What is the hydrological ratio drop method

Hydrographic ratio drop method is introduced as follows:

1, Definition: According to the measured water surface drop and and trough section information to calculate the flow rate measurement method, known as hydrographic ratio drop method, the water surface drop is the ratio of the water surface drop and the length of the section, the calculation of the flow rate is commonly used in the Manning's formula, the average flow rate and the cross sectional area of the product of the flow rate;

2, Characteristics: The accuracy of this method is poor, and it can only be used when the flow meter method and buoys cannot be used or only as an auxiliary method. Can not use the flow meter method and buoys when used, or only as an auxiliary method used;

3, Note: the use of this method to choose a straight and uniform section of the river, in the section at the same time to observe the water level, calculate the water surface than the drop, and measure the area of each cross-section to calculate the flow rate, the roughness should be used in this site flow meter method or the buoys method of the rate of the measured data in the section of non-uniform or unstable water flow, to