Friction Maps¶
Friction maps define zones with custom Manning's roughness coefficients. Areas not covered by a friction polygon use the default value (0.04).
Properties¶
| Property | Type | Description |
|---|---|---|
mannings |
number | Manning's roughness coefficient for this zone |
Common Manning's n values¶
| Surface | Manning's n |
|---|---|
| Smooth concrete | 0.012 |
| Short grass | 0.025 |
| Dense grass / crops | 0.035 |
| Light brush | 0.050 |
| Dense brush | 0.100 |
| Buildings (default) | 10.0 |
How it works¶
Friction polygons are combined into a composite function using ANUGA's composite_quantity_setting_function. The function evaluates polygons in order, with an ['All', 0.04] catchall applied last for any uncovered areas.
Building footprints (from the Structures input) automatically receive a Manning's n of 10.0, effectively blocking flow through them.