Sediment Transport Calculator

It compares bed shear stress (from water depth, slope, and gravity) against a critical shear stress derived from the Shields criterion, which scales with grain size and the density difference between sediment and water. When bed shear stress exceeds critical shear stress, `isTransporting` flips to true and a nonzero bedload rate is computed using the Meyer-Peter and Müller formula; otherwise bedload is reported as zero regardless of how close the two values are.

Transport mode is set by the Rouse number, which compares an estimated grain settling velocity to the flow's shear velocity. A high Rouse number (above 2.5) means grains are heavy relative to the turbulence lifting them, so transport stays as bedload rolling and sliding along the bed; progressively lower Rouse numbers indicate more of the sediment gets suspended in the water column, down to fully suspended wash load below 0.8.

The calculator hardcodes a Shields parameter of 0.047 (typical for turbulent flow over well-sorted sand and gravel) and quartz's density of 2650 kg/m³, since it only takes velocity, grain size, water depth, and slope as inputs. For carbonate sediments, heavy minerals, or poorly sorted mixtures, the true critical shear stress would differ from what's computed here, so the transport threshold and bedload rate should be read as approximate for those materials.

The Froude number is velocity divided by √(g × water depth), and it classifies the flow itself as subcritical (below 1, calmer, more common in natural rivers) or supercritical (above 1, fast and shallow, as in rapids or spillways) — independent of whether sediment is actively moving. It's a flow-regime indicator, not a sediment-transport threshold, though high Froude numbers generally coincide with the higher shear stresses that drive transport.