Runoff Coefficient

[c2h2u2]

Dr Quek,

Hi, thanks for the previous explanations.

Here are the questions that i would like to ask:

1. Land use - oil palm plantation, type of soil - peat soil, flat terrain.
How to determine the suitable Category of C value for this? Can it be under Category D? Can the C value obtained is around 0.7. From HP No.16, the C value for oil palm plantation is 0.5 regardless of the time of concentration. This C value is acceptable or not??

2. Different catchment area will get their own C value as it is due to the different in the rainfall intensity regardless that the catchment area is side by side? This is also same as for rainfall intensity? Which is governed by the time of concentration from each catchment area? Different catchment area will get their own C value, rainfall intensity & time of concentration regardless that the catchment area is side by side, same type of soil or land use? All mention above are different because they got their own size or catchment area. Can i say so??

Thank you.

Best regards,
c2h2u2

[drquek]

1. Land use - oil palm plantation, type of soil - peat soil, flat terrain.
How to determine the suitable Category of C value for this? Can it be under Category D? Can the C value obtained is around 0.7. From HP No.16, the C value for oil palm plantation is 0.5 regardless of the time of concentration. This C value is acceptable or not??

I agree with you- Type D of Design Chart 14.4 in MSMA appears to be a reasonable choice for your land use. I would not advise you to use HP16 to determine the C value.

2. Different catchment area will get their own C value as it is due to the different in the rainfall intensity regardless that the catchment area is side by side? This is also same as for rainfall intensity? Which is governed by the time of concentration from each catchment area? Different catchment area will get their own C value, rainfall intensity & time of concentration regardless that the catchment area is side by side, same type of soil or land use? All mention above are different because they got their own size or catchment area. Can i say so??

True. The rainfall intensity is affected by the time of concentration which in turn affects the runoff coefficient. In other words the catchment shape and size also affect your C value when applying the Rational Method in MSMA.