$5\mathrm{.}4\mathrm{.}2$ Perform the backwater computations at mile $2\mathrm{.}0$ for the situation in example $5\mathrm{.}4\mathrm{.}4.$ The Manning's n values at mile $2$ are $0\mathrm{.}02$ for the main channel and $0\mathrm{.}035$ for the overbanks. Use an assumed trial water surface elevation of $125\mathrm{.}5$ ft$.$