EIA, ICA, PA

[newtonjon]

Hi,

In ARR2019 Book 5 Chapter 3.4 and Book 9 Chapter 6.4, 3 surface types are listed:
Effective Impervious Areas (EIA)
– directly connected impervious areas
Indirectly Connected Areas (ICA)
– impervious areas not connected to drainage systems
– pervious areas connected to drainage systems
Pervious Areas (PA)
– pervious areas that are not connected to drainage systems e.g. parklands

However, RORB provides 3 surface types:
Directly connected impervious areas (DCIA)
Indirectly connected impervious areas (ICIA)
Pervious areas (PA)

It is noted that ICIA this does not include pervious areas connected to drainage systems.

Question 1: How does RORB model these areas i.e. pervious areas connected to drainage systems, such as road reserves and green median strips?

Question 2: Pre-burst losses are only applied to pervious areas (which, according to ARR2019, are parklands). How does RORB apply pre-burst losses to ICAs such as green median strips?

Thanks,
Newton

[Benson Liu]

Hi Newton,

RORB does not explicitly model the pervious areas connected to drainage systems. What RORB allows you to do is to split a subarea into 3 separate surface types with a different set of losses for each surface type. When you split the subarea into the 3 different surface types, RORB treats the losses the same way for each surface type, it is just the IL and CL change depending on user input. This means that it is up to you to decide how to apply the losses.

When you mention pre-burst losses are you referring to the losses supplied by the ARR data hub? If you are then you are correct that they are designed to be used for pervious areas. There is some guidance in ARR Book 5 Chapter 3 in how to apply losses for the different surfaces but you would need to decide whether this is appropriate for your catchment.

Kind regards,

Benson

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