Reply To: Apply direct and indirect impervious fractions

Hi Ben,

I have a RORB model with DCIA, and ICIA turned on. The event rainfall was an average of 18.4mm across the catchment. The following scenarios were run to identify the DCIA and ICIA functionality.

Scenario 1
IL=100mm, ROC=0 for pervious (No runoff from pervious areas)
IL=0mm, ROC=1.0 for DCIA (some runoff from DCIA)
IL=100mm ROC=0 for ICIA (No runoff from ICIA)

The calculated hydrograph shows no discharge. This means no discharge from DCIA. Why?

Scenario 2
IL=100mm, ROC=0 for pervious (No runoff from pervious areas)
IL=0mm, ROC=1.0 for DCIA (some runoff from DCIA)
IL=30mm ROC=0 for ICIA (No runoff from ICIA)

The calculated hydrograph shows some discharge though IL in ICIA is more than the Avg. Rainfall. Why?

Thank you,
Kind Regards,
Dinesh Ratnayake