IL-CL Sub-Catchment property sheet

IL-CL Sub-Catchment property sheet

This is used to enter data for the ARR 2019 IL-CL model. Different sheets are used for Horton (ILSAX) and the rational method, and other formats are used for storage routing model sub-catchments.

 

At the top there is a text box for the sub-catchment name, another for entering the sub-catchment area, and option buttons for the Hydrological Model that give the choices Default model and You specify.  If you choose the latter, a scrolling list appears below, enabling you to select from available models. You can vary the parameters.

Beside the Hydrological Model buttons there is another set of option buttons for selecting the level of data required as:

  • abbreviated data, or  

  • more detailed data.

If you select the second option,  more text boxes for data entry and display will appear. Text boxes for the effective impervious area (EIA)  and remaining catchment parts are arranged as an array with two columns.  In the first row, you can enter the percentages of each surface type within the sub-catchment.

For more information about defining the EIA, RIA & PA areas, refer to the IL-CL Hydrological model.

 

The following rows are for the information needed to determine times of entry or travel times. As options providing more detail are chosen, more text boxes appear for entering the data required to determine times of travel.



The times determined are additive and relate to different flow paths. For the EIA, the times involved are:
      +  a constant time (which can represent property drainage time plus street gutter flow time), 
      + an overland flow time calculated from length, slope and roughness (more detailed data option). Gymea Extended Rational Method Example - set up for 2019 ensemble storm modelling and the Lite hydraulic model.

By choosing different options or by setting factors such as constant times to zero, many choices are possible. Overland flow times are calculated using the kinematic wave equation described in Australian Rainfall and Runoff, 1987 (pages 300-301) or Friend's formula. The property drainage time can be taken to be 1 minute for new buildings and 2 minutes for older, deteriorated systems. The gutter flow time can be determined by assuming a suitable velocity, based on trial calculations with the gutter cross-section being used.

For a supplementary area, the times involved are:
      + a constant time (both options),
      + an overland flow time calculated from length, slope and roughness (defined in the more detailed data option).

For a grassed area, the times involved are:
      + a constant time, which can represent property drainage time (both options), 
      + an overland flow time calculated from length, slope and roughness (more detailed data option).

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