水力最佳断面底宽 b=4m ，水深 h =b/2=4/2=2m过水断面积 A =bh=4*2 = 8 m^2湿周 X=b+2h=4+2*2 = 8 m水力半径 R=A/X=8/8= 1 m谢才系数 C=R(1/6)/n=1^(1/6)/0.02 = 50流量=CA(Ri)^(1/2)=50*8*(1*0.0001)^(1/2)= 4 m^3/s
