{
 "tool": "time-of-concentration",
 "toolVersion": "1.1.0",
 "methods": [
  "tc 1.1.0"
 ],
 "commit": "ab22876",
 "date": "2026-11-04",
 "summary": "13 of 13 cases (23 values) within tolerance against NRCS TR-55 (1986), NRCS NEH 630 Ch. 15 (2010), FHWA HEC-22 4th ed. (2024), TxDOT HDM (Kerby-Kirpich example), Hand calculation of the published equation.",
 "note": "Generated by _workspace/tools/hh_verification.mjs from the fixtures; commit = code verified.",
 "cases": [
  {
   "id": "TR55-E3-1",
   "what": "TR-55 Example 3-1: sheet (dense grass, 100 ft), shallow (unpaved, 1,400 ft) and channel flow (7,300 ft)",
   "reference": "NRCS TR-55 (1986) (published example)",
   "compared": 6,
   "maxDiff": "1.37 %",
   "pass": true
  },
  {
   "id": "NEH630-15-LAG",
   "what": "NEH 630 example (a): watershed lag method, Mawney Brook, 3,865 ft, CN 63, slope 4.79%",
   "reference": "NRCS NEH 630 Ch. 15 (2010) (published example)",
   "compared": 1,
   "maxDiff": "0.40 %",
   "pass": true
  },
  {
   "id": "NEH630-15-SHEET",
   "what": "NEH 630 example (b): sheet flow, 100 ft of short-grass pasture at 8%",
   "reference": "NRCS NEH 630 Ch. 15 (2010) (published example)",
   "compared": 1,
   "maxDiff": "1.75 %",
   "pass": true
  },
  {
   "id": "NEH630-15-SHALLOW",
   "what": "NEH 630 example (b): shallow concentrated flow, 800 ft of short-grass pasture at 8% (V read from figure 15-4)",
   "reference": "NRCS NEH 630 Ch. 15 (2010) (published example)",
   "compared": 2,
   "maxDiff": "2.59 %",
   "pass": true
  },
  {
   "id": "HEC22-E4.2-SHEET",
   "what": "HEC-22 Example 4.2: sheet flow, 223 ft of Bermuda grass (47.1 min; over 100 ft, warning required)",
   "reference": "FHWA HEC-22 4th ed. (2024) (published example)",
   "compared": 1,
   "maxDiff": "0.03 %",
   "pass": true
  },
  {
   "id": "HEC22-E4.2-PIPE",
   "what": "HEC-22 Example 4.2: 15-in concrete pipe flowing full, 479 ft (1.4 min)",
   "reference": "FHWA HEC-22 4th ed. (2024) (published example)",
   "compared": 2,
   "maxDiff": "2.21 %",
   "pass": true
  },
  {
   "id": "TXDOT-KK",
   "what": "TxDOT Kerby-Kirpich example: 0.5 mi², 500 ft of average grass at 2%, 4,780 ft of channel (about 25 + 32 = 57 min)",
   "reference": "TxDOT HDM (Kerby-Kirpich example) (published example)",
   "compared": 3,
   "maxDiff": "1.39 %",
   "pass": true
  },
  {
   "id": "ARITH-KIRPICH",
   "what": "Kirpich, 4,000 ft main channel at 0.005 ft/ft",
   "reference": "Hand calculation of the published equation (published example)",
   "compared": 1,
   "maxDiff": "0.00 %",
   "pass": true
  },
  {
   "id": "ARITH-KERBY-KIRPICH",
   "what": "Kerby-Kirpich: 500 ft overland (N 0.40, 0.01 ft/ft) plus 4,000 ft channel",
   "reference": "Hand calculation of the published equation (published example)",
   "compared": 1,
   "maxDiff": "0.00 %",
   "pass": true
  },
  {
   "id": "ARITH-LAG",
   "what": "NRCS lag: 5,000 ft flow length, 4% slope, CN 75",
   "reference": "Hand calculation of the published equation (published example)",
   "compared": 2,
   "maxDiff": "0.00 %",
   "pass": true
  },
  {
   "id": "ARITH-KERBY-1300",
   "what": "Kerby overland flow of 1,300 ft (over the TxDOT 1,200-ft limit: refused)",
   "reference": "Hand calculation of the published equation (published example)",
   "compared": 1,
   "maxDiff": "both refuse",
   "pass": true
  },
  {
   "id": "ARITH-SHEET-150",
   "what": "TR-55 sheet flow, 150 ft of short-grass prairie (over the NEH 630 100-ft limit: warning required)",
   "reference": "Hand calculation of the published equation (published example)",
   "compared": 1,
   "maxDiff": "0.00 %",
   "pass": true
  },
  {
   "id": "ARITH-SHEET-350",
   "what": "TR-55 sheet flow of 350 ft (over the TR-55 300-ft limit: refused)",
   "reference": "Hand calculation of the published equation (published example)",
   "compared": 1,
   "maxDiff": "both refuse",
   "pass": true
  }
 ]
}