Question

Isochrones have been sketched on a catchment map and the areas between the isochrones are

Travel time (h)

Area (km²)

Time (h)

Rainfall (mm)

Loss (mm)

1

b)

In a storm on the catchment, the depths of rainfall and potential continuing losses (after

satisfaction of initial losses) in successive hourly intervals were

6

4

0-2

4.0

2

8

4

3

10

4

2-4

6.0

The initial loss for this storm event was 10mm.

4-6

10.0

4

5

14 12

3.5 3.0 2.5 2.0

6

7

8

17 19 13

a) Calculate the runoff hydrograph resulting from this storm event.

6-8

14.0

9 10

6

9

1.5 1.25 1.0

Will the resultant hydrograph be the hydrograph for the total flow leaving the

catchment? If not, what adjustment should be made to ensure that the hydrograph

represents the total flow from the catchment?