Question

Question 4

Travel time of a 4ha catchment of a residential land use (C₁₀ = 0.32) in Adelaide is 20 minutes. If the catchment area is equally divided into four parts by the 5-minute isochrones, compute 100yr design flood peak at the catchment outlet. What is the runoff volume generated from this storm event? Compute equivalent ø index of 100-year design storm event for this catchment.

Answer 1

Total Run off Volume

In questions they are dividing catchment area into equal 4 Parts By 5 min to total 20 minutes... As such Each Divided Portion will have the Seperate Runoff Coefficient and Volume.

Let us assume the Average annual Rainfall for the Area as

Like Wise the Area Under which the runoff calculation will be a Healthy indigenous Landscape..

As such the Total Volume of the Let us consider the area will have 300mm Average Rainfall

Area * Rainfall = Volume

1 Hectare = 10000 Sq.m

10000*300 = 3000000 Liters / Average Year for first Hectare

Then the Total Coefficient Given = 0.32 * 3000000 = 960000 Liters of Runoff Volume

There will be 5 - 20% of Lost of Water Volume = Consider 10 % = 864000 + 777600 + 699840 + 960000

= 3,301,440 m3

Infiltration Loss Index Calculations

= 1/100(3000000 - 3301440)

= 3014