Drainage formula (Water Overlay)

Drainage passive: First the flow capacity is calculated

$Q_{p,t}=\Delta t\cdot q_{t}$

$Q_{b}=A_{d}\cdot f_{s}\cdot {\frac {(w_{g}-w_{w})\cdot A_{w}}{A_{d}\cdot f_{s}+A_{w}}}$

if w_w > w_g then:

$Q_{max}=A_{w}\cdot (w_{w}-z_{w})$

else:

$Q_{max}=A_{d}\cdot (w_{d}-z_{d})\cdot f_{s}$

$Q_{d}=min(Q_{p,t},Q_{b},Q_{max})$

Drainage active:

where:

$w_{g}$ is the ground water level in meters

$w_{w}$ is the water level in the waterway

$z_{d}$ is the drainage datum height in meters.

$A_{d}$ is the drainage area size in square meters.

$f_{s}$ is the average storage percentage of the ground above the drainage.

$Q_{b}$ is the amount transfered for a balanced ground and surface water level

$Q_{max}$ is the amount available in the ground above the drainage.

$Q_{p_{t}}$ is the drainage capacity at time t

$Q_{d}$ is the actual drainage at time t

Related

The following topics are related to this formula.

Structures

Drainage

Models

Surface model

Underground model

---

Water Module

Water Module

Tutorials

Overview

Theory

Benchmarks

Models

Surface • Ground • Rain • Evaporation • Infiltration • Elevation • Breach • Sewer • Storage • Tracer flow • Border • Order

Model formulas

Timestep • Season • Surface water level • Groundwater level

Flow formulas

Surface flow • Surface infiltration • Ground flow • Ground infiltration • Surface evaporation • Ground evaporation • Ground bottom flow

Hydraulic structure formulas

Culvert • Weir • Breach growth • Breach flow • Pump • Sewer Overflow • Inlet • Drainage

Related

Building attributes • Hydrological features • Hydraulic structures •  Terrain attributes • Model attributes • Results • Simulation data