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eng.peak-flow-snyder Calculator
Calculates peak flow and time to peak for a synthetic unit hydrograph using the Snyder method from basin characteristics. The Snyder method estimates flood peak from basin lag time and unit hydrograph parameters — it's suitable for ungauged basins where no flow records exist.
Inputs
Basin Area Km2
Two-dimensional surface extent (m²). For complex shapes, break into simpler sub-shapes and sum.
Main Channel Length Km
Linear measurement. Ensure consistent units: 1 m = 1,000 mm = 3.281 ft.
Centroid Distance Km
Separation between two points or total path length. Check that units are consistent throughout the calculation.
Ct Coefficient
Reference formula or conversion factor shown for context.
Cp Coefficient
Reference formula or conversion factor shown for context.
Results
time to peak tp (hours)
The result expressed in hours. Divide by 24 to convert to days.
peak discharge Qp (m³/s)
Reference formula or conversion factor shown for context.
basin area
The computed two-dimensional surface area.
Snyder: tp = Ct(L·Lc)^0.3
Sample size or count used in the calculation.
Snyder: Qp = 2.78CpA/tp
Sample size or count used in the calculation.
duration of unit hydrograph
Weighted average time to receive the bond's cash flows (years). Also a price sensitivity measure: duration of 7 means a 1% rise in yields drops the bond price ~7%.