Q $1.$

A two$-$lane bridge is going to be constructed in Gundagai over Murrumbidgee River. The

length of bridge is $145$ m and its deepest point is $7$ m below the ground surface. Peak flood

discharges were recorded from $1991$ to $2020$ for Murrumbidgee River in Gundagai, NSW$,$

Australia. The latitude and longitude of the bridge location are as follows:

$$ Latitude: $35\mathrm{.}06\backslash$deg S

$$ Longitude: $148\mathrm{.}09\backslash$deg E

Table $1$: Proposed Recorded Peak Flood Discharges for Gundagai Murrumbidgee River $($from

$1991$ to $2020)$

No Year q $=$ Flow rate $($m $3/$s$)$

$119911100$

$21992544$

$319931086$

$41994897$

$519952080$

$619961732$

$71997543$

$819982013$

$2$

$91999412$

$102000954$

$1120011394$

$122002379$

$1320031168$

$1420041920$

$152005787$

$162006514$

$1720071597$

$182008395$

$1920091546$

$2020101640$

$212011463$

$222012442$

$232013870$

$242014424$

$252015324$

$262016631$

$272017671$

$2820181204$

$292019692$

$3020202418$

Q$1\mathrm{.}1.$ Based on Flood Frequency Analysis $($FFA$),$ find the flood discharge in m $3/$s $($qmax $)$ for

the Average Recurrence Interval $($ARI$)$ of $100$ years.

Q$1\mathrm{.}2.$ Based on Rational Method determine the flood discharge in m $3/$s $($Q max $)$ for the

Average Recurrence Interval $($ARI$)$ of $100$ years. Assume the area of the catchment is $630$

km $2,$ the average slope $2\%$ and the mainstream length in the catchment is $5\mathrm{.}37$ km$.$ The

impervious fraction of catchment area is $0\mathrm{.}36($f $=0\mathrm{.}36).$

Note: For the design purpose, select the flood discharge in the river in the location of the

bridge based on the maximum of these two flood discharges, calculated based on FFA and

the rational method.