Real stormwater and erosion-control problems — detention routing, sediment-basin sizing, RUSLE soil-loss, Camp's-equation, and forebay design — solved end-to-end with every formula, every assumption, and every number shown. Each example uses the same calculation engines that power the HydroComplete app, so you can open the scenario and tweak any input.
Full RUSLE → Camp's → 7-bin Stokes/Camp pipeline on a Charlotte residential subdivision. Comes out at 65.5% trap efficiency — below NCDEQ's 80%, so the example walks through forebay/PAM/upsizing remediation.
Same 1-acre Asheville site solved four times: bare grading, straw mulch, erosion blanket, temporary seed. Shows where the C-factor row in the RUSLE table actually moves the needle.
Inherited a basin design from a similar prior project. Run the math before submitting: A_s and Q give the capture particle, then 7-bin Stokes/Camp gives 67% trap efficiency — below NCDEQ. What to do.
A widely-repeated rule says forebays raise trap efficiency. The math says otherwise: 65.5% → 66.0% with 10% forebay, → 67.0% with 40% forebay. Forebays do other useful things — but they're not a capture-rate fix.
Same 5-acre basin from scenario 1. With 5 ppm anionic PAM dosed at the inflow, the 7-bin trap efficiency moves from 65.5% to ~92% — without enlarging the basin. Dosing rate, application methods, cost, and the NPDES turbidity story.
SCS runoff for pre and post conditions (14 cfs vs 41 cfs), TR-55 storage estimate, a two-stage outlet, and a full Modified Puls route that brings the 10-yr peak back under the allowable release. Every formula and number shown.
A grass-lined trapezoidal roadside ditch carrying 25 cfs: Manning's normal depth solved by iteration (1.17 ft), velocity 3.9 ft/s, critical depth 1.05 ft, Froude 0.81 (subcritical). Then the permissible-velocity lining check and freeboard. Pure hand math, no nomographs.
A 3-acre, 65%-impervious commercial site: runoff coefficient Rv = 0.635, Water Quality Volume = 6,900 ft³ from the 1-inch storm, and a bioretention cell sized by the Darcy filter-bed equation to ~1,540 ft² of surface with a 48-hour drawdown. Every formula shown.
A development catchment's flow path split into sheet flow (0.225 hr), shallow concentrated flow (0.197 hr), and channel flow (0.139 hr), summed to Tc = 0.56 hr (34 min). The single input that most distorts peak flow when engineers get it wrong.
An 8-acre mixed catchment to a storm-drain inlet: area-weighted C = 0.55, design intensity 5.8 in/hr at the 15-min Tc (10-yr IDF), Q = CiA = 25.5 cfs. Plus the assumptions that make the Rational method valid — and when it isn't.