Percentage Impervious - The impervious portion of the Inflows area. When the Use Land Uses/Soil Types layers box is checked, the Percentage Impervious is calculated from weighted averages of Land Uses.
Average Slope -The slope across the catchment.
Urban Creep - This scales the impermeable area by the amount specified. This can be used to take the increase of urban areas, or other factors into account. This value is only enabled (and used) when the analysis creep of the Analysis Criteria is set to "Use Catchment Areas ".
Equivalent Width – The width of the catchment.
Internal Routing - Extends SWMM's traditional surface runoff model to allow overland flow to be routed in three different ways:
Routing Percentage - The specified fraction for 'To Pervious' and 'To Impervious' Internal Routing methods
Area - Total Impervious area calculated from Area * Percentage Impervious
Manning's n - PERN is an adaption factor used to introduce the effect of catchment roughness as follows:
n |
PERN |
---|---|
0.01 |
0.4 |
0.015 |
0.5 |
0.025 |
1.0 |
0.10 |
3.0 |
Depression Storage Depth - The depth of depression storage on the Impervious portion of the catchment
No Depression - The percentage of the impervious area that has no depression storage.
Area - Total Pervious area calculated from Area * (1 - Percentage Impervious)
Manning's n - PERN is an adaption factor used to introduce the effect of catchment roughness as follows:
n |
PERN |
---|---|
0.01 |
0.4 |
0.015 |
0.5 |
0.025 |
1.0 |
0.10 |
3.0 |
Depression Storage Depth - The depth of depression storage on the Pervious portion of the catchment
Horton / Modified Horton
Green Ampt / Modified Green Ampt
SCS Curve Number
The Curve Number Calculator can be used when the Use Land Uses/Soil Types layers box is unchecked. The calculator can be accessed using the button to the right of the field. This provides a quick and easy way to select the appropriate curve number.
Constant
Allows specification of a constant conductivity/infiltration rate using the Green Ampt. Method.