The areas of low mountains and hills in the upperreaches of the Cao’e River, the largestfributary of the Qiantang in its lower reaches, are those where soil erosion has become the mostserious problem in Zhejiang Province. The average silt content of the Chengtan River, itsmain stream, has amounted to 0.2-0.5kg/m³ for years, and the average erosion modulus to405 t/km². The worsened soil erosion, in accelerating the barrenness of the soil, the continualsilting of reservoirs and the river course, and the disastrous aggravation of floods and wa-terlogging, lead to the over-all deterioration of the naturaI environment.The soil erosion is mainly effected by such physiographical factors as rock character. soil,geomorphology, and rainfall, combined with such artificial factors as deforestation, land recla-mation on steep slopes, etc.To bring the soil erosion under permanent control, biological measures should be takenin combination with engineering ones, namely, to put stress on free-planting and afforestation,fanse gullies and ravines by means of such a method as applicable to the whole valley, put anend to land reclamation on the slopes, and reform the cultivated slope land.The soil erosion in the upper Cao’e has been a deep concern of the people, and a seriesof measures, taken in recent years in particular. have achieved certain positive results. soil ero-sion, owing to various reasons, however, is still one of the serious problems that demands aprompt solution.