QUESTION $2[18$ Marks$]$

The storm hydrograph given bellow was measured at a point in a river at $2-$hr intervals from an isolated storm of $2-$hr duration for a stream with a drainage area of $\backslash (350\backslash$mathrm$\{$~km$\}^\{2\}\backslash ).$ The river is characterized by an X value of $0\mathrm{.}30$ and has an average flood wave velocity of $\backslash (1\mathrm{.}4\backslash$mathrm$\{$~m$\}/\backslash$mathrm$\{$s$\}\backslash )$ for a typical flood.

$2\mathrm{.}1.$ Evaluate the effect of flood at a point $12$ km downstream of the measuring point. Define the meaning of X and K and then determine the time required for the flood wave to travel from upstream to downstream. Also determine the flood attenuation and lag time. Assume the initial outflow as $\backslash (5\backslash$mathrm$\{$~m$\}^\{3\}/\backslash$mathrm$\{$s$\}\backslash ).$