MACE$20402$

Question $3$

Simple triangular one$-$hour unit hydrographs of two different catchment's $A,B$ have been fitted to data and are shown below.

$($a$)$ What is the area of each catchment?

$[5$ marks$]$

$($b$)$ Net rainfall of $10mm$ in the first hour, $20mm$ in the second hour and $10mm$ in the third hour falls on catchment A$.$ Calculate the resulting run$-$off as a function of time.

$[5$ marks$]$

$($c$)$ Net rainfall of $15mm$ in the first hour, $20mm$ in the second hour and $15mm$ in the third hour falls on catchment B$.$ Calculate the resulting runoff as a fun

$($e$)$ A $10m$ by $25m$ building is located in catchment B$.$ A few minutes after the start of the third hour $($when it is raining $15m\frac{m}{h}$our $),$ what flow rate would be draining off of the roof in litres per second?

$[5$ marks$]$