Bring terrain from an upload, any location on Earth, the Rhino document or the demo site. Flow mode reads where water runs and where it collects; Rainfall mode puts a design storm on the site and balances runoff against what ponds and what leaves; Grading mode lets you sculpt the ground and re-runs everything live, with cut and fill volumes as you go.
Terrain, Grading & Drainage
Runs in the browser — nothing to install.
| Input | .asc / .xyz / .obj / .3dm · a location (real elevation tiles) · the Rhino selection |
| Modes | Flow · Rainfall · Grading |
| Output | Flow lines, ponding sites, cut/fill volumes, .3dm bake |
Using it
Bring terrain
Drop a .asc, .xyz, .obj or .3dm of your site; load a location from real elevation tiles; pick the selection in the Rhino document; or start with the demo terrain.
Pick a mode
Flow reads the land. Rainfall tests a storm. Grading regrades and re-runs the whole chain.
Read the legend
Amber = ridges, cyan = valleys. Toggle contours, flow accumulation and ponding sites on top.
Test a storm
Set the storm depth and the surface type. Read runoff, ponded and outflow against each other — they should add up.
Grade and re-check
Sculpt the ground. Cut/fill volumes and flow update live, so you can see whether a move solves ponding or just relocates it.
Export or bake
Export a DXF plan, an SVG drawing, the data as GeoJSON or CSV, or a .3dm; in Rhino, bake straight into the open document. The PDF report (brief, evidence and hand-off) is part of Pro.
How it works
- Depression filling — Priority-Flood with an ε gradient (Barnes et al. 2014), so every cell has a downslope path to the edge. NaN / NODATA cells are treated as boundaries.
- Flow routing — D8 steepest-descent direction; flow accumulation and contributing area (m²) follow from it.
- Ponding sites — the depression inventory is filled − original: each site gets a spill level, a storage volume and an area.
- Rainfall — a water balance. SCS Curve Number runoff depth (USDA TR-55) per surface preset, routed by D8, then filled and spilled through the depressions in downstream order. The mass balance is shown: runoff = ponded + outflow.
- Grading — re-runs the chain on the edited terrain; cut / fill = Σ|Δz| · cell².
- Drawings vs analysis — contours are drawn from the original grid; slopes come from the filled grid. The drawings show the ground you have, the routing shows the ground water sees.
Limits
- D8 forces all flow from a cell into one of eight directions, so it exaggerates channelisation on gentle, broad slopes.
- The result is only as good as the DEM: resolution, vertical accuracy and vintage propagate straight through, whether uploaded or fetched from elevation tiles.
- No time-stepping: the storm is one runoff depth, not a hydrograph. Infiltration is only the Curve Number abstraction, not soil dynamics.
- Pipes, culverts, drains and anything buried are invisible; the terrain is the only path.
- A design-stage reading, not a hydraulic model or a regulatory flood study.
Tips
- Do — Smooth your DEM lightly before uploading — noise creates spurious micro-depressions.
- Check — Ponded + outflow should equal runoff. If a regrade increases outflow, you have pushed water off site, not solved it.
- Avoid — Treating the result as a hydraulic model — it is a topographic flow reading with a storm water balance, not full hydraulics.
Terrain, Grading & Drainage
Runs in the browser — nothing to install.