The lower part of a catchment in Mt Helen, Ballarat, Victoria shown as trapezoid BDEC in Fig. Q3,has undergone extensive urbanization. Pre-development runoff coefficient for the wholecatchment, ABDEC, is estimated 0.15 while post-development runoff coefficient for the lower part,BDEC, has changed to 0.6. Runoff coefficient for the upper part of the catchment, ABC, remainsthe same as that of pre-development. (Areas of ABC and BDEC are 125,000 and 250,000 m2respectively).a. Estimate time of concentration in minutes if velocity of flood flow in ABDECcatchment longest floodway, thalweg, reaches a maximum of 1m/s.b. Calculate flood peaks for 5 year return period at the outlet, G, for both pre andpost development conditions.c. Calculate flood peak for a culvert to be installed as the minor system of the artilleryroad shown on the map.d. What would be approximate diameter of the culvert if its full flow velocity is assumed