Example $2\mathrm{.}6($Gupta$)$: Construction

Intensity$-$Duration$-$Frequency Curves

For the precipitation data arranged for different durations in Table $3\mathrm{.}6,$ prepare intensity$-$

duration$-$frequency curves for $20-$year and $10-$year frequencies.

Computation Example, solution

Intensity for the $5$ min$-$

$20$ yr recurrence event

For each duration, the precipitation depths are arranged in descending order. The

highest value has been assigned a rank of $1$ and the lowest a rank of $22.$ The re$-$

turn periods are obtained in column $8$ of Table $3\mathrm{.}6.$

The depths of different duration corresponding to $20-$year frequency are interpo$-$

From interpolation between

$0\mathrm{.}4$ in$.(23$ yr$.)$ and $0\mathrm{.}38$ in$.$

lated from the plots for $23-$ and $11\mathrm{.}5-$year frequencies and converted to intensities

in Table $3\mathrm{.}7.$ Similar calculations are done for $10-$year frequency. These are plot$-$

ted in Figure $3\mathrm{.}6.$

$(11\mathrm{.}5$ yr$.)$ we get $P=0\mathrm{.}395in.$

$I=$ P$/$dt $=(0\mathrm{.}39in\frac{.}{5}$min${)}^{**}(60mi\frac{n}{h}r)=4\mathrm{.}74in/$hr