Debris flows in the NiuQuan valley-the epicentre of Wenchuan Earthquake

After 5.12 earthquake, NiuQuan valley becomes an area with frequent and dense debris flow disasters; so far, nine large-scale debris flows occurred. The three basic conditions making debris flow have well developed in this valley, namely the terrain conditions of high landform, deep canyon, steep slope angle, abundant loose solid materials and concentrative high strength precipitation in the annual rainy season, so it is in a developing stage now and large-scale rainfall induced debris flow disasters, with the larger damage and stronger wallop, will easily occur in the 5-10 year rainy season after earthquake. If considering to use directly the debris flow deposit in the main gully of NiuQuan valley, civil control engineering, constructed alternate landslide dams of earth and rock with about half of main gully width in the left and right sides of upper and middle of the accumulation area, landslide dams of earth and rock with approximately equal to main gully width in middle and lower of the accumulation area and slope with certain gradient and relative to gully orientation between two adjacent dam, can achieve dual-purpose of energy dissipation and consumption. The system for control engineering, combined civil control engineering with biological control engineering, has larger engineering practice to prevent debris flows in the valley.