Rational-method runoff API

Computes peak stormwater runoff via the SI Rational Method Q = C·i·A/360 from runoff coefficient, rainfall intensity and catchment area, returning peak flow in m3/s and L/s. Answers 'What is the peak runoff for C 0.7, 50 mm/hr, 2 ha?', 'How big must this drain be?'.

Price$0.04per request

MethodPOST

Route/v1/climate/rational-runoff

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

runoffrational-methodstormwaterdrainagehydrologypeak-flowcatchmentcivil

API URLhttps://x402.hexl.dev/v1/climate/rational-runoff

Integration docs

Example request

{
  "runoffCoefficient": 0.7,
  "rainfallIntensityMmHr": 50,
  "areaHectares": 2
}

Example response

{
  "peakFlowM3s": 0.1944,
  "peakFlowLs": 194.44,
  "runoffCoefficient": 0.7,
  "rainfallIntensityMmHr": 50,
  "areaHectares": 2,
  "interpretation": "Peak runoff ≈ 0.194 m³/s (194 L/s).",
  "formula": "Rational Method (SI): Q[m³/s] = C·i[mm/hr]·A[ha] / 360"
}

Input schema

{
  "type": "object",
  "required": [
    "runoffCoefficient",
    "rainfallIntensityMmHr",
    "areaHectares"
  ],
  "properties": {
    "runoffCoefficient": {
      "type": "number",
      "description": "Runoff coefficient C (0-1)",
      "examples": [
        0.7
      ]
    },
    "rainfallIntensityMmHr": {
      "type": "number",
      "description": "Rainfall intensity (mm/hr)",
      "examples": [
        50
      ]
    },
    "areaHectares": {
      "type": "number",
      "description": "Catchment area (hectares)",
      "examples": [
        2
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}