Solution Formula for Critical Water Depth of Semi-circular Section

Generally,the critical water depth of a semi-circular section could be solved by the approximate formula used for a circular section,so the calculation error is large.Here,the solusion formula for the critical water depth of the semi-circular section is drawn up by leading the nondimensional critical depth parameter into the basic equation.It is showed by the application and analysis that the solusion formula is simple and accurate,and its maximum relative error is smaller than 0.76%,so it could provide references for solving the critical water depth of a semi-circular culvert.