RAFTS Hydrology Explorer

Interactive demo of the RAFTS (Laurenson) runoff routing model. Adjust physically meaningful parameters to see impacts on the hydrograph.

Catchment parameters

Area A (Ha) 5.0

Mean slope S₍c₎ (%) 2.0

Urbanisation (% impervious) 30

RAFTS U (derived): 0.7

Equivalent roughness (Manning's n) 0.035

PERN (derived): 1.4

Rainfall and losses

Rainfall depth (mm) 50

Initial loss (mm) 20

Continuing loss (mm/h) 2.0

Advanced

Storm duration (h) 2.0

Simulation duration (h) 4.0

RAFTS exponent n 0.285

RAFTS Adapt Factor 1.00

Cascade reservoirs (N) 10

Time step (min) 1

Derived RAFTS parameters

B (storage delay coefficient): –

Qpeak: – at –

Runoff volume: – (ML) • Coeff: –

Relationships used: \( S = B\,q^{\,n+1} \), and \( B = 0.285\,A^{0.52}(1+U)^{-1.97}S_c^{-0.5}\,\text{PERN}\times\text{Adapt} \). Routing via a cascade of N identical non-linear reservoirs.

Peak flow

- m³/s

Time to peak

- h

Runoff volume

- m³

Runoff coefficient

This tool is for educational/illustrative purposes and uses a simplified RAFTS-like routing implementation. For design work, use approved software and guidance.