Land Cover Runoff - [source code]
Fetches land-cover polygons around a lat/lon from OpenStreetMap (open data, no key) and classifies each into a Curve Number and an overland Manning's n. This is the same Overpass query the Land Cover Roughness component makes, read for runoff instead of for wind — so wiring both on one site costs one fetch, not two. Unmapped tags are skipped rather than guessed at.
Input
| Name | Nickname | Description | Type |
|---|---|---|---|
| Latitude | Lat | Site latitude in decimal degrees. | Number |
| Longitude | Lon | Site longitude in decimal degrees. | Number |
| Radius | Half-width in metres of the square window fetched around the site. Keep it close to the terrain's own extent: Overpass returns the FULL geometry of anything touching the window, and a large one drags in metro-scale polygons. | Number | |
| Soil Group | Soil | Hydrologic soil group underneath. It shifts every Curve Number: the same lawn sheds far more on clay than on sand, so this is the single input here with the largest effect on the answer. B is the usual default when nothing local is known. | Text |
| Anchor | Model-space point the lat/lon maps to. Default is the origin. | Point |
Output
| Name | Nickname | Description | Type |
|---|---|---|---|
| Zones | Runoff zones for Stormwater Grid. | Generic Data | |
| Outlines | Curves | The classified polygons, so they can be edited or rebuilt by hand. | Curve |
| Classes | What each polygon was classified as. | Text | |
| Curve Numbers | CN | Curve Number assigned to each polygon, for the chosen soil group. | Number |