This is a cross-section view of the same Gilbert-type delta process as the 3D simulator, plotted as a strict elevation-vs-distance profile (a stratigraphic section) rather than a rendered 3D scene — the natural 2D representation of what is fundamentally a 1D bed-elevation model. A 1D array of bed-elevation bins runs from the river inlet (left) to the dam (right). Each simulated year, incoming sediment volume is distributed along the bins with an exponential decay away from the inlet — coarse grains settle almost immediately near the inlet, fine grains travel farther before settling:
V(t) = (sediment load × Δt) / bulk density [deposited volume]
w(x) = exp(−x / L_settle) [where it lands]
slope > tanθ_repose → material avalanches downslope until slope ≤ tanθ_repose
Any bin that would rise above the water surface is capped there and the overflow volume is carried forward to the next bin downstream (this is what actually drives progradation of the delta front — a bin that is already full cannot simply lose the extra sediment, it has to go somewhere). A live strip chart below the cross-section plots storage-capacity loss against simulated years, the same time-series a reservoir operator would read off a bathymetric-survey record.
- Grain size — coarse gravel has a short settling length and a steep repose angle (~32°), building a tall delta close to the inlet. Fine silt travels far (long settling length) at a gentle angle (~12°), spreading a low wedge most of the way to the dam.
- Sediment load — the mass of sediment entering per year; higher load fills storage faster.
- Storage remaining — the pool volume between the current bed and the water surface, divided by the original (unsedimented) volume. Reservoirs worldwide lose roughly 0.5–1% of their capacity per year to sedimentation on average, and some silt-heavy systems lose several percent a year.