Q $(4).($DURATION: $30$ MINS$)$ In a basin with an area of $1\mathrm{.}08k{m}^2,$ the hydrograph formed at the exit of the basin by the uniformly distributed precipitation of $30m\frac{m}{?}$ hour at a constant intensity is observed as shown in the figure. The infiltration index of this basin is $10m\frac{m}{h}r.$ Determine the unit hydrograph of this basin.

a$.$ Calculate the duration to of this unit hydrograph?

b$.$ Calculate the lag time $T_{\text{l}\text{a}\text{g}}$ of this unit hydrograph?

c$.$ Calculate the indirect flow height $R_D$ of this unit hydrograph?

D$.$ The rainfall hyetograph during a $90-$minute storm over this basin is given below. Draw the total hydrograph that this storm will generate at the basin outlet.

$Q(\frac{m^3}{s})$

Observed hydrograph

Observed Storm Hyetograph