A trapezoidal channel $($n $=0\mathrm{.}028)$ with a bottom width of $10$ m and a side slope

of $3\mathrm{.}0$ is laid on a physical slope of $0\mathrm{.}002.$ Classify the channel bed if the channel carries:

$(2)20$ m$3$ s$-1.$

answers: $(1)0\mathrm{.}72$ m; $(2)1\mathrm{.}07$ m

$(3)1\mathrm{.}33$ m