Calculate peak flood flows at ungauged sites using USGS regional regression equations. Estimate peak discharges for various return periods based on drainage area and basin characteristics. Professional-grade screening tool for civil engineers and hydrologists.
Screening-Level Tool
This calculator provides preliminary estimates only. Regional regression equations give approximate peak flows for ungauged sites. For final design, use state-specific USGS publications or USGS StreamStats.
Regional regression equations estimate peak streamflow at ungauged sites based on statistical relationships developed from streamgage data. The USGS has developed equations for all 50 states based on regional hydrologic characteristics.
The general equation form is:
Q = a × DAb × Sc × Pd × ...
Where Q is peak discharge, DA is drainage area, and other variables may include channel slope (S), mean annual precipitation (P), basin storage, impervious area, and forested area.
| Region | Description | DA Range (sq mi) |
|---|---|---|
| Northeast Highlands | Mountainous terrain with moderate precipitation, mixed forest cover | 0.1 - 1000 |
| Coastal Plain | Low-gradient terrain with sandy soils, higher water table | 0.05 - 500 |
| Piedmont | Rolling hills with clay soils, moderate forest cover | 0.1 - 800 |
| Appalachian Plateau | Mountainous terrain with high precipitation, steep valleys | 0.2 - 1500 |
| Great Lakes / Upper Midwest | Glaciated terrain with moderate topography, abundant lakes | 0.1 - 2000 |
| Central Plains | Low relief agricultural land, seasonal precipitation | 0.5 - 5000 |
| Southwest Semi-Arid | Arid to semi-arid terrain with ephemeral streams | 0.1 - 3000 |
| Pacific Northwest | High precipitation coastal and mountain terrain | 0.1 - 2500 |
Note: These are generalized regions for educational purposes. For actual design, use state-specific USGS publications or StreamStats.
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Educational Purpose: The calculations provided by DrainageCalculators.com are for informational and educational purposes only. While we strive for accuracy, these tools do not substitute for professional engineering judgment or designs stamped by a licensed Professional Engineer (PE) where required by law.
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