Non-Linear Routing Model

The Non-linear routing model routes flow using the Storage Function Method, used as a standard runoff model in Japan.

See the Japanese Runoff Methodology technical paper for further information.

The basic equations of the method are as follows:

1) 2) where: S: facade storage water depth in a river basin (mm) K, p: characteristic coefficients of basin q: runoff depth (mm/hr) re: intensity of effective rainfall (mm/hr)

To use the Non-linear routing model in InfoWorks ICM, set the Routing model field for the Runoff Surface to Non-linear.

The parameters for setting coefficients K and p are defined in the subcatchment properties (see Routing method below). Lag time is also defined in the subcatchment properties (see Lag time method below).

Routing method

Parameters for setting coefficients K and p are defined in the Subcatchment Data Fields.

To set K and p values, select a Non-linear routing method for the subcatchment:

• User - enter user defined values for Storage factor K and Exponent p data fields
• Izzard - calculate K and p using the Izzard method (see below)
• Equivalent roughness - calculate K and p using the Equivalent roughness method (see below)

Izzard method

The basic equations of the Izzard method are:

3) 4) where: C: equivalent roughness coefficient of basin I: catchment slope (m/m) L: catchment length (km)

The values in the following subcatchment data fields are applied when using the Izzard method:

• Equivalent roughness (C)
• Slope (I)
• Dimension (L)

 

Equivalent roughness method

The basic equations of the Equivalent roughness method are:

5) 6) where: N: equivalent roughness I: catchment slope (m/m) L: catchment length (km)

The values in the following subcatchment data fields are applied when using the Equivalent roughness method:

• Equivalent Manning's n (N)
• Slope (I)
• Dimension (L)

 

Lag time method

Parameters for setting lag time are defined in the Subcatchment Data Fields.

To set the lag time value, select a Lag time method for the subcatchment:

• User - enter user defined values for Lag time, tl data field
• Kimura - calculate lag time using Kimura method (see below)
• Flood velocity - calculate lag time using Flood velocity method (see below)

 

Kimura method

The basic equations of the Kimura method are:

6) where: T1: lag time (hr) L: catchment length (km)

The values in the following subcatchment data fields are applied when using the Izzard routing method:

• Dimension (L)

The lag time calculated is converted from hours into minutes.

Flood velocity method

The basic equations of the Flood velocity method are:

7) where: T1: lag time (s) L: catchment length (m) I: catchment slope (m/m) n: equivalent roughness R: hydraulic radius (m)

The values in the following subcatchment data fields are applied when using the Flood velocity method:

• Equivalent Manning's n (n)
• Slope (I)
• Dimension (L)

The lag time calculated is converted from seconds into minutes.