Interactive engineering model

SCS rainfall-runoff partition

Change rainfall depth and curve number to divide precipitation into abstraction, retention, and direct runoff.

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A cutaway soil block is a schematic retention reservoir: its depth represents the potential maximum retention S on a logarithmic scale, and a wetting front descends as retention F fills it. A stacked column splits rainfall into abstraction used, retention, and direct runoff at one shared inch scale. The blue runoff layer represents equivalent runoff depth over the parcel, not physical ponding. Readouts distinguish abstraction used from the runoff-onset threshold 0.2S. Land cover thins toward pavement as curve number rises, and the footprint follows the drainage area.

Diagram labels

Numbers match the callouts in the view. Drag to inspect the model; crowded callouts remain listed here.

    Focus the 3D view and use the arrow keys to orbit, plus or minus to zoom, and Home to reset the view.

    Text explanation and non-WebGL fallback

    A cutaway soil block is a schematic retention reservoir: its depth represents the potential maximum retention S on a logarithmic scale, and a wetting front descends as retention F fills it. A stacked column splits rainfall into abstraction used, retention, and direct runoff at one shared inch scale. The blue runoff layer represents equivalent runoff depth over the parcel, not physical ponding. Readouts distinguish abstraction used from the runoff-onset threshold 0.2S. Land cover thins toward pavement as curve number rises, and the footprint follows the drainage area.

    The numeric controls and readouts remain usable if WebGL is unavailable. Drag or swipe the 3D view to orbit and use a wheel or pinch gesture to zoom. With the 3D view focused, use the arrow keys to orbit, plus or minus to zoom, and Home to reset. The complete numeric lesson is also keyboard-accessible in the adjacent controls and readouts. This model is an educational aid and does not replace applicable design standards or professional review.