortest straight-line distance. Thus, the more curves there are in the rivers, the greater variety in the terrain. Larger amounts of mud and soil is washed off, so the water becomes more turbid. The more turbid the water, the more particles there are in the water. These particles are mostly soil particles or minerals washed away by the water into the rivers. When the flow of the rivers slows down, the particles and minerals settle down in the bottom, so the rivers become shallower. Construction work in the catchment area or heavy rainfall wash-off may lead to the rise in turbidity in the rivers and the increase in the concentration of suspended solids.