过水面积 A=b*h=5.1*3.08=15.71 m
湿周 X=b+2h=5.1+2*3.08=11.26 m
水力半径R=A/X=15.71/11.26=1.40 m
谢才系数C=(1/n)R^(1/6)=(1/0.014)*1.40^(1/6)=75.55
底坡 i=(Q/CA)^2/R=[25.6/(75.55*15.71)]^2/1.40=3.32*10^(-4)
流速V=Q/A=25.6/15.71=1.63 m/s